EFFECTS OF LEAF EXTRACT OF CAESALPINIA BONDUC (CAESALPINIACEAE) ON THE CONTRACTILE ACTIVITY OF UTERINE SMOOTH-MUSCLE OF PREGNANT RATS

The calcium dependency and the cholinergic effect of the leaf extract of Caesalpinia bonduc Roxb. (Caesalpiniaceae) was studied in isolated pregnant rat myometrium preparations. Isometric contractions were reco rded. The extract (Cebo) increased the contractile force in the isolat ed strips in a concentration-dependent manner. The effects were compar able to those obtained with acetylcholine. Contractions induced by Ceb o or acetylcholine were inhibited in the presence of atropine. The sti mulating action of Cebo on the contractile responses of isolated myome trium preparations inhibited by atropine may be mediated by cholinergi c receptors. In calcium-free solution Cebo induced a tonic contraction (contracture) of the muscle. Moreover, in high-potassium calcium-free solution Cebo caused contracture of the uterine smooth muscle. Cebo w as still able to elicit contractions in calcium-free solution containi ng EDTA or EGTA. These findings suggest the existence of cholinergic r eceptors sensitive to Cebo which could influence the influx of calcium (phasic contraction) and mobilization of calcium from cellular stores (tonic contraction), both of which are responsible for the increase o f contractile activity and development of the contracture of uterine s mooth muscle. (C) 1998 Elsevier Science Ireland Ltd. All rights reserv ed.