Effects of perinatal exposure to phthalate/adipate esters on hypothalamic gene expression and sexual behavior in rats

Our previous research has identified the granulin (grn) and p130 genes as sex steroid-regulated genes in the neonatal rat hypothalamus that might be involved in sexual differentiation of the brain. Since phthalate/adipate esters such as di-n-butyl phthalate (DBP), diisononyl phthalate (DINP), and di-2-ethylhexyl adipate (DEHA) are suspected to interfere with the endocrine system as environmental endocrine disruptors having estrogenic or antiandrogenic properties, these chemicals may affect sexual differentiation of the brain. The present study assessed the effects of perinatal exposure to DBP, DINP, and DEHA on grn and p130 mRNA expressions in the hypothalamus on postnatal day (PND) 7 and sexual behaviors after maturation in rats. Maternal rats were given a phytoestrogen-free diet containing different doses of DBP (20, 200, 2,000, and 10,000 ppm), DINP (40, 400, 4,000, and 20,000 ppm) and DEHA (480, 2,400, and 12,000 ppm) from gestational day 15 to the day of weaning (PND 21). DBP and DINP exposure during the perinatal period resulted in an increase in hypothalamic grn and p130 mRNA levels in females and males, respectively, but DEHA exposure decreased expression levels of grn in males and p130 in females, although the effects were not dose-dependent. After maturation, male rats that were exposed to several doses of DBP, DINP, and DEHA displayed decreased copulatory behavior. The lordosis quotient was decreased in females perinatally exposed to DBP, DINP, and DEHA at all the doses used. On the other hand, serum levels of LH and FSH in both sexes and the estrous cycles in females were not affected by the treatments. These results suggest that inappropriate expression of grn and/or p130 genes in the brains of male and female neonatal rats by perinatal exposure to these chemicals may exert permanent effects on the hypothalamus, thereby decreasing sexual behavior after maturation.     

Ivermectin impairs sexual behavior in sexually naïve, but not sexually experienced male rats

Ivermectin (IVM) is an antiparasitic drug, widely used in domestic animals. In mammals, IVM act as a GABA agonist. This neurotransmitter has an important role in the regulation of sexual behavior. Thus, this study sought to investigate the effects of various medically relevant doses IVM on the sexual behavior of male rats. In particular, we also wished to examine if previous sexual experience modulated responses to IVM. In the first experiment, the sexual behavior of inexperienced male rats was analyzed after they received 0.2, 0.6, 1.0 or 2.0 mg/kg IVM, 15 min prior to behavioral testing. In the second experiment, the effects of four previous sexual experiences on IVM treated rats (1.0 or 2.0 mg/kg, 15 min prior to the 5th session) were assessed. The standard therapeutic dose (0.2 mg/kg) did not impair the sexual behavior of inexperienced male rats. At a more concentrated dose (0.6 mg/kg), which is still within the therapeutic range, the appetitive phase of sexual behavior of inexperienced male rats was impaired. Likewise, 1.0 mg/kg impaired the appetitive phase. Previous sexual experience blocked almost entirely this sexual impairment, suggesting that previous sexual experience exerts a positive effect in attenuating the sexual impairment produced by IVM treatment. Therefore, the standard therapeutic dose of IVM can be used without producing side effects on sexual behavior. Use of more concentrated therapeutic doses is not recommended during reproductive periods, unless the animals have had previous sexual experience.     

Effects of zeranol implantation and late castration on sexual, agonistic and handling behavior in male feedlot cattle

Seventy-two Angus feedlot bulls were observed to determine the effects of implanting with zeranol (0, 36 or 72 mg; four groups of six/level) at 8 mo of age (d 0), and of castration midway through the feedlot period (d 115) vs remaining intact (six groups/treatment) on sexual, agonistic and handling behaviors. All 36-mg-treated cattle were re-implanted (36 mg) on d 112; 72-mg-treated cattle were not re-implanted. Each group was observed for a total of 8 h at the time of sunset +/- 30 min for sexual and agonistic behaviors during the trial. Observations on handling were made during 15 weighings and on seven occasions in the pens of the animals. Zeranol did not affect sexual or agonistic behavior. Before imposition of castration, implanted bulls entered the scales more quickly, took longer to stand still on the scales and were less quiet than non-implanted bulls (P less than .05). Castration decreased the sexual behaviors of masturbation (.75 vs .08 X pen-1 X h-1; P less than .05), attempted mounts (.75 vs .33 X pen-1 X h-1; P less than .05) and chinning (10.70 vs 4.75 X pen-1 X pen-1; P less than .10) and the agonistic behavior of butting (42.42 vs 31.50 X pen-1 X h-1; P less than .01) in contrast to intact bulls. Castrated animals entered (P less than .10) and exited (P less than .05) the scales more quickly than did intact males.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of prepubertal versus postpubertal castration on sexual and aggressive behavior in male horses

