Maintenance of intracranial self-stimulation in hippocampus and olfactory bulb following regional depletion of noradrenaline.
As a test of the 'noradrenergic' theory of brain-stimulation reward rats were trained to respond for stimulation at sites in the hippocampus and olfactory bulb. Inasmuch as there is evidence that the noradrenergic innervation of these two areas arisesexclusively from the locus coeruleus, the effects of 6-hydroxydopamine-induced lesions of this protection on hippocampal and olfactory bulb self-stimulation were examined. Depletion of hippocampal noradrenaline levels to less than 5% and olfactory bulb levels to less than 9% of controls had no significant effect on self-stimulation at these loci. Therefore noradrenaline does not seem to be an essential substrate of brain-stimulation reward in these regions of the brain. The effect of this lesion on the rate-increasing properties of d-amphetamine sulphate (1.0 mg/kg) was also examined with hippocampal placements. A significant increase in self-stimulation rate was observed both before and after the lesion, thus questioning traditional explanations of the facilitatory effect of amphetamine on self-stimulation.
Phillips
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AG
Department of Psychology and Division of Neurological Sciences, Department of Psychiatry, University of British Columbia, Vancouver, B.C. V6T 1W5 Canada.
Van Der Kooy
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D
Fibiger
H C
HC