Unilateral sectioning of the superior ovarian nerve of rats with polycystic ovarian syndrome restores ovulation in the innervated ovary

The present study tested the hypothesis that if polycystic ovary syndrome (PCOS) results from activating the noradrenergic outflow to the ovary, unilaterally sectioning the superior ovarian nerve (SON) will result in ovulation by the denervated ovary, and the restoration of progesterone (P4), testosterone (T) and estradiol (E2) normal serum level. A single 2 mg dose of estradiol valerate (EV) to adult rats results in the development of a syndrome similar to the human PCOS. Ten-day old rats were injected with EV or vehicle solution (Vh) and were submitted to sham surgery, unilateral or bilateral sectioning of the SON at 24-days of age. The animals were sacrificed at 90 to 92 days of age, when they presented vaginal estrus preceded by a pro-estrus smear. In EV-treated animals, unilateral sectioning of the SON restored ovulation by the innervated ovary and unilateral or bilateral sectioning of the SON normalized testosterone and estradiol levels. These results suggest that aside from an increase in ovarian noradrenergic tone in the ovaries, in the pathogenesis of the PCOS participate other neural influences arriving to the ovaries via the SON, regulating spontaneous ovulation. Changes in P4, T and E2 serum levels induced by EV treatment seem to be controlled by neural signals arising from the abdominal wall and other signals arriving to the ovaries through the SON, and presents asymmetry.     

Effect of cervical sympathetic trunk transection on renal sympathetic nerve activity in rats

Stellate ganglion blockade (SGB) with a local anesthetic increases muscle sympathetic nerve activity in the tibial nerve in humans. However, whether this sympathetic excitation in the tibial nerve is due to a sympathetic blockade in the neck itself, or due to infiltration of a local anesthetic to adjacent nerves including the vagus nerve remains unknown. To rule out one mechanism, we examined the effects of cervical sympathetic trunk transection on renal sympathetic nerve activity (RSNA) in anesthetized rats. Seven rats were anesthetized with intraperitoneal urethane. RSNA together with arterial blood pressure and heart rate were recorded for 15 min before and 30 min after left cervical sympathetic trunk transection. The baroreceptor unloading RSNA obtained by decreasing arterial blood pressure with administration of sodium nitroprusside was also measured. Left cervical sympathetic trunk transection did not have any significant effects on RSNA, baroreceptor unloading RSNA, arterial blood pressure, and heart rate. These data suggest that there was no compensatory increase in RSNA when cervical sympathetic trunk was transected and that the increase in sympathetic nerve activity in the tibial nerve during SGB in humans may result from infiltration of a local anesthetic to adjacent nerves rather than a sympathetic blockade in the neck itself.     

Different effects of amygdaloid lesions on compensatory ovarian hypertrophy in cyclic and prepubertal female rats.

Cyclic and 28-day-old immature female rats were hemiovariectomized and partly bilaterally lesioned in the cortical amygdaloid nucleus (CAN). The compensatory ovarian hypertrophy (COH) recorded in the adult females on the 8th day after hemicastration was completely prevented by the amygdaloid lesions. In contrast, damage to the CAN did not alter the ovarian weight in prepubertal females, although COH was also induced in these animals by unilateral ovariectomy.     

The effects of superior ovarian nerve sectioning on ovulation in the guinea pig

The effects on spontaneous ovulation associated with the unilateral or bilateral sectioning of the superior ovarian nerves (SON) were analyzed in guinea pigs at different time intervals of the estrous cycle. Day 1 of the estrous cycle was defined as the day when the animal presents complete loss of the vaginal membrane (open vagina). Subsequent phases of the cycle were determined by counting the days after Day 1. All animals were autopsied on the fifth day of the estrous cycle after surgery. Sectioning the right, left, or both SONs on day 5 (early luteal phase) resulted in a significant increase in the number of fresh corpora lutea. Ovulation increased significantly when the left SON (L-SON) was sectioned during late follicular phase (day 1) and medium luteal phase (day 8). When surgery was performed on days 1 or 8, neither sectioning the right SON (R-SON) nor sectioning the SON bilaterally had an apparent effect on ovulation rates. Similarly, ovulation rates were not affected when unilateral (right or left) or bilateral sectioning of the SON was performed during late luteal phase two (day 12). Unilateral or bilateral sectioning of the SON performed during the early luteal phase (day 5) was associated with a significant decrease in uterine weight. A comparable effect was observed when the L-SON was sectioned during late follicular phase (day 1), or medium luteal phase (day 8). No effects on uterine weight were observed when unilateral or bilateral sectioning of the SON was performed during late luteal phase. Our results suggest that in the guinea pig the SON modulates ovulation, and that the degree of modulation varies along the estrous cycle. The strongest influence of the SONs on ovulation occurs during early luteal phase, and decrease thereafter, being absent by late luteal phase. In addition, sectioning the left or the right SON caused different responses by the ovaries of adult guinea pigs. This paper discusses the mechanisms by which ovulation increased when the SON was surgically cut.     

