RESUMEN
Febrile seizures (FS) are the most common seizure type in children and recurrent FS are a risk factor for developing temporal lobe epilepsy. Although the mechanisms underlying FS are largely unknown, recent family, twin and animal studies indicate that genetics are important in FS susceptibility. Here, a forward genetic strategy was used employing mouse chromosome substitution strains (CSS) to identify novel FS susceptibility quantitative trait loci (QTLs). FS were induced by exposure to warm air at postnatal day 14. Video electroencephalogram monitoring identified tonic-clonic convulsion onset, defined as febrile seizure latency (FSL), as a reliable phenotypic parameter to determine FS susceptibility. FSL was determined in both sexes of the host strain (C57BL/6J), the donor strain (A/J) and CSS. C57BL/6J mice were more susceptible to FS than A/J mice. Phenotypic screening of the CSS panel identified six strains(CSS1, -2, -6 -10, -13 and -X) carrying QTLs for FS susceptibility. CSS1, -10 and -13 were less susceptible (protective QTLs), whereas CSS2, -6 and -X were more susceptible (susceptibility QTLs) to FS than the C57BL/6J strain. Our data show that mouse FS susceptibility is determined by complex genetics, which is distinct from that for chemically induced seizures. This is the first dataset using CSS to screen for a seizure trait in mouse pups. It provides evidence for common FS susceptibility QTLs that serve as starting points to fine map FS susceptibility QTLs and to identify FS susceptibility genes. This will increase our understanding of human FS, working toward the identification of new therapeutic targets.
Asunto(s)
Cromosomas de los Mamíferos/genética , Sitios de Carácter Cuantitativo/genética , Convulsiones Febriles/genética , Animales , Conducta Animal/fisiología , Temperatura Corporal/genética , Temperatura Corporal/fisiología , Interpretación Estadística de Datos , Electroencefalografía , Femenino , Ligamiento Genético/genética , Masculino , Ratones , Ratones Endogámicos A , Ratones Endogámicos C57BL , Fenotipo , Convulsiones Febriles/psicologíaRESUMEN
Febrile seizures (FS) are the most prevalent seizures in children. Although FS are largely benign, complex FS increase the risk to develop temporal lobe epilepsy (TLE). Studies in rat models for FS have provided information about functional changes in the hippocampus after complex FS. However, our knowledge about the genes and pathways involved in the causes and consequences of FS is still limited. To enable molecular, genetic and knockout studies, we developed and characterized an FS model in mice and used it as a phenotypic screen to analyze FS susceptibility. Hyperthermia was induced by warm air in 10- to 14-day-old mice and induced FS in all animals. Under the conditions used, seizure-induced behavior in mice and rats was similar. In adulthood, treated mice showed increased hippocampal Ih current and seizure susceptibility, characteristics also seen after FS in rats. Of the seven genetically diverse mouse strains screened for FS susceptibility, C57BL/6J mice were among the most susceptible, whereas A/J mice were among the most resistant. Strains genetically similar to C57BL/6J also showed a susceptible phenotype. Our phenotypic data suggest that complex genetics underlie FS susceptibility and show that the C57BL/6J strain is highly susceptible to FS. As this strain has been described as resistant to convulsants, our data indicate that susceptibility genes for FS and convulsants are distinct. Insight into the mechanisms underlying seizure susceptibility and FS may help to identify markers for the early diagnosis of children at risk for complex FS and TLE and may provide new leads for treatment.
