Apomorphine-induced inhibition of neostriatal activity is enhanced by lesions induced by 6-hydroxydopamine but not by long-term administration of amphetamine

K. D. Alloway, G. V. Rebec

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Single-unit activity was recorded in the neostriatum of locally-anesthetized, immobilized rats which had received either a unilateral injection of 6-hydroxydopamine (6-OHDA) into the nigroneostriatal dopamine pathway, or repeated injections (twice daily for 6 days) of saline, 1.0, 5.0 or 10.0 mg kg (+)-amphetamine. A staircase regimen of apomorphine was administered intravenously to each rat to determine if the long-term administration of amphetamine changed the sensitivity of postsynaptic dopamine receptors in a way comparable to that produced by 6-hydroxydopamine. In all groups, the most frequent response to apomorphine was inhibition of neostriatal activity. In saline-treated rats, most units were moderately excited by small doses of apomorphine (0.0025-0.02 mg kg) and then inhibited by doses exceeding 0.04 mg kg. In rats with lesions induced by 6-hydroxydopamine, apomorphine caused significantly more inhibition than in saline-treated animals. By contrast, neuronal responses in amphetamine-treated rats were not significantly different from those of saline controls. These results indicate that the long-term administration of amphetamine produces an augmentation of behavior by some mechanism other than an increase in the sensitivity of postsynaptic dopamine receptors.

Original languageEnglish (US)
Pages (from-to)1033-1039
Number of pages7
JournalNeuropharmacology
Volume23
Issue number9
DOIs
StatePublished - Sep 1984

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Cellular and Molecular Neuroscience

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