Neonatal transection alters the percentage of substance-P-positive trigeminal ganglion cells that contribute axons to the regenerate infraorbital nerve

Neonatal transection results in a marked reduction of the number of trigeminal (V) ganglion cells that contribute axons to the regenerate infraorbital nerve (ION; Jacquin and Rhoades, 1985; Chiaia et al., 1987). Such lesions also produce a profound deafferentation of the V brain stem complex that appears to spare the innervation of layers I and II of subnucleus caudalis (SpC) by substance-P-positive (SP-positive) primary afferents (Jacquin and Rhoades, 1985; Rhoades et al., 1988). In the present study, we combined retrograde tracing with immunocytochemistry to determine whether neonatal transection of the ION alters the percentage of SP-positive V ganglion cells that contribute axons to this V branch upon regeneration. In V ganglia ipsilateral to the intact ION (n = 8), 11.6% +/- 3.2% of the cells labeled after application of true blue (TB) to the ION were also SP-positive. In ganglia ipsilateral to the neonatally damaged nerve (n = 8), 18.6% +/- 4.7% of the cells labeled after application of TB to the regenerate ION were also SP-positive (p less than 0.001). We also compared the SP content of intact ganglia (n = 10) with that of ganglia ipsilateral to the damaged nerve (n = 10) by means of radioimmunoassay. The normal V ganglia contained (mean +/- SD) 3496 +/- 774 pg SP/mg protein. The value for the ganglia ipsilateral to the damaged nerve was 5533 +/- 1746 pg SP/mg protein (p less than 0.01). There was no significant difference between SP levels on the control and partially deafferented sides of the brain stem in neonatally nerve-damaged adult rats. In one additional experiment, we injected TB into both vibrissa pads of seven rats on the day of birth prior to transection of the ION. After an 8-hr delay, the nerve on one side was then cut and allowed to regenerate, and both V ganglia were then processed for immunocytochemistry. On the nerve-damage side, 25.8% of the TB-labeled cells were SP-positive. The value for the intact side was 12.0% (p less than 0.000001). This result demonstrated that the lesion-induced change in the percentage of SP-positive ION cells was not the result of either late-growing axons from SP-positive ganglion cells that may have been missed by our nerve cuts or collateral sprouting into the regenerate ION by undamaged SP-positive ganglion cells.     

Decline of IXth nerve taste responses following nerve transection

Summated impulse discharges to taste solutions were recordedfrom intact and transected IXth nerves in the Mongolian gerbil(Meriones unguiculatus). Five taste stimuli were used: 0.3 MNH₄Cl, 0.3 M NaCl, 0.01 M HCl, 0.01 M quinine hydrochloride,and 0.5 M sucrose. 0.3 M NH₄Cl was the most effective stimulus.Taste responses from intact nerves were stable for more than10 hours. Following IXth nerve transection, the peak summatedresponse to 0.3 M NH₄Cl declined by 50% in a mean of 119 min.(Some animals failed to show this taste response decline inthe winter months.) The transected IXth nerve's spontaneousactivity and responses to other taste solutions also typicallydeclined. The continued presence of normal compound action potentialsindicated that the transection-induced decline in taste responsesdid not result from a failure of impulse propagation mechanismsin the nerve trunk. The results are consistent with the propositionthat transection interferes with axonal transport of materialsvital to the short-term maintenance of taste responses.     

Hypothalamic cyclic AMP after the injection of ovarian steroids into ovariectomized rats

The effect of ovarian steroids on the concentration of adenosine 3',5'-cyclic monophosphate (cAMP) in the hypothalamus was studied in ovariectomized rats. Ovariectomized rats exhibited a lower cAMP concentration than intact rats. The administration of a single dose of estradiol benzoate (50 micrograms/kg body weight) resulted 3 days later in a rise of cAMP values, but levels did not reach those observed in estrous rats. Progesterone (2 mg/rat) injected 3 days after the priming dose of estradiol benzoate produced 4 h later no further changes in hypothalamic cAMP. The changes in hypothalamic cAMP concentration induced by estrogen treatment depend, at least in part, on noradrenergic inputs, since they were prevented by the injection of the norepinephrine synthesis inhibitor, diethyldithiocarbamate. In addition, administration of the beta-blocking agent, propranolol, to estradiol- and estradiol-progesterone-treated rats lowered the concentration of cAMP in the hypothalamus in a dose-dependent manner. In contrast, the administration of an alpha-blocking agent, phenoxybenzamine, had no effect at the tested concentration. The results of this study indicate that estrogen increases cAMP concentration in the hypothalamus by a noradrenergic mechanism involving beta-receptors. Moreover, the findings suggest that estrogen induces an increase in the number of beta-receptor sites, whereas progesterone increases the apparent propranolol sensitivity for these receptor sites.     

Regulation of the bacterial microflora of the vagina in cyclic female rats.

