Changes in dopaminergic neurotransmission do not alter somatic or motivational opiate withdrawal-induced symptoms in rats.
Behavioral Neuroscience. 2003-01-01; 117(5): 995-1005
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Opiate withdrawal has been correlated with decreased extracellular dopamine (DA)
levels in the nucleus accumbens (NAC) of morphine-dependent rats. The authors
tested the hypothesis that DA transmission plays a critical role in the induction
of motivational and somatic withdrawal symptoms. First, the authors used a
6-hydroxydopamine-induced lesion of the NAC to chronically disrupt mesolimbic DA
transmission. Second, global DA neurotransmission was acutely stimulated by the
nonselective DA agonist (apomorphine) or inhibited by nonselective DA antagonists
(droperidol or flupentixol). Morphine-dependent rats bearing
6-hydroxydopamine-induced lesions displayed naloxone-precipitated motivational
and somatic withdrawal symptoms similar to those of sham-lesioned rats.
Administration of apomorphine did not reduce naloxone-induced opiate withdrawal.
Moreover, in total absence of naloxone, DA antagonists did not precipitate either
conditioned place aversion or somatic abstinence signs in dependent rats. Taken
together, these findings suggested that DA transmission is not critical for the
induction of opiate withdrawal syndrome.
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