Males horses castrated prepubertally occasionally display stallion-like sexual and aggressive behavior as adults. A retrospective survey of 140 horse owners was undertaken to compare the effectiveness of prepubertal versus postpubertal castration on objectionable sexual and aggressive behavior. Of 94 geldings that had been castrated prepubertally (before 2 years of age), 20% to 30% displayed stallion-like sexual behavior and aggression toward horses, and 5% were aggressive toward people in a stallion-like manner. This occurrence of problem behavior was not significantly different from the occurrence of these behavioral patterns in 46 geldings that had been castrated as stallions (over 3 years of age). When castration was examined as a therapeutic measure to eliminate sexual and aggressive behavior in stallions in which the behavior had become objectionable, it was found that the operation was effective on sexual behavior and aggression toward people in 60% to 70% of horses and on aggression toward horses in 40% of horses.     

Early embryonic administration of xenoestrogens alters vasotocin system and male sexual behavior of the Japanese quail

The copulatory behavior and the parvocellular vasotocin (VT) system of the nucleus of the stria terminalis (BST) are sexually dimorphic in the Japanese quail. Embryonic administration of estradiol benzoate (EB) induces an organizational effect determining the disappearance of such a dimorphism (male shows behavior and cerebral phenotype of the female). The VT parvocellular system can therefore be considered an accurate marker of the sexual differentiation of brain circuits and a very sensitive indicator of the activity of estrogen-like substances on neural circuits. To test this hypothesis we administered diethylstilbestrol (DES), a powerful synthetic xenoestrogen, genistein (GEN), a phytoestrogen produced by soy, and bisphenol A (BPA). After 3 days of incubation, quail eggs were injected with vehicle, EB, DES, GEN or BPA. Administration of BPA caused an early blockage of development and no further analyses were done on the BPA groups. At puberty, the copulatory behavior of EB- or DES-treated male quail was totally abolished, whereas only the highest doses of GEN determined a significant decrease of the behavior. After the tests, the animals were sacrificed and perfused. The fractional area (FA) covered by VT immunoreactivity was analyzed in BST, medial preoptic nucleus, and lateral septum by computerized image analysis. The FA was significantly reduced after treatment with EB, DES and GEN at high doses. These results confirm that the sexually dimorphic VT system of the Japanese quail is a sensible indicator of the effects of xenoestrogens at the level of the central nervous system.     

Differentiation of sexual behavior in cattle, sheep and swine

Gonadal steroid hormones influence an animal's sexual behavior through two primary means. During development they affect differentiation of the brain (primarily in males), and after puberty, circulating concentrations of steroids influence expression of sexual behaviors. In mammals, sexual behaviors of females are regarded as inherent (independent of steroids secreted by the developing ovary). Males, on the other hand, must undergo active differentiation that is brought about by actions of testicular steroids on the brain during discrete sensitive periods of early development. Sexual differentiation in mammals is referred to as processes of defeminization and masculinization. Defeminization is loss of behavioral traits inherent to females and occurs prenatally in sheep but postnatally in swine. Comparative data are lacking for cattle, but preliminary evidence indicates prenatal defeminization of sexual behaviors. Masculinization is acquisition of behavioral traits characteristic of males. Adult females of all three species show mounting behavior after prolonged treatment with testosterone, and in cattle and swine, there is, as yet, no strong evidence that males undergo masculinization of sexual behaviors. In sheep, limited observations are suggestive of two sensitive periods for masculinization; one prenatally and one postnatally. The earlier concept that differentiation of sexual behaviors in mammals occurs prenatally in species with a long gestation and postnatally in species with a short gestation must now be modified in view of recent findings in swine, in which defeminization occurs postnatally. Further studies will likely identify additional species differences with respect to differentiation of sexual behaviors.     

