Effects of amphetamine on catecholamine levels and turnover in discrete hypothalamic areas

Abstract

The effects of d-amphetamine (AMPH, 0.5 mg/kg, i.p.) on catecholamine (CA) levels and turnover in 5 discrete hypothalamic areas were examined using a sensitive radioenzymatic assay. Amphetamine, injected 10 or 45 min prior to sacrifice, produced little change in CA content of hypothalamic nuclei, except in the lateral perifornical area where dopamine (DA) content was significantly decreased, by 48%. The CA synthesis inhibitorα-methy- p-tyrosine (α-MpT, 300 mg/kg, i.p.), injected 3 h prior to sacrifice, produced a significant decline in DA (60–90%) and norepinephrine (NE, 20–80%) levels in most hypothalamic areas, whereas epinephrine (EPI) was only slightly affected. In α-MpT-pretreated rats, the impact of AMPH on the disappearance or turnover of hypothalamic CA was evaluated. The most dramatic effect was within the paraventricular nucleus, where AMPH significantly decrease NE and DA turnover, as reflected by an increase in the presence of these CA. In the dorsomedial nucleus, CA depletion appeared to be enhanced. These results demonstrate that, within the hypothalamus, the effects of AMPH on CA levels or turnover are anatomically localized, and that opposite effects on turnover may occur in nearby nuclei. The significance of these biochemical changes, relative to hypothalamically mediated behavioral effects of AMPH, is discussed.