RESUMEN
Sarizotan exhibited high affinities only to serotonin 5-HT1A receptors and dopamine DA D4>D3>D2 receptors with the profile of a 5-HT1A agonist and DA antagonist demonstrated by the inhibition of cAMP-stimulation and guinea pig ileum contraction, decreased accumulation of the 5-HT precursor 5-hydroxytryptophan and increased levels of 5-HT metabolites, increased accumulation of DA precursor dihydroxyphenylalanine (DOPA) and the reduced levels of DA metabolites in intact rats. However, sarizotan at higher doses decreased DA precursor accumulation in reserpinized rats and induced contralateral rotational behavior in unilaterally substantia nigra lesioned rats, indicating some intrinsic dopaminergic activity; at D2 receptors sarizotan may act as a partial agonist, depending on the dopaminergic impulse flow. Sarizotan represents a new approach for the treatment of extrapyramidal motor complications such as l-DOPA-induced dyskinesia in Parkinson's disease.
Asunto(s)
Antiparkinsonianos/metabolismo , Encéfalo/metabolismo , Receptores Dopaminérgicos/metabolismo , Agonistas del Receptor de Serotonina 5-HT1 , Agonistas de Receptores de Serotonina/metabolismo , Animales , Antiparkinsonianos/farmacología , Encéfalo/efectos de los fármacos , Células CHO , Bovinos , Cricetinae , Relación Dosis-Respuesta a Droga , Cobayas , Humanos , Ligandos , Masculino , Compuestos Orgánicos , Unión Proteica/efectos de los fármacos , Unión Proteica/fisiología , Ratas , Receptor de Serotonina 5-HT1A/metabolismo , Agonistas de Receptores de Serotonina/farmacología , PorcinosRESUMEN
As part of our research program toward new, potential antidepressants, a series of unsymmetrical ureas has been prepared and evaluated as 5-HT reuptake inhibitors with 5-HT(1B/1D) antagonistic activities. The design of these compounds was based on coupling of various indole derivatives, previously shown to inhibit 5-HT reuptake, to three different aniline moieties, which are part of known 5-HT(1B/1D) ligands. Binding experiments in rat frontal cortex using [(125)I]iodocyanopindolol, in calf striatum using [(3)H]5-HT, and in rat hippocampus using [(3)H]8-OH-DPAT as radioligands, respectively, revealed significantly higher affinity at the 5-HT(1B) receptor as compared to the affinities for the 5-HT(1A) and 5-HT(1D) receptors for a number of compounds, among them 4-(5-fluoro-1H-indol-3-yl)piperidine-1-carboxylic acid [4-methoxy-3-(4-methylpiperazin-1-yl)phenyl]amide (5), the corresponding 4-fluoro-1H-indol-3-yl analogue 21a, and the corresponding 6-fluoro-1H-indol-3-yl analogue 21b. Conformational restriction of the aniline moiety in 5 only slightly enhanced the 5-HT(1B) affinity, whereas introduction of an aniline moiety with higher conformational flexibility resulted in a less potent 5-HT(1B) receptor ligand as compared to 5. The functional 5-HT(1B/1D) antagonistic activity was investigated using the rabbit saphenous vein model as well as the [(3)H]5-HT release from guinea pig cortical slices. All new compounds tested in the rabbit saphenous vein model were shown to antagonize the sumatriptan-evoked contractile responses with pA(2) values ranging from 7.3 to 8.7. These observations were consistent with the results of the cortical slice model, in which the ureas were found to block the sumatriptan-induced inhibition of potassium-evoked [(3)H]5-HT release. The 5-HT reuptake inhibition of the ureas determined in rat brain synaptosomes was found to be either increased or decreased as compared to the uncoupled indole derivatives indicating that the reuptake inhibition shown by the ureas is not only due to the indole part but also affected by the aniline moiety of the molecule. Among this series of compounds described the ureas 5, 21a, and 21b seem to be the most interesting candidates showing both 5-HT reuptake inhibition and 5-HT(1B/1D) antagonism in vitro. This dual pharmacological profile should in theory lead to a pronounced enhancement in serotonergic neurotransmission and consequently to a more efficient treatment of depression.
