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Apelin is a ubiquitous peptide that can elevate arterial blood pressure (ABP) yet understanding of the mechanisms involved remain incomplete. Bilateral microinjection of [Pyr1]apelin-13 into the rostral ventrolateral medulla (RVLM), a major source of sympathoexcitatory neurones, increases ABP and sympathetic nerve activity. We sought to investigate the potential involvement of neurotransmitter systems through which the apelin pressor response may occur within the RVLM. Adult male Wistar rats were anaesthetised and ABP was monitored via a femoral arterial catheter. Bilateral RVLM microinjection of [Pyr1]apelin-13 significantly increased ABP (9±1mmHg) compared to saline (-1±2mmHg; P<0.001) which was blocked by pretreatment with the apelin receptor antagonist, F13A (0±1mmHg; P<0.01). The rise in ABP was associated with an increase in the low frequency spectra of systolic BP (LFSBP) (13.9±4.3 % total power; P<0.001), indicative of sympathetic vasomotor activation. The [Pyr1]apelin-13-mediated pressor response and the increased LFSBP response were fully maintained despite RVLM pretreatment with the angiotensin (ANG) II type 1 receptor (AT1) antagonist losartan, the oxytocin (OT) receptor antagonist dOVT, the ionotropic glutamate receptor antagonist kynurenate or the GABAA antagonist bicuculline (P>0.05). In contrast, the [Pyr1]apelin-13 induced pressor and sympathoexcitatory effects were abolished by pretreatment of the RVLM with the vasopressin (VP) V1a receptor antagonist, SR 49059 (-1±1mmHg; 1.1±1.1 % total power respectively; P<0.001). These findings suggest that the pressor action of [Pyr1]apelin-13 in the RVLM of normotensive rats is not mediated via AT1, OT, ionotropic glutamate or GABAA receptors but involves a close relationship with the neuropeptide modulator VP.
- blood pressure
- Sympathetic Nervous System
Griffiths, P., Lolait, S., Harris, L., Paton, J., & O'Carroll, A-M. (2017). Vasopressin V1a receptors mediate the hypertensive effects of [Pyr1]apelin-13 in the rat rostral ventrolateral medulla. Journal of Physiology, 595(11), 3303-3318. https://doi.org/10.1113/JP274178