Journal of Neuroscience, Vol 7, 3888-3896, Copyright © 1987 by Society for Neuroscience
The role of dopamine in intracranial self-stimulation of the ventral tegmental area
HC Fibiger, FG LePiane, A Jakubovic and AG Phillips
Department of Psychiatry, University of British Columbia, Vancouver, Canada.
The role of dopaminergic (DA) neurons in brain stimulation reward produced
by electrical stimulation of the ventral tegmental area (VTA) was
investigated in the rat. In the first experiment, extensive 6-
hydroxydopamine lesions of the ascending fibers of the mesotelencephalic DA
projections resulted in significant changes in intracranial
self-stimulation (ICS) rate-current intensity functions when the lesion was
ipsilateral to the stimulating electrode. Similar contralateral lesions had
no effect on these functions, thus ruling out lesion-induced performance
deficits as being responsible for the decreases in ICS rates across the
wide range of current intensities that occurred after the ipsilateral
lesions. In the second experiment, ICS obtained from electrodes in the VTA
resulted in significant increases in the DA metabolites,
3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the
striatum, nucleus accumbens, and olfactory tubercle ipsilateral to the
stimulating electrode. The ratios of DOPAC and HVA to DA, considered to be
indices of DA utilization, were also increased in these brain regions
ipsilateral to the electrode. No changes were observed in the contralateral
striatum, nucleus accumbens, and olfactory tubercle. Similar increases were
observed in stimulated "yoked" animals that received brain stimulation at
identical rates and currents but did not lever-press for this stimulation.
The third experiment examined the effects of lever- pressing for food on an
FR8 schedule of reinforcement on DA utilization in the striatum, nucleus
accumbens, and olfactory tubercle. Despite high rates of responding, no
effects were observed on DOPAC:DA or HVA:DA ratios in these brain
regions.(ABSTRACT TRUNCATED AT 250 WORDS)