Asunto(s)
Antidepresivos/síntesis química , Indoles/síntesis química , Receptores de Serotonina/efectos de los fármacos , Inhibidores Selectivos de la Recaptación de Serotonina/síntesis química , Antagonistas de la Serotonina/síntesis química , Animales , Antidepresivos/química , Antidepresivos/metabolismo , Antidepresivos/farmacología , Encéfalo/metabolismo , Encéfalo/ultraestructura , Cuerpo Estriado/metabolismo , Lóbulo Frontal/metabolismo , Cobayas , Hipocampo/metabolismo , Técnicas In Vitro , Indoles/química , Indoles/metabolismo , Indoles/farmacología , Contracción Muscular/efectos de los fármacos , Contracción Muscular/fisiología , Músculo Liso Vascular/efectos de los fármacos , Músculo Liso Vascular/fisiología , Conejos , Ensayo de Unión Radioligante , Ratas , Receptor de Serotonina 5-HT1B , Receptor de Serotonina 5-HT1D , Receptores de Serotonina/metabolismo , Vena Safena/efectos de los fármacos , Vena Safena/fisiología , Serotonina/metabolismo , Antagonistas de la Serotonina/química , Antagonistas de la Serotonina/metabolismo , Antagonistas de la Serotonina/farmacología , Inhibidores Selectivos de la Recaptación de Serotonina/química , Inhibidores Selectivos de la Recaptación de Serotonina/metabolismo , Inhibidores Selectivos de la Recaptación de Serotonina/farmacología , Sinaptosomas/metabolismoRESUMEN
A series of 2- or 8-trifluoromethylsulfonyloxy (TfO) and 2- or 8-methylsulfonyloxy (MsO) 11-piperazinyldibenzodiazepines, -oxazepines, and -thiazepines were synthesized and evaluated in pharmacological models for their potential clozapine-like properties. In receptor binding assays, the 2-TfO analogues (18a, GMC2-83; 24, GMC3-06; and previously reported GMC1-169, 9a) of the dibenzazepines have profiles comparable to that of clozapine, acting on a variety of CNS receptors except they lack M1 receptor affinity. Introduction of 2-TfO to clozapine leads to compound 9e (GMC61-39) which has a similar binding profile as that of clozapine including having M1 receptor affinity. Interestingly, the MsO analogues, as well as the 8-TfO analogues, have no or weak dopaminergic and serotonergic affinities, but all 8-sulfonyloxy analogues do have M1 affinities. In behavioral studies performed to indicate the potential antipsychotic efficacy and the propensity to induce EPS, 2-TfO analogues blocked effectively the apomorphine-induced climbing in mice in a dose-dependent manner with ED50 values (mg/kg) of 2.1 sc for 9a, 1.3 po for 18a, 2.6 sc for 24, and 8.2 sc for 9e. On the other hand, they showed a clear dose separation with regard to their ED50 values (mg/kg) for indicating catalepsy in rats (>44 sc for 9a, 28 po for 18a, 30 sc for 24, and >50 sc for 9e, respectively), thus implicating a more favorable therapeutic ratio (K/A, ED50 climbing/ED50 catalepsy) in comparison with typical neuroleptics such as haloperidol and isoclozapine. Furthermore, compound 18a was also demonstrated to be an orally potent DA antagonist with an ED50 value of 0.7 mg/kg po in the ex vivo L-DOPA accumulation model. The present study contributes to the SAR of 11-piperazinyldibenzazepines, and the 2-TfO analogues of 11-piperazinyldibenzazepines are promising candidates as clozapine-like atypical antipsychotics with low propensity to induce EPS.
Asunto(s)
Antipsicóticos/síntesis química , Benzazepinas/síntesis química , Piperazinas/síntesis química , Animales , Antipsicóticos/química , Antipsicóticos/metabolismo , Antipsicóticos/farmacología , Benzazepinas/química , Benzazepinas/metabolismo , Benzazepinas/farmacología , Encéfalo/metabolismo , Células CHO , Catalepsia/inducido químicamente , Cricetinae , Antagonistas de Dopamina/síntesis química , Antagonistas de Dopamina/química , Antagonistas de Dopamina/metabolismo , Antagonistas de Dopamina/farmacología , Humanos , Técnicas In Vitro , Masculino , Ratones , Estructura Molecular , Piperazinas/química , Piperazinas/metabolismo , Piperazinas/farmacología , Ratas , Ratas Wistar , Receptor Muscarínico M1 , Receptores Adrenérgicos alfa/metabolismo , Receptores Dopaminérgicos/efectos de los fármacos , Receptores Dopaminérgicos/metabolismo , Receptores Histamínicos H1/metabolismo , Receptores Muscarínicos/metabolismo , Receptores de Serotonina/metabolismo , Relación Estructura-ActividadRESUMEN
We examined whether increases in blood-brain barrier (BBB) permeability occurring after stroke can be exploited to apply protective substances selectively to ischemic tissue. To do this, the actions of the peripherally selective OP2 agonists, EMD-61569 and EMD-61747, have been compared with those of the centrally acting OP2 agonist, GR-89696, in the rat permanent focal ischemia model. EMD-61569, EMD-61747 and GR-89696 all bound with high affinity to OP2 receptors and were potent agonists in the rabbit vas deferens functional assay. These substances also potently inhibited electrically-induced overflow of dopamine from slices of rat nucleus accumbens. EMD-61747 and EMD-61569 penetrate poorly into the CNS under normal conditions and reverse haloperidol-induced L-DOPA accumulation in the nucleus accumbens of the rat only at high doses, in contrast to GR-89696. Permanent unilateral occlusion of the middle cerebral artery (MCAO) was associated with a disruption of the BBB and an increase in the concentration of EMD-61747 in the area of the infarct. GR-89696 at a dose of 0.1 mg/kg s.c. produced a reduction in infarct volume by 38% after MCAO, EMD-61569 and EMD-61747 had no influence on swelling and ischemic damage. We conclude that EMD-61747 and EMD-61569 are potent OP2 agonists, which usually have a limited ability to penetrate the BBB. The change in the properties of the BBB in ischemic tissue was not sufficient to elicit neuroprotection, since both EMD-61747 and EMD-61569 were inactive in the focal ischemia model. Conversely, GR-89696 had a robust protective action, and probably powerful OP2-typical side effects as a consequence of its unrestricted central activity.
