RESUMO
35S-cysteine injected adjacent to the supraoptic nucleus (SON) of the rat is rapidly incorporated into proteins. These 35S-cysteine-labeled proteins in the SON (1-24 h after injection) were separated by polyacrylamide gel electrophoresis, and the distribution of radioactive proteins on the gels was analyzed. 1 h after injection, about 73% of the radioactivity appeared in two peaks (both about 20,000 mol wt). With time, these peaks (putative precursors of neurophysin) decreased, as a 12,000 mol wt peak (containing two distinct neurophysins) increased in radioactivity. Both the 20,000- and 12,000-mol wt proteins are transported into the axonal (median eminence) and nerve terminal (posterior pituitary) regions of the rat hypothalamo-neurohypophysial system. Conversion of the larger precursor protein to the smaller neurophysin appears to occur, in large part, intra-axonally during axonal transport. Six distinct 35S-cysteine-labeled peptides (less than 2500 mol wt), in addition to arginine vasopressin and oxytocin, are also synthesized in the SON and transported to the posterior pituitary where they are released together with labeled neurophysin by potassium depolarization in the presence of extracellular calcium. These data provide support for the hypothesis that the neurohypophysial peptides (vasopressin and oxytocin) and neurophysins are derived from the post-translational clevage of protein precursors synthesized in the SON, and that the conversion process can occur in the neurosecretory granule during axonal transport.
Assuntos
Axônios/metabolismo , Sistema Hipotálamo-Hipofisário/metabolismo , Eminência Mediana/metabolismo , Neurofisinas/metabolismo , Ocitocina/metabolismo , Neuro-Hipófise/metabolismo , Vasopressinas/metabolismo , Animais , Transporte Biológico/efeitos dos fármacos , Colchicina/farmacologia , Neurofisinas/análise , Neurofisinas/biossíntese , Ocitocina/biossíntese , Peptídeos/metabolismo , Biossíntese de Proteínas , Ratos , Núcleo Supraóptico/metabolismo , Vasopressinas/biossínteseRESUMO
[35S]Cysteine injected adjacent to the supraoptic nucleus of the rat is rapidly incorporated into a 20,000-dalton protein that, in time, is converted to a 12,000-dalton labeled protein, neurophysin. This putative precursor of neurophysin appears to be synthesized in the supraoptic nucleus and transformed to neurophysin and related peptides during axonal transport to the neurohypophysis.
Assuntos
Sistema Hipotálamo-Hipofisário/metabolismo , Neurofisinas/biossíntese , Precursores de Proteínas/metabolismo , Animais , Transporte Axonal , Feminino , Eminência Mediana/metabolismo , Peso Molecular , Neuro-Hipófise/metabolismo , Ratos , Núcleo Supraóptico/metabolismo , Fatores de Tempo , Vasopressinas/biossínteseRESUMO
Heavy use of marijuana is claimed to damage critical skills related to short-term memory, visual scanning and attention. Motor skills and driving safety may be compromised by the acute effects of marijuana. The aim of this study was to investigate the acute effects of 13 mg and 17 mg Delta 9-tetrahydrocannabinol (THC) on skills important for coordinated movement and driving and on subjective and autonomic measures in regular users of marijuana. Fourteen regular users of marijuana were enrolled. Each subject was tested on two separate days. On each test day, subjects smoked two low-nicotine cigarettes, one with and the other without THC. Seventeen mg THC was included in the cigarette on one test day and 13 mg on the other day. The sequence of cigarette types was unknown to the subject. During smoking, heart rate and blood pressure were monitored, and the subjects performed a virtual reality maze task requiring attention and motor coordination, followed by 3 other cognitive tasks (Wisconsin Card Sorting Test (WCST), a "gambling" task and estimation of time and distance from an approaching car). After smoking a cigarette with 17 mg THC, regular marijuana users hit the walls more often on the virtual maze task than after smoking cigarettes without THC; this effect was not seen in patients after they smoked cigarettes with 13 mg THC. Performance in the WCST was affected with 17 mg THC and to a lesser extent with the use of 13 mg THC. Decision making in the gambling task was affected after smoking cigarettes with 17 mg THC, but not with 13 m THC. Smoking cigarettes with 13 and 17 mg THC increased subjective ratings of pleasure and satisfaction, drug "effect" and drug "high". These findings imply that smoking of 17 mg THC results in impairment of cognitive-motor skills that could be important for coordinated movement and driving, whereas the lower dose of 13 mg THC appears to cause less impairment of such skills in regular users of marijuana.
