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Interaction of Orexin A and Vasopressin in the Brain Plays a Role in Blood Pressure Regulation in WKY and SHR Rats

Stanisław Kowalewski, Katarzyna Czarzasta, Liana Puchalska, Ewa Szczepańska-Sadowska, Agnieszka Wsol, Agnieszka Cudnoch-Jędrzejewska

Department of Experimental and Clinical Physiology, Laboratory of the Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland

Med Sci Monit 2020; 26:e926825

DOI: 10.12659/MSM.926825

Available online: 2020-08-25

Published: 2020-10-13

BACKGROUND: Orexin A (OXA) and vasopressin (AVP) exert a central hypertensive effect due to an increase in sympathetic nerve activity. To date, little is known about the interaction of these 2 neuropeptides in the central regulation of blood pressure. The present study compared the consequences of infusion into the left cerebral ventricle (ICV) of OXA on mean arterial blood pressure (MABP) in normotensive (WKY) and spontaneously hypertensive (SHR) rats, and explored whether the central pressor action of OXA in these 2 strains depends on activation of brain AVP V1a receptors (V1aR).
MATERIAL AND METHODS: Ten groups of experiments were performed on 12-week-old WKY and SHR rats implanted with ICV cannulas for infusion of OXA (3 nmol) and V1aR antagonist (V1aRANT, 500 ng), administered separately and together. Levels of V1aR and OXR in the medulla oblongata of WKY and SHR rats were compared in separate series.
RESULTS: We found that: 1) OXA significantly increased MABP only in WKY rats, 2) V1aRANT prevented an increase in MABP induced by OXA in WKY rats and decreased MABP in SHR rats, 3) OXA abolished the hypotensive action of V1aRANT in SHR rats, and 4) SHR rats had significantly higher levels of OX1R and V1aR proteins and OX1R mRNA in the brain medulla.
CONCLUSIONS: The present study shows that OXA and AVP can interact in the brain to affect blood pressure regulation, and that this interaction differs in normotension and hypertension.

Keywords: arterial pressure, orexin receptors, Rats, Inbred SHR, Rats, Inbred WKY, Receptors, Vasopressin