RESUMEN
Adenosine is an endogenous anticonvulsant that activates pre- and postsynaptic adenosine A1 receptors. A1 receptor agonists increase the latency for the development of seizures and status epilepticus following pilocarpine administration. Although hippocampal adenosine is increased in the chronic phase of the pilocarpine model, it is not known whether the modulation of A1 receptors may influence the frequency of spontaneous recurrent seizures (SRS). Here, we tested the hypothesis that the A1 receptor agonist RPia ([R]-N-phenylisopropyladenosine) and the A1 antagonist DPCPX (8-Cyclopentyl-1,3-dipropylxanthine) administered to chronic pilocarpine epileptic rats would respectively decrease and increase the frequency of SRS and hippocampal excitability. Four months after Pilo-induced SE, chronic epileptic rats were video-monitored for the recording of SRS before (basal) and after a 2-week treatment with RPia (25µg/kg) or DPCPX (50µg/kg). Following sacrifice, brain slices were studied with electrophysiology. We found that rats given RPia had a 93% nonsignificant reduction in the frequency of seizures compared with their own pretreatment baseline. In contrast, the administration of DPCPX resulted in an 87% significant increase in seizure rate. Nontreated epileptic rats had a similar frequency of seizures along the study. Corroborating our behavioral data, in vitro recordings showed that slices from animals previously given DPCPX had a shorter latency to develop epileptiform activity, longer and higher DC shifts, and higher spike amplitude compared with slices from nontreated Pilo controls. In contrast, smaller spike amplitude was recorded in slices from animals given RPia. In summary, the administration of A1 agonists reduced hippocampal excitability but not the frequency of spontaneous recurrent seizures in chronic epileptic rats, whereas A1 receptor antagonists increased both.
Asunto(s)
Agonistas del Receptor de Adenosina A1/farmacología , Antagonistas del Receptor de Adenosina A1/farmacología , Convulsivantes/farmacología , Epilepsia/inducido químicamente , Agonistas Muscarínicos/farmacología , Pilocarpina/farmacología , Convulsiones/inducido químicamente , Convulsiones/prevención & control , Animales , Encéfalo/fisiopatología , Electroencefalografía/efectos de los fármacos , Epilepsia/fisiopatología , Masculino , Fenilisopropiladenosina/farmacología , Ratas , Ratas Wistar , Convulsiones/fisiopatología , Xantinas/farmacologíaRESUMEN
Aiming at a better understanding of the role of A(2A) in temporal lobe epilepsy (TLE), we characterized the effects of the A(2A) antagonist SCH58261 (7-(2-phenylethyl)-5-amino-2(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine) on seizures and neuroprotection in the pilocarpine model. The effects of SCH58261 were further analyzed in combination with the A(1) agonist R-Pia (R(-)-N(6)-(2)-phenylisopropyl adenosine). Eight groups were studied: pilocarpine (Pilo), SCH+Pilo, R-Pia+Pilo, R-Pia+SCH+Pilo, Saline, SCH+Saline, R-Pia+Saline, and R-Pia+SCH+Saline. The administration of SCH58261, R-Pia, and R-Pia+SCH58261 prior to pilocarpine increased the latency to SE, and decreased either the incidence of or rate of mortality from SE compared with controls. Administration of R-Pia and R-Pia+SCH58261 prior to pilocarpine reduced the number of Fluoro-Jade B-stained cells in the hippocampus and piriform cortex when compared with control. This study showed that pretreatment with R-Pia and SCH58261 reduces seizure occurrence, although only R-Pia has neuroprotective properties. Further studies are needed to clarify the neuroprotective role of A(2A) in TLE.
