Pharmacological evidence against the involvement of the D1 subtype of dopamine receptors in apomorphine-induced hypothermia.

In chloral anaesthetized rats, apomorphine, bromocriptine, lergotrile, piribedil and its presumed active metabolite S 584, induced a hypothermia antagonized, except for S 584, by stereotactically controlled microinjections of haloperidol into the preopticus medialis nucleus. Hypothermia was also produced by these dopamine agonists when they were injected directly into the preopticus medialis nucleus. Furthermore, apomorphine-induced hypothermia was antagonized by an infusion of sulpiride into the preopticus medialis nucleus. These data suggest that the dopamine receptors located in the preopticus medialis nucleus which are involved in dopamine agonists-induced hypothermia do not possess the same pharmacological characteristics as the D1 subtype.