Asunto(s)
Isquemia Encefálica/tratamiento farmacológico , Fármacos Neuroprotectores/uso terapéutico , Piperazinas/uso terapéutico , Pirroles/farmacología , Pirrolidinas/uso terapéutico , Receptores Opioides kappa/agonistas , Animales , Unión Competitiva/efectos de los fármacos , Edema Encefálico/tratamiento farmacológico , Arterias Cerebrales/efectos de los fármacos , Arterias Cerebrales/fisiología , Levodopa/química , Ligadura , Masculino , Conejos , Ratas , Ratas Endogámicas F344 , Ratas WistarRESUMEN
SAR for a novel series of dopamine D4 receptor ligands is shown. Very selective, highly potent compounds like 1-(2-pyrimidinyl)-4-(3-(3-thienyl)-benzyl)-piperazine (5f) and 2-(4-(1-fluorenylmethyl)-1-piperazinyl)-pyrimidine (8c) were obtained.
Asunto(s)
Metilaminas/química , Receptores de Dopamina D2/metabolismo , Animales , Antagonistas de Dopamina/metabolismo , Antagonistas de Dopamina/farmacología , Ligandos , Metilaminas/metabolismo , Metilaminas/farmacología , Ratones , Receptores de Dopamina D4 , Relación Estructura-ActividadRESUMEN
EMD 61753 (N-methyl-N-[(1S)-1-phenyl-2-((3S)-3-hydroxypyrrolidin-1-yl) -ethyl ]- 2,2-diphenyl-acetamide hydrochloride) is a peripherally selective kappa-opiate agonist. It exhibits antihyperalgesic activity in animal models of inflammatory pain at doses which do not cause signs of central action. The structure of this compound was varied in different ways and the resulting derivatives were tested for affinity to the kappa-receptor. Furthermore, those compounds with binding values comparable to that of EMD 61753 were tested for central activity. This was done by measuring the extent to which the haloperidol-induced L-DOPA accumulation in the nucleus accumbens of the rat could be reversed after application of 10 mg/kg s.c. of the test compound. Structure-activity relationships revealed that none of the analogues or reference compounds tested is superior to the parent compound with regard to its favourable ratio between kappa-receptor affinity and peripheral selectivity.
Asunto(s)
Acetamidas/farmacología , Analgésicos Opioides/farmacología , Sistema Nervioso Periférico/efectos de los fármacos , Pirrolidinas/farmacología , Receptores Opioides kappa/agonistas , Acetamidas/química , Animales , Cerebelo/metabolismo , Antagonistas de Dopamina/farmacología , Cobayas , Haloperidol/farmacología , Levodopa/metabolismo , Masculino , Núcleo Accumbens/efectos de los fármacos , Núcleo Accumbens/metabolismo , Pirrolidinas/química , Ratas , Ratas WistarRESUMEN
Roxindole, a structurally novel psychotropic indolylbutyl-4-phenyltetrahydropyridine, was studied with respect to the formation of potentially neurotoxic pyridinium metabolites in comparison to MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). In contrast to MPTP, roxindole failed to serve as a substrate for monoamine oxidases (MAO) from mouse, monkey and human brain in vitro. Accordingly, neither the putative MAO-oxidation product of roxindole (ROX+) nor MPP+ (1-methyl-4-phenylpyridinium ion) was detected in mouse striatum after high subcutaneous doses of roxindole in spite of the presence of approximately 6 micrograms of roxindole per g of striatum in these animals. After multiple subcutaneous treatments with 95.2 mg/kg roxindole, no long-term striatal dopamine depletions were observed in contrast to MPTP. Furthermore, unlike MPP+, ROX+ did not induce release of previously accumulated 3H-dopamine in mouse striatal slices indicating that ROX+ cannot utilize the dopamine uptake carrier to enter neurones. ROX+ at doses up to 100 mg/kg subcutaneously failed to alter striatal biogenic amine levels and gross behaviour of mice. Thus, no MPTP-like neurotoxic metabolites are formed from roxindole in vivo and neurotoxic effects of ROX+, even if formed in minute amounts by some MAO-independent pathway, are highly unlikely.
Asunto(s)
Cuerpo Estriado/metabolismo , Dopaminérgicos/farmacología , Indoles/farmacología , Monoaminooxidasa/metabolismo , Neuronas/metabolismo , Piridinas/farmacología , 1-Metil-4-fenil-1,2,3,6-Tetrahidropiridina/farmacología , Animales , Cromatografía Líquida de Alta Presión , Cuerpo Estriado/efectos de los fármacos , Dopamina/metabolismo , Dopaminérgicos/metabolismo , Interacciones Farmacológicas , Humanos , Indoles/metabolismo , Macaca , Masculino , Ratones , Neuronas/efectos de los fármacos , Oxindoles , Piridinas/metabolismo , Especificidad por SustratoRESUMEN
The selective presynaptic dopamine D2 receptor agonist roxindole was studied in specific pre- and postsynaptic models in rats to see whether it induced changes in dopamine D2 receptor sensitivity. Following treatment with 0.3 or 3 mg/kg per day i.p. for 21 days, the reversal of gamma-butyrolactone-induced striatal dihydroxyphenylalanine accumulation was unchanged as compared to that after acute treatment. The efficacy of roxindole in this model was not decreased after long-term treatment. Likewise, treatment for 19 days with up to 10 mg/kg per day i.p. failed to induce behavioral supersensitivity, i.e. potentiation of apomorphine-induced stereotypies. In a cotreatment paradigm with haloperidol (1 mg/kg per day p.o.), roxindole (10mg/kg per day i.p.) did not alter the behavioral supersensitivity measured after a drug washout phase as compared to the effect of haloperidol alone; however, stereotypies were observed after termination of haloperidol but continuation of roxindole treatment. In contrast, roxindole (10 mg/kg i.p.) induced only weak stereotypies in haloperidol-sensitized rats when given after the washout phase instead of apomorphine. The results indicate that roxindole induces neither desensitization of presynaptic nor supersensitization of postsynaptic dopamine D2 receptors. Nevertheless, in add-on clinical studies with neuroleptics, switching of treatment regimens should be performed gradually over several days until further experience is available.
