The role of the adrenergic innervation of the oviduct in the regulation of mammalian ovum transport

Histological studies have revealed a fairly rich adrenergic innervation to the circular muscle of the isthmus, while pharmacological investigations have demonstrated the presence of α-excitatory and β-inhibitory adrenoceptors in oviductal smooth muscle. These findings suggested that the distal isthmus might function as a sphincter under the control of the sympathetic nervous system. The adrenergic transmission could in turn be regulated by the prevailing hormonal dominance. It has been proposed that estrogen enhances α-adrenoceptor activity and thus constriction of the isthmus, and that by the third postovulatory day the production of progesterone has enhanced β-adrenoceptor activity with a consequent reduction in constriction of the isthmus thus allowing ova to continue their journey to the uterus. This review is concerned with evaluating this hypothesis and the possible role of the adrenergic innervation of the oviduct in the regulation of ovum transport.