PERINUCLEAR ZONE AND DIAGONAL BAND LESIONS ENHANCE ANGIOTENSIN RESPONSES OF RAT SUPRAOPTIC NEURONS

Sinoaortic denervation in the rat is associated with an increased sensitivity of vasopressin neurons in the supraoptic nucleus (SON) to peripheral angiotensin II (ANG II). Lesion studies have indicated that the diagonal band of Broca (DBB) and the perinuclear zone of the SON in the lateral hypothalamus (PNZ) are essential components in the central pathway for the baroreceptor inhibition of vasopressin SON neurons. The present study examined the effect of ibotenate lesions in either the DBB or the lateral hypothalamus, which includes the PNZ, on the responses of SON neurons to peripherally administered ANG II (500 pmol/kg ia). Extracellular recordings obtained from vasopressin SON neurons in pentobarbital-anesthetized rats indicate that DBB and PNZ lesions not only interrupted the baroreceptor-mediated inhibition of SON neurons but also significantly increased the excitatory effects of ANG II on putative vasopressin SON neurons. These results suggest that ibotenate lesions of the DBB and the lateral hypothalamus that include the PNZ affect the ANG II-induced activation of putative vasopressin SON neurons in a manner consistent with results obtained from baroreceptor-denervated rats.