Asunto(s)
Predisposición Genética a la Enfermedad/genética , Ratones Endogámicos C57BL/genética , Convulsiones Febriles/genética , Convulsiones Febriles/fisiopatología , Animales , Conducta Animal , Convulsivantes/farmacología , Electrofisiología , Fiebre/genética , Fiebre/fisiopatología , Hipocampo/fisiopatología , Masculino , Ratones , Ratones Endogámicos AKR , Ratones Endogámicos BALB C , Ratones Endogámicos C3H , Ratones Endogámicos DBA , Pentilenotetrazol/farmacología , Fenotipo , Ratas , Ratas Sprague-Dawley , Convulsiones Febriles/inducido químicamente , Especificidad de la EspecieRESUMEN
The adult peripheral nervous system is able to regenerate after injury. Regeneration is associated with the expression of new genes and proteins. Proteins abundant in developing axons increase in expression after injury, whereas proteins involved in neurotransmission are downregulated. It has been hypothesized that molecular mechanisms underlying regeneration-associated alterations in gene expression may be a recapitulation of developmental processes. These gene expression changes are likely to be regulated by changes in the gene expression of transcription factors. As homeobox genes play important roles in embryonic development of the nervous system, it makes them candidates for a regulatory role in the process of regeneration. Here we show that the relative mRNA expression levels of Isl1 decreased shortly after crush, but those of DRG11, Lmx1b, and Pax3 did not change after crush. These data indicate that the developmental expression patterns of the homeobox genes studied here are not recapitulated during regeneration of the dorsal root ganglia neurons. We conclude that developmental gene expression programs controlled by these homeobox genes are not directly involved in sciatic nerve regeneration.
Asunto(s)
Ganglios Espinales/fisiopatología , Genes Homeobox/genética , Regeneración Nerviosa/genética , Plasticidad Neuronal/genética , Neuronas Aferentes/metabolismo , Neuropatía Ciática/genética , Animales , Proteínas de Unión al ADN/genética , Lateralidad Funcional/genética , Ganglios Espinales/citología , Regulación del Desarrollo de la Expresión Génica/genética , Proteínas de Homeodominio/genética , Proteínas con Homeodominio LIM , Masculino , Ratones , Ratones Endogámicos C57BL , Proteínas del Tejido Nervioso/genética , Neuronas Aferentes/citología , Factor de Transcripción PAX3 , Factores de Transcripción Paired Box , Recuperación de la Función/genética , Neuropatía Ciática/metabolismo , Neuropatía Ciática/fisiopatología , Factores de Transcripción/genética , Regulación hacia Arriba/genéticaRESUMEN
Since the melanocortin MC3 and melanocortin MC4 receptors are the main melanocortin receptor subtypes expressed in rat brain, we characterized the activity and affinity of nine melanocortin receptor ligands using these receptors in vitro, as well as their activity in a well-defined melanocortin-induced behavior in the rat: grooming behavior. We report here that [D-Tyr4]melanotan-II and RMI-2001 (Ac-cyclo-[Cys4, Gly5, D-Phe7, Cys10]alpha-MSH-NH2) have significantly higher affinity and potency on the rat melanocortin MC4 receptor as compared to the rat melanocortin MC3 receptor. Nle-gamma-MSH (melanocyte-stimulating hormone) was the only ligand with higher affinity and potency on the rat melanocortin MC3 receptor. The potency order of melanocortin MC4 receptor agonists, but not that of melanocortin MC3 receptor agonists, fitted with the potency of these ligands to stimulate grooming behavior, when administered intracerebroventricularly. SHU9119 (Ac-cyclo-[Nle4, Asp5, D-Nal(2)7, Lys10]alpha-MSH-(4-10)-NH2) and RMI-2005 (Ac-cyclo-[Cys4, Gly5, D-Na](2)7, Nal(2)9, Cys10]alpha-MSH-(4-10)-NH2) were able to inhibit alpha-MSH-induced melanocortin receptor activity in vitro, as well as alpha-MSH-induced grooming behavior. Melanotan-II, [Nle4-D-Phe7]alpha-MSH and RMI-2001 were also effective in inducing grooming behavior when administered intravenously. In the absence of purely selective melanocortin MC(3/4) receptor ligands, we demonstrated that careful comparison of ligand potencies in vitro with ligand potencies in vivo, could identify which melanocortin receptor subtype mediated alpha-MSH-induced grooming behavior. Furthermore, blockade of novelty-induced grooming behavior by SHU9119 demonstrated that this physiological stress response is mediated via activation of the melanocortin system.
