Adipsia and Aphagia after 6‐Hydroxydopamine Induced Degeneration of the Nigro‐striatal Dopamine System

TLDR

The nigro‑striatal dopamine system’s role has been investigated using detailed mapping and selective lesioning with 6‑hydroxydopamine. The study aimed to examine adipsia, aphagia, hypokinesia, and catalepsia following lateral hypothalamic lesions that may disrupt ascending dopamine axons. Bilateral electrocoagulation or 6‑OH‑DA lesions were applied at multiple sites along the dopamine pathway, and behavioral effects were assessed relative to histochemically confirmed lesions. Bilateral complete degeneration of the nigro‑striatal dopamine pathway produced persistent adipsia, aphagia, hypoactivity, initiation difficulties, and loss of exploratory behavior; dopamine receptor drugs confirmed these effects, while catalepsy and somnolence were linked to other pathways, highlighting the system’s key role in behavior and suggesting that symptoms once attributed to the hypothalamus may stem from nigro‑striatal disruption.

Abstract

Abstract The functional role of the nigro‐striatal dopamine (DA) system has been investigated on the basis of a recent detailed mapping of its path and a new method of lesioning the catecholamine systems selectively by intracerebral injection of 6‐hydroxydopamine (6‐OH‐DA). The investigation was especially focused on the symptoms of adipsia, aphagia, hypokinesia and catalepsia after lateral hypothalamic lesions as such lesions may interrupt the ascending DA axons. Electrocoagulations or 6‐OH‐DA lesions were performed bilaterally at several sites along the DA pathway and the behavioural effects were evaluated in relation to the histochemically detected lesion of the DA pathway. It was concluded that bilateral complete degeneration of the nigro‐striatal DA pathway produces severe, long lasting adipsia and aphagia, hypoactivity, difficulties to initiate activity and loss of exploratory behaviour and curiosity. Experiments with DA receptor stimulating and blocking drugs supported the lesion results. Catalepsia and somnolence were attributed to the interruption of other pathways. The results suggest an important role for the nigro‐striatal DA system and the striatum in the control of behaviour. A number of symptoms earlier related to the hypothalamus may in fact be due to disturbance of the nigro‐striatal DA system.