title: Baroreceptor-mediated activation of sympathetic nerve activity to salivary glands.
abstract: Salivary gland function is regulated by both the sympathetic and parasympathetic nervous systems. Previously we showed that the basal sympathetic outflow to the salivary glands (SNA(SG)) was higher in hypertensive compared to normotensive rats and that diabetes reduced SNA(SG) discharge at both strains. In the present study we sought to investigate how SNA(SG) might be modulated by acute changes in the arterial pressure and whether baroreceptors play a functional role upon this modulation. To this end, we measured blood pressure and SNA(SG) discharge in Wistar-Kyoto rats (WKY-intact) and in WKY submitted to sinoaortic denervation (WKY-SAD). We made the following three major observations: (i) in WKY-intact rats, baroreceptor loading in response to intravenous infusion of the phenylephrine evoked an increase in SNA(SG) spike frequency (81%, p<0.01) accompanying the increase mean arterial pressure (ΔMAP: +77 ± 14 mmHg); (ii) baroreceptor unloading with sodium nitroprusside infusion elicited a decrease in SNA(SG) spike frequency (17%, p<0.01) in parallel with the fall in arterial blood pressure (ΔMAP: -30 ± 3 mmHg) in WKY-intact rats; iii) in the WKY-SAD rats, phenylephrine-evoked rises in the arterial pressure (ΔMAP: +56 ± 6 mmHg) failed to produce significant changes in the SNA(SG) spike frequency. Taken together, these data show that SNA(SG) increases in parallel with pharmacological-induced pressor response in a baroreceptor dependent way in anaesthetised rats. Considering the key role of SNA(SG) in salivary secretion, this mechanism, which differs from the classic cardiac baroreflex feedback loop, strongly suggests that baroreceptor signalling plays a decisive role in the regulation of salivary gland function.
authors.affiliation: Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil. robinsonsabino@gmail.com
authors.forename: Robinson
authors.initials: R
authors.lastname: Sabino-Silva
authors.forename: Alexandre
authors.initials: A
authors.lastname: Ceroni
authors.forename: Tadachika
authors.initials: T
authors.lastname: Koganezawa
authors.forename: Lisete C
authors.initials: LC
authors.lastname: Michelini
authors.forename: Ubiratan F
authors.initials: UF
authors.lastname: Machado
authors.forename: Vagner R
authors.initials: VR
authors.lastname: Antunes
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology*; D018686:Anesthetics, Intravenous / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D003714:Denervation / Q000379:methods; D006339:Heart Rate / Q000187:drug effects; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011921:Rats, Inbred WKY; D012469:Salivary Glands / Q000187:drug effects / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000293:injuries / Q000502:physiology*; D013566:Sympathomimetics / Q000494:pharmacology; D014520:Urethane / Q000494:pharmacology
chemical_list: D018686:Anesthetics, Intravenous; D000959:Antihypertensive Agents; D013566:Sympathomimetics; D009599:Nitroprusside; D010656:Phenylephrine; D014520:Urethane