Asunto(s)
Receptor de Adenosina A1/metabolismo , Receptor de Adenosina A2A/metabolismo , Estado Epiléptico/metabolismo , Adenosina/farmacología , Análisis de Varianza , Animales , Encéfalo/patología , Recuento de Células , Modelos Animales de Enfermedad , Interacciones Farmacológicas , Fluoresceínas , Masculino , Degeneración Nerviosa/etiología , Degeneración Nerviosa/metabolismo , Degeneración Nerviosa/patología , Fármacos Neuroprotectores/farmacología , Fármacos Neuroprotectores/uso terapéutico , Compuestos Orgánicos/metabolismo , Fenilisopropiladenosina/farmacología , Fenilisopropiladenosina/uso terapéutico , Pilocarpina/toxicidad , Pirimidinas/uso terapéutico , Ratas , Ratas Wistar , Tiempo de Reacción/efectos de los fármacos , Estado Epiléptico/inducido químicamente , Estado Epiléptico/tratamiento farmacológico , Estado Epiléptico/patología , Triazoles/uso terapéuticoRESUMEN
The effect of N(G)-nitro-L-arginine methyl ester (L-NAME), a competitive inhibitor of enzyme nitric oxide synthase (NOS), on spontaneous sleep during the light period, was studied in adult rats implanted for chronic sleep recordings. L-NAME was injected by subcutaneous (s.c.) route or was infused directly into the dorsal raphe nucleus (DRN). Subcutaneous (46.0--185.0 micromol/kg) administration of L-NAME increased waking (W), slow wave sleep (SWS) and rapid-eye-movement sleep (REMS) latency, whereas SWS, REMS and the number of REM periods were reduced. Direct application of L-NAME into the DRN (0.37--1.1 micromol) induced an increment of W and a reduction of SWS and REMS. Values corresponding to SWS and REMS latency, and the number of REM periods remained within control levels. Subcutaneous administration of the GABA(A) receptor agonist muscimol (1.7--3.5 micromol/kg) or the adenosine A(1) receptor agonist L-PIA [L(-)N(6)-(2-phenylisopropyl)adenosine] (0.1--0.3 micromol/kg) induced slight but inconsistent changes of W, light sleep (LS), SWS and REMS that did not attain significance. Pretreatment with muscimol (1.7--3.5 micromol/kg, s.c.) or L-PIA (0.1--0.3 micromol/kg, s.c.) antagonized the increase of W and reduction of SWS and REMS induced by s.c. (92.0 micromol/kg) or intra-DRN (0.74 micromol) administration of L-NAME. However, neither muscimol nor L-PIA prevented the increase of REMS latency induced by L-NAME 92.0 micromol/kg, s.c. Our findings tend to indicate that the change of behavioral state observed after systemic or intra-DRN administration of L-NAME is partly related to the reduction of GABA and adenosine at critical sites in the CNS.
Asunto(s)
Inhibidores Enzimáticos/farmacología , Agonistas del GABA/farmacología , Agonistas de Receptores de GABA-A , NG-Nitroarginina Metil Éster/farmacología , Óxido Nítrico Sintasa/antagonistas & inhibidores , Agonistas del Receptor Purinérgico P1 , Sueño REM/fisiología , Sueño/fisiología , Vigilia/efectos de los fármacos , Animales , Inyecciones Subcutáneas , Masculino , Microinyecciones , Muscimol/farmacología , NG-Nitroarginina Metil Éster/antagonistas & inhibidores , Fenilisopropiladenosina/farmacología , Núcleos del Rafe , RatasRESUMEN
To study the role of extracellular nucleosides and nucleotides in the regulation of Sertoli cells, the effects of agonists which occupy A1 and P2 purinergic receptors on aromatase and gamma-glutamyl transpeptidase (gamma-GTP) activities and on transferrin secretion were tested. Sertoli cell treatment with purinergic agonists for a prolonged period of time (72 h) resulted in an increase in aromatase activity under basal conditions. In cultures stimulated with FSH, purinergic agonists counteracted the inhibitory effect on aromatase activity that long-term treatment with FSH promoted. The effects of prolonged treatments with purinergic agonists on the other two parameters of Sertoli cell function were less pronounced. Neither gamma-GTP activity nor transferrin secretion was modified under basal conditions. On the other hand, under conditions where cell differentiation was favored by FSH treatment, reductions in gamma-GTP activity and transferrin secretion were usually observed. The results obtained in dbcAMP-stimulated cultures suggested that A1 agonists exert their regulatory function at the level of cAMP formation while P2 agonists act at a more distal point. The fact that morphological changes induced by FSH were reversed by both types of agonists, while those induced by dbcAMP were only abrogated by P2 agonists, supports this hypothesis. In summary, these results demonstrate that purinergic agonists may be important in the regulation of Sertoli cell function.
