The innervation of the rat cervix and its pharmacology in vitro and in vivo.

1 Contractions of the rat cervix and uterine horns were measured both in vitro and in vivo as changes in luminal perfusion pressure during perfusion at constant flow.2 Spontaneous cervical and uterine horn contractions in vitro were reduced from rats pre-treated with 17beta-oestradiol compared to those ovariectomized only or those pre-treated with 17beta-oestradiol plus progesterone.3 The rat cervix exhibited similar in vitro sensitivities to methacholine, oxytocin, isoprenaline and phenylephrine as did the uterine horns.4 Transmural stimulation produced cervical and uterine horn contractions, which were blocked by hyoscine or tetrodotoxin, suggesting a cholinergic motor innervation. This was supported by histological findings.5In vivo, the injections of propranolol (1.9 x 10(-7) mol/kg) or pempidine (3.2 or 6.4 x 10(-6) mol/kg) were followed by large cervical and smaller uterine horn contractions, suggesting an adrenergic inhibitory tone mediated by beta-adrenoceptors.6 The evidence for a cervical sphincter is discussed.