RESUMEN
To investigate whether endogenous opioid peptides (EOP) play an important role in intragonadal regulation of testicular function and regulation of the hypothalamic-pituitary-gonadal axis of the male rat, the authors employed two principal methods: culture of testicular Leydig cells and Sertoli cells, and in vitro perifusion of hypothalamo-pituitary Leydig cells of the adult rat. The results demonstrated that incubation of Leydig cells with B-endorphin (B-EP 10(-9) = 10(-6) mol/L) or naloxone (NAL 10(-5) = 10(-8) mol/L) manifested no significant changes of non-stimulated or hCG-stimulated testosterone secretion both in 20 and 60 day-old rats. Similar results were obtained when the cells were treated with B-EP (10(-10) = 10(-7) mol/L) for 48 h during culture. Pretreatment of incubated Leydig cells with B-EP in similar concentrations for 48 h showed no effect on the response to hCG stimulation. In addition, treatment with B-EP in vitro for 24 or 72 h manifested no effects on estradiol production by aromatization of cultured Sertoli cells. Neither NAL 10(-5) given in vitro nor NAL (5 mg/body weight) injected subcutaneously 1 h before decapitation affected LH and testosterone release from the perifused hypothalamo-pituitary Leydig cells system. These results could not support the hypothesis that B-EP is a local regulator of testicular function. The physiological significance of EOP in regulating the function of gonadal axis of adult male rat remains to be investigated further.
Asunto(s)
Células Intersticiales del Testículo/metabolismo , Naloxona/farmacología , Células de Sertoli/metabolismo , Testosterona/metabolismo , betaendorfina/fisiología , Animales , Aromatasa/metabolismo , Células Cultivadas , Hipotálamo/fisiología , Células Intersticiales del Testículo/efectos de los fármacos , Hormona Luteinizante/metabolismo , Masculino , Perfusión , Hipófisis/fisiología , Ratas , Ratas Endogámicas , Células de Sertoli/efectos de los fármacos , Células de Sertoli/enzimologíaRESUMEN
We have reported that intracerebroventricular (i. c. v.) injection of 1-4 ng of CCK-8 to the rat produced a remarkable antagonistic effect on morphine analgesia. In order to study the species specificity and the site of action, CCK-8 was microinjected into the PAG of the rabbit, and its influence on morphine analgesia and electroacupuncture analgesia was observed. The latency of the escape response (ERL) to radiant heat focused on the snout was measured as an index of the pain threshold. Microinjections were made via cannulae chronically implanted into the PAG. The drug solutions were delivered in a volume of 1 microliter, at a speed of 0.125 microliter/min. The ERL was measured for a period of 60 or 70 minutes at 10 min intervals. 1. CCK-8 administered unilaterally to the PAG of the rabbit at a dose of 3 ng antagonized the analgesia induced by morphine (4 mg/kg, i. v.) by 73% (P less than 0.001), and reduced the analgesic effect of electroacupuncture by 67% (P less than 0.001). These effects were dose-dependent within the range from 1.5 ng to 6.0 ng. The effect of CCK-8 was reversed by CCK receptor blocker proglumide (4 microliters, intra-PAG injection). Unsulfated CCK-8 (CCK-us) had no effect in this regard. These results indicate that in the PAG of the rabbit, exogenously administered CCK-8 was capable of antagonizing opioid analgesia by the activation of CCK receptors. 2. Two groups of rabbits were given with morphine (2 mg/kg, i. v.) and simultaneous injection of CCK-8 antiserum (CCK-AS, 1 microliter) or normal rabbit serum (NRS) into the PAG.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Analgesia por Acupuntura , Electroacupuntura , Morfina/antagonistas & inhibidores , Sustancia Gris Periacueductal/fisiología , Sincalida/farmacología , Animales , Inyecciones Intraventriculares , Masculino , Conejos , Sincalida/administración & dosificaciónRESUMEN
The endogenous opioid peptide enkephalin (EK) is known to be degraded mainly by two enzymes, the dipeptidyl carboxypeptidase 'enkephalinase' and aminopeptidase. Microinjection of the enkephalinase inhibitor thiorphan or the aminopeptidase inhibitor bestatin into the nucleus accumbens of the rabbit produced a dose-dependent analgesic effect. This analgesic effect was totally reversed by the narcotic antagonist naloxone or by antibodies against [Met5]enkephalin (MEK) administered to the same site. Antibodies against [Leu5]enkephalin were not effective. Moreover, microinjection of thiorphan or bestatin into the nucleus accumbens resulted in a marked potentiation of the aftereffect of electroacupuncture (EA) produced analgesia, as well as the analgesia induced by a small dose of morphine. It is concluded that the analgesic effect elicited by EA and morphine is mediated, at least in part, by MEK-like immunoreactive substance(s) in the nucleus accumbens.