Assuntos
Nível de Alerta/efeitos dos fármacos , Atenção/efeitos dos fármacos , Condução de Veículo/psicologia , Sistema Nervoso Autônomo/efeitos dos fármacos , Tomada de Decisões/efeitos dos fármacos , Dronabinol/toxicidade , Abuso de Maconha/fisiopatologia , Abuso de Maconha/psicologia , Memória de Curto Prazo/efeitos dos fármacos , Destreza Motora/efeitos dos fármacos , Testes Neuropsicológicos , Desempenho Psicomotor/efeitos dos fármacos , Adulto , Afeto/efeitos dos fármacos , Afeto/fisiologia , Nível de Alerta/fisiologia , Atenção/fisiologia , Sistema Nervoso Autônomo/fisiopatologia , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Tomada de Decisões/fisiologia , Percepção de Distância/efeitos dos fármacos , Percepção de Distância/fisiologia , Relação Dose-Resposta a Droga , Feminino , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Humanos , Fumar Maconha/efeitos adversos , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , Memória de Curto Prazo/fisiologia , Destreza Motora/fisiologia , Orientação/efeitos dos fármacos , Orientação/fisiologia , Desempenho Psicomotor/fisiologia , Tempo de Reação/efeitos dos fármacos , Tempo de Reação/fisiologia , Jogos de VídeoRESUMO
Using in vitro methods we have studied the effect of dynorphin (DYN) a natural k opioid receptor ligand upon hCG secretion in the first trimester placenta. In superfusion, where we have recently reported that hCG secretion is episodic, we found that the addition of 1-min pulses of DYN had a significant stimulatory effect upon pulsatile hCG secretion. This effect was seen at concentrations of 10(-8) mol/L-10(-11) mol/L. Higher doses (10(-6) mol/L) and lower doses (10(-12) mol/L) were ineffective. A 10-min administration was more effective than the 1-min pulses. Prolonged administration (90 min) caused an initial increase in pulsatile hCG secretion which was followed by a decrease to control values. However, upon stopping the prolonged opiate administration there was a substantial increase in hCG secretion. The involvement of opioid receptors in mediating the effect of DYN on hCG release was demonstrated by using naloxone, an opioid receptor antagonist. Coadministration of DYN, 10(-11) mol/L, and naloxone, 10(-10) mol/L, reduced markedly the effect of DYN. This was followed by a delayed increase in hCG secretion. Furthermore, des-tyrosine-DYN, the nonopioid derivative of DYN was 1000 times less potent in stimulating hCG release than DYN. The involvement of DYN in physiological control of placental hCG secretion is suggested.
Assuntos
Gonadotropina Coriônica/metabolismo , Dinorfinas/farmacologia , Placenta/metabolismo , Ciclos de Atividade/efeitos dos fármacos , Células Cultivadas , Feminino , Humanos , Técnicas In Vitro , Naloxona/farmacologia , Perfusão , Placenta/efeitos dos fármacos , Gravidez , Primeiro Trimestre da Gravidez , Fatores de TempoRESUMO
Long-term regulation of opioid binding was studied in the human neuroblastoma NMB and in the murine lymphoma R1.1 and R1.EGO cell lines. Binding was down-regulated following prolonged exposure to opioid agonists and up-regulated following exposure to antagonist. Down-regulation was inhibited by the metabolic blocker sodium-azide and by the protein kinase H-7. Up-regulation was blocked by the protein and mRNA synthesis blockers cycloheximide, alpha-amanitin and actinomycin D. A significant difference was found between the response of neuronal and immune cells to ethanol exposure: while opioid binding in neuroblastoma culture underwent a pronounced (75%) up-regulation, no effect of ethanol on opioid receptors in lymphoma cultures was detected. The described cell lines present an excellent experimental model to study long-term regulation of opioid receptors in the nervous and immune systems and to elucidate the biological effects of chronic use of opiates and alcohol.