Asunto(s)
Cuerpo Estriado/efectos de los fármacos , Indoles/farmacología , Piridinas/farmacología , Receptores de Dopamina D2/efectos de los fármacos , Conducta Estereotipada/efectos de los fármacos , 4-Butirolactona/farmacología , Animales , Apomorfina/farmacología , Cuerpo Estriado/metabolismo , Dihidroxifenilalanina/metabolismo , Dopaminérgicos/farmacología , Regulación hacia Abajo/efectos de los fármacos , Interacciones Farmacológicas , Haloperidol/farmacología , Indoles/administración & dosificación , Inyecciones Intraperitoneales , Masculino , Oxindoles , Piridinas/administración & dosificación , Ratas , Ratas Wistar , Receptores de Dopamina D2/metabolismoRESUMEN
1. The pharmacological characteristics of the kappa-opioid receptor agonist, EMD 60400, have been investigated, with particular reference to its central and peripheral sites of action and its ability to influence nociception. The kappa agonists ICI 197067 and ICI 204448 were tested for purposes of comparison. 2. EMD 60400 and ICI 197067 bind with high affinity (IC50 values of 2.8 and 1.5 nM, respectively) and high selectivity to kappa-opioid receptors. ICI 204448 has a lower binding affinity (IC50 13.0 nM) and selectivity for kappa-opioid receptors. 3. EMD 60400, ICI 197067, and ICI 204448 are full and potent agonists in the rabbit vas deferens in vitro assay for kappa-opioid receptors (IC50 values of 41.8, 15.7 and 15 nM, respectively). 4. Ex vivo binding experiments in mice revealed that EMD 60400 and ICI 197067 were well taken up after s.c. administration. Brain levels of EMD 60400 were lower than those of ICI 197067 at comparable doses, indicating that EMD 60400 does not penetrate into the CNS as well as ICI 197067. 5. Haloperidol-induced DOPA accumulation in the nucleus accumbens of the rat was dose-dependently reversed by s.c. application of EMD 60400 and ICI 197067 at doses of and above 3 and 0.3 mg kg-1, respectively. ICI 204448 had no effect on DOPA accumulation at 30 mg kg-1, s.c. 6. Prolongation of hexobarbitone-induced sleeping time in mice and motor impairment in the rat rotarod test were observed for EMD 60400 at doses above 3 and 2.5 mg kg-1, s.c., respectively, and for ICI 197067 at doses above 0.3 and 0.25 mg kg-1, s.c., respectively. ICI 204448 was inactive in these tests at doses of 30 and 100 mg kg-1, s.c., respectively.7. EMD 60400 applied s.c. produced dose-dependent naloxone-reversible antinociception in the mouse formalin test (1st and 2nd phase ID50 0.44 and 0.47 mg kg-1, respectively) and rodent writhing test (ID50 mouse 0.55 mg kg-1 and rat 0.3mg kg-1). Furthermore, EMD 60400 was considerably more potent in the rat pressure pain test after the induction of inflammation with carrageenin than under normalgesic conditions (ID50 values 0.1 Microg kg-1 and 4.0 mg kg-1, s.c., respectively). The action of EMD 60400 (50 microgkg-1, s.c.) in the hyperalgesic pressure pain test was completely antagonized by injection of the K-opioid antagonist, norbinaltorphimine (100 microg) into the inflamed tissue, thus demonstrating the peripheral opioid nature of this effect.8. EMD 60400 produced dose-dependent inhibition of neurogenic plasma extravasation elicited byantidromic electrical stimulation of the rat saphenous nerve (ID50 value 0.3 mg kg-1, i.v.). This inhibition was completely antagonized by intraplantar injection of norbinaltorphimine (50 microg).9. EMD 60400, ICI 197067, and ICI 204448 have diuretic effects in rats at doses of and above 0.1, 0.01,and 0.3 mg kg-1, s.c., respectively. An antidiuretic action was also observed with ICI 197067 at very low doses (3 and 6 microgkg-1, s.c.).10. Pharmacological and biochemical data therefore indicate that the three K-opioid receptor agonists tested here have different tendencies to elicit centrally-mediated sedation and putative aversion(ICI 197067 > EMD 60400 > ICI 204448) which correspond to their ability to cross the blood-brain barrier. EMD 60400 combines high affinity and selectivity for the K receptor with a degree of peripheral selectivity. The peripheral actions of systemically-applied EMD 60400 against hyperalgesic pressure pain and neurogenic inflammation are very probably mediated by opioid receptors on the endings of sensory nerve fibres.
