Facilitatory role of central dopamine in the osmotic release of vasopressin.

In conscious rats, intracerebroventricular (i.c.v.) injection of the dopamine antagonist haloperidol (0.15 mumol) blocked increases in plasma vasopressin (AVP) and arterial pressure caused by i.c.v. administration of a hypertonic solution (990 mOsm/kg, 10 microliters), without affecting plasma osmolality, electrolytes or hematocrit. The application of the alpha-adrenergic antagonist phenoxybenzamine (0.15 mumol), however, did not significantly inhibit the responses of plasma AVP and arterial pressure to the hypertonic solution. We concluded that brain dopamine may play a facilitatory role in the osmotically stimulated AVP secretion.