Asunto(s)
Aseo Animal/efectos de los fármacos , Ligandos , Receptores de Corticotropina/metabolismo , Secuencia de Aminoácidos , Animales , Unión Competitiva , Cateterismo , Línea Celular , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Humanos , Inyecciones Intravenosas , Inyecciones Intraventriculares , Hormonas Estimuladoras de los Melanocitos/farmacología , Datos de Secuencia Molecular , Fragmentos de Péptidos/farmacología , Ensayo de Unión Radioligante , Ratas , Ratas Wistar , Receptor de Melanocortina Tipo 3 , Receptor de Melanocortina Tipo 4 , Receptores de Corticotropina/antagonistas & inhibidores , Receptores de Corticotropina/efectos de los fármacos , Receptores de Corticotropina/genética , Receptores de Melanocortina , Proteínas Recombinantes de Fusión/efectos de los fármacos , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Homología de Secuencia de Aminoácido , Factores de Tiempo , alfa-Galactosidasa/efectos de los fármacos , alfa-Galactosidasa/genética , alfa-Galactosidasa/metabolismo , alfa-MSH/metabolismo , alfa-MSH/farmacologíaRESUMEN
Although neurotrophic effects of alpha-melanocyte-stimulating hormone (alpha-MSH) are well established, the mechanism underlying these effects is unknown. To identify candidate components of the signaling system that may mediate these effects, in the present study rat spinal cord, dorsal root ganglia, sciatic nerve and soleus muscle were analysed for the expression of the neural MC3, MC4 and MC5 receptors and for the expression of the melanocortin precursor pro-opiomelanocortin (POMC). In rat lumbar spinal cord, the MC4 receptor was the only MC receptor subtype for which mRNA was detectable using RNAse protection assays. In situ binding studies using 125I-NDP-MSH, a synthetic alpha-MSH analogue, demonstrated MC receptor protein in the rat spinal cord, predominantly localised in substantia gelatinosa and area X, surrounding the central canal. Furthermore, POMC mRNA was demonstrated in rat spinal cord and dorsal root ganglia. These findings suggest a functional melanocortin system in the rat spinal cord, that might be involved in peripheral nerve repair. Regulation of POMC or MC receptor transcripts does not appear to be involved in the response to peripheral nerve crush in rats, since no change in mRNA expression patterns was detected after sciatic nerve crush, using quantitative RNAse protection assays. Nevertheless, subtle changes in melanocortin receptor binding did occur postsurgically in several regions of the spinal cord in both sham-operated and sciatic nerve-lesioned rats. The robust expression of MC receptor protein in spinal cord regions that are generally associated with nociception suggests a potentially broader involvement of endogenous melanocortins in spinal pathways which mediate the responses to peripheral injury, in addition to any direct melanocortin effects on sprouting and neurite outgrowth.
Asunto(s)
Hormonas Estimuladoras de los Melanocitos/farmacología , Factores de Crecimiento Nervioso/farmacología , Proopiomelanocortina/biosíntesis , Receptores de Corticotropina/biosíntesis , Médula Espinal/efectos de los fármacos , Animales , Ganglios Espinales/efectos de los fármacos , Ganglios Espinales/metabolismo , Ganglios Espinales/patología , Masculino , Neuronas Motoras/efectos de los fármacos , Neuronas Motoras/metabolismo , Compresión Nerviosa , Regeneración Nerviosa , Neuronas Aferentes/efectos de los fármacos , Neuronas Aferentes/metabolismo , ARN Mensajero/análisis , Ratas , Ratas Wistar , Receptores de Melanocortina , Nervio Ciático/lesiones , Médula Espinal/metabolismo , Médula Espinal/patologíaRESUMEN
Two separate experiments were carried out in order to evaluate the influence of moderate swim training and treadmill running on the rate of recovery of sensorimotor function following sciatic nerve injury in the rat. Nerve injury was induced by sciatic nerve crush. In the first experiment, rats were subjected to swim exercise (180 m daily), either for 7 days before, or for 14 consecutive days after nerve injury. In the second experiment rats were exercised on a motor driven treadmill device (10 m/min for 30 min twice daily) for 21 days. The recovery from nerve injury was assessed by means of an analysis of the free walking pattern (motor function) and the foot withdrawal reflex (sensory function) by electrical stimulation. The swim training program before or after crush did not affect the recovery of locomotor or sensory function. Treadmill running significantly deteriorated the gradual return of motor function (p < 0.05), but did not influence sensory recovery. We conclude that swim training does not interfere with functional sensorimotor recovery after sciatic nerve injury, and that a mild program of treadmill running retards recovery. We hypothesize that the retardation of recovery as a result of treadmill running is the consequence of the stress inflicted by the negative reinforcement used in the treadmill, or due to the severity of the training. /Ø?>
