Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 43-54). Also available via the Internet.

The aim of this study was to determine the contractile responses of normal virgin rat uterine smooth muscle to the ⍺₂ adrenergic agonist, xylazine HCl, in the presence or absence of the selective ⍺₂ adrenoceptor blocker, idazoxan HCl. Sections of full thickness uterus measuring 5 x 1 x 1 mm taken from mature, virgin Sprague-Dawley rats were used in isolated tissue baths containing 37°C Krebs-bicarbonate solution, and continually aerated with 95% O₂ and 5% CO₂. Following stabilization of spontaneous contractions, the tissues were exposed to either no idazoxan (control), 10⁻⁵ M idazoxan (low), 10⁻⁴ M idazoxan (medium), or 10⁻³ M idazoxan (high). Five minutes later, xylazine was added to all baths in a cumulative manner at quarter log increments from 1 x 10⁻⁵ through 1 x 10⁻³ M. The % response in peak developed tension and effective concentration resulting in a 50% response (EC₅₀) for the four treatment groups were examined. Results indicated that xylazine alone, at a concentrations greater than 1 x 10⁻⁴ M, caused a significant negative inotropic response. Pre-treatment with idazoxan at a concentration greater than 10⁻⁴ M enhanced the negative inotropic effect of xylazine in a dose-dependent manner. The mechanism of this synergism is unknown but is proposed to be a local anesthetic action due to sodium channel blockade. / Master of Science