AJP - Regulatory, Integrative and Comparative Physiology, Vol 273, Issue 1 143-R152, Copyright © 1997 by American Physiological Society
Vasopressin and V1-receptor antagonists modulate the activity of NTS neurons receiving baroreceptor input
A. A. Hegarty and R. B. Felder
Cardiovascular Center, University of Iowa College of Medicine, Iowa City 52242, USA. ahegarty@blue.weeg.uiowa.edu
Arginine vasopressin (AVP) may act as a neurotransmitter or neuromodulator
in the solitary tract nucleus (NTS). To determine whether AVP influences
the activity of NTS neurons receiving cardiovascular afferent input, we
used single-unit extracellular recording combined with local microinjection
to test the effects of AVP and V1-receptor antagonists (antAVP) on
spontaneously active NTS neurons in anesthetized rats.
Phenylephrine-induced increases in arterial pressure were used to identify
neurons receiving baroreceptor input. Phenylbiguanide was used to stimulate
chemosensitive cardiopulmonary receptors. AVP excited 31 of 81 NTS neurons
tested and inhibited 15 of 81 neurons. AntAVP had independent effects on
NTS neurons: in addition to blocking the effects of AVP, antAVP inhibited
26 of 72 neurons but excited only 13. Eighty-two percent of NTS neurons
receiving excitatory or inhibitory baroreceptor inputs responded to AVP;
61% of these were excited by AVP. Fifty-eight percent of neurons receiving
cardiopulmonary receptor input responded to AVP. These results suggest that
AVP in rat NTS has a tonic, predominantly excitatory influence on a
significant proportion of baroreceptor-related neurons.
