CNS PATHWAYS MEDIATING CARDIOVASCULAR REGULATION OF VASOPRESSIN

1. The release of vasopressin from the neurohypophysial terminals of h ypothalamic magnocellular neurosecretory neurons is subject to regulat ion by peripheral baroreceptors, cardiopulmonary volume receptors and circulating angiotensin II, Information from these sources is transmit ted through different pathways to achieve different influences on the excitability of the vasopressin-secreting cells. 2, A brief increase i n arterial pressure, sufficient to activate baroreceptors, is associat ed with a transient and selective GABAergic inhibition of these neuros ecretory neurons, achieved through a multisynaptic pathway that involv es ascending catecholaminergic fibres and neurons in the diagonal band of Broca, A decrease in arterial pressure activates peripheral low vo lume receptors and initiating neural inputs that result in an increase in the excitability of vasopressin-secreting neurons, achieved via pa thways that include direct projections from caudal ventrolateral medul la Al neurons, 3, Hypotension also releases renal renin and leads to t he formation of angiotensin II; binding of this hormone to AT(1) recep tors on subfornical organ neurons promotes activation of a central ang iotensinergic input that evokes a predominantly excitatory effect on v asopressin neurons.