Asunto(s)
Compresión Nerviosa , Condicionamiento Físico Animal , Nervio Ciático/fisiopatología , Neuropatía Ciática/fisiopatología , Animales , Masculino , Actividad Motora , Ratas , Ratas Wistar , Recuperación de la Función , Sensación , NataciónRESUMEN
The aim of the present study was to monitor the influence of chronic stress on functional recovery from a sciatic nerve crush lesion in the rat. Male Wistar rats underwent standard unilateral sciatic nerve crush. Subsequently, chronic stress was induced during the recovery phase using a daily 30 min shock box session where rats received three electric footshocks each session (0.5 sec, 1 mA). Reduced body weight gain, adrenal gland hypertrophy, and thymus involution indicated that the stress rats were chronically stressed. Evaluation of sensorimotor function revealed significant differences in recovery between control and stress groups. Correlational analysis of individual stress rats indicated that recovery of the walking pattern was negatively correlated with adrenal gland and medulla enlargement, thymus involution, and plasma levels of adrenocorticotrophic hormone (ACTH) and corticosterone 45 min following the final stress session. In control rats, the index of sciatic nerve function (SF index, expressed as the difference between the injured paw and the intact contralateral paw as a percentage) was significantly correlated with adrenal medulla weight only. The present study reveals that chronic intermittent footshock stress impedes sensorimotor recovery following a sciatic nerve crush lesion and that the consequences of chronic intermittent stress are individually determined. We suggest that the quality of functional locomotor recovery after nerve crush lesion is related to the adaptive capacity or coping style of the individual rat.
Asunto(s)
Adaptación Fisiológica , Regeneración Nerviosa , Nervio Ciático/fisiología , Estrés Fisiológico/fisiopatología , Corteza Suprarrenal/patología , Médula Suprarrenal/patología , Hormona Adrenocorticotrópica/sangre , Animales , Peso Corporal , Enfermedad Crónica , Corticosterona/sangre , Electrochoque , Variación Genética , Hipertrofia , Locomoción , Masculino , Trastornos del Movimiento/etiología , Trastornos del Movimiento/fisiopatología , Trastornos del Movimiento/rehabilitación , Compresión Nerviosa , Tamaño de los Órganos , Ratas , Ratas Wistar , Nervio Ciático/lesiones , Trastornos de la Sensación/etiología , Trastornos de la Sensación/fisiopatología , Trastornos de la Sensación/rehabilitación , Estrés Fisiológico/sangre , Estrés Fisiológico/patología , Timo/patologíaRESUMEN
OBJECTIVE: To observe the effects of exercise training on recuperation of sensorimotor function in the early phase of regeneration, and to monitor the long-term effects of exercise on electrophysiological aspects of the regenerating nerve. DESIGN: After sciatic nerve crush in 20 male Wistar rats, one random selected group was subjected to 24 days of exercise training, whereas the other group served as sedentary controls. INTERVENTIONS: Exercise training was induced for 24 days, starting the first postoperation day, by placing bottles of water at such a height that the exercising rats had to maximally erect on both hindpaws to drink. MAIN OUTCOME MEASURES: Recovery of motor and sensory function in the early phase was monitored by analysis of the free walking pattern and the foot reflex withdrawal test, respectively. Electrophysiological measurements on postoperation days 50, 75, 100, 125, and 150 were used to evaluate the late phase of recovery of nerve conduction velocity. RESULTS: During the early phase of the recovery period, exercise training enhanced functional recovery. The motor nerve conduction velocity (MNCV), as measured in the late phase of recovery, was significantly better in the trained group than in the control group (p < .01). CONCLUSIONS: We conclude that exercise training enhances the return of sensomotoric function in the early phase of recovery from peripheral nerve lesion. Furthermore, these results suggest that the beneficial effects of 24 days of exercise training after crush persist in the late phase of peripheral nerve recovery.
