In vitro response of rabbit utero-ovarian ligament to catecholamines

The response of the rabbit utero-ovarian ligament to catecholamines has been studied in vitro, with contractile activity being recorded isometrically from whole rabbit ligaments obtained under various hormonal conditions. Both the catecholamines norepinephrine (NE) and epinephrine (EPI) produced dose-dependent (10(-2) mug/ml threshold; 10(2) mug/ml maximum) tetanic contractions of rabbit ligament. There was no difference (P less than 0.05) between estrous and ovulatory ligaments either in terms of the dose-response curves or maximal force of contraction. Both agonists were 100% antagonized by the alpha-blockers, phentolamine and phenoxybenzamine. The beta-agonist, isoproterenol, had little effect on ligament tonus but did inhibit spontaneous activity and attenuated the response to both NE and EPI. Propranolol, a beta-blocker, slightly (less than 10%) potentiated the stimulatory effects of NE and EPI. It is concluded that the utero-ovarian ligament of the rabbit contains predominately alpha-stimulatory and possibly weak beta-inhibitory receptors analogous to receptors in ovarian and oviductal smooth muscles.