Asunto(s)
Adenosina Trifosfato/farmacología , Adenosina/análogos & derivados , Fenilisopropiladenosina/farmacología , Agonistas Purinérgicos , Células de Sertoli/efectos de los fármacos , Adenosina/farmacología , Animales , Aromatasa/metabolismo , Bucladesina/farmacología , Células Cultivadas , Estradiol/metabolismo , Hormona Folículo Estimulante/farmacología , Masculino , Ratas , Ratas Sprague-Dawley , Células de Sertoli/metabolismo , Factores de Tiempo , Transferrina/metabolismo , gamma-Glutamiltransferasa/metabolismoRESUMEN
Adenosine is a hormonal modulator of metabolic processes. In some tissues the effect of adenosine on glycolysis is well established. Nevertheless, there are controversial data in heart. We believe that these discrepancies in the literature are due to haemodynamic factors which are not unified in those reports. We studied the direct effect of adenosine in cardiac myocytes in culture, isolated from neonatal rat heart, which are not influenced by haemodynamics forces as whole heart. Myocytes were isolated using conventional methods. Glycolysis was measured following the formation of tritium water from D-[3-3H]glucose. The results obtained showed that the nonmetabolizable adenosine analogue, N6-(L-2-phenylisopropyl)adenosine, (10 microM) stimulates basal glycolysis (49.86%). This effect was observed in the absence or presence of (5 mM) glucose. In separated group of experiments we examined different concentrations of N6-(L-2-phenylisopropyl)adenosine, (1, 10 and 100 microM, glucose 5 mM). Concentrations of 1 y 10 microM of the adenosine analogue stimulated glycolysis in a concentration-dependent fashion, however 100 microM of N6-(L-2-phenylisopropyl)adenosine inhibited glycolysis by 83% possibly through a toxic effect on the myocardial cells. The natural agonist adenosine, (100 microM) also stimulated glycolysis but with less potency. Stimulation of glycolysis by insulin (1 microM) or isoproterenol (1 microM) was potentiated by N6-(L-2-phenylisopropyl)adenosine. We concluded that adenosine stimulates basal or stimulated glycolysis in the myocardial isolated cells. It could be of benefit for the energetic economy in situations were the nucleoside is released.
Asunto(s)
Adenosina/farmacología , Fármacos Cardiovasculares/farmacología , Glucólisis/efectos de los fármacos , Miocardio/metabolismo , Animales , Animales Recién Nacidos , Células Cultivadas , Sinergismo Farmacológico , Glucosa/metabolismo , Isoproterenol/farmacología , Miocardio/citología , Fenilisopropiladenosina/farmacología , Ratas , Ratas WistarRESUMEN
1. The nerve-evoked contractions elicited by transmural electrical stimulation of mouse urinary bladders superfused in modified Krebs Ringer buffer containing 1 microM atropine plus 3.4 microM guanethidine were inhibited by adenosine (ADO) and related nucleoside analogues with the following rank order of potency: R-phenylisopropyladenosine (R-PIA) greater than cyclohexyladenosine (CHA) greater than 5'N-ethylcarboxamido adenosine (NECA) greater than ADO greater than S-phenylisopropyladenosine (S-PIA). Tissue preincubation with 8-phenyltheophylline (8-PT) displaced to the right, in a parallel fashion, the NECA concentration-response curve. 2. The contractions elicited by application of exogenous adenosine 5'-triphosphate (ATP) were also inhibited by ADO and related structural analogues. The rank order of potency to reduce the motor response to ATP was: NECA greater than 2-chloroadenosine (CADO) greater than R-PIA greater than ADO greater than CHA greater than S-PIA. 3. The ADO-induced ATP antagonism was of a non-competitive nature and was not specific. Tissue incubation with 10 microM NECA not only reduced the motor responses elicited by ATP, but also 5-hydroxytryptamine, acetylcholine and prostaglandin F2 alpha. The action of NECA was antagonized following tissue preincubation with 8-PT. The inhibitory action of NECA was not mimicked by 10 microM CHA. 4. The maximal bladder ATP contractile response was significantly increased by tissue preincubation with 5-30 microM 8-PT. 5. The 0.15 Hz evoked muscular twitch was significantly increased by 8-PT while dipyridamole consistently reduced the magnitude of the twitch response. These results are consonant with the hypothesis that an endogenous ADO tone modulates the bladder neurotransmission. 6. A working model is proposed suggesting the presence of ADO-Al and A2 receptors in the mouse urinary bladder. The A1 receptor subpopulation is probably of presynaptic origin whereas the smooth muscle membranes contain a population of the A2 receptor subtype.
