[Desensitization of the isolated rat myometrium to biologically active substances].

The isometric contractile activity of longitudinal myometrial strips of nonpregnant rats (oestrus phase) initiated by acetylcholine, oxitocine and serotonine gradually diminished during continuous and prolonged perfusion with the biologically active substances. The decrease in the contractile activity was due to a loss of sensitivity of the myometrium cells in respect to the substances, which may be regarded as desensitization. The myometrium contractile activity was more stable during intermittent perfusion. The findings suggest that desensitization is a general biological phenomenon only developing in case of interaction of active substances with specific receptors.