CENTRAL CARDIOVASCULAR AND ANTI-DIURETIC ACTION OF ADRENERGIC-DRUGS

Central noradrenergic mechanisms are reportedly involved in blood pressure and fluid balance regulating mechanisms. The results of the present experiments suggest that, in unanaesthetized water-loaded rats. intracranial injections of norepinephrine and tyramine will produce presser and antidiuretic effects by the release of antidiuretic hormone (ADH). These responses are blocked by central α-adrenergic blockade but not by peripheral ganglionic blockade with hexamelhonium. Longer latency depressor responses were also seen with α-adrenergic stimulation. Central injections of clonidine, an α-adrenergic agonist, produced depressor effects, but no antidiuresis. Clonidine also inhibited the antidiuretic effects of central angiotensin II stimulation. These results suggest that central α-adrenergic stimulation can produce pressor and depressor effects. ADH release or inhibition of that release. These seemingly conflicting effects may be resolved by pharmocological characterization of central α-adrenergic receptors or isolation of separate sites of action within the brain. © 1979.