Neurovascular function in the rat during pregnancy.

Activity of the vascular neuroeffector junction was examined in pregnant (PG) and nonpregnant (NPG) rats to determine whether changes could account for the reported alterations in sympathetic control of the maternal circulation. Caudal and mesenteric arteries were removed from NPG and 19-21 day PG rats and prepared for isometric tension recording. Frequency-response measurements were obtained, followed by norepinephrine (NE) and tyramine concentration-response measurements. The caudal artery developed more tension in response to NE, tyramine, and electrical stimulation than did the mesenteric artery; however, there were no differences between vessels from NPG and PG rats. NE content, [3H]NE accumulation, and effects of plasma on [3H]NE accumulation of NPG and PG caudal arteries were also compared and found to be similar. Therefore, vascular neuroeffector functions of NE release, receptor sensitivity, and NE accumulation are not modified in the rat during pregnancy. Changes in sympathetic control of the maternal circulation are likely to be dependent on alterations at sites other than the neuroeffector junction.