Asunto(s)
Adenosina/fisiología , Sistema Nervioso Autónomo/fisiología , Receptores Purinérgicos/fisiología , Transmisión Sináptica/efectos de los fármacos , Vejiga Urinaria/inervación , Adenosina/análogos & derivados , Adenosina/farmacología , Adenosina Trifosfato/farmacología , Adenosina-5'-(N-etilcarboxamida) , Animales , Dipiridamol/farmacología , Estimulación Eléctrica , Ratones , Contracción Muscular/efectos de los fármacos , Músculo Liso/efectos de los fármacos , Músculo Liso/fisiología , Fenilisopropiladenosina/farmacología , Receptores Purinérgicos/efectos de los fármacos , Teofilina/análogos & derivados , Teofilina/farmacología , Vejiga Urinaria/efectos de los fármacos , Vejiga Urinaria/fisiologíaRESUMEN
1. Tolerance to and physical dependence on alprazolam were induced in mice by administering two doses of a slow release preparation. 2. Physical dependence was evaluated by the abstinence syndrome induced by flumazenil. Tolerance was studied by measuring the motor incoordination induced by a test dose of alprazolam. 3. The intensity of tolerance was decreased by the administration of L-phenylisopropyl adenosine (L-PIA), cyclopentyl adenosine (CPA), cyclohexyl adenosine (CHA), N-ethylcarboxamide adenosine (NECA), 8-phenyltheophylline (8-PTP) and theophylline (TP). 4. The intensity of the abstinence syndrome induced by flumazenil was attenuated by L-PIA, CPA NECA, TP and 8-PTP. 5. The results suggest that benzodiazepines may exert, at least in part, their effects by involving adenosine in the central nervous system.
Asunto(s)
Adenosina/análogos & derivados , Alprazolam , Trastornos Relacionados con Sustancias/fisiopatología , Adenosina/farmacología , Adenosina/fisiología , Animales , Tolerancia a Medicamentos/fisiología , Masculino , Ratones , Fenilisopropiladenosina/farmacología , Teofilina/análogos & derivados , Teofilina/farmacologíaRESUMEN
Effects of chronic exposure of cultured atrial myocytes to R-N6-(2-phenylisopropyl)-adenosine (R-PIA) on the A1 adenosine receptor-mediated inhibition of adenylate cyclase activity and myocyte contractility were examined. Chronic exposure of atrial myocytes cultured from 14-day-old chick embryos to R-PIA desensitized the myocyte to the inhibitory effects of R-PIA on contractility and adenylate cyclase activity in a time- and dose-dependent manner. Desensitization of the negative inotropic response was only partial, whereas the adenosine receptor-mediated inhibition of adenylate cyclase activity was almost completely absent after 24 hours of R-PIA (1 microM) exposure. Furthermore, the contractile response to R-PIA desensitized more slowly than the desensitization of A1 adenosine receptor-mediated inhibition of adenylate cyclase (t1/2 = 11.4 +/- 0.7 hours versus 7.5 +/- 1 hours, mean +/- SEM, n = 12 and 6, respectively). Thus, the two A1 adenosine receptor-linked functional responses desensitized differently in response to chronic exposure of the myocyte to R-PIA. Binding of the antagonist radioligand [3H]-8-cyclopentyl-1,3-dipropylxanthine [( 3H]CPX) in membranes from myocytes preexposed to R-PIA demonstrated a time-dependent decrease in receptor density without any change in the affinity for the antagonist radioligand. Computer analyses of agonist competition with [3H]CPX binding in membranes from control and R-PIA-treated myocytes revealed a conversion of the high-affinity A1 adenosine receptor to a low-affinity form such that after 24 hours of 1 microM R-PIA exposure, all of the receptors were in a low-affinity form.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Adenosina/análogos & derivados , Adenilil Ciclasas/metabolismo , Corazón/fisiología , Isoproterenol/farmacología , Contracción Miocárdica/efectos de los fármacos , Fenilisopropiladenosina/farmacología , Receptores Purinérgicos/fisiología , Animales , Membrana Celular/metabolismo , Células Cultivadas , Embrión de Pollo , Guanosina Trifosfato/farmacología , Corazón/efectos de los fármacos , Cinética , Miocardio/enzimología , Ensayo de Unión Radioligante , Receptores Purinérgicos/efectos de los fármacosRESUMEN
1. The analogs of adenosine D- and L-phenylisopropyladenosine (D- and L-PIA) and chloroadenosine (CADO) induced analgesia in mice (hot-plate test). 2. The antinociceptive effects of the three adenosine agonists were antagonized by caffeine but were unaffected by naloxone. 3. Morphine-induced antinociception was increased by pretreatment with adenosine agonists. 4. Whereas CADO significantly attenuated the induction of morphine tolerance, D- and L-PIA did not affect the process.