Effects of chlorpheniramine, pyrilamine and astemizole on intracranial self-stimulation in rats.

Rats implanted in the lateral hypothalamus were used to assess lever pressing for brain stimulation. Lever pressing was increased dose-dependently by chlorpheniramine and decreased dose-dependently by pyrilamine. Astemizole, a new orally long-acting antihistamine did not affect self-stimulation. Evidence from pharmacological tests based on altered neurotransmitter functions suggests that the central anticholinergic activity of chlorpheniramine is probably responsible for the increased response rate, whereas the central dopamine receptor blocking activity of pyrilamine may be responsible for the decreased response rate. Astemizole is a specific antihistamine devoid of any central activity.