Assuntos
Linfoma/química , Neuroblastoma/química , Receptores Opioides/análise , Diprenorfina/metabolismo , Regulação para Baixo , Etanol/farmacologia , Humanos , Receptores Opioides/efeitos dos fármacos , Células Tumorais CultivadasRESUMO
1. A series of opioid agonists, antagonists and their (+)-stereoisomers were tested for antiarrhythmic activity in the rat coronary artery occlusion model. 2. Naloxone (0.01-2 mg kg-1) significantly reduced the incidence and severity of cardiac arrhythmias, in accordance with previous published studies. 3. The non-opioid stereoisomer, (+)-naloxone, was equipotent with naloxone against occlusion-induced arrhythmia. 4. Similar non-stereospecific antiarrhythmic effects were induced by another opioid antagonist, Win 44,441-3 and its stereoisomer Win 44,441-2. 5. The opioid agonists, morphine and levorphanol, protected against occlusion-induced arrhythmia as did the opioid antagonists, and the (+)-stereoisomer, dextrorphan, was equipotent to levorphanol. 6. It is concluded that the antiarrhythmic effects of opioid drugs are not mediated by opioid receptors. A direct effect on ionic currents in cardiac muscle is suggested as the mechanism of opioid antiarrhythmic activity.
Assuntos
Antiarrítmicos/farmacologia , Azocinas/farmacologia , Levorfanol/farmacologia , Morfina/farmacologia , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Animais , Masculino , Ratos , EstereoisomerismoRESUMO
Various mechanisms have been proposed for opioid receptor down regulation in different experimental preparations. The present study was aimed to test whether distinct mechanisms can mediate opioid receptor down regulation within the same cell. For this purpose we transfected HEK-293 cells with rat delta-opioid receptor (DOR). We exposed the cells to the opioid agonist etorphine in the absence or presence of various pharmacological agents and measured the binding of the opioid ligand [(3)H]diprenorphine to either isolated cell membranes or whole cells. We found that internalization of the receptors into the cell was mediated by clathrin coated pits and that the internalized receptors were degraded either in lysosomes or by proteosomes. Down regulation involved phosphorylation and at least two different kinases, a tyrosine kinase (TK) and MAPK kinase (MEK), mediated DOR down regulation in parallel routes. G-protein-coupled receptor kinase (GRK) was found to have only a minor role in DOR down regulation in HEK-293 cells. On the other hand, in N18TG2 cells that endogenously express delta-opioid receptors, GRK was the predominant kinase mediating DOR down regulation, with only a minor role for TK and MEK. We conclude that down regulation can take place via divers pathways within the same cell, and that in different cells down regulation is mediated by different mechanisms, depending on the kinase profile of the cells and the compartmentalization of the receptors within the cells.
Assuntos
Acetilcisteína/análogos & derivados , Regulação para Baixo/fisiologia , Sistema de Sinalização das MAP Quinases/fisiologia , Receptores Opioides delta/metabolismo , Acetilcisteína/farmacologia , Analgésicos Opioides/farmacologia , Animais , Antirreumáticos/farmacologia , Cloroquina/farmacologia , Inibidores de Cisteína Proteinase/farmacologia , Diprenorfina/metabolismo , Diprenorfina/farmacologia , Regulação para Baixo/efeitos dos fármacos , Etorfina/farmacologia , Flavonoides/farmacologia , Proteínas de Ligação ao GTP/metabolismo , Genisteína/farmacologia , Humanos , Rim/citologia , Antagonistas de Entorpecentes/metabolismo , Antagonistas de Entorpecentes/farmacologia , Neuroblastoma , Fosforilação , Ensaio Radioligante , Receptores Opioides delta/genética , Estaurosporina/farmacologia , Teprotida/farmacologia , Transfecção , Trítio , Células Tumorais CultivadasRESUMO
Basal morning humoral (H)-endorphin blood levels were assessed in ten autistic patients, 12 chronic schizophrenic patients and 11 healthy control subjects. Four autistic patients and four schizophrenic patients were drug free for at least 6 months while all other psychiatric patients were under treatment with antidopaminergic agents. Significantly reduced opioid levels were observed in the autistic group (827 +/- 103 vs 1121 +/- 75 pg-eq/ml, P less than 0.025), although the difference was actually only 26% of the control mean. A similar tendency toward low H-endorphin levels was also observed in the schizophrenic patients; however this difference was not significant (919 +/- 129 vs 1121 +/- 75 pg-eq/ml; NS). No significant difference was obtained between subjects suffering from the two psychiatric disorders (827 +/- 103 vs 919 +/- 129 pg-eq/ml; NS). Various interpretations of the decreased secretion of H-endorphin are discussed.
