Vagal influence on compensatory ovarian growth is important only briefly after hemicastration

Hemicastration induces growth of the remnant ovary in the rat. As evidenced by the effects of total abdominal vagotomy, vagal innervation markedly influences this compensatory ovarian growth. In the present experiments, vagotomy inhibited compensatory ovarian growth when performed immediately after hemicastration, but not when delayed until 4.5 hr after hemicastration. Brief exposure of subdiaphragmal portion of the vagi nerves to 2% lidocaine shortly before hemicastration also inhibited compensatory growth. Fifteen minutes after hemicastration, markedly elevated tissue concentrations of cyclic adenosine monophosphate (cAMP) were recorded in the remnant ovaries. This accumulation of cAMP was inhibited by vagotomy that preceded hemicastration, as well as by lidocaine pretreatment of the vagi nerves, and partly by vagotomy that followed 10 min after hemicastration. At 5 hr after hemicastration, tissue cAMP concentrations in the remnant ovaries were not elevated and were not affected by vagotomy. The present results suggest that vagal influence on the compensatory ovarian growth is important only during a short period of time after hemicastration (apparently shorter than 4.5 hr), and that it, at least briefly after hemicastration, includes neural input to the ovary.