Castrated Female Rats Research Articles

Influence of S-adenosyl-L-methionine on chronic mild stress-induced anhedonia in castrated rats.

1. S-adenosyl-L-methionine (SAMe) is the most important methyl donor in the brain and is essential for polyamine synthesis. Methyl group deficiency in the brain has been implicated in depression; on the other hand, polyamines enhance phosphorylation processes, and phosphorylation of functional proteins in neurons in involved in the therapeutic mechanisms of antidepressants. 2. The effect of SAMe in an animal model of 'depression', the chronic mild stress-induced anhedonia, was studied using long-term castrated male and female Lister hooded rats. 3. Chronic daily exposure to an unpredictable sequence of mild stressors produced, within 3 weeks, a significant reduction of the consumption of a sucrose solution. SAMe (100, 200 or 300 mg kg-1 daily i.m.) while having no influence on sucrose intake in non-stressed animals, dose-dependently reinstated sucrose consumption within the first week of treatment, both in male and in female stressed rats. Imipramine (10 mg kg-1 daily i.p.) produced a similar effect after a 3 week treatment. 4. Similarly, a palatable food reward-induced place preference conditioning was developed in SAMe (200 or 300 mg kg-1 daily i.m.)--and in imipramine (10 mg kg-1 daily i.p.)--treated chronically stressed animals (males and females), whilst it could not be obtained in vehicle-treated rats. 5. Moreover, the same doses of SAMe (but not of imipramine) restored the exploratory activity and curiosity for the environment (rearing), in the open-field test. 6. While imipramine caused a blockade of the growth throughout the treatment, SAMe produced only a transient growth arrest during the first week of treatment. 7. These results show that SAMe reverses an experimental condition of 'depression-like' behaviour in rats, the effect being more rapid and complete than that of imipramine, and without apparent side effects.

Influence of the Hormonal Replacement in the Collagen and Muscular Fibers in the Urethra and Bladder Wall in Castrated Female Rats

Haidar, M A; Sartori, M G.F; Girão, M J.B.C; Baracat, E C; Lima, G R Author Information

Effect of an Aproteic Diet on Gonadotropin Release Response to GnRH and Estrogen-Progesterone in Rats

The fasting-induced gonadotropin function decrease is unspecific, because in this situation there is a lack of all nutrients. We report here the effect of specific protein lack in the diet during 21 days, on pituitary gonadotropin synthesis and response to exogenous GnRH in adult male rats. We also studied the effect of the aproteic diet (AP) on the positive feedback mechanism in adult female castrated rats. The AP diet decreased significantly, both LH and FSH pituitary concentration and also basal gonadotropin plasma levels in male rats. GnRH produced a significantly increment in LH secretion in both treated and control groups, reaching similar levels after stimulation. Nevertheless, the percentile increment from basal levels in the aproteic group was almost four times the controls, suggesting an increased sensitivity in pituitary response to GnRH in rats fed with AP diet. In female castrated rats, the aproteic diet imposed 3 weeks after the surgery was unable to reduce basal gonadotropin secretion, and so also prolactin secretion. Estradiol/progesterone (EP) administration produced the activation of positive feedback mechanism, increasing significantly LH and FSH secretion in both controls and AP groups. Nevertheless, both gonadotropin responses to EP were significantly greater in rats fed with AP diet. Basal prolactin levels and response to EP were not different between both groups. This results suggest that selective protein lack in a diet, reduced pituitary LH and FSH synthesis and secretion. This type of diet also increments pituitary sensitivity to GnRH administration in male rats, and gonadotropin response to positive feedback mechanism in female rats.

Differential orderliness of the GH release process in castrate male and female rats.

