Histochemistry and ultrastructure of adrenergic and acetylcholinesterase-containing nerves supplying follicles and endocrine cells in the guinea-pig ovary

The effects of sensorial denervation on the ovarian function, by the local administration of capsaicin, depend on the day of the oestrous cycle when the treatment was performed

There is evidence that sensory innervation plays a role in the regulation of puberty. The present study investigates the effects of functional sensorial desensitisation induced by capsaicin administration to adult female rats in the days of diestrus 1, diestrus 2, pro-oestrus or oestrus on ovulation and serum oestradiol and progesterone concentration. The animals were allotted at random to one of the following groups: (1) animals with capsaicin administration into the bursa ovarica (local administration) (2) animals with vehicle administration into the bursa ovarica and (3) untreated animals group. The animals treated were killed on the day of oestrus after three consecutive 4-day oestrous cycles. No differences were observed in oestrous cyclicity or the average number of ova shed between the sensorial desensitisation animals and the vehicle-treated groups. Capsaicin administration resulted in a significant increase in the intra-ovarian noradrenaline levels in the day of diestrus 2 and pro-oestrus. Serum oestradiol and progesterone concentrations were different, depending on the day of the oestrous cycle in which the treatment was performed. These results suggest that in adult normal female rats, ovarian sensorial innervations participate together with the sympathetic innervation in the ovarian function regulating the hormone secretion and this participation varies along the oestrous cycle.

Norepinephrine stimulates progesterone production in highly estrogenic bovine granulosa cells cultured under serum-free, chemically defined conditions

BACKGROUND

Since noradrenergic innervation was described in the ovarian follicle, the actions of the intraovarian catecholaminergic system have been the focus of a variety of studies. We aimed to determine the gonadotropin-independent effects of the catecholamine norepinephrine (NE) in the steroid hormone profile of a serum-free granulosa cell (GC) culture system in the context of follicular development and dominance.

METHODS

Primary bovine GCs were cultivated in a serum-free, chemically defined culture system supplemented with 0.1% polyvinyl alcohol. The culture features were assessed by hormone measurements and ultrastructural characteristics of GCs.

RESULTS

GCs produced increasing amounts of estradiol and pregnenolone for 144h and maintained ultrastructural features of healthy steroidogenic cells. Progesterone production was also detected, although it significantly increased only after 96h of culture. There was a highly significant positive correlation between estradiol and pregnenolone production in high E2-producing cultures. The effects of NE were further evaluated in a dose-response study. The highest tested concentration of NE (10 (-7) M) resulted in a significant increase in progesterone production, but not in estradiol or pregnenolone production. The specificity of NE effects on progesterone production was further investigated by incubating GCs with propranolol (10 (-8) M), a non-selective beta-adrenergic antagonist.

CONCLUSIONS

The present culture system represents a robust model to study the impact of intrafollicular factors, such as catecholamines, in ovarian steroidogenesis and follicular development. The results of noradrenergic effects in the steroidogenesis of GC have implications on physiological follicular fate and on certain pathological ovarian conditions such as cyst formation and anovulation.

Immunoreactivities to protein gene product 9.5, neurofilament protein and neuron specific enolase in the ovary of the sexually immature ostrich (Struthio camelus)

The innervation of the ovary has been studied in various species of birds and mammals. Despite the fact that the innervation of any organ is an essential factor in controlling its growth and function, no information is available on the distribution of nerve fibers in the ovary of the sexually immature ostrich. Thus, the present study was undertaken to investigate the distribution of nerve fibers in the ovary of the sexually immature ostrich, using antibodies against neurofilament protein type M of 160 kD (NP), protein gene product 9.5 (PGP 9.5) and neuron specific enolase (NSE). A total of 26 sexually immature female ostriches, aged between 12 and 14 months were used in the present study. Immunostaining was performed using a LSAB plus kit (Dakocytomation, Denmark). Antibodies against NP and PGP 9.5 were used at dilutions of 1:25 and 1:50, respectively. A ready-to-use solution containing antibodies against NSE was also used. Strong immunostaining for NP, PGP 9.5 and NSE was observed in nerve bundles, which coursed through the ovarian stalk and extended into the medulla and cortex. In addition, NSE immunoreactive nerve cell bodies were observed in the cortex and medulla. NP, PGP 9.5 and NSE immunoreactive nerve fibers were present in the thecal layer of the follicular wall. The current study has highlighted the distribution of NP, PGP 9.5 and NSE-immunoreactive nerve fibers in the ovary of the sexually immature ostrich. The findings of the present study suggest that the distribution of nerve fibers in the immature ostrich is similar to that of the domestic fowl.