Assuntos
Transtorno Autístico/sangue , Endorfinas/sangue , Esquizofrenia Infantil/sangue , Adolescente , Criança , Feminino , Humanos , MasculinoRESUMO
Radioimmunoassay and column chromatography techniques were used to study the postnatal development of two different opioid ligands, humoral endorphin and enkephalin in the rat brain. Similar patterns were observed for both male and female animals during the period examined (from birth to the seventh week of life). Humoral endorphin content of the developing rat brain was found to increase in parallel to enkephalin, exhibiting a 'lag' period of 2 weeks. The most dramatic increase in opioid levels was detected during the third week of life; this stage was followed by a gradual change up to the adult levels.
RESUMO
The opiate agonist etorphine elevated [Ca2+]i in two neuroblastoma cell lines. Fura-2 imaging of single cells revealed a small and variable calcium elevation in only 20% of cultures. Three factors were found to increase the probability (up to 70%) and the amplitude of the response to etorphine: (a) synchronization of the cultures; (b) differentiation of the cells; and (c) synergism with other stimulatory agents (carbachol in SK-N-SH and bradykinin in NG108-15 cells). The establishment of a reproducible experimental protocol may facilitate the study of the molecular mechanism(s) underlying the stimulatory activity of opiates.
Assuntos
Cálcio/metabolismo , Etorfina/farmacologia , Membranas Intracelulares/metabolismo , Entorpecentes/farmacologia , Neuroblastoma/metabolismo , Bradicinina/farmacologia , Carbacol/farmacologia , Diferenciação Celular , Sinergismo Farmacológico , Fura-2 , Neuroblastoma/patologia , Fatores de Tempo , Células Tumorais CultivadasRESUMO
Reports by several investigators have shown that both opioid and non-opioid analgesia can be induced by non-pharmacological manipulations such as the administration of electric shock, and that such analgesia depends on shock parameters, the affective state of the animal and the region of the body shocked. We tested several manipulations which have been reported to induce opioid analgesia using a local strain of rats (CR). Such manipulations included the used of 30 min of intermittent footshock (3 mA, 1 s on, 5 s off), brief shock to the forepaws, transpinal electroconvulsive shock (ECS) and tail shock induced helplessness. Administration of either naloxone or naltrexone to rats of the CR strain failed to attenuate the analgesic effect of these manipulations and in some cases even enhanced analgesia. The existence of functional opioid analgesia systems in CR rats was evident from the fact that electrical stimulation of the periaqueductal gray area produced naloxone sensitive analgesia. In additional experiments we compared the analgesic effect of brief continuous (3 min) footshock, prolonged intermittent footshock (30 min) and ECS in young (less than 75 days of age) and old (greater than 75 days of age) rats of the Sabra strain. Young Sabra rats showed naloxone sensitive analgesia following all 3 manipulations while adult rats displayed analgesia which was naloxone insensitive. Furthermore, no decrement in learning, indicative of helplessness, could be demonstrated in young Sabras following 3 min of shock which induced naloxone sensitive analgesia.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Endorfinas/fisiologia , Dor/fisiopatologia , Estresse Fisiológico/fisiopatologia , Fatores Etários , Animais , Ritmo Circadiano , Eletrochoque , Pé , Ratos , Ratos EndogâmicosRESUMO
