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Repeated naltrexone administration accelerates resolution of morphine somatic withdrawal signs in morphine-dependent rats
No full textMARKED DECREASE OF A10-DOPAMINE NEURONAL FIRING DURING ETHANOL WITHDRAWAL SYNDROME IN RATS
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Mesoprefrontal and mesolimbic dopamine neurons: Role of general anaesthesia and immobilization stress
No full textEffects of acute, chronic ethanol and withdrawal on dorsal raphe neurons: Electrophysiological studies
No full textEthanol withdrawal does not induce a reduction in the number of spontaneously active dopaminergic-neurons in the mesolimbic system
No full textThe effect of ethanol withdrawal, after chronic administration, on the electrophysiological properties of antidromically identified mesoaccumbens dopaminergic neurons was studied in two groups of rats with relative controls (withdrawal from chronic saline). The first group was anesthetized with chloral hydrate whereas the second was immobilized with D-tubocurarine. In chloral hydrate anesthetized rats, a significant reduction in the number of spontaneously active dopamine neurons was observed as compared with chronic saline withdrawn controls. In contrast, in ethanol-withdrawn D-tubocurarine treated rats, the number of spontaneously active dopamine neurons, as measured by the cells/track index, was found not different than chronic saline withdrawn controls. Further, intravenous administration of apomorphine, did not reverse the reduced cells/track index in chloral-hydrate anesthetized rats but consistently inhibited dopaminergic firing. Apomorphine-induced inhibition of firing was significantly more pronounced in ethanol withdrawn chloral-hydrate anesthetized rats. Firing rate and firing pattern were found decreased during ethanol withdrawal irrespective of experimental conditions. The results do not support the possibility that dopaminergic neurons of the mesoaccumbens pathway might be affected by depolarization inactivation during ethanol withdrawal. Rather, they confirm a reduction of neuronal activity already reported by previous studies. The reduced cells/track index observed in chloral hydrate anesthetized rats during ethanol withdrawal awaits an alternative explanation to the depolarization inactivation mechanism
HETEROGENEOUS RESPONSES OF SUBSTANTIA-NIGRA PARS-RETICULATA NEURONS TO GAMMA-HYDROXYBUTYRIC ACID ADMINISTRATION
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Effects of acute, chronic ethanol and withdrawal on dorsal raphe neurons: Electrophysiological studies
No full textThe effect of a single intravenous administration of ethanol (0.25-1.0 g/kg) on the spontaneous activity of putative serotonin neurons of the dorsal raphe nucleus was studied in unanesthetized rats. Ethanol produced a slight but progressive decline in neuronal activity in 67% (six of nine) of all neurons tested. The remaining 33% (three of nine) were unresponsive. Upon withdrawal of chronic ethanol treatment (1-5 g/kg every 6 h for six consecutive days, 12 h from last ethanol administration), the mean firine rate of dorsal raphe neurons was found to be significantly reduced, by about 30% (n=71), as compared with the control group (n=83), whereas the cells/track index was unaltered. Under these conditions, ethanol administration further reduced firing rate in 67% (four of six) of all the neurons tested. In the remaining 33% (two of six), no response was observed. At 72 h after the last ethanol administration, the mean firing rate of dorsal raphe neurons was found to be within control values (n=90). Further, to evaluate the functional status of the autoreceptors under control conditions and after withdrawal from chronic ethanol, the selective serotonin-1A receptor agonist 8-hydroxy-(2-di-n-propylamino)tetralin was administered intravenously in cumulative doses (1-16 microg/kg) and dose-response curves were generated for both groups. Autoreceptor sensitivity of dorsal raphe neurons was found to be not statistically different in control and ethanol withdrawn rats (n=6 for both groups) as indexed by a similar potency displayed by 8-hydroxy-(2-di-n-propylamino)tetralin in reducing the spontaneous activity of dorsal raphe neurons. The results indicate that, in spite of the widespread use of serotonin transmission potentiating agents in the treatment of alcoholism, neither acute nor withdrawal from chronic ethanol administration produces drastic effects on dorsal raphe neurons. However, the inhibition of dorsal raphe neuronal activity after acute ethanol may be due to the reported ability of ethanol to increase serotonin release from terminal areas. This increased serotonin tone could, at the level of recurrent axon collaterals in the dorsal raphe nucleus, reduce the spontaneous activity of the cells. On the other hand, a similar reduction in spontaneous activity after withdrawal from ethanol correlates well with the reduction in serotonin levels observed under these conditions in microdialysis studies
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