Norepinephrine modulates the effect of neuropeptides in coeliac ganglion on ovarian hormones release: its relationship with ovarian nitric oxide and nerve growth factor.

OBJECTIVE: Ovarian steroids are modulated by neural influences. In this work we investigate whether norepinephrine (NE) modifies the vasoactive intestinal peptide (VIP) or neuropeptide Y (NPY) actions in coeliac ganglion (CG) on the ovarian hormone release, and evaluate the participation of nitric oxide (NO), measured as nitrite, and of inducible nitric oxide synthetase (iNOS) protein, nerve growth factor (NGF) and its trkA receptor gene expression in the ovarian response.

METHODS: The study was performed in the ex vivo CG-superior ovarian nerve (SON)-ovary system of rats on diestrus day 2 (D2). CG and ovary were placed in separate compartments connected by the SON and incubated with Krebs-Ringer buffer. After addition of 50 ng/ml VIP, 50 ng/ml NPY, 10-6 M NE, or a mix of VIP+NE or NPY+NE in ganglion, samples from the ovarian compartment were taken at different times throughout 180 minutes to measure progesterone, androstenedione and nitrite levels.

RESULTS: VIP and NPY in ganglion induced an increase of progesterone release that was associated for VIP, but not NPY, with a decrease of ovarian nitrite levels, iNOS protein, and NGF/trkA receptor mRNA expression. By contrast, NE in ganglion decreased progesterone, an effect that was suppressed by addition of propranolol in ganglion, and increased nitrites/iNOS and NGF/trkA receptor expression in ovary. GABA A receptor antagonist bicuculline (20 muM) added in ovarian compartment prevented the inhibitory effect on progesterone caused by NE in CG. Androstenedione was not modified under neuropeptides or NE ganglionic stimulation.

CONCLUSIONS: Finally, results from VIP+NE or NPY+NE in ganglion showed that ovarian response on D2 induced by VIP or NPY alone is moderated by the opposite action of NE, and occurs only on progesterone, the most sensitive steroid to neural action.