Hypothalamic paraventricular nucleus non‐NMDA receptors mediate the pressor response to noradrenaline microinjected into the bed nucleus of the stria terminalis of unanesthetized rats.

Abstract

Noradrenaline microinjected into the bed nucleus of the stria terminalis (BST) evoke pressor response, which is mediated by acute systemic vasopressin release. Hypothalamic paraventricular nucleus (PVN), but not the supraoptic nucleus, mediates this pressor response. Thus, the aim of the present work was to evaluate the involvement of PVN‐glutamatergic neurotransmission on the pressor response to noradrenaline microinjected into the BST of unanesthetized rat. For this, male Wistar rats had guide cannulas implanted in the BST and ipsilaterally in the PVN. Catheters was implanted in the femoral artery for mean arterial pressure (MAP) and heart rate (HR) recording. PVN pretreatment with the selective NMDA glutamatergic receptor antagonist LY235959 did not affect the pressor (30±4 vs 31±2 mmHg; p>0.05) and bradycardiac (‐35±6 vs‐37±2 bpm; p>0.05) responses to noradrenaline microinjected into the BST. However, when the selective non‐NMDA glutamatergic receptor antagonist NBQX was microinjected into the PVN the pressor (31±3 vs 8±2 mmHg; p<0.001) and bradycardiac (‐36±5 vs ‐8±1 bpm; p<0.003) responses were significantly reduced. Thus, our results suggest that PVN non‐NMDA receptors mediate the pressor response to noradrenaline microinjected into the BST.