Asunto(s)
Analgésicos/farmacología , Pirrolidinas/farmacología , Receptores Opioides kappa/efectos de los fármacos , Receptores Opioides kappa/fisiología , Analgésicos/sangre , Analgésicos/metabolismo , Animales , Encéfalo/metabolismo , Carragenina , Dihidroxifenilalanina/metabolismo , Diuresis/efectos de los fármacos , Estimulación Eléctrica , Formaldehído , Haloperidol/farmacología , Hiperalgesia/inducido químicamente , Masculino , Ratones , Ratones Endogámicos , Neuritis/tratamiento farmacológico , Neuritis/prevención & control , Nociceptores/efectos de los fármacos , Dimensión del Dolor/efectos de los fármacos , Pirrolidinas/sangre , Pirrolidinas/metabolismo , Conejos , Ensayo de Unión Radioligante , Ratas , Ratas Wistar , Receptores Opioides kappa/metabolismo , Sueño/efectos de los fármacos , Conducto Deferente/fisiologíaRESUMEN
The synthesis and dopaminergic properties of a novel type of dopamine agonist is described. The number and kind of essential structural elements differ significantly from that of the rigid apomorphine-type dopamine agonists. Using standard molecular modeling techniques, a conformational model is developed proposing a U-shaped conformation which might be energetically preferred through aromatic pi-pi-interactions between both of the electron rich aromatic structural elements of this class of compounds. Superimposition of conformations of the lead compound 28 with apomorphine yields a novel model explaining the atypical structure-activity relationships found in this class of indolealkylamines.
Asunto(s)
Dopaminérgicos/síntesis química , Indoles/síntesis química , Animales , Unión Competitiva , Cuerpo Estriado/metabolismo , Dopaminérgicos/metabolismo , Dopaminérgicos/farmacología , Técnicas In Vitro , Indoles/metabolismo , Indoles/farmacología , Masculino , Modelos Moleculares , Conformación Molecular , Ratas , Ratas Wistar , Receptores de Dopamina D2/metabolismo , Conducta Estereotipada/efectos de los fármacos , Relación Estructura-ActividadRESUMEN
In the past, nearly all major mechanisms involved in the regulation of blood pressure have become targets of antihypertensive drugs. They include the brain stem with its neuronal circuits of central cardiovascular regulation, the sympathetic neuro-effector system, the kidney, the renin angiotensin aldosterone system and the vascular smooth muscle cell. There are various ways of influencing the function of the sympathetic nervous system, but the clinical potential of one mechanism of action has not yet been explored in detail. Drugs that inhibit noradrenaline release through stimulation of inhibitory receptors located at adrenergic nerve terminals in the cardiovascular system (inhibitory presynaptic receptors) are not available for the treatment of hypertension. Among the multiple presynaptic receptors, dopamine receptors which belong to the dopamine2 subtype, are of particular interest. Carmoxirole is a novel indole derivative with a potent agonist action selective for dopamine2-receptors of the periphery. Experimental evidence shows that carmoxirole lowers blood pressure in various models of hypertension mainly or exclusively through inhibition of noradrenaline release from sympathetic nerve endings. This effect of carmoxirole is mediated by presynaptic dopamine receptors with the characteristic that release inhibition is restricted to low rates of sympathetic nerve discharge.
Asunto(s)
Antihipertensivos/farmacología , Dopaminérgicos/farmacología , Hipertensión/fisiopatología , Indoles/farmacología , Piridinas/farmacología , Receptores de Dopamina D2/efectos de los fármacos , Animales , Presión Sanguínea/efectos de los fármacos , Presión Sanguínea/fisiología , Frecuencia Cardíaca/efectos de los fármacos , Frecuencia Cardíaca/fisiología , Humanos , Músculo Liso Vascular/inervación , Norepinefrina/sangre , Receptores de Dopamina D2/fisiología , Sistema Nervioso Simpático/efectos de los fármacos , Sistema Nervioso Simpático/fisiopatologíaRESUMEN
A new potential antihypertensive drug, EMD 45609 (carmoxirole), has been characterized in various in vivo and in vitro models. EMD 45609 displayed high affinity for dopamine D2-receptors combined with negligible binding to D1-receptors in binding assays in vitro. However, in tests in vivo for central D2-receptor activity, EMD 45609 exhibited only weak activity. Thus, after p.o. administration, striatal L-DOPA accumulation in intact rats was unchanged up to 100 mg/kg p.o., i.e. doses 100 times higher than those reported to induce depressor activity. Central dopamine agonistic activity could only be verified in the more sensitive model of the reserpinized rat. EMD 45609 was more than 30 times less potent, however, than LY 141865 in reserpinized rats after s.c. administration. Similarly, in rats with 6-hydroxydopamine induced unilateral lesions of the substantia nigra, EMD 45609 was only marginally active. The shallow dose response