Morphodynamics of the follicular-luteal complex during early ovarian development and reproductive life

Female reproductive activity depends upon cyclic morphofunctional changes of the ovarian tissue during the female's fertile period, but the primum movens of an active gonadal rearrangement can be found from early phases of embryo development. To offer a basic account of the main steps of ovarian dynamics, we review the morphofunctional behavior of the follicular-luteal complex in an integrated study using light microscopy and transmission and scanning electron microscopy as well as through the use of numerous drawings. Particular emphasis is given to some reproductive aspects including (1) germ-somatic cell relationships and onset of folliculogenesis during early gonadal development; (2) follicular development and oocyte-follicle cell associations through adult folliculogenesis, finally leading to ovulation; (3) morphodynamics of corpus luteum formation, development, and regression, and (4) degenerative processes involving germ and somatic cells. The results reported, many of which originated in our laboratory, arise from some experiments on laboratory mammals but mostly from a large selection of human specimens. The data obtained are integrated and correlated with classic reports as well as with current views. Crucial biochemical, histophysiological, and clinical aspects are also emphasized.

Activation of volume-regulated Cl(-) channels by ACh and ATP in Xenopus follicles

Osmolarity-dependent ionic currents from follicle-enclosed Xenopus oocytes (follicles) were studied using electrophysiological techniques. Whole follicle currents were monitored using a two-electrode voltage clamp and single-channel activity was measured using the patch-clamp technique. In follicles held at -60 mV two chloride currents were activated in external hyposmotic solutions. One was the habitual volume-regulated current elicited by external hyposmolarity (ICl,swell), and the second was a slow and smooth current (Sin) generated by ACh or ATP application. In follicles, the permeability ratios for different anions with respect to Cl- were similar for both ICl,swell and Sin, with a sequence of: SCN- > I- > Br- >= NO3- >= Cl- > gluconate >= cyclamate > acetate > SO42-. Extracellular ATP blocked the outward component of Sin. Also, extracellular pH modulated the inactivation kinetics of Sin elicited by ACh; e.g. inactivation at +80 mV was approximately 100 % slower at pH 8.0 compared with that at pH 6.0. Lanthanides inhibited ICl, swell and Sin. La3+ completely inhibited ICl,swell with a half-maximal inhibitory concentration (IC50) of 17 +/- 1.9 microM, while Sin was blocked up to 55 % with an apparent IC50 of 36 +/- 2.6 microM. Patch-clamp recordings in follicular cells showed that hyposmotic challenge opened inward single-channel currents. The single channel conductance (4.7 +/- 0.4 pS) had a linear current-voltage relationship with a reversal membrane potential close to -20 mV. This single-channel activity was increased by application of ACh or ATP. The ICl,swell generation was not affected by pirenzepine or metoctramine, and did not affect the purinergic activation of the chloride current named Fin. Thus, ICl,swell was not generated via neurotransmitters released during cellular swelling. All together, equal discrimination for different anions, similar modulatory effects by extracellular pH, the blocking effects by ATP and La3+, and the same single-channel activity, strongly suggest that ICl,swell and Sin currents depend on the opening of the same type or a closely related class of volume-regulated chloride channels.

