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Vasopressin induced rhythmic activity in rat basilar artery
Authors:Nancy J. Rusch  Kent Hermsmeyer
Affiliation:(1) Department of Pharmacology The Cardiovascular Center, University of Iowa, 52242 Iowa City, Iowa
Abstract:The effects of vasopressin on membrane potential and tension were studied in isolated segments of basilar arteries from the University of Iowa colonies of normotensive inbred Kyoto-Wistar rats (WKY) and stroke-prone spontaneously hypertensive rats (SP-SHR). In the presence of vasopressin (0.01–0.3 IU/ml), basilar arteries from WKY, but not from SP-SHR, developed rhythmic contractions. These contractions were recorded in 13 of 14 WKY basilar arteries, were unaffected by pretreatment with 6-hydroxydopamine, and were characterized by 20–100 dyne oscillations in tension, occurring 1–3 cycles/min, and superimposed on the vasopressin-induced contraction (averaging 60 dynes at 0.01 IU/ml or 160 dynes at 0.3 IU/ml). However, resting membrane potentials were not different in SP-SHR vs. WKY at 37°C, and both strains showed about the same (11 mV) depolarization by 0.1 IU/ml of vasopressin. The rhythmic contractions were enhanced by K+-free solution, and abolished in the presence of high K+ solution (30 mM), suggesting that active Na+−K+ transport may be involved in modulating the rhythmic activity. These findings are consistent with the hypothesis that the vasopressin-induced rhythmic contractions in WKY basilar arteries are at least partly dependent on a reduced activity of electrogenic Na+−K+ active transport in WKY as compared to SP-SHR. This research was supported by Grant Nos. HL14388 and HL16328 from the National Institutes of Health. Dr. Rusch is the recipient of Postdoctoral Fellowship HL06907.
Keywords:ADH  Oscillating tension  Vascular muscle  Cerebral artery  Membrane potential  Electrogenic Na+ pump
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