The Effects of GABA on embryonic gonadotropin-releasing hormone neurons in rat hypothalamic primary culture

Gonadotropin-releasing hormone (GnRH) neurons arise in the olfactory placode, migrate into the preoptic area (POA), and then extend axons to the median eminence during embryogenesis. Little information is available concerning the properties of GnRH neurons during the late gestational period when GnRH neurons reach the POA and form neuronal networks, although many studies have examined such properties during earlier developmental stages or the postnatal period. The present study was performed to elucidate the involvement of gamma-aminobutyric acid (GABA), one of the major neurotransmitters modifying GnRH neural activity, in regulation of GnRH gene expression on embryonic day 18.5 (E18.5) using transgenic rats expressing enhanced green fluorescence protein (EGFP) under the control of GnRH promoter. First, using RT-PCR, the mRNA of two isoforms of the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD), GAD65 and GAD67 was detected in E18.5 embryonic POA-containing tissues. GAD67-positive cells were also demonstrated in close vicinity to GnRH-positive cells by immunohistochemistry, and immunoreactivity for both the GABA-A and GABA-B receptor subunits was detected in GnRH neurons. Next, primary cultures derived from anterior hypothalamic tissue of E18.5 embryos were prepared, and the effects of GABA and its agonists on GnRH promoter activity were evaluated using EGFP expression as a marker. GABA and the GABA-A receptor agonist muscimol, but not the GABA-B receptor agonist baclofen, significantly increased the EGFP-positive/GnRH-positive cell ratio. These results suggest that GABA plays a role in stimulating GnRH gene expression through GABA-A receptors in embryonic GnRH neurons in late gestational stages.     

Influence of castration and estrogen replacement on sexual behavior of female-oriented, male-oriented, and asexual rams

An experiment was conducted to determine whether exogenous estradiol-17beta (E2) could restore sexual behavior in castrated rams. The protocol consisted of three sequential 6-wk periods during which rams were studied while 1) intact, 2) bilaterally castrated, or 3) implanted s.c. with two 7.6-cm silastic implants each containing 309+/-16 mg of E2. Rams (classified as female-oriented [FOR, n = 7], male-oriented [MOR, n = 7], or asexual [n = 7]) were subjected to 30-min sexual behavior tests every 2 wk during the ensuing 18 wk. Rams were observed for mounts and ejaculations using two ovariectomized, estrous ewes and two intact males secured in stanchions. Behavioral data were analyzed using the signed rank test, but asexual rams showed no sexual behavior and therefore were not evaluated statistically. Jugular blood was collected prior to castration and at the end of the 18-wk period, and testicular venous (n = 21) and arterial (n = 8) bloods were collected immediately prior to castration. Radioimmunoassay was used to quantify systemic levels of estrone (E1), E2, and testosterone (T) and testicular serum concentrations of oxytocin (OT). Mounting behavior of MOR and FOR declined after castration (P < .05 and P < .10, respectively). Castration reduced the number of ejaculations by FOR (P < .05), but not by MOR (P > .10). Mounting behavior of castrated MOR and FOR was not affected by E2 treatment relative to that observed if castrated only (P > .10). Treatment of asexual rams with E2 did not stimulate sexual behavior in these rams. There were no marked differences (P > .10) among ram groups with regard to serum concentrations of E1, E2, or T prior to castration (overall mean +/- SE, 12.8+/-.7, 7.6+/-.5, and 2,670+/-780 pg/mL, respectively) or any difference (P > .10) in systemic concentration of E1 or E2 among ram groups after rams were implanted with E2 (overall mean +/- SE, 9.7+/-.7 and 9.0 +/-.7 pg/mL, respectively). Serum concentrations of E2 after implantation of the steroid did not differ from those present while rams were intact (P > .10). Testicular venous and arterial serum concentrations of OT were low and did not differ within or between rams. These results suggest that restoration of E2 concentrations to physiological levels in castrated adult rams (regardless of sexual orientation) cannot stimulate or reestablish sexual behaviors to levels observed prior to castration.     

Effect of lighting treatment on the productivity,health, behaviour and sexual maturity of heavy male Turkeys

1. Turkey poults (1620) were used to compare the effects of three lighting programmes on heavy strain males reared to 188 d: constant light (24L:0D, CON); increasing light (6L:18D at 7 d gradually increasing to 20L:4D by 63 d, INC); a pattern identical to INC followed by a decrease in daylength from 84 d to 10L:14D at 112 d (DID).