Asunto(s)
Aminoácidos Sulfúricos/administración & dosificación , Analgesia , Leucina/análogos & derivados , Morfina/administración & dosificación , Núcleo Accumbens/efectos de los fármacos , Núcleos Septales/efectos de los fármacos , Tiopronina/administración & dosificación , Animales , Relación Dosis-Respuesta a Droga , Encefalina Metionina/inmunología , Sueros Inmunes , Leucina/administración & dosificación , Leucina/metabolismo , Masculino , Microinyecciones , Morfina/metabolismo , Naloxona/administración & dosificación , Conejos , Tiorfan , Factores de Tiempo , Tiopronina/análogos & derivados , Tiopronina/metabolismo , Estimulación Eléctrica Transcutánea del NervioAsunto(s)
Terapia por Acupuntura , Analgesia , Terapia por Estimulación Eléctrica , Morfina , Núcleo Accumbens/fisiología , Núcleos Septales/fisiología , Estimulación Eléctrica Transcutánea del Nervio , Animales , Cloruro de Calcio/farmacología , Quelantes/farmacología , Ácido Edético/análogos & derivados , Ácido Edético/farmacología , Magnesio/farmacología , Cloruro de Magnesio , Masculino , Dolor/fisiopatología , Conejos , Umbral Sensorial/efectos de los fármacosAsunto(s)
Terapia por Acupuntura , Cloruro de Calcio/farmacología , Terapia por Estimulación Eléctrica , Morfina/antagonistas & inhibidores , Sustancia Gris Periacueductal/fisiología , Estimulación Eléctrica Transcutánea del Nervio , Analgesia , Animales , Masculino , Mesencéfalo/fisiología , Microinyecciones , ConejosAsunto(s)
Terapia por Acupuntura , Analgesia , Terapia por Estimulación Eléctrica , Encefalina Metionina/metabolismo , Morfina/farmacología , Núcleo Accumbens/fisiología , Núcleos Septales/fisiología , Estimulación Eléctrica Transcutánea del Nervio , Aminopeptidasas/antagonistas & inhibidores , Animales , Endopeptidasas , Encefalina Leucina/metabolismo , Leucina/análogos & derivados , Leucina/farmacología , Masculino , Neprilisina , Inhibidores de Proteasas , Conejos , Tiorfan , Tiopronina/análogos & derivados , Tiopronina/farmacologíaAsunto(s)
Terapia por Acupuntura , Terapia por Estimulación Eléctrica , Encefalina Metionina/análogos & derivados , Sustancia Gris Periacueductal/fisiología , Estimulación Eléctrica Transcutánea del Nervio , Adyuvantes Inmunológicos , Animales , Captopril/farmacología , Encefalina Metionina/antagonistas & inhibidores , Encefalina Metionina/fisiología , Sueros Inmunes , ConejosAsunto(s)
Terapia por Acupuntura , Terapia por Estimulación Eléctrica , Sustancia Gris Periacueductal/fisiología , Médula Espinal/fisiología , Sustancia P/farmacología , Estimulación Eléctrica Transcutánea del Nervio , Animales , Masculino , Dolor/fisiopatología , Conejos , Umbral Sensorial/efectos de los fármacosRESUMEN
The present study was undertaken to investigate whether the C-terminal extended Met-enkephalin heptapeptide (Met-enkephalin-Arg6-Phe7, MEAP) played a role in mediating the analgesic effect of electroacupuncture in rabbits. MEAP and its degrading enzyme inhibitor captopril as well as antiserum against MEAP were injected into the periaqueductal gray (PAG) via a previously implanted cannula. Their effects on nociception were tested by the escape response latency (ERL) elicited by radiant heat applied on the skin of the snout. (1) Microinjection of MEAP (30-240 nmol) into PAG produced a dose-dependent analgesic effect which was 2.5 times more potent than Met-enkephalin (MEK) and 3 times less potent than morphine. The complete reversal of the analgesia elicited by 240 nmol of MEAP by a small dose of naloxone (0.1 mg/kg, i.v.) indicates that the effect of MEAP is mediated by naloxone sensitive opioid receptors. (2) In rabbits, a dose-dependent analgesia was elicited by an intra-PAG injection of captopril (60-240 nmol). A single dose of 240 nmol captopril increased ERL by more than 100%. This effect could be reversed by 30 nmol of naloxone injected into the same site, or by antiserum recognizing MEAP (1 microliter, titer 1:1500) but not by antiserum recognizing MEK (1 microliter, 1:8000) suggesting that captopril was able to protect MEAP from degradation. (3) Intra-PAG injection of 60 nmol of captopril significantly potentiated the after effect of electroacupuncture (EA) induced analgesia. This effect could be blocked either by 30 nmol (but not 7.5 nmol) of naloxone, or by 1 microliter (but not 0.1 microliter) of MEAP antiserum.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Terapia por Acupuntura , Encefalina Metionina/análogos & derivados , Manejo del Dolor , Sustancia Gris Periacueductal/fisiopatología , Animales , Mapeo Encefálico , Captopril/uso terapéutico , Terapia Combinada , Terapia por Estimulación Eléctrica , Encefalina Metionina/fisiología , Masculino , Naloxona/farmacología , Dolor/fisiopatología , ConejosAsunto(s)