Male- and female-specific modes of episodic growth hormone (GH) release are presumptively imposed by sex steroid hormones, and, although typically evident visually, are vividly distinguished quantitatively via a regularity statistic, approximate entropy (ApEn), in both the rat and human. GH secretory patterns may determine GH-stimulated growth and specific hepatic and muscle gene expression in the rat. Consequently, it is important to discern mechanisms that underlie their regulation. Here we have examined the impact of prepubertal gonadal suppression (at 4 wk of age) via surgical or pharmacological [gonadotropin-releasing hormone (GnRH) agonist] intervention on the regularity (ApEn) of GH release in male and female rats (at 10-11 wk of age) sampled at 10-min intervals for 10 h (n = 60 points) during a lights-out (dark) period. We observed a graded hierarchy of mean disorderliness of GH release that was quantifiable by ApEn measures, with maximal to minimal disorderliness in the following rank order: intact female, GnRH agonist-treated female, ovariectomized female, orchidectomized male, GnRH agonist-treated male, and intact male. These observations suggest a continuum of sex steroid actions on the regularity of GH secretion and, by inference, on the interplay among GH-releasing hormone, somatostatin, and GH/insulin-like growth factor I negative feedback.

Tests and symptoms in keratoconjunctivitis sicca and their correlations: Bjerrum KB: Acta Ophthalmol 1996;74:436–441

The purpose of this investigation was to determine whether the known gender-related differences in, and the endocrine control of, the production of secretory component (SC) by the rat lacrimal gland are associated with alterations in SC mRNA content. Levels of SC mRNA were measured in lacrimal tissues of intact, sham-operated, castrated, hypophysectomized, and testosterone-treated male and female adult rats by Northern blot procedures, which utilized a specific, [alpha-32P]-labelled rat SC cDNA probe. For control purposes, SC mRNA amounts were standardized to the β-actin content in experimental blots. The location of SC mRNA in lacrimal glands was evaluated by in situ hybridization techniques, which involved exposure of tissue sections to sense or anti-sense [35S]-labelled SC RNA probes. Our results demonstrate that: (1) lacrimal glands of male rats contain a significantly greater amount of SC mRNA than those of female rats, and that this difference co-exists with distinct, gender-associated variations in the distribution of SC mRNA in lacrimal tissue; (2) orchiectomy or hypophysectomy, but not ovariectomy or sham surgery, leads to a marked decline in the lacrimal SC mRNA content; and (3) testosterone, but not placebo, administration to castrated male and female rats induces a significant increase in the SC mRNA levels in lacrimal tissue. Overall, these findings show that gender, androgens and the hypothalamic-pituitary axis exert a considerable influence on the SC mRNA content in the rat lacrimal gland.

Inhibin A and inhibin B are inversely correlated to follicle-stimulating hormone, yet are discordant during the follicular phase of the rat estrous cycle, and inhibin A is expressed in a sexually dimorphic manner.

Inhibin A and inhibin B are related dimeric protein hormones and endocrine regulators of the reproductive axis. Specifically, inhibin inhibits FSH secretion from the anterior pituitary. The inhibins are synthesized by the gonads and are themselves modulated by FSH. Although the activity of these ligands has been well characterized, the circulating concentrations of dimeric inhibin A and dimeric inhibin B have not previously been reported for the rat. Our group examined the serum concentration of inhibin A and inhibin B in normally cycling female rats, male rats, and in gonadectomized animals. Both inhibin isoforms are detected in intact female rat serum. Interestingly, inhibin B, but not inhibin A, is detected in intact male rat serum. Neither inhibin isoform is detected in long-term castrate female or male rats. In normally cycling female rats, inhibin A was low on the morning of metestrus and rose steadily to a peak on proestrus. In contrast, inhibin B was elevated on the mornings of metestrus, diestrus, and proestrus. Both ligands persisted in the serum until proestrus evening. Serum inhibins then declined beginning at 2100 h (inhibin A) or 1800 h (inhibin B) on proestrus, and the concentrations reached a nadir on the morning of estrus (0600 h). The nadir coincided with the peak of the secondary FSH surge. Both inhibins rebounded later on the morning of estrus. The results of this study demonstrate that dimeric, ovarian-derived inhibin A and inhibin B circulate in the female rat. The inverse relationship of the inhibins during the secondary FSH surge is consistent with the hypothesis that they participate in the regulation of reproductive cyclicity. The differing patterns of inhibin A and inhibin B during the period of follicular development on metestrus and diestrus suggest different follicle sources or regulation of these molecules during this period. We further demonstrate that inhibin B is the dominant form of FSH regulating protein in the male rat.