Previous studies have indicated that stressful footshock can induce both opioid, naloxone-sensitive, and non-opioid, naloxone-insensitive forms of analgesia, depending on stimulation parameters used with 30 min of intermittent footshock (3 mA, 1 s on, 5 s off) producing opioid analgesia and 3 min of continuous shock (3 mA) producing non-opioid analgesia. Using a local strain of Charles River (CR)-derived rats we conducted a parametric investigation of footshock-induced analgesia applying both AC and DC scrambled shock ranging from 1 to 4 mA, continuous shock of 1, 3 and 5 min in duration and intermittent shock lasting 1, 3, 5, 10, 20, 30 and 80 min. All shock parameters produced potent analgesia. In no case did 10 mg/kg of naloxone block this analgesia. Varying the dose of the antagonist (0.1-10 mg/kg) and testing the animals at different points in the diurnal cycle did not result in the emergence of naloxone-sensitive anangesia. Based on the assumption that non-opioid systems may mask the activity of opioid analgesia systems, we attempted to either enhance opioid analgesia by: preventing enkephalin degradation by the use of D-phenylalanine; increasing the entry of blood-borne opioids into the brain by the use of DMSO; and the attenuation of non-opioid analgesia by the use of reserpine. In no case did a naloxone-sensitive component of analgesia emerge. To test whether the animals possess an intact opioid analgesia system, both electrical stimulation of, and injection of opiates into the periaqueductal gray (PAG) were examined. Both procedures produced analgesia which was reversed by naloxone.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Endorfinas/fisiologia , Dor/fisiopatologia , Analgesia , Animais , Eletrochoque , Pé , Naloxona/farmacologia , Substância Cinzenta Periaquedutal/fisiopatologia , Fenilalanina/farmacologia , Ratos , Ratos Endogâmicos , Ratos Endogâmicos WKY , Especificidade da EspécieRESUMO
Depolarization-evoked 3H-norepinephrine release from SK-N-SH cells was found to be regulated by opioid ligands. Opioids exerted either inhibition or augmentation of 3H-norepinephrine release. Both effects were mediated by opioid receptors. In addition, a nonopioid inhibitory effect of opiates on release was observed. The SK-N-SH cell-line provides a suitable model for studying the various mechanisms underlying the opioid regulatory pathways within single cells.
Assuntos
Entorpecentes/farmacologia , Norepinefrina/metabolismo , Linhagem Celular , Dextrorfano/farmacologia , Interações Medicamentosas , Ala(2)-MePhe(4)-Gly(5)-Encefalina , D-Penicilina (2,5)-Encefalina , Encefalinas/farmacologia , Humanos , Cinética , Levorfanol/farmacologia , Morfina/farmacologia , Naloxona/farmacologia , Neuroblastoma/metabolismo , Receptores Opioides/efeitos dos fármacos , Receptores Opioides/fisiologia , Trítio , Células Tumorais CultivadasRESUMO
Opioids induce dual (inhibitory and excitatory) regulation of depolarization-evoked [3H]dopamine release in SK-N-SH cells through either mu or delta receptors. The potentiation of dopamine release by opioid agonists is mediated by N-type voltage-dependent calcium channels and does not involve Gi/Go proteins. Removal of the excitatory opioid effect by blockade with omega-conotoxin, an N-channel antagonist, reveals the inhibitory effect of opioids on release, thus suggesting that both modulatory effects of opioids are exerted in parallel.
Assuntos
Neoplasias Encefálicas/metabolismo , Canais de Cálcio/metabolismo , Neuroblastoma/metabolismo , Neurotransmissores/metabolismo , Peptídeos Opioides/farmacologia , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio/efeitos dos fármacos , Dopamina/metabolismo , Proteínas de Ligação ao GTP/metabolismo , Humanos , Levorfanol/farmacologia , Morfina/farmacologia , Entorpecentes/farmacologia , Células Tumorais CultivadasRESUMO
The selective kappa-opioid agonist trans-(+/-)-3, 4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl] benzenacetamidemethansulfonate (U50,488) potentiates both basal and depolarization-evoked [3H]dopamine release from NMB cells. The potentiation of dopamine release by U50,488 is mediated by N-type voltage-dependent calcium channels since it is blocked by omega-conotoxin, and is resistant to pertussis toxin (PTX)-treatment. When the stimulation of release by U50,488 is blocked by the N-channel antagonist omega-conotoxin, an inhibitory effect on dopamine release is revealed, suggesting that stimulatory and inhibitory effects of U50,488 are exerted in parallel.
