Effects of drugs and ionic variations on contractions of rat smooth muscles

Abstract

Chemical agents, Acetycholine (5.0 x 10^-9M - 4.0 x 10^-8M), Noradrenaline (6.6 x 10^-5M - 5.2 x 10^-4M) and Potassium (25mM, 50mM) which stimulate different receptor populations in smooth muscle contractions and their ionic channel properties have been examined in different isolated preparations of Rat ileum (RI), Rat Stomach Strip (RSS), and Rat Vas Deferens (RVD) using known Ca²⁺ channel and specific receptor blockers. Atropine and Phentolamine respectively blocked Ach and NA competitively. While effect on K⁺- induced contraction was unaffected. The Rat ileum and Rat Stomach Strip has more pool of intracellular Ca²⁺ store than the RVD because in Ca²⁺-free medium, contraction declined markedly. The Vas Deferens showed unstable contraction in depolarised medium. The result of this suggests that as membrane depolarisation increases contraction in Rat Vas Deferens smooth muscle declined, while Verapamil and Nifedipine were more sensitive in blocking K⁺ than Ach and NA induced contractions.

Keywords: Smooth muscle, Ileum, Stomach strip, Vas deferens, Contractions, Rat.