Effects of aging on N-methyl- d-aspartate (NMDA)-induced GnRH and LH release in female rats

In order to evaluate if the changes of the hypothalamic-pituitary-ovary axis that induce a decrease in fertility and modifications in the sexual cycles during senescence involve modifications in the regulatory action of excitatory amino acid neurotransmission on GnRH neurons, we measured the in vitro effects of NMDA on GnRH release by the anterior preoptic and medial basal hypothalamic areas (APOA-MBH) of castrated aging (18 months old) and young (90 days of age) rats. In a second series of experiments the in vivo LH release response to intrahypothalamic (push-pull) administration of NMDA to aged and young castrated female rats was also determined. A similar rate of basal GnRH release was observed in old and young rats during the incubation time. The addition of NMDA to the medium significantly increased GnRH release in both groups; nevertheless, the GnRH release response to NMDA was significantly lower in old ( P < 0.01) than in young rats (Young: Basal: 50 ± 10; NMDA 15′: 410 ± 63, 22,5′: 1,469 ± 300; Old; Basal: 47±10 NMDA 15′:210 ± 30; 22,5′: 350 ± 65 ng/GnRH/mg . protein). The LH levels measured throughout the in vivo experiments indicated that basal LH concentrations were significantly lower in the aged group. The mean LH concentrations (fractions 1 to 6) was significantly lower in the aged group (Young: 3.9 ± 0.07, Old: 2.4 ± 0.03 ng/ml, P < 0.01). The LH release response to NMDA measured 10 min after the intrahypothalamic administration of the glutamate agonist was significantly lower in aged rats (4 .2 ± 1.6 ng/ml) as compared to young animals (18.0 ± 6.1 ng/ml; P < 0.05). LH levels in young rats increased to 580% vs., and only 47% in aged rats as compared to previous basal values. In conclusion, present results demonstrate that the GnRH responses to NMDA neurotransmission, which has a predominantly excitatory effects on GnRH neurons, is significantly decreased in old rats, these data give further support to the hypothesis that a decrease in the excitatory inputs to GnRH neurons could be directly involved in the reduction of the hypothalamic-pituitary-ovary axis activity observed during aging.

Effects of sex hormones on protein and collagen content of the temporomandibular joint disc of the rat

Purpose: The effect of sex hormones on the protein and collagen content of the temporomandibular joint (TMJ) disc of adult male and female rats. Materials and Methods: One hundred forty-four Wistar rats were assigned to 14 groups of 12 each. Two groups, one female and one male, served as a control and received no treatment, and two other groups (one female and one male) received a sham gonadectomy and placebo hormone. The remaining 10 groups (five males and five females) received either orchiectomy or ovariectomy, followed by administration of estrogen, progesterone, combined estrogen and progesterone, or testosterone. The total protein and collagen content of the TMJ disc were determined using the calorimetric hydroxyproline method. Results: The collagen content of TMJ discs of control males was statistically greater than the collagen content of the control female rats. This difference disappeared after ovariectomy of females and orchiectomy of males. Also, there was a general trend for a decrease in collagen and protein content to be produced by estrogen, progesterone, and by estrogen combined with progesterone in castrated male and female rats, and by orchiectomy of male rats. There was also a trend toward an increase in collagen and protein content after ovariectomy in female rats and administration of testosterone to castrated male and female rats. However, the only statistically significant effect of the drugs tested was that of estrogen combined with progesterone in ovariectomized female rats (a lowering effect on the total protein) and of estrogen alone in orchiectomized male rats (a lowering effect on the collagen content). Conclusion: Steroid sex hormones have an effect on the collagen and protein content of the TMJ disc of the rat as indicated by the difference in the values between control males and females and by the disappearance of this difference on castration of both male and female animals. This was also manifested by the significant effect of estradiol on collagen content of castrated males, by the effect of estrogen combined with progesterone on the protein content of castrated females.

