Chapter 59: Effect of arginine vasopressin on blood vessels of the perfused choroid plexus of the sheep

The perfused sheep choroid plexus was used to evaluate the response of the plexus blood vessels to systemically administered arginine vasopressin (AVP). AVP was found to decrease the diameter of the choroid plexus arterioles with a maximum change of 28 ± 5% (mean ± S.E.) at a plasma peptide concentration of 10 −7 M. This effect was blocked by the specific V 1 -vasopressinergic antagonist, d(CH 2 ) 5 Tyr(Me)AVP. In contrast, venules were found not to show any appreciable response to AVP. Plasma AVP concentrations necessary to evoke a significant response of the choroid plexus arterioles are much higher than the highest plasma peptide levels observed in different physiological or pathophysiological situations. Some indirect evidence suggests, however, that AVP might be released within the choroid plexus from the vasopressinergic synaptic terminals, thus reaching a considerably high local concentration. It is possible then that the plexus vessels' tone could be controlled by the putative vasopressinergic neuronal fibers ending in the choroid plexus.