The bacterial microflora was examined in the vagina of cyclic female rats kept under normal laboratory conditions. Large variations occurred during the cycle with high numbers of bacteria (10(5)-10(8) per vagina) during proestrus and estrus and low numbers (10(1)-10(4) per vagina) during the diestrus period. Histological analysis of in situ vaginal tissue and transplanted vaginal tissue revealed an association of high bacterial numbers with the presence of large amounts of cellular debris in the vaginal lumen during the period of epithelial keratinization. Absence of phagocytosis in leucocytes at mestestrus suggested that leucocytes did not play an active role in reduction of bacterial numbers between estrus and metestrus. Accurate measurement of the pH in the vaginal lumen failed to reveal differences which could explain the reduction in bacterial numbers between estrus and metestrus. The cyclic changes in the bacterial population-consisting of species which are normally present in the intestinal flora-- seem to be controlled by cyclic changes in the amounts of cellular debris in the vaginal lumen.     

Acute effects of unilateral sectioning the superior ovarian nerve of rats with unilateral ovariectomy on ovarian hormones (progesterone,testosterone and estradiol) levels vary during the estrous cycle

The present study analyzed the participation of the left and right superior ovarian nerves (SON) in regulating progesterone, testosterone, and estradiol serum levels in unilaterally ovariectomized rats on each day of the estrous cycle. For this purpose, ovarian hormone concentrations in serum were measured in animals with either sham-surgery, unilateral ovariectomy (ULO), unilateral sectioning of the SON, or sectioning of the SON innervation of the in situ ovary in rats with ULO.     

Possible antiestrogenic activity of lindane in female rats

During chronic peroral (PO) treatment of weanling, female Fischer 344 rats with daily injections (0.069 mmol/kg) of either 1,1′-(2,2,2-trichloroethylidene) bis [4-chlorobenzene] (p,p′-DDT), 2,4-dichlorophenoxy acetic acid (2,4-D), or γ-hexachlorocyclohexane (lindane), the lindane treatment induced a significant 20% increase in body weight after 110 days. Further investigation with 0,5,10,20, and 40 mg/kg lindane confirmed a significant increase in average body weight gain at the two highest doses after ten weeks of treatment. Significantly greater food consumption was observed, and the Lee index indicated that lindane treatment induced obesity. In addition to obesity, lindane caused a delay in vaginal opening, disrupted estrous cycling, reduced pituitary and uterine weight, and elevated food consumption during proestrus (when appetite is normally suppressed by estradiol). These responses suggest that, by inducing alterations in the reproductive function of the female rat and by interfering with hormonal regulation of energy balance, lindane may be antiestrogenic rather than estrogenic as previously proposed.     

Regulation of sociosexual communication in female Long-Evans rats by ovarian hormones

Two experiments examined the role of the steroid hormones, estradiol (E2), progesterone (P), and testosterone (T), in activating scent marking and 50-kHz ultrasonic vocalizations in ovariectomized Long-Evans rats in response to a devocalized male rat. In Experiment 1, females received, in a counterbalanced order, a series of six hormone treatments consisting of two injections (48-54 and 4 hr before behavioral tests). The six treatments were 8 micrograms E2 followed by 500 micrograms P or oil, 2 micrograms E2 followed by 500 micrograms P or oil, and oil followed by 500 micrograms P or oil. Injections of either the high or low dose of E2 followed by P resulted in high levels of vocalizations. Neither E2 by itself or P by itself were very effective. Surprisingly, none of the hormone treatments were effective in activating marking above the level seen when the females received control injections of oil. Four other hormone treatments were examined in Experiment 2: daily injections of 500 micrograms T, daily injections of 50 micrograms E2, implantation of silastic capsules of E2 (5% E2, 5 mm length) followed by 500-micrograms P injections before behavioral tests, and implantation of silastic capsules of E2 followed by oil injections. Animals receiving E2 by silastic capsule followed by P injection displayed the highest levels of marking and vocalizations across the five weekly tests. These results suggest that while E2 and P synergize for the display of female-typical behaviors similar to the hormonal regulation of lordosis, the mechanism of E2 action may be different for the two signaling behaviors. Scent marking appears to be responsive to the tonic levels of E2 released from silastic capsules.     

Neonatal phenobarbital administration results in increased cytochrome P450-dependent monooxygenase activity in adult male and female rats

The effects of neonatal exposure to phenobarbital during the first five days after birth on the enzymatic activity of the adult male and female rat liver P₄₅₀-dependent monooxygenase system were investigated. Although liver weight per 100 grams of body weight and total hepatic microsomal protein content were not altered in adult rats treated neonatally with phenobarbital, both sexes did show significant increases in cytochrome P₄₅₀ content, cytochrome P₄₅₀ reductase activity, cytochrome c reductase activity, ethoxycoumarin-O-deethylase activity and in the activity of a specific glucuronyl-transferase. Several of these activities were increased to a larger extent in the females, suggesting that females may be more sensitive to this phenomenon.