An in-vivo model for the rapid assessment of skeletal effects of anabolic agents.

We recently developed an in vivo model which can be used to rapidly assess the local skeletal effects of anabolic agents. In this model, 160 g Sprague-Dawley (SD) rats were used. A stainless steel cannula was inserted into the marrow cavity of the proximal tibia through the anterior-medial cortex 6 mm distal to the knee joint. The outer opening of the cannula was covered by skin. Agents with known anabolic skeletal effects or vehicle were injected daily for 10 days into the marrow region by a small needle passing through the cannula. Rats were also injected subcutaneously with a fluorescent bone marker to label the newly formed bone. Injection sites were fixed, embedded, and sectioned for histomorphometric analysis of trabecular bone. PTH and PGE2 stimulated a large amount of new trabecular bone formation in regions proximal and distal to the injection site as measured by histomorphometry. Control groups showed minimal bone formation, limited to formation of a thin layer of bony shell immediately surrounding the cannula. The profound anabolic skeletal effects of PTH and PGE2 seen in this Local Injection Model are similar to those seen in systemic injection (i.e. subcutaneous injection in intact or castrated male and female rats) previously reported. This Local Injection Model combines numerous advantages of in vivo models (systemic injection) and in vitro models when assessing agents with anabolic skeletal activities. Compared to conventional in vivo systemic injection models, this model enables detection of anabolic skeletal effects using very small quantities (in microgram) of test agents in a short treatment period (< 10 days).(ABSTRACT TRUNCATED AT 250 WORDS)

Androgen control of secretory component mRNA levels in the rat lacrimal gland.

The purpose of this investigation was to determine whether the known gender-related differences in, and the endocrine control of, the production of secretory component (SC) by the rat lacrimal gland are associated with alterations in SC mRNA content. Levels of SC mRNA were measured in lacrimal tissues of intact, sham-operated, castrated, hypophysectomized, and testosterone-treated male and female adult rats by Northern blot procedures, which utilized a specific, [alpha-32P]-labelled rat SC cDNA probe. For control purposes, SC mRNA amounts were standardized to the beta-actin content in experimental blots. The location of SC mRNA in lacrimal glands was evaluated by in situ hybridization techniques, which involved exposure of tissue sections to sense or anti-sense [35S]-labelled SC RNA probes. Our results demonstrate that: (1) lacrimal glands of male rats contain a significantly greater amount of SC mRNA than those of female rats, and that this difference co-exists with distinct, gender-associated variations in the distribution of SC mRNA in lacrimal tissue; (2) orchiectomy or hypophysectomy, but not ovariectomy or sham surgery, leads to a marked decline in the lacrimal SC mRNA content; and (3) testosterone, but not placebo, administration to castrated male and female rats induces a significant increase in the SC mRNA levels in lacrimal tissue. Overall, these findings show that gender, androgens and the hypothalamic-pituitary axis exert a considerable influence on the SC mRNA content in the rat lacrimal gland.

LHRH effects on hippocampal neurons are modulated by estrogen in rats.

The effect of luteinizing hormone releasing hormone (LHRH) on the neuronal activity of CA1 and CA3 regions of the hippocampus was studied by means of extracellular recordings in the castrated male, intact male, castrated female, and castrated female injected s.c. with 20 micrograms estradiol benzoate (EB) for 3 days. The basal firing rate of the CA3 neurons of castrated EB-treated female rats was significantly lower than that of the neurons in castrated EB-untreated female rats as well as male rats, either intact or castrated, whereas that of the CA1 neurons was not significantly different from castrated EB-untreated female rats. Iontophoretically applied LHRH predominantly resulted in facilitation of the neuronal firing in most of the animal groups. In the CA3 region of castrated EB-treated female rats, however, inhibition occurred in a large percentage of neurons, and the ratio of facilitation, inhibition and no response was significantly different from that in castrated EB-untreated female rats. In the CA1 region of castrated EB-treated female rats, the predominant effect of LHRH was facilitation and the ratio of facilitation, inhibition and no response was not significantly different from that in castrated EB-untreated female rats. These results suggest that LHRH is involved in increasing the neuronal activity of the CA3 region in the hippocampus, and estrogen reduces this LHRH action.