Amígdala del Cerebelo/efectos de los fármacos , Analgesia , Morfina/farmacología , Núcleo Accumbens/efectos de los fármacos , Núcleos Septales/efectos de los fármacos , Tálamo/efectos de los fármacos , Animales , Masculino , Dolor/fisiopatología , Conejos , Umbral Sensorial/efectos de los fármacosRESUMEN
Injection of protein-A purified antibodies against Met-enkephalin and beta-endorphin into the periaqueductal gray matter (PAG) was shown to decrease the analgesic effect of electroacupuncture (EA) in rabbits. Met-enkephalin antibodies were more potent than the beta-endorphin antibodies in causing a statistically-significant effect on electroacupuncture analgesia. Antibodies to Met-enkephalin were also active at the spinal level, whereas antibodies against beta-endorphin were without effect: this is in agreement with a rich enkephalinergic innervation and absence of beta-endorphin-containing fibres in the spinal cord. Substance P, the other neuropeptide of this study, also seems to be important in mediating effects of electroacupuncture. Injection of antibodies into the periaqueductal gray caused decrease of the effect of electroacupuncture whereas intrathecal administration of Fab-fragment substance P antibodies caused a marked potentiation. The demonstration of site specificity of the neuropeptides in mediating analgesia induced by electroacupuncture supports the validity of this experimental approach.
Asunto(s)
Terapia por Acupuntura/métodos , Anticuerpos/administración & dosificación , Endorfinas/inmunología , Encefalina Metionina/inmunología , Sustancia P/inmunología , Analgesia/métodos , Animales , Estimulación Eléctrica , Sueros Inmunes/administración & dosificación , Inyecciones Espinales , Masculino , Microinyecciones , Sustancia Gris Periacueductal/fisiología , Conejos , betaendorfinaRESUMEN
Electroacupuncture (EA) of the hind limb points of the rabbit for 10 min elicited a significant increase of the latency of aversive responses (ARL) induced by radiant heat stimulation of the snout. This effect of analgesia was found to be gradually diminished when EA was applied repeatedly for 6 hr, implying the development of tolerance. A reversal of EA tolerance was achieved by microinjection of 5-hydroxytryptophan (5-HTP) (the direct precursor of 5-hydroxytryptamine (5-HT)), either intracerebroventricularly (200 micrograms) or into bilateral nuclei accumbens (10 micrograms). Injection of the same amount of 5-HTP into brain structures adjacent to nucleus accumbens, e.g., globus pallidus, corpus callosum, internal capsule, etc., was ineffective. It is concluded that a functional insufficiency of 5-HT in the brain, especially in nucleus accumbens, may constitute one of the mechanisms for the development of EA tolerance.
Asunto(s)
5-Hidroxitriptófano/farmacología , Terapia por Acupuntura , Nociceptores/efectos de los fármacos , Núcleo Accumbens/efectos de los fármacos , Núcleos Septales/efectos de los fármacos , Animales , Miembro Posterior/inervación , Inyecciones Intraventriculares , Masculino , Conejos , Umbral SensorialRESUMEN
Although there are unequivocal evidences indicating the participation of endogenous opiate-like substances in acupuncture analgesia, their exact sites of action remain to be elucidated. From the results of localization studies by injecting minute amount of narcotic antagonist naloxone into discrete brain areas and assessing its effect on acupuncture analgesia in rabbits it is concluded that nuclei accumbens, amygdala, habenula and periaquaductal grey are the strategic sites for endogenous opioids to exert their analgesic effect. These brain areas are also of extreme importance for the realization of morphine analgesia.
Asunto(s)
Terapia por Acupuntura , Analgesia , Morfina/antagonistas & inhibidores , Naloxona/farmacología , Amígdala del Cerebelo/fisiología , Animales , Endorfinas/fisiología , Masculino , Microinyecciones , Naloxona/administración & dosificación , Núcleo Accumbens/fisiología , Dolor/fisiopatología , Conejos , Receptores Opioides/efectos de los fármacos , Umbral SensorialRESUMEN
The role played by central neurotransmitters in acupuncture analgesia was evaluated by correlating neurochemical changes in central nervous system with the acupuncture effect, as well as modification of the acupuncture effects by pharmacological manipulations of central neurotransmitters. The results of experimental studies which were performed mainly on rats and rabbits indicated that central serotonin and endogenous opiate-like substances (OLS) seem to be the most important substrates for mediation of acupuncture analgesia while central catecholamines, especially norepinephrine through alpha receptors, may exert an antagonistic effect. It was also found that prolonged and repeated acupuncture resulted in a gradual decrease of the acupuncture effects. The development of some endogenous anti-opiate substrates (AOS) in central nervous system was tentatively implicated.