A dopamine-acetylcholine link in the caudate-putamen complex which mediates metabolic rate

In order to investigate the possible involvement of the dopaminergic and the cholinergic neurons of caudate-putamen complex (CP) in temperature regulation, we have assessed the effects of administration of either acetylcholine (Ach), atropine (Ach receptor antagonist), apomorphine (DA receptor agonist), or haloperidol (DA receptor antagonist) into the CP on metabolic, respiratory, vasomotor and temperature responses in conscious rats at various ambient temperature (Ta). The results show that intra-CP injection of either Ach or apomorphine caused hypothermia, decreased metabolism and cutaneous vasoconstriction at Ta 8 and 22 degrees C, as well as hyperthermia and cutaneous vasoconstriction at Ta 30 degrees C. On the other hand, intra-Cp injection of either atropine or haloperidol caused hyperthermia, increased metabolism and cutaneous vasoconstriction at all Ta (8, 22, and 30 degrees C) studied. There was no change in respiratory evaporative heat loss in response to these agents at all Ta studied. Furthermore, the Ach-induced hypothermia or hypo-metabolism was antagonized by pretreatment with atropine, but not with haloperidol. However, the apomorphine-induced hypothermia or hypo-metabolism at Ta 8 and 22 degrees C was antagonized by pretreatment with either atropine or haloperidol. These observations tend to indicate that a dopamine-acetylcholine link occurs in the caudate-putamen complex which mediate metabolic rate in the rat.