curves and the submaximal effects obtained for central dopaminergic activity, as reflected in the inhibition of striatal L-DOPA accumulation, suggest that EMD 45609 is a partial dopamine D2-receptor agonist and in addition, owing to its ionizable structure, passes less readily into the brain than several reference compounds. A marked affinity was found towards 5-HT1A-receptors in vitro, whereas affinity for alpha 1- and alpha 2-adrenoceptors was low; accordingly, central alpha 2-adrenoceptor activity was not detected as EMD 45609 failed to affect hypothalamic L-DOPA accumulation even at 100 mg/kg s.c. In accordance with its high affinity for D2-receptors in vitro, EMD 45609 inhibited field stimulated noradrenaline release from rabbit ear arteries in nanomolar threshold concentrations at 0.5 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Encéfalo/efectos de los fármacos , Dopaminérgicos/farmacología , Indoles/farmacología , Levodopa/metabolismo , Actividad Motora/efectos de los fármacos , Piridinas/farmacología , Animales , Aminas Biogénicas/metabolismo , Encéfalo/metabolismo , Clonidina/farmacología , Cuerpo Estriado/efectos de los fármacos , Cuerpo Estriado/metabolismo , Dopamina/metabolismo , Dopaminérgicos/metabolismo , Interacciones Farmacológicas , Ergolinas/farmacología , Corazón/efectos de los fármacos , Hipotálamo/efectos de los fármacos , Hipotálamo/metabolismo , Indoles/metabolismo , Masculino , Norepinefrina/metabolismo , Oxidopamina/farmacología , Piridinas/metabolismo , Quinpirol , Ratas , Ratas Endogámicas , Receptores Dopaminérgicos/metabolismo , Reserpina/farmacología , Sulpirida/farmacologíaRESUMEN
Intra- and interassay imprecision was evaluated in 3 in vitro ligand binding assays using different types of filtering devices, glass fiber filters and variations in methodology. In the [3H]-spiroperidol test, the already low unspecific binding seemed to be dependent on the type of filters employed, whereas in the [3H]-ketanserin- and [3H]-GR 65630-binding tests, differences were within the range of the normal variabilities. However, in the latter test, which is problematic owing to the high unspecific binding of [3H]-GR 65630, it was found that although the percentage of specific binding was fairly constant on different sheets, large differences in the absolute amounts of total and unspecific binding were observed on consecutive sheets in the same experiment. Thus, it is critically important to filter samples for total and unspecific binding together on the same filter sheet for the calculation of specific binding. Under these precautions, highly reproducible results for IC50-values in the screening of potential 5HT3-receptor ligands were obtained in spite of using rat entorhinal cortex, a relatively large area with suboptimal 5HT3-receptor density. In contrast, when using rat area postrema, which is optimal with respect to receptor density, more than 10 times the number of rats is necessary for a competition experiment due to the small size of this brain part. Since IC50-values for both areas compare favorably, entorhinal cortex should be used for ethical reasons and to minimize costs.
Asunto(s)
Ketanserina/metabolismo , Receptores de Serotonina/metabolismo , Espiperona/metabolismo , Animales , Unión Competitiva , Encéfalo/metabolismo , Filtración , Imidazoles/metabolismo , Indoles/metabolismo , Ligandos , Masculino , Ratas , Ratas EndogámicasRESUMEN
A high-performance liquid chromatographic method capable of separating a large number of C- and N-terminal degradation fragments of dynorphin A (1-17) (dyn 1-17) in 1 h has been developed. The system has been applied to study the metabolism profiles of various dyn 1-17-derived peptides following in vitro incubation with rat striatum and spinal cord nerve terminal membranes. In addition to the removal of the N-terminal amino acid Tyr, major sites of cleavage between the following amino acids could be established: Leu5-Arg6 in dyn 1-7 (formation of dyn 1-5); Arg6-Arg7 and Leu5-Arg6 in dyn 1-8 (formation of dyn 1-6 and dyn 1-5, respectively); Arg7-Ile8 in dyn 1-9 (formation of dyn 1-7) and Arg9-Pro10 in dyn 1-10 (formation of dyn 1-9). Studies with inhibitors of the enzymes involved show that dyn 1-5 is formed directly from dyn 1-8 via an endopeptidase insensitive to the angiotensin-converting enzyme inhibitor MK 422 acting on the scissile Leu5-Arg6 bond in dyn 1-8. The method circumvents the use of [3H]Tyr-labelled dynorphins, which have the inherent drawback that fragments lacking the N-terminal Tyr cannot be detected. Owing to the high resolution, also for the larger dynorphins dyn 1-14, dyn 1-15 and dyn 1-16, the chromatographic system should prove especially useful in the elucidation of the enzymolysis pattern of dyn 1-17. Furthermore, the method offers a way to evaluate simultaneously the selectivity of new enzyme inhibitors for several cleavage sites in the same assay.
