Antihistamine-sensitive vasodilatation in the canine hindlimb evoked by electrical stimulation rostral to the hypothalamus.

Electrical stimulation was carried out at various sites in the brain of anaesthetized dogs pretreated with guanethidine. Stimulation at some sites elicited cholinergic vasodilator responses in the femoral vascular bed while stimulation at other sites produced non-cholinergic vasodilator responses which were prevented by histamine antagonists administered into the hindlimb. The central sites mediating the two types of responses were anatomically distinct.