2. Lighting affected growth pattern but had no effect on body weight at 118 d or overall food to gain ratio.

3. Both INC and DID lighting reduced overall mortality in comparison to CON light primarily because of a reduction in the incidence of skeletal disease and spontaneous cardiomyopathy. INC and DID lighting increased the incidence of cannibalism.

4. Turkeys given INC or DID lighting had a superior ability to walk in comparison to those birds given CON light.

5. INC and DID males stood, ate and drank more frequently, and sat less often than CON turkeys during behavioural observation.

6. There were no lighting effects on carcase composition except that INC and DID birds had heavier keel bones. The ultimate force per cm² (stress) required to break femora was greater for turkeys given INC and DID lighting (P = 0.065).

7. Plasma testosterone concentrations at 117 d were 272.5, 115.2 and 29.5 pg/ml for turkeys given CON, INC and DID lighting, respectively (P= 0.072). Testosterone concentration was not related to growth rate.     

Reflections on mare behavior: Social and sexual perspectives

Among horse owners “mare-ishness” is easily recognized, if poorly defined, as generally awkward or recalcitrant behavior. In common with other mammals, however, horses do show a range of female-specific behavior patterns concerned particularly with sexual and maternal functions but also encompassing aspects of social peer interaction. Many of these behavior patterns are observed more easily in free living feral populations and are repressed at least partially under standard domestic management regimes. Feral horses form small stable breeding groups within which mares create linear dominance hierarchies based on the outcomes of aggressive encounters and positive social bonding. Rank within the social hierarchy may also influence reproductive success, with dominant mares having shorter foaling intervals and earlier foaling than lower ranking subordinate mares. Advantageous early foaling may reflect preferential mating by the group stallion based either simply on enhanced physical condition leading to earlier reproductive cycling in dominant mares or on an increased attractiveness to dominant mares by the stallion contingent on some aspect of dominance characteristics. The endocrine axis responsible for regulation of sexual behavior in the mare shows a degree of commonality with systems underlying social dominance. Both these behavior patterns are driven by a complex interaction of endocrine and neuro-endocrine factors sensitive to physical and social environmental cues and in feral free-living horses these are interlinked to an extent that may be under appreciated in domestic breeding populations.     

公犬性功能障碍的原因及防制措施

公犬性功能障碍通常是指公犬达到配种年龄却不能正常交配的疾病。临床上较为常见,主要有两种症状：一是公犬在与发情母犬接触时不爬跨母犬,阴茎不能勃起,不产生性反射;二是公犬有性欲,但却不能自然交配,需要人工辅助。     

Alteration of the gene and protein levels of insulin-like growth factors in streptozotocin-induced diabetic male rats

Insulin-like growth factor (IGFs: IGF-I and IGF-II) systems have been reported to be associated with the onset of diabetic mellitus. Therefore, we investigated the effect of diabetes on regulation of the IGF system in the liver, kidneys and heart, which are important organs in the pathogenesis of diabetes. The experimental groups were subdivided into three groups: 1) controls, 2) streptozotocin (STZ)-induced untreated diabetic group, and 3) an insulin-treated group (plus diabetic rats). In the present study, starting on the second day after STZ treatment, the diabetic group exhibited hyperglycemia, polyuria, and polydipsia, which are characteristic of diabetes melittus. Serum levels of IGF-I were decreased, but those of IGF-II were increased in the diabetic group compared with the controls. The expression levels of IGF-I and IGF-II protein in the livers of the diabetic group had a similar pattern to the serum. In addition, the expression levels of liver IGF-I mRNA and IGF-II mRNA were decreased in the diabetic groups. In the heart, IGF-I levels were decreased, but IGF-II levels were increased in the untreated diabetic groups, which was consistent with the expression levels of their mRNA. However, both the IGF-I and IGF-II levels in the kidneys were increased in the untreated diabetic groups, but the mRNA levels were decreased. Insulin treatment ameliorated the changes of IGF system in the serum, liver, kidneys, and heart. In conclusion, diabetes induced alteration of the IGF system tissue-specifically, and this was blocked by insulin treatment.     

