NK1-receptor-expressing paraventricular nucleus neurones modulate daily variation in heart rate and stress-induced changes in heart rate variability

Abstract

The paraventricular nucleus of the hypothalamus (PVN) is an established center of cardiovascular control, receiving projections from other nuclei of the hypothalamus such as the dorsomedial hypothalamus and the suprachiasmatic nucleus. The PVN contains a population of “pre‐autonomic neurones” which project to the intermediolateralis of the spinal cord and increase sympathetic activity, blood pressure, and heart rate. These spinally projecting neurones express a number of membrane receptors including GABA and substance P NK1 receptors. Activation of NK1‐expressing neurones increases heart rate, blood pressure, and sympathetic activity. However, their role in the pattern of overall cardiovascular control remains unknown. In this work, we use specific saporin lesion of NK1‐expressing PVN rat neurones with SSP‐SAP and telemetrically measure resting heart rate and heart rate variability (HRV) parameters in response to mild psychological stress. The HRV parameter “low frequency/high frequency ratio” is often used as an indicator of sympathetic activity and is significantly increased with psychological stress in control rats (0.84 ± 0.14 to 2.02 ± 0.15; P < 0.001; n = 3). We find the stress‐induced increase in this parameter to be blunted in the SSP‐SAP‐lesioned rats (0.83 ± 0.09 to 0.93 ± 0.21; P > 0.05; n = 3). We also find a shift in daily variation of heart rate rhythm and conclude that NK1‐expressing PVN neurones are involved with coupling of the cardiovascular system to daily heart rate variation and the sympathetic response to psychological stress.

Antagonism of the Neurokinin-1 Receptor Improves Survival in a Mouse Model of Sepsis by Decreasing Inflammation and Increasing Early Cardiovascular Function

“…Neurons within the paraventricular nucleus express NK-1R which modulate stress induced changes in heart rate [33]. In our studies, treatment with the NK-1RA did not alter the heart rate (Fig 6C).…”

Diurnal, seasonal, and sex patterns of heart rate in grip-restrained African giant rats (Cricetomys gambianus, Waterhouse)

“…It was also not feasible with the methodology used in the present study to obtain reasonable values for the time between heart beats in order to deduce HR variability (HRV) in the AGRs. The HRV parameter, which is often used to complement HR as an indicator of autonomic activity (Acharya et al 2006), was shown in some rodents to be significantly increased/higher (lower sympathetic/ higher parasympathetic activity) during summer (Weil et al 2009), in females (Johnson et al 2011), during the "inactive period" of the day (Albarwani et al 2013), and with mild psychological stress (Feetham and Barrett-Jolley 2014). It is conceivable that the HRV in AGRs may be elevated/higher during the rainy season, in does, during the afternoon (since AGRs are nocturnal), and in freemoving, unrestrained rats.…”

“…The HR, which is an indicator of cardiovascular activity, is defined as the rate of heart beat, expressed in beats per minute (bpm). Although the paraventricular nucleus in the hypothalamus is an established center of cardiovascular control in rats (Feetham and Barrett‐Jolley ), the HR may be altered rapidly due to inputs from environmental cues (zeitgebers), such as ambient temperature and photoperiod, psychosocial factors like housing, or due to intense activity, including feeding, by the animal (van den Buuse ; Swoap et al. ; Azar et al.…”

“…The HR, which is an indicator of cardiovascular activity, is defined as the rate of heart beat, expressed in beats per minute (bpm). Although the paraventricular nucleus in the hypothalamus is an established center of cardiovascular control in rats (Feetham and Barrett-Jolley 2014), the HR may be altered rapidly due to inputs from environmental cues (zeitge-bers), such as ambient temperature and photoperiod, psychosocial factors like housing, or due to intense activity, including feeding, by the animal (van den Buuse 1999; Swoap et al 2004;Azar et al 2011;Carnevali and Sgoifo 2014). A modest diurnal rhythm of resting HR was described in some rodents, including rats (Sei et al 1997) and mice (Sei et al 2008), which was independent of locomotor activity (Sheward et al 2010); and the rhythm of activity itself was modulated mainly by photoperiod and ambient temperature, and to a lesser degree by food availability (Refinetti 2015).…”

The autonomic regulation of heart rate in young individuals with visual dysfunctions

“…In simplified form, non-circadian physiological effects of light on the autonomic regulation of heart rate realized through polysynaptic excitation glutamate-ergic projection from the retina to (1) the "pre-autonomic" [7] hypothalamic neurons that affect the autonomic centers of the brain stem and spinal cord, as well as (2) neuroendocrine hypothalamic centers responsible for the hormones secretion [5]. The first pathway is associated with projections from the suprahiazmatic nucleus to the parvocellular GABA-ergic neurons of paraventricular nucleus in hypothalamus.…”