1. Effects of several drugs (adrenergic, cholinergic & prostaglandins) and field stimulation on the isolated rat uterus were investigated in estrus and nonestrus (di-and proestrus) stage. Regular and potent spontaneous motilities were observed in the npnestrus, while irregular and weak spontaneous motilities were observed in the estrus.
2. Acetylcholine and methacholine contracted all uterus and the contraction was inhibited by atropine.
3. The responses of the nonestrus to norepinephrine (NE) and methoxamine (ME), al -adrenoceptor agonists, differed from preparation to preparation. Some showed coiltraction, while others showed inhibition. The contractile responses were reduced by thymoxamine and phentolamine but not affected by yohimbine, an a2-adrenoceptor antagonist. The inhibitory responses were antagonized by propranolol.
4. The responses of the estrus to NE and ME and were inhibitory. Isoproterenol (ISP) inhibited the motility in both stages. These inhibitions including the inhibition by NE and ME were all decreased in the presence of propranolol. Clonidine, a2-adren oceptor agonist, did not cause any responses.
5. Transient contractile responses were caused by field stimulation in all preparations. The contraction was markedly inhibited by tetrodotoxin, atropine and indomethacin, and increased by physostigmine and PGF2a. The contraction, however, was not affected by clonidine, yohimbine,, and thymoxamine.
6. The above results suggest that excitatory a1-adrenoceptors and inhibitory (3adrenoceptors exist in the uterus, and that endogenous ACh and prostaglandins seem to participate in the contractile response to field stimulation.
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