DNA binding of hypothalamic nuclear proteins on estrogen response element and preproenkephalin promoter: modification by estrogen.

Preproenkephalin (PPE) gene expression is specifically induced by estrogen in hypothalamus of ovariectomized (OVX) females, better than in male rats. To study estrogen actions on gene regulation, we have presently characterized protein-DNA interactions by use of a consensus estrogen response element (ERE) and a putative ERE from PPE gene, with nuclear extracts from hypothalamus. By use of the electrophoretic mobility shift assay (EMSA), ERE binding activity was detected in nuclear extracts from neuronal tissues including hypothalamus, hippocampus, striatum, cerebellum and frontal cortex, and non-neuronal tissues such as pituitary and uterus, but not lung of OVX female rats with a consensus ERE, as well as a 129-bp PCR fragment from PPE promoter and a hairpin oligonucleotide that contains a putative ERE of the rat PPE gene. The ERE binding was eliminated by the addition of specific ERE-containing oligonucleotide, but not control oligonucleotides. Protein and DNA associated and dissociated very rapidly. By use of supershift assay, interactions of estrogen receptor with ERE were demonstrated in hypothalamic nuclear extracts. The initial levels of specific ERE binding in the hypothalamic nuclear extracts were comparable between castrated male and OVX female rats. However, estrogen treatment, either estradiol or estradiol benzoate, produced a rapid and tissue-specific induction of a slow mobility complex of ERE binding in hypothalamic nuclear extracts from females, better than in male rats, presumably from other associated factors, or a conformational change or other posttranslational modifications. This estrogen-induced slow mobility complex of ERE binding in hypothalamus was not observed after treatment with progesterone or tamoxifen. These results suggest that specific ERE binding is present in rat hypothalamic nuclear proteins, which may contribute to the upregulation of PPE gene expression by estrogen, and that the sexually differentiated action of estrogen may be related to an estrogen-induced conformational change, but not to the initial level of ERE-binding activity.

The Effect of Prenatal Exposure to the Phytoestrogen Genistein on Sexual Differentiation in Rats

Exposure to naturally occurring estrogens during critical periods of development can alter morphologic and physiologic markers of sexual differentiation. The current experiment characterizes the effects of in utero treatment with genistein, an isoflavonoid phytoestrogen, on birth weight, anogenital distance (AGD) at birth. GnRH stimulated luteinizing hormone (LH) secretion, volume of the sexually dimorphic nucleus in the preoptic area of the hypothalamus (SDN-POA), puberty onset, and vaginal cyclicity. Pregnant Charles River CD rats were injected sc daily on gestation day 16-20 with either 25,000 micrograms genistein (G25), 5,000 micrograms genistein (G5), 5 micrograms diethylstillbestrol (DES), 50 micrograms estradiol benzoate (E), or corn oil alone for controls. Birth weights and anogenital distance was taken and exposed progeny were subsequently used in two experiments. In Experiment 1 intra-atrial catheters were placed in adult castrated rats, GnRH was given iv, serial blood samples were drawn and sera were assayed for LH by radioimmunoassay (RIA). Brains obtained by subsequent decapitation were saved for histology. In Experiment 2, females were monitored for timing of vaginal opening as a marker of puberty onset, and vaginal smears were taken to monitor cyclicity. G25-treated females and DES- and E-treated animals of both sexes had decreased weights at birth compared with controls. G5- and E-treated animals of both sexes and DES males had smaller AGD than controls. No significant differences in pituitary responsiveness to GnRH were found among treatment groups. There was a nonsignificant decrease in SDN-POA volume in G5-treated females while DES- and E-treated females had increased SDN-POA volume compared with controls. G5-treated females had delayed puberty onset, and DES-treated females had atypical vaginal cycles in comparison with controls. The results confirm that prenatal exposure to estrogens in the environment can influence sexual differentiation. Our previous experiments have demonstrated that castrate female rats exposed as neonates to genistein have decreased pituitary responsiveness to GnRH challenge and enlarged SDN-POA volume in comparison with controls. Prenatal genistein at these dosages did not significantly alter these markers. However, genistein did mimic other estrogens' effects on AGD and birth weight and had a unique influence on puberty onset. Not only are genistein's effects different from other estrogens, but dosage and timing of exposure during development appear to be important factors in genistein's ability to modify these end points.

