Nesfatin‐1 activates cardiac vagal neurons of nucleus ambiguus and elicits bradycardia in conscious rats

Abstract

Nesfatin-1, a peptide whose receptor is yet to be identified, has been involved in the modulation of feeding, stress and metabolic responses. More recently, increasing evidence supports a modulatory role for nesfatin-1 in autonomic and cardiovascular activity. This study was undertaken to test if the expression of nesfatin-1 in the nucleus ambiguus, a key site for parasympathetic cardiac control, may be correlated with a functional role. Since we have previously demonstrated that nesfatin-1 elicits Ca2+ signaling in hypothalamic neurons, we first assessed the effect of this peptide on cytosolic Ca2+ in cardiac preganglionic neurons of nucleus ambiguus. We provide evidence that nesfatin-1 increases cytosolic Ca2+ concentration via a Gi/o-coupled mechanism. The nesfatin-1-induced Ca2+ rise is critically dependent on Ca2+ influx via P/Q-type voltage-activated Ca2+ channels. Repeated administration of nesfatin-1 leads to tachyphylaxis. Further, nesfatin produces a dose-dependent depolarization of cardiac vagal neurons via a Gi/o-coupled mechanism. In vivo studies, using telemetric and tail-cuff monitoring of heart rate and blood pressure, indicate that microinjection of nesfatin-1 into the nucleus ambiguus produces bradycardia not accompanied by a change in blood pressure in conscious rats. Taken together, our results identify for the first time that nesfatin-1 decreases heart rate by activating cardiac vagal neurons of nucleus ambiguus.

Nesfatin-1: functions and physiology of a novel regulatory peptide

“…Both neuronal depolarization (Brailoiu et al 2013) as well as the increase in intracellular Ca 2+ (Brailoiu et al 2007, Ozcan et al 2016 were prevented by pretreatment with pertussis toxin, indicating the involvement of a G i -protein-coupled receptor. Accordingly, no increase 232:1 in cyclic adenosine monophosphate (cAMP) formation was observed (Ishida et al 2012).…”

“…Local injection of nesfatin-1 into the median NTS increased both blood pressure and heart rate (Mimee et al 2012). In contrast, site-specific injection into the nucleus ambiguus, a key site for parasympathetic cardiac control (Mendelowitz 1999), induced bradycardia, although MAP was not affected (Brailoiu et al 2013). The existence of NUCB2/nesfatin-1 immunoreactivity in this nucleus in rodents implies a physiological function of the peptide.…”

“…As a universal principle, in most cell types, nesfatin-1 stimulates Ca 2+ influx either through L- (Brailoiu et al 2007, Nakata et al 2011, Ishida et al 2012, P/Q- (Brailoiu et al 2007(Brailoiu et al , 2013 or N- (Iwasaki et al 2009) type Ca 2+ channels. Both neuronal depolarization (Brailoiu et al 2013) as well as the increase in intracellular Ca 2+ (Brailoiu et al 2007, Ozcan et al 2016 were prevented by pretreatment with pertussis toxin, indicating the involvement of a G i -protein-coupled receptor.…”

HIV-1-Tat excites cardiac parasympathetic neurons of nucleus ambiguus and triggers prolonged bradycardia in conscious rats

“…Preganglionic cardiac vagal neurons of nucleus ambiguus were retrogradely labeled by intrapericardial injection of rhodamine [X-rhodamine-5-(and-6)-isothiocyanate; 5(6)-XRITC], 40 l, 0.01% (Invitrogen, Carlsbad, CA), as reported by Brailoiu et al (8,9,12). Medullary neurons were dissociated and cultured 24 h after rhodamine injection, as previously described (8,9,12).…”

“…Measurements of intracellular Ca 2ϩ concentration, [Ca 2ϩ ]i were performed as previously described (8,9,12). Briefly, cells were incubated with 5 M Fura-2 AM (Invitrogen) in HBSS at room temperature for 45 min and washed with dye-free HBSS.…”