M. Diana et al., ETHANOL WITHDRAWAL DOES NOT INDUCE A REDUCTION IN THE NUMBER OF SPONTANEOUSLY ACTIVE DOPAMINERGIC-NEURONS IN THE MESOLIMBIC SYSTEM, Brain research, 682(1-2), 1995, pp. 29-34
The effect of ethanol withdrawal, after chronic administration, on the
electrophysiological properties of antidromically identified mesoaccu
mbens dopaminergic neurons was studied in two groups of rats with rela
tive controls (withdrawal from chronic saline). The first group was an
esthetized with chloral hydrate whereas the second was immobilized wit
h D-tubocurarine. In chloral hydrate anesthetized rats, a significant
reduction in the number of spontaneously active dopamine neurons was o
bserved as compared with chronic saline withdrawn controls. In contras
t, in ethanol-withdrawn D-tubocurarine treated rats, the number of spo
ntaneously active dopamine neurons, as measured by the cells/track ind
ex, was found not different than chronic saline withdrawn controls. Fu
rther, intravenous administration of apomorphine, did not reverse the
reduced cells/track index in chloral-hydrate anesthetized rats but con
sistently inhibited dopaminergic firing. Apomorphine-induced inhibitio
n of firing was significantly more pronounced in ethanol withdrawn chl
oral-hydrate anesthetized rats. Firing rate and firing pattern were fo
und decreased during ethanol withdrawal irrespective of experimental c
onditions. The results do not support the possibility that dopaminergi
c neurons of the mesoaccumbens pathway might be affected by depolariza
tion inactivation during ethanol withdrawal. Rather, they confirm a re
duction of neuronal activity already reported by previous studies. The
reduced cells/track index observed in chloral hydrate anesthetized ra
ts during ethanol withdrawal awaits an alternative explanation to the
depolarization inactivation mechanism.