Assuntos
(trans)-Isômero de 3,4-dicloro-N-metil-N-(2-(1-pirrolidinil)-ciclo-hexil)-benzenoacetamida/farmacologia , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio Tipo N/fisiologia , Dopamina/metabolismo , Receptores Opioides kappa/agonistas , Analgésicos/farmacologia , Canais de Cálcio Tipo N/efeitos dos fármacos , D-Penicilina (2,5)-Encefalina/farmacologia , Encefalina Leucina/análogos & derivados , Encefalina Leucina/farmacologia , Humanos , Neuroblastoma , Toxina Pertussis , Cianeto de Potássio/farmacologia , Células Tumorais Cultivadas , Fatores de Virulência de Bordetella/farmacologia , ômega-Conotoxinas/farmacologiaRESUMO
N18TG2 neuroblastoma cells co-express delta-opioid and CB1-cannabinoid receptors. Both receptors are negatively coupled to adenylyl cyclase through pertussis toxin-sensitive GTP-binding proteins. In the present study, we confirmed the independent activity of opioid and cannabinoid agonists, and investigated chronic interactions between the two signal transduction pathways in these cells. Opioid and cannabinoid agonists stimulated [35S]guanosine-5'-O-(3-thiotriphosphate) binding to N18TG2 membranes. When the opioid agonist etorphine and the cannabinoid agonist desacetyllevonantradol (DALN) were applied together, the stimulation was similar to the arithmetic sum of the two separate effects. This additivity existed even after partial ablation of the G-proteins reservoir with a low concentration of pertussis toxin, indicating that opioid and cannabinoid receptors activate different pools of G-proteins in N18TG2 cells. Chronic treatment of the cells with either opioid or cannabinoid agonists induced desensitization to the respective drug. In addition, asymmetric cross-desensitization was found: while long-term exposure to DALN induced homologous desensitization, and did not reduce the effect of etorphine, long-term exposure to etorphine attenuated the cannabinoid activation of G-proteins. Chronic exposure to either DALN or etorphine not only induced desensitization, but also elevated the basal activity of G-proteins in the exposed cells. The combination of the two drugs did not yield an additive activation, suggesting that chronic exposure of N18TG2 cultures to cannabinoid and opioid agonists modified a common responding element within the cells. This work presents the N18TG2 neuroblastoma as a suitable experimental model to study the molecular mechanism(s) underlying chronic interactions between opioid and cannabinoid drugs.
Assuntos
Receptores de Droga/fisiologia , Receptores Opioides/fisiologia , Transdução de Sinais/fisiologia , Toxina Adenilato Ciclase , Animais , AMP Cíclico/biossíntese , Interações Medicamentosas , Etorfina/farmacologia , Proteínas de Ligação ao GTP/metabolismo , Guanosina 5'-O-(3-Tiotrifosfato)/metabolismo , Camundongos , Entorpecentes/farmacologia , Toxina Pertussis , Fenantridinas/farmacologia , Receptores de Canabinoides , Receptores de Droga/agonistas , Receptores Opioides/agonistas , Fatores de Tempo , Células Tumorais Cultivadas/efeitos dos fármacos , Células Tumorais Cultivadas/metabolismo , Fatores de Virulência de Bordetella/farmacologiaRESUMO
The present study examines the modulation by opiates of intracellular calcium levels and calcium entry, using fura-2 imaging and 45Ca2+ uptake, in three neuronal cell lines. We show that opiates (10(-7)-10(-5) M morphine and 10(-9)-10(-7) M etorphine) exert both inhibitory and excitatory effects on KCl-induced elevation in intracellular calcium level in SK-N-SH, NG108-15 and NMB cell lines. In addition, opiates elevate basal (non KCl-stimulated) intracellular calcium level in all three cell cultures. 45Ca2+ uptake is augmented by opiates in SK-N-SH cells and this stimulatory effect is not blocked by pertussis toxin. In NMB cells, an additional inhibitory effect of opiates on basal calcium takes place: opiates reduce intracellular calcium level as measured by fura-2, and decrease calcium influx as detected by 45Ca2+ uptake. The heterogeneity in the opioid regulation of calcium could not be attributed to the type of opioid drug, neither to its concentration nor to the experimental conditions, since neighboring cells within the same culture responded differently.
