A Glutamatergic Neurotransmission in Paraventricular Nucleus of the Hypothalamus Modulates Cardiovascular Responses and Vasopressin Release Evoked By Osmotic Stimulus in Conscious Rats

Presentation Number: LB SUN 67
Date of Presentation: April 2nd, 2017

Eduardo Albino Trindade Fortaleza*1, Cristiane Busnardo2, Aline Fassini2, Jose Antunes-Rodrigues3 and Fernando Morgan de Aguiar Correa2
1School of Medicine of Ribeirão Preto, Ribeirão Preto, BRAZIL, 2School of Medicine of Ribeirão Preto, Ribeirão Preto, Brazil, 3School of Medicine of Ribeirao Preto, University of Sao Paulo, Ribeirao Preto, Brazil

Abstract

A Glutamatergic Neurotransmission in paraventricular nucleus of the hypothalamus modulates cardiovascular responses and vasopressin release evoked by osmotic stimulus in conscious rats. Fortaleza, E.A.T.; Busnardo, C.; Fassini, A.; Antunes-Rodrigues J.; Corrêa, F.M.A. Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil.

Introduction and aim: The paraventricular nucleus of the hypothalamus (PVN) contains magnocellular cells that release vasopressin (AVP) and oxytocin (OT), which are involved in osmoregulation and cardiovascular control. The Osmotic stimulus (OS) evokes cardiovascular changes, as well as AVP and OT release. Therefore, the aim of the present study was to investigate the effects of bilateral microinjections of selective NMDA-receptor antagonist (LY235959) or a selective non-NMDA receptor antagonist (NBQX) in the PVN on the cardiovascular responses, as well as AVP and OT release, evoked by OS in conscious rats. Methods: We used Wistar rats. Guide cannulas were implanted into the PVN. A catheter was implanted into the femoral artery for blood pressure recording. The OS used was i.p. injection of hypertonic saline (0.6M NaCl). Blood samples were collected for AVP and OT measurements by radioimmunoassay. Results: Cardiovascular changes evoked by osmotic stimulus - Two-way ANOVA indicated a significant effect of LY235959 (n=7) on OS-induced MAP responses (F1.78= 7.85, P = 0.006), without significant effect on HR (F1.78= 1.75, P = 0.18) when compared with aCSF-treated animals (n=8). Two-way ANOVA indicated a significant effect of NBQX (n=8) on OS-induced MAP responses (F1.90= 12.94, P = 0.0005), without effect on HR (F1.90= 0.88, P = 0.34) when compared with aCSF-treated animals (n=9). Changes in AVP levels evoked by osmotic stimulus - Two-way ANOVA indicated a significant effect of LY235959 (n=15) on OS-induced AVP levels (F5,37=5.35, P<0.05) when compared with aCSF-treated animals (n=28) at times 5, 15 and 30min after the OS. Two-way ANOVA indicated a significant effect of NBQX (n=16) on OS-induced AVP levels (F5,38=4.09, P<0.05) when compared with aCSF-treated animals (n=28) at times 5, 15, 30 min after the OS. Changes in OT levels evoked by osmotic stimulus - Two-way ANOVA indicated a significant effect of LY235959 (n=15) on OS-induced AVP levels (F5,37=10.37, P<0.05) when compared with aCSF-treated animals (n=28) at times 5, 15 and 30min after the OS. Two-way ANOVA indicated a significant effect of NBQX (n=16) on OS-induced AVP levels (F5,38=7.62, P<0.05) when compared with aCSF-treated animals (n=28) at times 5, 15, 30 min after the OS. Conclusion: Our results suggest a facilitatory influence of NMDA and non-NMDA - receptors from the PVN on the vascular component of OS-evoked cardiovascular changes, as well as on the AVP and OT release evoked by OS.

Financial Support: FAPESP 2012/18556-2.

 

Nothing to Disclose: EATF, CB, AF, JA, FMDAC