Abstract
Hypovolemia induced by hemorrhage is a common clinical complication, which stimulates vasopressin (AVP) secretion by the neurohypophysis in order to retain body water and maintain blood pressure. To evaluate the role of brain L-glutamate and angiotensin II on AVP secretion induced by hypovolemia we induced hemorrhage (∼25% of blood volume) after intracerebroventricular (icv) administration of AP5, NBQX, or losartan, which are NMDA, AMPA, and AT1 receptor antagonists, respectively. Hemorrhage significantly increased plasma AVP levels in all groups. The icv injection of AP5 did not change AVP secretion in response to hemorrhage. Conversely, icv administration of both NBQX and losartan significantly decreased plasma AVP levels after hemorrhage. Therefore, the blockade of AMPA and AT1 receptors impaired AVP secretion in response to hemorrhage, suggesting that L-glutamate and angiotensin II acted in these receptors to increase AVP secretion in response to hemorrhage-induced hypovolemia.
Highlights
Hemorrhage is common in clinical settings and can have several causes such as injuries, diseases, surgeries, childbirth, gastrointestinal pathologies, among others (1)
Hemorrhage significantly increased plasma arginine vasopressin (AVP) (F(1,48)=23.73, Po0.001) while icv administration of AP5 did not change AVP plasma levels (F(2,48)=0.54, P=0.59), with no interaction between the two factors (F(2,48)=0.48, P=0.62), suggesting that the N-methyl-D-aspartic acid (NMDA) receptors were not involved in the AVP secretion in response to hemorrhage (Figure 1)
The post hoc analysis showed that losartan administration did not significantly change plasma AVP secretion in control rats; hemorrhage-induced AVP secretion was abolished in rats submitted to previous icv losartan administration (Po0.001) (Figure 3)
Summary
Hemorrhage is common in clinical settings and can have several causes such as injuries, diseases, surgeries, childbirth, gastrointestinal pathologies, among others (1). The present study aimed to evaluate the participation of L-glutamate AMPA and NMDA receptors and ANG II AT1 receptors in the brain on hemorrhage-induced AVP secretion.
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