title: Administration of AVP to the area postrema alters response of NTS neurons to afferent inputs.
abstract: This study was designed to determine if arginine vasopressin (AVP) facilitates the response of nucleus of the solitary tract (NTS) neurons to baroreceptor input. In anesthetized sinoaortic-denervated vagotomized rabbits, AVP was intravenously infused (15 microg x kg(-1) x min(-1), 1 min) or microinjected into the area postrema (AP; 1 ng/nl, 10 nl). Extracellular recordings of evoked NTS neuronal responses to electrical stimulation of the aortic depressor nerve (ADN) or vagus nerve (1 Hz, 2-20 V, 0.05-0.6 ms) were evaluated before and after AVP administration. In neurons receiving input from the ADN (n = 19), 58% of them increased their responses after AVP (40.3 +/- 5.0 to 71.5 +/- 4,8%, P < 0.001). Similarly, in neurons activated by vagal stimulation (n = 22), 55% of them were facilitated during AVP administration (59.7 +/- 12.8 to 90.8 +/- 10.7%, P < 0.01). This action of AVP was independent of the mode of AVP administration, since either microinjection or venous infusion was effective in augmenting responses of NTS neurons to aortic/vagal stimulation. In an additional 37 spontaneous NTS neurons, AVP showed no effect on the mean baseline firing rate (8.9 +/- 1.3 vs. 9.6 +/- 1.3 spikes/s, P > 0.05), but increased neuronal activity in 54% of neurons (6.9 +/- 1.3 vs. 13.1 +/- 1.7 spikes/s, P < 0.01). In two rabbits pretreated with vasopressin antagonist (15 microg/kg iv), AVP failed to produce facilitatory effects (n = 8). The results of this study provide evidence in support of the hypothesis that circulating peptides modulate the arterial baroreflex via activation of neurons in the AP.
authors.affiliation: Department of Physiology, The University of Texas Health Science Center at San Antonio, 78284-7756, USA.
authors.forename: L
authors.initials: L
authors.lastname: Qu
authors.forename: M
authors.initials: M
authors.lastname: Hay
authors.forename: V S
authors.initials: VS
authors.lastname: Bishop
mesh_terms: D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001127:Arginine Vasopressin / Q000008:administration & dosage / Q000494:pharmacology*; D002552:Cerebral Ventricles / Q000187:drug effects / Q000502:physiology*; D003714:Denervation; D005260:Female; D007262:Infusions, Intravenous; D008297:Male; D008845:Microinjections; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D012850:Sinus of Valsalva / Q000294:innervation; D017552:Solitary Nucleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology
chemical_list: D001127:Arginine Vasopressin