Overexpression of oxytocin receptors in the hypothalamic PVN increases baroreceptor reflex sensitivity and buffers BP variability in conscious rats

Abstract

Experiments were performed in conscious male Wistar rats equipped with a radiotelemetric device. The PVN was unilaterally co-transfected with an adenoviral vector (Ad), engineered to overexpress OT receptors, and an enhanced green fluorescent protein (eGFP) tag. Control groups: PVN was transfected with an Ad expressing eGFP alone or untransfected, sham rats (Wt). Recordings were obtained without and with selective blockade of OT receptors (OTX), during both baseline and stressful conditions. Baroreceptor reflex sensitivity (BRS) and cardiovascular short-term variability were evaluated using the sequence method and spectral methodology respectively. KEY RESULTSUnder baseline conditions, rats overexpressing OT receptors (OTR) exhibited enhanced BRS and reduced BP variability compared to control groups. Exposure to stress increased BP, BP variability and HR in all rats. In control groups, but not in OTR rats, BRS decreased during stress. Pretreatment of OTR rats with OTX reduced BRS and enhanced BP and HR variability under baseline and stressful conditions. Pretreatment of Wt rats with OTX, reduced BRS and increased BP variability under baseline and stressful conditions, but only increased HR variability during stress. CONCLUSIONS AND IMPLICATIONSOT receptors in PVN are involved in tonic neural control of BRS and cardiovascular short-term variability. The failure of this mechanism could critically contribute to the loss of autonomic control in cardiovascular disease.

Vasopressin V1a receptors mediate the hypertensive effects of [Pyr1]apelin‐13 in the rat rostral ventrolateral medulla

“…Spectral analysis of heart rate variability (HRV) and systolic blood pressure variability (SBPV) allows the calculation of power in the very low frequency (VLF: 0-0.3 Hz), low frequency (LF: 0.3-0.8 Hz) and high frequency (HF: 0.8-3.3 Hz) bands (Japundzic-Zigon 1998; Parati et al 1995). It is known that LF:HF-HRV and LF-SBPV can be used as indicative measures of cardiac and vasomotor sympathetic tone, respectively (Lozić et al 2014;Abdala et al 2012); however, we have acknowledged that spectral analysis is an indirect measure of global change in sympathetic activity. Analysis of systolic blood pressure and heart rate was performed using the HRV1 script for Spike 2 to calculate power in the VLF (0-0.3 Hz), LF (0.3-0.8 Hz) and HF (0.8-3.3 Hz) bands of across a 500 s period, including time points before and after microinjection of each drug.…”

“…It is known that LF:HF‐HRV and LF‐SBPV can be used as indicative measures of cardiac and vasomotor sympathetic tone, respectively (Lozić et al . ; Abdala et al . ); however, we have acknowledged that spectral analysis is an indirect measure of global change in sympathetic activity.…”

Maternal Separation Induces Long-Term Alterations in the Cardiac Oxytocin Receptor and Cystathionine γ-Lyase Expression in Mice

“…In view of a possible reciprocal regulation between the Oxtr and CSE systems and the fact that mice lacking CSE show reduced endothelialmediated vasorelaxation [45], this provides further evidence for a crucial role of Oxtr in blood pressure regulation. This view is further supported by the fact that Oxtr activation enhances baroreceptor sensitivity and, thus, enhances the capacity of blood pressure control [46,47]. Finally, in ovariectomized spontaneously hypertensive rats, Oxtr blockade causes adverse cardiac remodeling [48] and monocrotalineinduced pulmonary hypertension leads to right ventricular Oxtr downregulation [49].…”

Sudden death: Neurogenic causes, prediction and prevention

“… 58 Their role is to prime magnocellular neurons and also to integrate the activity of neurons located in the magnocellular and the parvocellular parts of the PVN, 59 involved respectively in humoral and autonomic neural control of the circulation. 60 Lozić and colleagues 61 , 62 have demonstrated that upregulation of vasopressin V 1A and OT receptors in PVN modulates autonomic control of the cardiovascular system and changes the vulnerability of the rat phenotype to stress, thus pointing to possible targets for new drug development in cardioprotection from neurocardiogenic injuries.…”