Asunto(s)
Terapia por Ejercicio , Regeneración Nerviosa , Nervio Ciático/lesiones , Nervio Ciático/fisiología , Animales , Electrofisiología , Masculino , Neuronas Motoras/fisiología , Compresión Nerviosa , Conducción Nerviosa , Ratas , Ratas WistarRESUMEN
The relation between recovery of function following a sciatic nerve crush lesion and an individual behavioural characteristic, the locomotor activity in an open field, was investigated in rats. Ten high-active (HA) and ten low-active (LA) rats were selected from a stock of sixty male, random-bred Wistar rats, by measuring travelled distance in an open field. Subsequently, both HA and LA rats underwent an unilateral sciatic nerve crush. Recovery of motor function revealed no significant differences between both groups, whereas recovery of sensory function in HA rats was significantly more rapid than in the LA rats (P < 0.01). These observations suggest the existence of a relationship between individual behavioural characteristics, and the sensory recovery of nerve function following crush lesion in rats.
Asunto(s)
Conducta Exploratoria/fisiología , Actividad Motora/fisiología , Regeneración Nerviosa , Nervio Ciático/fisiología , Glándulas Suprarrenales/patología , Animales , Estimulación Eléctrica , Masculino , Trastornos del Movimiento/etiología , Trastornos del Movimiento/fisiopatología , Compresión Nerviosa , Tamaño de los Órganos , Ratas , Ratas Wistar , Nervio Ciático/lesiones , Trastornos de la Sensación/etiología , Trastornos de la Sensación/fisiopatología , Timo/patología , Factores de TiempoRESUMEN
The effect of moderate exercise training on acute and chronic neuropathy in two separate experiments was examined. Acute nerve dysfunction was induced by sciatic nerve crush lesion and chronic neuropathy by streptozotocin-induced diabetes mellitus (experimental diabetic neuropathy; EDN). Moderate exercise training was achieved by placing food and water, separately, at either end of a U-shaped tubular home cage (8 m). Recovery from the crush lesion and the development of EDN were monitored by evaluating the free walking pattern and nerve conduction velocity (NCV), respectively. In the acute neuropathy model, 24 days of exercise after the crush lesion resulted in an enhanced return of motor function in the early phase of recovery (P < 0.01) and an increased sensory NCV after 250 days in the late phase (P < 0.001). Diabetic rats benefited from this exercise training by showing fewer signs of EDN, as evidenced by a superior motor function (toespreading, calculated from the free walking pattern; P < 0.05) and an improvement in both motor and sensory NCV (both P < 0.05). We conclude that moderate exercise training is effective in enhancing recovery from acute peripheral neuropathy and in ameliorating the consequences of experimental chronic neuropathy in diabetic rats.
RESUMEN
The possible involvement of alpha-MSH-like peptides in the regenerative response of peripheral nerves was investigated with a competitive antagonist of alpha-MSH, the synthetic hexapeptide [D-Trp7,Ala8,D-Phe10)alpha-MSH(6-11)-amide. Subcutaneous administration of the alpha-MSH antagonist during the first 10 days following sciatic nerve crush significantly decreased functional recovery as measured by the foot flick withdrawal test and the walking pattern analysis. Hypophysectomy delayed both the initial sprouting response and the outgrowth rate after major caudal nerve crush. When hypophysectomized rats were treated with the alpha-MSH antagonist, a further delay in initial sprouting was observed, whereas the outgrowth rate of nerve fibers was not affected. These results suggest that 1) endogenous alpha-MSH-like peptides stimulate nerve outgrowth following peripheral nerve injury and 2) alpha-MSH-like peptides derived from a source other than the pituitary may contribute to the physiological stimulus leading to sprouting.