Long-term in vivo desipramine or estrogen treatment fails to affect serotonin-induced outward current in hippocampal pyramidal cells of the rat

The effect of castration combined with either long-term treatment with the tricyclic antidepressant drug desipramine or the sex steroid 17β-estradiol on serotonin responses in area CA1 of the hippocampus of male and female rats was examined. Using single-electrode current and voltage-clamp techniques serotonin-induced hyperpolarizations and outward currents were recorded from hippocampal pyramidal cells. Neither in male nor in female castrated rats treatment effects were observed on the magnitude of the 5-hydroxytryptamine 1A mediated outward currents (0.26 nA) and membrane hyperpolarizations (11 mV) induced by superfusion of serotonin (15 μM), or on the effect of serotonin on the afterhyperpolarization and extracellularly recorded population spike. In voltage-clamp experiments using microelectrodes filled with potassium-chloride, but not with potassium-acetate, the sole observable effect was that the membrane resistance drop due to application of serotonin was significantly larger in the ovariectomized group (31% ≈ 19MΩ) as compared to the ovariectomized/estrogen suppleted group (23% ≈ 15 MΩ). Spiperone (3 μM) completely antagonized the serotonin-induced outward currents and input resistance changes under all treatments. Apart from these changes the majority of passive and active membrane properties of cells from ovariectomized animals were not affected by chronic desipramine or steroid treatment. Neither did castration alone, nor in combination with long-term 17β-estradiol treatment, affect CA1 pyramidal cell membrane properties of male rats. Since we attained physiological levels of 17β-estradiol in the blood plasma (30–50 pg/ml) using subcutaneous silastic implants containing a mixture of cholesterol/estrogen, we conclude that both long-term estrogen and long-term desipramine treatment do not affect serotonergic neurotransmission in CA1 of the rat hippocampus.

Effects of sex steroids on myocardial anoxic resistance.

Eight treatment groups of CD strain castrate male or female rats were injected daily with cottonseed oil (sham), testosterone propionate (50 micrograms/100 g body wt), estradiol benzoate (7 micrograms/100 g body wt), or a combination of both steroids dissolved in cottonseed oil. These physiologic replacement dosages of sex steroids, determined by bioassay procedures, were injected in a 0.1-ml bolus of cottonseed oil daily (intraperitoneally) for 16 weeks. Myocardial anoxic resistance was quantified by means of an in vitro right ventricular strip preparation that evaluated the ability of the isolated right ventricle to maintain contractions in response to electrical pacing at 1 Hz after 10 min of anoxia. While this parameter was elevated 2- to 3-fold in the estrogen-treated groups of male and female castrates compared with the sham (oil)-injected groups, neither testosterone treatment alone nor combination steroid treatment produced anoxic resistance values that differed significantly from those of the sham-injected animals. Thus, although estrogen alone may afford anoxic protection to the myocardium, testosterone is able to abolish this hormone-induced protection.

Steroid hormone effects on NMDA receptor binding and NMDA receptor mRNA levels in the hypothalamus and cerebral cortex of the adult rat.

