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 115 μg · kg-1min-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 pg/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.
Original language | English (US) |
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Pages (from-to) | R519-R525 |
Journal | American Journal of Physiology - Regulatory Integrative and Comparative Physiology |
Volume | 272 |
Issue number | 2 41-2 |
DOIs | |
State | Published - 1997 |
Keywords
- aortic depressor nerve
- baroreflex
- medulla
- sympathetic nerve
ASJC Scopus subject areas
- Physiology
- Physiology (medical)