Asunto(s)
Ventrículos Cerebrales/fisiología , Regeneración Nerviosa/fisiología , Neuronas Aferentes/fisiología , Fragmentos de Péptidos/farmacología , Nervio Ciático/fisiología , alfa-MSH/análogos & derivados , alfa-MSH/fisiología , Animales , Ventrículos Cerebrales/efectos de los fármacos , Aseo Animal/efectos de los fármacos , Hipofisectomía , Inyecciones Intraventriculares , Masculino , Compresión Nerviosa , Regeneración Nerviosa/efectos de los fármacos , Neuronas Aferentes/efectos de los fármacos , Fragmentos de Péptidos/administración & dosificación , Nervios Periféricos/fisiología , Ratas , Ratas Wistar , Nervio Ciático/efectos de los fármacos , Cola (estructura animal)/inervación , Factores de Tiempo , alfa-MSH/administración & dosificación , alfa-MSH/antagonistas & inhibidores , alfa-MSH/farmacologíaRESUMEN
Antagonists for the melanocortin receptor family were identified by analysis of the effects of four melanocortin analogues on alpha-MSH(alpha-melanocyte-stimulating hormone)-induced cAMP accumulation in 293 human embryonal kidney (HEK) cells that expressed either the rat melanocortin MC3 receptor, the human melanocortin MC4 receptor or the ovine melanocortin MC5 receptor. Two peptides, [D-Arg8]ACTH(adrenocorticotrope hormone)-(4-10) and [Pro8,10,Gly9]ACTH-(4-10), antagonized the action of alpha-MSH on the melanocortin MC4 and MC5 receptors, but not the melanocortin MC3 receptor. [Ala6]ACTH-(4-10) inhibited the alpha-MSH activation of the melanocortin MC3 and MC5, but only weakly antagonized the activation of the melanocortin MC4 receptor. [Phe-I7]ACTH-(4-10) antagonized the melanocortin MC3, MC4 and MC5 receptors equally well. These antagonists were also tested to block a behavioral response induced by alpha-MSH. alpha-MSH-induced excessive grooming behavior in rats was inhibited by [Phe-I7]ACTH-(4-10), [D-Arg8]ACTH-(4-10) and [Pro8,10,Gly9]ACTH-(4-10), but not by [Ala6]ACTH-(4-10). This suggests that alpha-MSH-induced excessive grooming behavior is mediated by melanocortin MC4 receptors.
Asunto(s)
Hormona Adrenocorticotrópica/farmacología , Riñón/efectos de los fármacos , Hormonas Estimuladoras de los Melanocitos/farmacología , Fragmentos de Péptidos/farmacología , Receptores de Corticotropina/antagonistas & inhibidores , Receptores de Péptidos/antagonistas & inhibidores , Hormona Adrenocorticotrópica/administración & dosificación , Hormona Adrenocorticotrópica/análogos & derivados , Hormona Adrenocorticotrópica/química , Secuencia de Aminoácidos , Animales , Conducta Animal/efectos de los fármacos , Línea Celular , AMP Cíclico/metabolismo , Relación Dosis-Respuesta a Droga , Aseo Animal/efectos de los fármacos , Humanos , Inyecciones Intravenosas , Riñón/citología , Riñón/embriología , Riñón/metabolismo , Masculino , Datos de Secuencia Molecular , Fragmentos de Péptidos/administración & dosificación , Fragmentos de Péptidos/química , Ratas , Ratas Wistar , Receptor de Melanocortina Tipo 3 , Receptor de Melanocortina Tipo 4 , Receptores de Melanocortina , Ovinos , Relación Estructura-ActividadRESUMEN
Nimodipine, a Ca2+ antagonist of the dihydropyridine type, is known to display a variety of neuropharmacological effects including facilitation of functional recovery following a crush of the sciatic nerve in the rat. In the present study, we investigated the effect of nimodipine, nifedipine (another Ca2+ antagonist with a lesser penetration in neural parenchyma) and Bay K 8644 (a Ca2+ agonist) treatment following a crush of the major caudal nerve. The caudal nerve crush model was used because this model provided the opportunity for longitudinal evaluation of nerve repair. Recovery of sensory function was tested by vocal reaction following local stimulation with a small electric current. The results suggest that nimodipine (20 mg/kg) both enhances the initial sprouting response and exerts an effect on the outgrowth rate of newly developed sprouts. Neither nifedipine (20 mg/kg) nor Bay K 8644 (0.5 mg/kg) had any influence on the recovery of nerve function. Furthermore, it was demonstrated that nimodipine, nifedipine and Bay K 8644 had no influence on nerve conduction velocity of the non-injured sciatic nerve indicating that there was no general beneficial effect of these agents on the peripheral nerve.