Asunto(s)
Cromatografía Líquida de Alta Presión/métodos , Dinorfinas/análisis , Terminaciones Nerviosas/enzimología , Fragmentos de Péptidos/análisis , Animales , Membrana Celular/enzimología , Ratas , Ratas Endogámicas , Médula Espinal/citologíaRESUMEN
EMD 49,980 proved to be a potent and selectively presynaptic D-2 dopamine receptor agonist in biochemical studies with rats. Thus, the gamma-butyrolactone-induced accumulation of dihydroxyphenylalanine, used as a presynaptic model, was antagonized with ED50 values of 0.29 and 0.09 mumol/kg in striatum and t. olfactorium, respectively, with high maximal effects. In contrast, striatal acetylcholine concentrations, reflecting actions at normosensitive postsynaptic D-2 receptors, were only moderately increased by about 30% over a dose range of 2.3-68 mumol/kg. In rats with unilateral nigrostriatal lesions, EMD 49,980 induced long-lasting contralateral turning, indicative of agonistic actions at denervated postsynaptic D-2 receptors. In addition, EMD 49,980 potently inhibited serotonin (5-HT) uptake in vitro and in vivo. Binding studies confirmed D-2 activity in the nM range but, similarly potent effects were observed at 5-HT1A binding sites. Measurement of 5-hydroxytryptophan (5-HTP) accumulation in the n. raphe revealed that, in vivo, the net effect of EMD 49,980 on 5-HT systems is an agonistic one. Control experiments indicate that inhibition of 5-HTP accumulation by EMD 49,980 is induced mainly via direct activation of 5-HT1A receptors, although some contribution due to 5-HT uptake inhibition is likely. Furthermore, results with various reference compounds make it unlikely that there are indirect effects, also via alpha 2-receptors in the models used and support the view that D-2 agonistic, 5-HT uptake inhibiting and 5-HT1A agonistic actions are independent properties of EMD 49,980.
Asunto(s)
Química Encefálica/efectos de los fármacos , Dopaminérgicos/farmacología , Indoles/farmacología , Piridinas/farmacología , Serotonina/fisiología , 4-Butirolactona/farmacología , 5-Hidroxitriptófano/metabolismo , 5-Hidroxitriptófano/farmacología , Acetilcolina/metabolismo , Animales , Dihidroxifenilalanina/metabolismo , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Hidroxidopaminas/farmacología , Masculino , Oxidopamina , Oxindoles , Ratas , Ratas Endogámicas , Reserpina/farmacología , Serotonina/metabolismo , Sinaptosomas/efectos de los fármacos , Sinaptosomas/metabolismo , p-Cloroanfetamina/antagonistas & inhibidoresRESUMEN
In investigations carried out in young and old rats with pyritinol (pyrithioxin, Encephabol), a substance that is frequently applied in cognitive function disturbances, besides effects on general cerebral functions, possible interactions with cholinergic transmission were determined. The following results were obtained: 1. The adenosine triphosphate (ATP) content of the blood was determined as a possible biochemical parameter of erythrocyte flexibility. After acute oral administration of 30, 100 and 300 mg/kg pyritinol, the ATP content of whole blood increased by 8%, 17% and 20% respectively compared with placebo. 2. According to the literature, brain glucose utilisation is considerably reduced at higher age. This was confirmed in old rats in the investigation presented here. Pyritinol (200 mg/kg p.o.) induced a significant increase in glucose utilisation in striatum, cortex, hypothalamus and cerebellum in 24- to 36-month-old rats. 3. The high-affinity choline uptake in striatal synaptosomes of old rats was significantly lower than that of young ones. Pyritinol (600 mg/kg p.o.) increased choline uptake in young rats as well as in old ones. 4. cGMP can serve as a postsynaptic marker for the activity of the cholinergic system. Pyritinol (200, 600, 1000 mg/kg p.o., 16-23 days) increased the cGMP level in the cortex by 25%, 42% and 71% respectively. Our results are in accordance with the recently described (Martin, 1987) elevation of cortical acetylcholine levels and facilitation of acetylcholine release under pyritinol and extend the functional relevance of these findings to the postsynaptic, cholinergically innervated cortical neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Química Encefálica/efectos de los fármacos , Piridinas/farmacología , Piritioxina/farmacología , 5-Hidroxitriptófano/metabolismo , Adenosina Trifosfato/sangre , Animales , Monoaminas Biogénicas/fisiología , Colina/metabolismo , AMP Cíclico/metabolismo , GMP Cíclico/metabolismo , Glucosa/metabolismo , Levodopa/metabolismo , Masculino , Neurotransmisores/metabolismo , Ratas , Ratas Endogámicas , Receptores Adrenérgicos beta/efectos de los fármacos , Receptores Adrenérgicos beta/metabolismo , Sinaptosomas/efectos de los fármacos , Sinaptosomas/metabolismoRESUMEN
The effects of the dopamine (DA) agonist EMD 23,448 on central normosensitive and supersensitive DA receptors were investigated. EMD 23,448 only slightly inhibits rat striatal DOPA synthesis in vivo and does not inhibit the enhanced striatal DOPA synthesis elicited by acute administration of haloperidol. Also unlike other DA agonists it does not increase striatal acetylcholine levels. However, it inhibits striatal DOPA synthesis in rats with DA receptors rendered supersensitive by chronic treatment with haloperidol. EMD 23,448 also effectively inhibits the enhanced striatal DOPA synthesis elicited by administration of GBL. Furthermore, EMD 23,448 selectively reduces, in a dose-dependant way, DA utilization in nerve terminals of the central caudate and in dotted terminals of the ventral striatum but DA utilization in the substantia nigra is unaffected. The most marked reduction of DA utilization was induced in the anteromedial frontal cortex. These results indicate that EMD 23,448 selectively stimulates presynaptic DA receptors and supersensitive postsynaptic DA receptors. Behavioral experiments in animals with normosensitive and supersensitive DA receptors also indicate that EMD 23,448 effectively stimulates presynaptic and supersensitive postsynaptic DA receptors. Receptor binding studies have shown that EMD 23,448 has a high affinity for the D2 DA receptors, but it ineffectively promotes the coupling of the DA receptors with the guanine nucleotide regulatory protein. However, at supersensitive striatal DA receptors the coupling is shown to be enhanced by EMD 23,448. The selectivity of EMD 23,448 for presynaptic DA receptors might, at least in part, be related to the presence of DA receptor reserves which are sensitive to EMD 23,448. With regard to the selectivity of EMD 23,448 for supersensitive postsynaptic DA receptors an increase in the efficiency of the coupling mechanism upon activation by EMD 23,448 is probably involved.