Effects of the age of male and female broiler breeders on sexual behaviour, fertility and hatchability of eggs

1. The effects of the age of male and female broiler breeders on fertility, hatchability and sexual behaviour were determined in two 2x2 factorial experiments. In the 1st, male and female birds 27 to 29 and 35 to 37 weeks and in the 2nd at 35 to 37 and 55 to 57 weeks of age were compared. 2. Fertility was not affected by the age of the males or females. 3. Early embryo deaths were higher and hatchability of fertile eggs was lower in eggs from females aged 27 to 29 and 55 to 57 weeks compared with eggs from birds aged 35 to 37 weeks. 4. There were no differences in male display behaviours at any age. The number of observed matings were higher in young males 27 to 29 weeks old compared with males 35 to 37 and 55 to 57 weeks of age. There were no detectable differences in the responses of the females to the males at different ages. 5. Plasma testosterone concentration in males increased from 24 to 30 weeks of age and was relatively constant from 36 to 60 weeks. Plasma oestrogen in females was high at 24 and lowest at 30 weeks of age after which it increased. 6. The results suggest that there may be little difference in the fertility of male and female broiler breeders at different ages when body weight is adequately controlled to at least 60 weeks of age.     

Effect of hypothalamic electrolytic lesions in White Leghorn and broiler male cockerels

1. This study compared the effect of bilateral electrolytic lesions of the basomedial hypothalamus (HL) in broiler and White Leghorn (WL) males. 2. Hypothalamic lesions were placed in WL at 10 weeks of age (body weight 1.1 kg) and in broilers, either at 6 weeks (body weight 1.5kg) or at 10 weeks of age (body weight 3.4kg). They were fed ad libitum until autopsy at 16 and 17 weeks of age for broilers and WL, respectively. 3. Hypothalamic lesions caused obesity (high percentage weight of abdominal adipose tissue) in both strains. Obese fowls with unimpaired reproductive systems were classified as OB and those with functional castration as FC (functionally castrated) or FCLC (functionally castrated with large comb). 4. All post-HL syndromes-OB, FC and FCLC-were present in WL, whereas all obese broilers (which are immature at this age) were classified as OB. 5. The percentage weight of abdominal adipose tissue in OB broilers was lower than in OB WL (3% vs 5%, respectively). 6. Daily food intake of OB broilers was higher than control at 12 to 15 weeks of age, regardless of time of placement of HL, whereas daily food intake of OB WL was significantly higher than that of control WL only during the first 2 weeks following HL. 7. Body weight of OB broilers at autopsy was 20% higher than control broilers, whereas body weight of OB WL was not significantly affected. 8. An additional group of broilers was reared to sexual maturity under food restriction until 28 weeks of age. HL were placed at 10 weeks of age (body weight 1.7 kg). Autopsy was performed after a 4-week period of ad libitum feeding. 9. There were OB as well as FC and FCLC among the HL, food-restricted broilers. Percentage weight of testes and spleen were reduced in OB fowls of both strains, but more so in OB WL. 10. Hyperphagia and weight gain were not observed during the ad libitum feeding period of those obese broilers after HL, indicating that hyperphagia and weight gain are secondary to obesity.     

Effects of cyclophosphamide on the kaolin consumption (pica behavior) in five strains of adult male rats

It is known that pica, the consumption of non-nutritive substances such as kaolin, can be induced by administration of toxins or emetic agents in rats. In the present study, we examined the effects of intraperitoneal (i.p.) administration of cyclophosphamide on pica behavior and on the concentration of 5-hydroxyindoleacetic acids (5HIAA) in cerebrospinal fluid (CSF) in the following five strains of adult male rats: Sprague Dawley (SD), Wistar, Fischer 344 (F344), Wistar-Imamichi (WI) and Long Evans (LE). Cyclophosphamide (25 mg or 50 mg/kg) was injected (i.p.) into the rats and kaolin and food intake were measured at 24 hr after injection. The animals were anesthetized with urethane (1 g/kg) at 3 hr after injection of cyclophosphamide, and CSF was collected from the cisterna magna. WI and LE rats clearly showed pica behavior as compared with the other strains. In LE rats, the concentration of 5HIAA in CSF also increased in a dose-dependent manner of cyclophosphamide. The pretreatment with ondansetron (5-HT(3) antagonist) restored both changes (kaolin consumption and 5HIAA levels) induced by cyclophosphamide. These results suggest that the LE rat is sensitive to cyclophosphamide, that pica induced by cyclophosphamide mimics many aspects of emesis including the serotonergic response in the central nervous system and that use of the pica model would be a practical method for evaluating the effects of antiemetic drugs in addition to the mechanism of emesis.