Hypothalamic action of adrenoreceptor blocking agents.

In cats anaesthetized with pentobarbital sodium, the posterior hypothalamus was superfused and electrically stimulated with a push-pull cannula. The pressor response to stimulation of this hypothalamic area was inhibited when the hypothalamus was superfused with drugs blocking either alpha-adrenoreceptors (piperoxan, tolazoline), or beta-adrenoreceptors--(+/-)-propranolol, (-)-propranolol, practolol, sotalol, metoprolol. (+)-Propranolol and a concentration of procaine equianaesthetic to propranolol were ineffective.

Inhibition by locally applied alpha-adrenoreceptor blocking drugs of the depressor response to stimulation of the anterior hypothalamus.

Cats were anaesthetized with pentobarbital sodium and the anterior hypothalamus was superfused with artificial cerebrospinal fluid through a push-pull cannula. Electrical stimulation of the superfused area with the tip of the cannula elicited a fall of the arterial blood pressure which was dependent on frequency and voltage. Maximal depressor response was obtained at 60 Hz with 2-4V; further increase of the voltage often led to a rise of the arterial blood pressure.