Muscarinic receptor heterogeneity in follicle-enclosed Xenopus oocytes

1. Ionic current responses elicited by acetylcholine (ACh) in follicle-enclosed Xenopus oocytes (follicles) were studied using the two-electrode voltage-clamp technique. ACh generated a fast chloride current (Fin) and inhibited K+ currents gated by cAMP (IK,cAMP) following receptor activation by adenosine, follicle-stimulating hormone or noradrenaline. These previously described cholinergic responses were confirmed to be of the muscarinic type, and were independently generated among follicles from different frogs. 2. Inhibition of IK,cAMP was about 100 times more sensitive to ACh than Fin activation; the half-maximal effective concentrations (EC50) were 6.6 +/- 0.4 and 784 +/- 4 nM, respectively. 3. Both responses were blocked by several muscarinic receptor antagonists. Using the respective EC50 concentrations of ACh as standard, the antagonist 4-diphenylacetoxy-N-methylpiperidine methiodide blocked the two effects with very different potencies. Fin was blocked with a half-maximal inhibitory concentration (IC50) of 2.4 +/- 0.07 nM, whilst the IC50 for IK,cAMP inhibition was 5.9 +/- 0.2 microM. 4. Oxotremorine, a muscarinic agonist, preferentially stimulated IK, cAMP inhibition (EC50 = 15.8 +/- 1.4 microM), whilst Fin was only weakly activated. In contrast, oxotremorine inhibited Fin generated by ACh with an IC50 of 2.3 +/- 0.7 microM. 5. Fin elicited via purinergic receptor stimulation was not affected by oxotremorine, indicating that the inhibition produced was specific to the muscarinic receptor, and suggesting that muscarinic actions do not exert a strong effect on follicular cell-oocyte coupling. 6. Using reverse transcription-PCR, transcripts of a previously cloned muscarinic receptor from Xenopus (XlmR) were amplified from the RNA of both the isolated follicular cells and the oocyte. The pharmacological and molecular characteristics suggest that XlmR is involved in IK,cAMP inhibition. 7. In conclusion, follicular cells possess two different muscarinic receptors, one resembling the M2 (or M4) subtype and the other the M3 subtype. These receptors are coupled to distinct membrane mechanisms leading to independent regulation of two membrane conductances.

A heterogeneous population of alpha 1-adrenoceptors mediates contraction of the isolated follicle wall from the bovine ovary

Strips from Graafian follicles of bovine ovaries were tested for their contractile response in vitro in order to characterize the type of post-junctional alpha-adrenoceptor involved. Electrically induced contractions were inhibited concentration-dependently by the alpha 1-antagonist, prazosin. Besides noradrenaline the alpha 1-selective agonists, methoxamine and phenylephrine, caused the strips to contract, whereas the alpha 2-selective agonists clonidine, oxymetazoline and B-HT920 were without effect. However, the alpha 1-selective antagonist prazosin gave a line with a slope less than unity in the Schild plots with noradrenaline and methoxamine. From results obtained with or without the presence of two classes of neuronal uptake blockers (desipramine and cocaine) it is concluded that the post-junctional alpha 1-receptor population is inhomogeneous. The regular appearance of the Schild plot obtained with phenylephrine may be due to involvement also of a component of noradrenaline release by this agonist. The pA2 value in the test with phenylephrine was 9.27, with a corresponding kB of 3.81 +/- 1.15 X 10(-10) M.

Catecholaminergic regulation of ovarian function in mammals: current concepts

A review of the rapidly accumulating data in the literature continues to support the notion that catecholamines regulate ovarian function, and extends the complexity of catecholaminergic effects on the ovary via interactions with pituitary and adrenal hormones. It is clear that catecholamines affect growth and differentiation of ovarian follicles, but their role in follicular rupture during ovulation and in corpus luteum function remains unclear. The effects of catecholamines (mediated by membrane receptors) on ovarian function probably should be considered paracrine but classic endocrine regulation of ovarian function cannot be ruled out. Myogenic tonus of ovarian vasculature appears to be regulated by catecholamines, and estrogens may enhance adrenergic receptors in ovarian smooth muscle cells.

Evidence for prejunctional GABAB receptors mediating inhibition of ovarian follicle contraction induced by nerve stimulation

The motor effects of gamma-aminobutyric acid (GABA) on the bovine ovarian follicle were studied in vitro using strips from follicle walls. Electrical field stimulation of nerves in the preparation, secured by tetrodotoxin blockade, caused a contraction that was almost totally abolished by phentolamine and only slightly affected by atropine. This mainly adrenergic neurogenic response was inhibited by GABA in a dose-dependent way. The GABAA-receptor antagonists, bicuculline and picrotoxin, did not affect the GABA action whereas the GABAB-receptor antagonist, homotaurine, significantly inhibited the GABA effect. The GABAA-receptor agonist, muscimol, did not affect the contractile response while the GABAB-receptor agonist, baclofen, imitated the action of GABA. On the other hand, GABA had no direct contractile or relaxing effect on the follicle strips nor did it interfere with the contractile response induced by noradrenaline or acetylcholine. The findings suggest that activation of prejunctional GABAB receptors inhibits transmitter release from mainly adrenergic nerves associated with the follicle, thereby affecting nerve-mediated tension in the follicle wall.