Previous work has demonstrated that N-methyl-D-aspartate (NMDA) is capable of stimulating luteinizing hormone release in a variety of species. Interestingly, the ability of NMDA to stimulate luteinizing hormone release is significantly compromised in castrated male and female rats as compared to intact animals. The purpose of the present study was to determine if a difference exists in the number or affinity of NMDA receptors in the hypothalamus of intact or castrated adult male and female rats and whether steroid replacement has any effect on NMDA receptor binding. NMDA receptor mRNA levels were also determined in the respective models. The cerebral cortex was used as a control to check for specificity of any observed differences. The number of NMDA binding sites in the hypothalamus was found to be approximately 25% of that found in the cerebral cortex and the equilibrium association constant was similar in both tissues. In the female rat, neither ovariectomy nor ovariectomy with estrogen pellet replacement or estrogen and progesterone injections altered NMDA receptor binding or the equilibrium association constant in the hypothalamus or cerebral cortex as compared to intact controls. Similar to the case in the female, NMDA receptor binding in the hypothalamus and cerebral cortex of male rats did not change after castration or after treatment with testosterone propionate. Neither ovariectomy nor ovariectomy with estradiol replacement brought about any change in the NMDA receptor mRNA levels in the hypothalamus. However, in the cerebral cortex ovariectomy with estrogen replacement brought about a small but significant increase in NMDA receptor mRNA levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Dopamine and sex steroid regulation of POMC gene expression in the hypothalamus.

Previous studies have shown that POMC mRNA and peptide levels are increased in the medial basal hypothalamus (MBH) of the chronically castrated rat and are suppressed with sex steroid replacement. In a parallel time course, hypothalamic dopamine turnover similarly changes after chronic castration and sex steroid replacement. In this study we have examined the effects of dopamine on POMC in the MBH and questioned whether the increase in dopamine activity which occurs in the MBH of chronically castrated rats is responsible for the stimulation of POMC seen under these conditions. We have therefore measured POMC gene expression and peptide content in the MBH of chronically castrated male and female rats in response to the dopamine antagonist haloperidol, and in intact or sex steroid replaced animals in response to the dopamine agonist pergolide. Adult male and female rats were studied 3-4 weeks after castration with and without testosterone (T) or estradiol (E2) replacement. POMC mRNA was measured by a solution hybridization S1 nuclease protection assay; beta-endorphin (beta-EP) and alpha-MSH were measured by RIA. In the first study 4 groups of ovariectomized (OVX) rats were treated with saline, haloperidol, E2 or E2 + pergolide. The mean POMC mRNA concentration in the MBH was 0.85 +/- 0.04 pg/microgram RNA in the saline group and decreased to 0.62 +/- 0.06 pg/microgram with haloperidol (p < 0.01). A similar decrease to 0.53 +/- 0.03 pg/microgram was seen with E2 (p < 0.01); pergolide however prevented the E2 induced decrease in POMC mRNA. In the second study ORCX rats received saline or haloperidol and sham-ORCX rats received saline or pergolide.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-response characteristics of neonatal exposure to genistein on pituitary responsiveness to gonadotropin releasing hormone and volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) in postpubertal castrated female rats

Estrogen exposure during critical periods of development promotes androgenization of the brain, which is reflected in altered morphology, behavior, and cyclic hormone secretion in females. Previous work in our laboratory demonstrated that neonatal female rats injected with pharmaceutical or naturally occurring estrogens had decreased GnRH-induced LH secretion and increased volume of the SDN-POA as 42 day castrates. The current experiment defines the dose-response characteristics of neonatal exposure to the isoflavonoid phytoestrogen genistein (G) on pituitary sensitivity to GnRH and SDN-POA volume. Litters of rat pups received subcutaneous injections of either corn oil, 1, 10, 100, 200, 400, 500, or 1000 μg of G on days 1 to 10 of life. The litters were ovariectomized and weaned on day 21. On day 42 blood was drawn from right atrial catheters immediately prior to, 5, 10, 15, and 30 min following a single injection of 50 ng/kg of GnRH. Only the 10 μg dose of G was associated with increased pituitary response to GnRH, while progressive increases in exposure levels of G were associated with decreasing LH secretion. The SDN-POA volume was increased in only the 500 μg and 1000 μg exposure groups compared to controls. The results confirm that low doses of G have nonandrogenizing, pituitary-sensitizing effects, while higher doses of G mimic the more typical effects of estrogens. The use of both morphologic and physiologic end points more completely defines the reproductive consequences of environmental estrogen exposure during critical periods of CNS development.