Assuntos
Cálcio/metabolismo , Entorpecentes/farmacologia , Neurônios/metabolismo , Radioisótopos de Cálcio , Linhagem Celular , Diagnóstico por Imagem , Fura-2 , Proteínas de Ligação ao GTP/metabolismo , Humanos , Neurônios/efeitos dos fármacos , Toxina Pertussis , Cloreto de Potássio/farmacologia , Células Tumorais Cultivadas , Fatores de Virulência de Bordetella/farmacologiaRESUMO
The significance of the protein metabolism in crayfish peripheral nerve was studied in relation the ability of crayfish motor axons to survive for over 200 days following axotomy. In contrast to frog peripheral nerves, the crayfish nerves appear to more closely resemble ganglia in their profiles of synthesis expressed on sodium dodecyl sulfate (SDS) gels, and have higher incorporation rates of [3H]leucine into protein than ganglia. Since anisomycin inhibits over 95% of protein synthesis in crayfish peripheral nerve, it was concluded that this local protein synthesis was dependent upon a eukaryotic ribosomal mechanism. Radioautography of isolated nerves reveals newly synthesized proteins in glial sheaths, and also within the axoplasm of large motor fibers. Based upon the data available at present, a hypothesis that the glia surrounding the axons are responsible for the local protein synthesis, and that some of these newly synthesized proteins are transported into the axon, is presented. Transection of crayfish peripheral nerves proximal to the neuron cell bodies produced a more than two-fold increase in [3H]leucine incorporation, but no significant changes in labeling profiles of the proteins on SDS gels. The data suggest that while an active local protein synthesis may be necessary for the maintenance of several crayfish motor axons, it is not a sufficient condition.
Assuntos
Astacoidea/metabolismo , Denervação , Proteínas do Tecido Nervoso/biossíntese , Sistema Nervoso/metabolismo , Animais , Anisomicina/farmacologia , Autorradiografia , Cloranfenicol/farmacologia , Depressão Química , Gânglios Espinais/metabolismo , Leucina/metabolismo , Neurônios Motores/metabolismo , Denervação Muscular , Neurônios/ultraestrutura , Puromicina/farmacologia , Rana catesbeiana , Especificidade da Espécie , Raízes Nervosas Espinhais/metabolismoRESUMO
The activities of three enzymes of neurotransmitter metabolism (choline acetyl-transferase, CAT; acetylcholinesterase, AChE; and glutamic acid decarboxylase, GAD) were studied in normal, transected, and organ cultured crayfish nerves. CAT (to a lesses extent AChE) was dramatically decreased in activity when the nerve was cut proximal to the nerve cell bodies. GAD activity was unaffected by such procedures. In organ cultured nerve, where both motor and sensory axons degenerated, the CAT and AChE activities were virtually absent, whereas GAD activity remained close to normal levels. Inhibition of protein synthesis in cultured nerve caused the GAD activity to decrease rapidly. In view of these data, and the well documented fact that motor axons survive axotomy whereas sensory axons do not, a hypothesis that GAD is synthesized in the peripheral nerve is presented.
Assuntos
Astacoidea/metabolismo , Carboxiliases/biossíntese , Glutamato Descarboxilase/biossíntese , Sistema Nervoso/enzimologia , Acetilcolinesterase/metabolismo , Animais , Colina O-Acetiltransferase/metabolismo , Denervação , Degeneração Neural , Técnicas de Cultura de ÓrgãosRESUMO
Acetylcholine release from the nerve terminals of the purely cholinergic Torpedo electric organ is inhibited by morphine in a dose-dependent, naloxone-reversible fashion. In addition, it is shown that this preparation contains an enkephalin-like substance which, like acetylcholine, is present in a high concentration at the nerve terminals. These findings and the chemical homogeneity of the electric organ nerve terminals render this preparation an excellent model for the study of opiate regulation of neurotransmitter release.