CARDIOVASCULAR-RESPONSES PRODUCED BY THE INJECTION OF DOPAMINE INTO THE CEREBRAL-VENTRICLES OF THE UNANESTHETIZED DOG

The injection of dopamine (100 to 500 μg) into the cerebral ventricles (i.c.v.) of 10 unanaesthetized dogs produced a dose‐dependent increase in arterial blood pressure and heart rate. The dogs licked, swallowed, sometimes vomited and became sedated. Autonomic ganglion blockade with hexamethonium (10 mg/kg, i.v.) abolished cardiovascular responses to i.c.v. dopamine, indicating that dopamine was exerting its effect within the central nervous system. The dopamine receptor antagonists, haloperidol (500 μg), chlorpromazine (200 μg) and ergometrine (500 μg), each given i.c.v., subsequently abolished the cardiovascular responses to dopamine. Pretreatment with either the β‐adrenoceptor antagonist, propranolol (600 μg) or the α‐adrenoceptor antagonist, phentolamine (1 mg) given i.c.v. had no significant effect on the response to dopamine. It is suggested that dopamine injected into the cerebral ventricles of the unanaesthetized dog causes hypertension and tachycardia by activating central dopamine receptors. 1979 British Pharmacological Society