Determinant Role of Testosterone in the Pathogenesis of Urolithiasis in Rats

By using an ethylene glycol-induced urolithiasis model, we assessed the role of testosterone in the pathogenesis of urolithiasis. The intact and castrated male and female rats were fed with 0.5% ethylene glycol in drinking water for four weeks. The renal excretions of oxalate, citrate and other electrolytes were measured, and the stone and crystal deposit were examined microscopically. The results showed that drinking a loading of 0.5% ethylene glycol for four weeks produced hyperoxaluria in all rats, but the intact male rats excreted more urinary oxalate than any other groups of rats. The ethylene glycol-fed rats exhibited hypocitraturia except the castrated male rats. However, urolithiasis occurred in intact male but not female rats. Castration in male rats fed with ethylene glycol dramatically decreased the incidence of renal stone from 71.4% (5/7) to 14.3% (1/7). On the other hand, there was still no renal stone formed in the oophorectomized female rats which received ethylene glycol treatment. These data indicate that serum testosterone level plays a determinant role in urolithiasis formation.

Oral Prophylaxis with Itraconazole of Experimental Aspergillus and Candida Infections

The prophylactic activity of the liphophilic triazole itraconazole was evaluated in systemic aspergillosis and sytemic candidosis in guinea-pigs and in vaginal candidosis in rats. Systemic invasive aspergillosis in guinea-pigs was obtained by intravenous inoculation of <i>Aspergillus fumigatus, </i>25,000 CFU/g body weight. The administration of 4 doses of itraconazole, 5 mg/kg, before infection was able to prolong the survival of the animals compared with the excipient- treated group (p &#60; 0.001; Mann-Whitney U-test, 2-tailed probability). Systemic and disseminated candidosis in guinea-pigs was obtained by intravenous inoculation of <i>Candida albicans, </i>1,000, 2,000 or 4,000 CFU/g body weight. Oral prophylaxis with itraconazole, 5 or 10 mg/kg, or with the excipient was given for 1, 2, or 3 days. All excipient-treated animals (n = 38) showed skin folliculitis and gave positive cultures of the skin and kidneys; the number of CFU/g organ weight was higher with heavier inocula. In the itraconazole-treated animals (n = 114), <i>Candida </i>folliculitis was absent in 89%, and skin and kidney cultures were negative in 84% and 82%, repectively. In animals given the higher dose of itraconazole and inoculated with 1,000 or 2,000 CFU/g body weight (n = 60), however, <i>Candida </i>folliculitis was absent in 97%, and skin and kidney cultures were negative in 93% and 88%, respectively. The effectiveness of itraconazole was also related to the number of treatments before inoculation. Oral itraconazole was more effective than parenteral amphotericin B, 1.25 or 2.5 mg/kg, given 24 h and 1 h before inoculation. Female castrated rats maintained in permanent pseudo-oestrus by oestrogen injections were infected intravaginally with C. albicans and pre-treated orally with the excipient or with itraconazole, 1.25-40 mg/kg, in various regimens at 1, 24, 48 and 72 h before infection with 1, 2 or 3 doses. The animals were protected against infection at higher doses or when more than 1 dose was administered. No drug-related side-effects were observed. The broad-spectrum therapeutic value of itraconazole is well established. Prophylaxis with this antifungal agent opens new possibilities for the prevention of chronic diseases and for the protection of immunocompromised patients.