Angiotensin II receptor binding sites in the ventral portion of the bed nucleus of the stria terminalis are reduced by interruption of the medial forebrain bundle

Many techniques have been utilized to discern the localization of angiotensin II (Ang II) receptors to specific cellular components (glia, neuronal cell bodies and nerve terminals) in the brain. In the present study, we used lesioning techniques to localize Ang II receptors to cellular components in the rat forebrain. In the first experiment, axons ascending to the hypothalamus and forebrain from neurons in the brainstem were destroyed by unilaterally cutting the medial forebrain bundle (MFB). In the second experiment, a single injection of the neurotoxin, ibotenic acid, was injected unilaterally into the ventral portion of the bed nucleus of the stria terminalis (BSTV) to destroy neuronal cell bodies, thus determining if Ang II receptors are present on neuronal cell bodies. In both experiments, the animals were sacrificed after two weeks recovery and the brains processed for in vitro receptor autoradiography using ¹²⁵I-sar¹,ile⁸ Ang II (¹²⁵I- SI Ang II). Unilateral knife-cut lesions of the MFB caused a significant reduction in ¹²⁵I-SI Ang II binding in the BSTV (30 ± 6%) and the piriform cortex (PC; 26 ± 4%) ipsilateral to the knife cut. Unilateral injection of the neurotoxin into the BSTV failed to alter ¹²⁵I-SI Ang II binding in this nucleus. These experiments suggest that at least a subpopulation of Ang II receptors in the BSTV and PC are located on terminals of neurons that have their cell bodies in the brainstem and their axons in the MFB.