The celiac ganglion modulates LH-induced inhibition of androstenedione release in late pregnant rat ovaries

Abstract

Background: Although the control of ovarian production of steroid hormones is mainly of endocrine nature, there is increasing evidence that the nervous system also influences ovarian steroidogenic output. The purpose of this work was to study whether the celiac ganglion modulates, via the superior ovarian nerve, the anti-steroidogenic effect of LH in the rat ovary. Using mid- and late-pregnant rats, we set up to study: 1) the influence of the noradrenergic stimulation of the celiac ganglion on the ovarian production of the luteotropic hormone androstenedione; 2) the modulatory effect of noradrenaline at the celiac ganglion on the anti-steroidogenic effect of LH in the ovary; and 3) the involvement of catecholaminergic neurotransmitters released in the ovary upon the combination of noradrenergic stimulation of the celiac ganglion and LH treatment of the ovary.

Methods: The ex vivo celiac ganglion-superior ovarian nerve-ovary integrated system was used. This model allows studying in vitro how direct neural connections from the celiac ganglion regulate ovarian steroidogenic output. The system was incubated in buffer solution with the ganglion and the ovary located in different compartments and linked by the superior ovarian nerve. Three experiments were designed with the addition of: 1) noradrenaline in the ganglion compartment; 2) LH in the ovarian compartment; and 3) noradrenaline and LH in the ganglion and ovarian compartments, respectively. Rats of 15, 19, 20 and 21 days of pregnancy were used, and, as an end point, the concentration of the luteotropic hormone androstenedione was measured in the ovarian compartment by RIA at various times of incubation. For some of the experimental paradigms the concentration of various catecholamines (dihydroxyphenylalanine, dopamine, noradrenaline and adrenaline) was also measured in the ovarian compartment by HPLC.

Results: The most relevant result concerning the action of noradrenaline in the celiac ganglion was found on day 21 of pregnancy resulting in the inhibition of androstenedione release from the ovarian compartment. In addition on day 15 of pregnancy, LH placed in the ovarian compartment led to an inhibition of the release of androstenedione, and this inhibitory effect was further reinforced by the joint action of noradrenaline in the celiac ganglion and LH in the ovary. The levels of catecholamines in the ovarian compartment showed differences among the experiments; of significance, the joint treatment of noradrenaline in the celiac ganglion and LH in the ovary resulted in a remarkable increase in the ovarian levels of noradrenaline and adrenaline when compared to the effect achieved by either one of the compounds added alone.

Conclusion: Our results demonstrate that the noradrenergic stimulation of the celiac ganglion reinforces the LH-induced inhibition of androstenedione production by the ovary of late pregnant rats, and that this effect is associated with marked changes in the release of catecholamines in the ovary.

Figure 1

Schematic representation of the celiac ganglion-superior ovarian nerve-ovary ex vivo incubation system. NA, noradrenaline; CG, celiac ganglion; SON, superior ovarian nerve; OV, ovary; CAT, catecholamines; A₂, androstenedione.

Figure 2

Effect of noradrenaline (NA) in the ganglion compartment on the release of ovarian androstenedione (A₂), using the celiac ganglion-superior ovarian nerve-ovary system obtained from pregnant rats on days 19 (A), 20 (B) and 21 (C). The systems were incubated in Krebs-Ringer solution, at 37°C in an atmosphere of 95% O₂-5% CO₂ for 180 min. Ascorbic acid (0.1 mg/ml in Krebs-Ringer) without (Control) and with 10^-6 M NA was added to the ganglionic compartment (NA groups). Results are expressed as mean ± S.E.M. of six animals per group. Repeated measures analysis of variance followed by Tukey's test was used; * p < 0.01 and ^•p < 0.05.

Figure 3

Effect of noradrenaline (NA) in the celiac ganglion and LH in the ovary on the production of ovarian androstenedione (A₂), using the celiac ganglion-SON-ovary system obtained from rats on day 15 of pregnancy. The systems were incubated in Krebs-Ringer solution, at 37°C in an atmosphere of 95% O₂-5% CO₂ for 180 min. LH (50 ng/ml) was added to the ovarian compartment and ascorbic acid (0.1 mg/ml in Krebs-Ringer) without (Control-LH group) and with NA (10^-6 M) added to the ganglion compartment (NA-LH group). Control group was in absence of NA in the ganglion compartment and LH in the ovarian compartment. In the NA group, 10^-6 M NA was added to the ganglionic compartment. Results are expressed as mean ± S.E.M. of six animals per group. Repeated measures analysis of variance followed by Tukey's test was used. The same font denote differences of statistical significance; ^ap < 0.05 between 60 and 180 min of Control-LH group; ^b,c and ^d p < 0.05 in Control-LH group compared with Control group; ^ep < 0.01 NA-LH group compared with NA group.; *p < 0.01 and ^• p < 0.05 in NA-LH group compared with Control-LH group; ^• p < 0.05 in NA group compared with Control group.

Figure 4

Levels of catecholamines in the incubation liquid of the ovarian compartment at 180 min using the celiac ganglion-superior ovarian nerve-ovary system obtained from rats on day 15 of pregnancy. The systems were incubated in Krebs-Ringer solution, at 37°C in an atmosphere of 95% O₂-5% CO₂ for 180 min. LH (50 ng/ml) was added to the ovarian compartment and ascorbic acid (0.1 mg/ml in Krebs-Ringer) without (Control-LH group) and with NA (10^-6 M) added to the ganglion compartment (NA-LH group). Control group was in absence of NA in the ganglion compartment and LH in the ovarian compartment. NA group was in absence of LH in the ovarian compartment. Dihydroxyphenylalanine (DOPA), dopamine (DA), noradrenaline (NA), adrenaline (A). Results are expressed as mean ± S.E.M. of six animals per group. One-way analysis of variance followed by Tukey's test was used. Control, NA, Control-LH and NA-LH groups were compared. The same fonts denote differences of statistical significance.