Decrease in Selected Temperature After Intracranial Dopamine Injections in Goldfish

Goldfish (Carassius auratus) (40-80g) were injected with dopamine into the forebrain to study the possible involvement of this amine in central temperature regulation in these fish. Dopamine caused a decrease in selected temperature after injection into the rostral nucleus preopticus periventricularis (NPP). This effect was dependent on the dose of dopamine administered. Doses of 25, 50, 100 and 250 ng were used, injected in a volume of 0.2μ1. Injections in regions adjacent to the NPP elicited hypothermic effects only at the higher dosages. These effects were not consistent. Injections in caudal regions of the NPP elicited no effect. The effects of dopamine were blocked by haloperidol, a selective antagonist of dopamine. It is suggested that dopamine acts on central thermoregulatory neurons, present in the rostral NPP, in the mediation of thermoregulatory behavior. Further, it is suggested that this action is mediated via dopaminergic receptors