Asunto(s)
Agonistas Adrenérgicos/farmacología , Indoles/farmacología , Receptores Dopaminérgicos/efectos de los fármacos , Acetilcolina/metabolismo , Animales , Apomorfina/farmacología , Conducta Animal/efectos de los fármacos , Encéfalo/metabolismo , Catecolaminas/metabolismo , Dihidroxifenilalanina/biosíntesis , Dopamina/metabolismo , Masculino , Ratas , Ratas EndogámicasRESUMEN
The conversion of selected prodynorphin fragments to form the octapeptide Dynorphin A 1-8 was studied in rat brain or spinal cord fractions, and the results compared to the action of purified carboxypeptidases and angiotension converting enzyme. The particulates were shown to convert Dynorphin A or 1-13 to the octapeptide as measured by radioimmunoassay, and by reverse phase high performance liquid chromatography. Detergent extracts of these particulates contained and enzyme converting 1-13 to 1-12 with release of C-terminal lysine, and active over a wide pH range of 4.8-7.6. Purification of these extracts by affinity chromatography (p-amino-benzoyl-arginine-Sepharose-6B) using Bz-Ala-Arg as the substrate led to isolation of a carboxypeptidase converting 1-13 to 1-12 active over the same pH range. Since Dynorphin 1-13 was converted to 1-8 by the consecutive use of purified carboxypeptidase B and angiotensin converting enzyme, the possibility exists that this mechanism might account for some octapeptide production in situ. The properties and substrate specificity of the carboxypeptidase B were compared to a carboxypeptidase A active optimally at pH 5.5 and assayed with Z-Glu-Tyr. The carboxypeptidase B acted only on prodynorphins with C-terminal basic residues as contrasted to a nonspecific action by the carboxypeptidase A. The carboxypeptidase B was characterized by a strong activation by -SH agents and Zn(2+), and thus could be differentiated from other opioid converting enzymes. The enzyme was inhibited by guanidinoethyl succinic acid (GEMSA), and p-chloromercuriphenyl-sulphonic acid (PCMS) but not by benzylsuccinic acid, a potent inhibitor of carboxypeptidase A.
RESUMEN
An automated, highly stable HPLC system is described allowing the quantitation of monoamines and related compounds with virtually online data processing and statistical evaluation of the mean values of various differently treated groups of animals. The system is highly suited to the screening of drugs involving large numbers of samples. To ensure long-term, uninterrupted performance, two robust chromatographic systems were developed optimized to separate neighboring peaks as widely as possible. This was achieved by using mobile phases of relatively low pH to retard acidic compounds, and optimal concentrations of the ion-pairing reagent to manipulate the retention times of amines on the RP-18 column, resulting also in clearcut separations from the solvent/tissue peak. Direct injection of deproteinized tissue samples, requiring no clean up procedures is used. One faster system allows measurement of the main biogenic amines, metabolites and TRP, whereas another system allows the simultaneous quantitation of DOPA, 5HTP, NA, MOPEG, NMN, A, MN, VMA, DA, 3MT, DOPAC, HVA, 5HT, 5HIAA and TYR. By pretreatment of animals with a decarboxylase inhibitor the latter system offers the possibility of detecting drug effects in the same animal on either dopamine and serotonin turnover or noradrenaline and serotonin turnover, depending on the brain area chosen. The system described has been running for over a year without major disturbance and with minimal technician attendance.
Asunto(s)
Monoaminas Biogénicas/análisis , Animales , Química Encefálica , Cromatografía Líquida de Alta Presión/métodos , Electroquímica , Masculino , Ratas , Ratas Endogámicas , Estándares de Referencia , Espectrometría de FluorescenciaRESUMEN
The properties of tazasubrate (2-phenyl-2-[(6-ethoxy-2-benzothiazolyl)thio]propionic acid), a potent hypocholesterolemic agent, were studied in rats. Tazasubrate was found to be a reliable and highly effective hypocholesterolemic agent. There was a marked and reproducible reduction of serum cholesterol in various rat models differing in age, sex and diet, an improvement of the pathological lipoprotein pattern, slight but variable effects on serum triglycerides and phospholipids, no accumulation of intermediates of cholesterol biosynthesis, no inhibition of phospholipid metabolism (i.e. no induction of phospholipidosis), no interaction with the thyroid gland, and in contrast to fibrates, only minimal induction of peroxisomes in hepatocytes.