RESUMEN
1. The systemic absorption and the neurotrophic effect of the metabolically stabilized ACTH (4-9) analogue, Org2766, were investigated following intranasal (i.n.) administration. 2. Without additives the nasal bioavailability of the peptide was in the order of 15 and 10% in rats and rabbits, respectively. The absorption could be improved by addition of a variety of absorption enhancers to the nasal preparation. The beta-cyclodextrin derivative, dimethyl-beta-cyclodextrin (DM beta CD) at a concentration of 5% (w/v) improved the absorption in rats about 5 fold from 13 +/- 4% (mean +/- s.d.) for administration of the peptide alone to 65 +/- 21%, and in rabbits 1 to 2 fold, from 10 +/- 6% to 17 +/- 8%. 3. The increased permeability of the rat nasal mucosa for Org2766 caused by DM beta CD in rats reversed substantially within 1 h. However, the nasal absorption had not yet completely returned to the level without enhancer. 4. S.c. administered Org2766 accelerated the functional recovery from peripheral nerve damage in rats. However, the peptide did not facilitate nerve repair following i.n. administration with DM beta CD, in spite of the fact that Org2766 was well absorbed. I.v. injection of Org2766 was also ineffective.
Asunto(s)
Hormona Adrenocorticotrópica/análogos & derivados , Mucosa Nasal/metabolismo , Fragmentos de Péptidos/farmacocinética , beta-Ciclodextrinas , Absorción , Administración Intranasal , Hormona Adrenocorticotrópica/administración & dosificación , Hormona Adrenocorticotrópica/farmacocinética , Hormona Adrenocorticotrópica/farmacología , Animales , Ciclodextrinas/farmacología , Interacciones Farmacológicas , Masculino , Regeneración Nerviosa/efectos de los fármacos , Fragmentos de Péptidos/administración & dosificación , Fragmentos de Péptidos/farmacología , Nervios Periféricos/efectos de los fármacos , Conejos , Ratas , Ratas WistarRESUMEN
Reduced glutathione (GSH) is reported to diminish cisplatin-induced neurotoxicity, and it was for this reason that we studied GSH in an animal model of cisplatin neuropathy. The neuropathy was evaluated by measuring the sensory nerve conduction velocity (SNCV) in young adult Wistar rats. GSH injections (i.v.) were given twice weekly, within five minutes before cisplatin was injected (i.p.). In a first experiment GSH (500 mg/kg) in combination with a low-dose cisplatin treatment (1 mg/kg, 10 weeks) was investigated. Animals treated with cisplatin and placebo developed a neuropathy (SNCV at week 10: age controls, 61.9 m/s; cisplatin alone, 44.2 m/s), whereas rats treated with cisplatin and GSH did not (SNCV, 61.9 m/s). The same dose of GSH was used in combination with a high-dose cisplatin schedule (2 mg/kg, 5 weeks' treatment plus 5 weeks' recovery). Again, GSH protected animals against the development of neuropathy (SNCV at week 10: age controls, 61.9 m/s; cisplatin alone, 50.6 m/s; cisplatin plus GSH, 61.1 m/s). In another experiment four lower doses of GSH (25, 50, 100, and 200 mg/kg) were tested in combination with the low-dose cisplatin protocol (1 mg/kg, 11 weeks). The cisplatin group developed a neuropathy (SNCV at week 11: cisplatin alone, 50.2 m/s; age controls, 60.6 m/s). Only the dose of 200 mg GSH/kg was found to protect against the development of a neuropathy (SNCV, 61.0 m/s). In an antitumor study GSH administered at 300 mg/kg in combination with cisplatin at 1.5 mg/kg did not diminish the curative effect of cisplatin. We conclude that GSH prevents cisplatin-induced neuropathy and that it should be investigated further in the clinic.
Asunto(s)
Cisplatino/toxicidad , Glutatión/uso terapéutico , Enfermedades del Sistema Nervioso/prevención & control , Animales , Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Peso Corporal/efectos de los fármacos , Cisplatino/administración & dosificación , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Electrofisiología , Glutatión/administración & dosificación , Masculino , Neoplasias Mamarias Experimentales/tratamiento farmacológico , Enfermedades del Sistema Nervioso/inducido químicamente , Conducción Nerviosa/efectos de los fármacos , Neuronas Aferentes/efectos de los fármacos , Neuronas Aferentes/fisiología , Ratas , Ratas WistarRESUMEN
1. In rats, recovery of sensory-motor function following a crush lesion of the sciatic or tibial nerve was monitored by measuring foot reflex withdrawal from a local noxious stimulation of the foot sole. 2. Putative neurotrophic compounds were tested on this functional recovery model: melanocortins (peptides derived from ACTH (corticotropin) and alpha-MSH (melanotropin], gangliosides and nimodipine were effective whereas isaxonine and TRH (thyrotropin releasing hormone) were not. 3. Structure-activity studies with melanocortins revealed a similar effectiveness of alpha-MSH, [N-Leu4, D-Phe7]-alpha-MSH, desacetyl-alpha-MSH and the ACTH analogue ORG 2766, questioning the validity of the previously suggested notion that the melanotrophic properties of these peptides are responsible for their neurotrophic effect. 4. As recovery of function after peripheral nerve damage follows a similar time course in hypophysectomized (five days post operation) and sham-operated rats, effective melanocortin therapy does not mimic an endogenous peptide signal in the repair process from pituitary origin. 5. Subcutaneous treatment with ORG 2766 (7.5 micrograms kg-1 48 h-1) facilitates recovery of function following peripheral nerve damage in young (6-7 weeks old), mature (5 month old) and old (20 month old) rats. 6. In view of the diversity in structure of the effective neurotrophic factors and the complexity of nerve repair, the present data support the notion that peripheral nerve repair may be facilitated by different humoral factors likely to be active on different aspects of the recovery process.
Asunto(s)
Neurotransmisores/fisiología , Nervios Periféricos/efectos de los fármacos , Hormona Adrenocorticotrópica/análogos & derivados , Hormona Adrenocorticotrópica/farmacología , Envejecimiento/fisiología , Animales , Anticonvulsivantes/farmacología , Femenino , Hipofisectomía , Hormonas Estimuladoras de los Melanocitos/análogos & derivados , Hormonas Estimuladoras de los Melanocitos/farmacología , Nimodipina/farmacología , Fragmentos de Péptidos/farmacología , Pirimidinas/farmacología , Ratas , Ratas Endogámicas , Reflejo/efectos de los fármacos , Nervio Ciático/efectos de los fármacos , Relación Estructura-ActividadRESUMEN
The major caudal nerves of the rat provide an excellent model for longitudinal evaluation of nerve repair following a crush lesion. The surgical procedure and the method for testing sensory recovery are described in detail. Using this technique a clear, positive effect of ORG.2766 (an ACTH (4-9) analog) on the regeneration of sensory nerves could be shown. Results support the suggestion that ORG.2766 enhances the initial sprouting response, rather than exerting an effect on the growth rate of newly developed sprouts.
Asunto(s)
Hormona Adrenocorticotrópica/análogos & derivados , Regeneración Nerviosa/efectos de los fármacos , Neuronas Aferentes/fisiología , Fragmentos de Péptidos/farmacología , Traumatismos de los Nervios Periféricos , Hormona Adrenocorticotrópica/farmacología , Animales , Masculino , Compresión Nerviosa , Neuronas Aferentes/efectos de los fármacos , Nervios Periféricos/efectos de los fármacos , Nervios Periféricos/fisiología , Ratas , Ratas Endogámicas , Factores de TiempoRESUMEN
The efficacy of melanocortins (alpha-MSH and an ACTH-(4-9) analog, Org.2766) in accelerating functional recovery from sciatic nerve damage following various types of subcutaneous and oral administration was assessed in the rat. Furthermore, the effectiveness of the local delivery of melanocortins to the site of injury was examined. An accelerated recovery was evident following subcutaneous constant delivery of Org.2766 from an osmotic mini-pump and from biodegradable polymere microspheres, and was as effective as repeated subcutaneous injections of alpha-MSH or Org.2766. Oral administration of Org.2766 was ineffective. Local application of Org.2766, achieved by wrapping a peptide-impregnated biodegradable gelatine foam matrix around the site of injury, facilitated recovery as well. The biodegradable microspheres and gelatine foam matrix may be of importance in eventual clinical use as effective vehicles for administration of melanocortins in the treatment of peripheral nerve damage.