Responses to copulatory stimulation in neonatally androgenized female rats.

Five experiments evaluated the extent to which copulatory stimulation could ameliorate the anestrus and sterility exhibited by neonatally androgenized female Long-Evans rats (N?=?102). The age at which Ss began to exhibit persistent vaginal estrus and the degree of sexual receptivity exhibited under several testing paradigms were found to be inversely related to the dose of testosterone propionate (TP) injected neonatally. With increasing numbers of mounts received, both the number of androgenized Ss exhibiting sexual receptivity and the quality of the estrous behavior exhibited tended to increase. Ss injected with high doses of TP (500 μg) usually showed little or no receptive behavior even in the most extensive behavioral tests. However, under some testing conditions Ss receiving 50 μg of TP neonatally, while showing little or no receptivity during initial mounts, showed increased receptivity as behavioral tests were extended. Following matings that included 1–5 ejaculations, only control Ss were observed to become pregnant. However, when androgenized females cohabited with males for an extended period, Ss that had neonatally received .5 μg of TP, but not higher doses, did become pregnant. It is concluded that (1) the capacity of systems mediating reproductive physiology and behavior is facilitated by stimuli associated with males; and (2) mating is a characteristic of the female rat, which can be manipulated by injection of hormones during the neonatal period. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Kindling-induced emotional behavior in male and female rats.

Modeling fear in animals is a critical approach for identifying the neural mechanisms involved in human disorders such as generalized anxiety and panic. Amygdala kindling has proven useful in this regard because it produces dramatic increases in fearful behavior. The purpose of this experiment was to compare the behavioral effects of kindling in male and female rats. Compared with the sham-stimulated rats, the kindled male and female rats showed similar increases in fearful behavior, with some sex differences in fear-related open-field activity. They also showed decreased immobility in the forced-swim test and increased sucrose consumption. These results suggest that kindling-induced fear is generally similar in male and female rats and that kindling does not appear to induce depression-like behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial learning in male and female Long-Evans rats.

Male and female Long-Evans rats were tested in the Morris water maze at age 6 mo. A place training procedure, in which rats learned the position of a camouflaged platform, was followed by cue training, in which rats escaped to a visible platform. No sex difference was found in place learning ability. Search accuracy on probe trials, when the platform was unavailable, was also equivalent for the male and female groups. These results contrast with previous studies of rodents at younger ages, which have reported a male advantage in spatial learning. It is suggested that the age at which rats are assessed may be an important factor, possibly reflecting a different course in the relatively protracted maturation of the hippocampus in male and female rats. The results of this investigation are also discussed with reference to studies of sex differences for spatial abilities in humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dextromethorphan affects ventilation differently in male and female rats

Subcutaneous administration of aspartic acid results in a long-lasting but reversible depression of ventilation in male but not in female rats. Aspartic acid acts on N-methyl-D-aspartate receptors. The present study tested the hypothesis that a noncompetitive N-methyl-D-aspartate-receptor antagonist, dextromethorphan (Dex), would depress ventilation in female rats and stimulate it in male rats. Moreover, Dex administered prior to aspartic acid should prevent the aspartic acid-induced depression of ventilation in male rats. In female rats, Dex caused a 30% depression of ventilation relative to saline at 5 and 10 mg/kg (P < 0.01) but not at the highest dose (20 mg/kg). In male rats, Dex had no effect on ventilation. At a dose of 20 mg/kg, Dex depressed oxygen consumption to 50% of the saline value at all time points in female rats (P < 0.001) and in male rats 45 and 60 min after administration. The time points when Dex depressed ventilation and oxygen consumption were different in female rats, suggesting that the depression of ventilation was not the result of a depression in oxygen consumption. During a hypercapnic challenge (7% CO2), female rats treated with 5 and 10 mg/kg of Dex exhibited a smaller increase in ventilatory response relative to saline treatment. At a dose of 20 mg/kg, the hypercapnic responsiveness of male rats was markedly stimulated (85.8 +/- 8.95 ml/min) relative to saline (50.6 +/- 9.14 ml/min; P < 0.001). Finally, Dex administered before aspartic acid prevented the aspartic acid-induced depression of ventilation in male rats. Thus, in rats, Dex has gender-specific effects on ventilation and these effects are not associated with changes in oxygen consumption.     

Plasma apolipoprotein profiles of male and female rats

To determine if sex differences exist in the apolipoprotein profile of the rat, the concentrations of the major apolipoproteins and lipids of 12-week-old male and female rats were measured in the plasma as well as in the individual lipoprotein fractions. Plasma apo B, triglyceride, and cholesterol concentrations were significantly higher in male rats than in female rats. Plasma concentrations of apo A-I, apo E, apo A-IV, and apo C-III did not differ between the sexes. Male rats had higher concentrations of apo B in the very low density lipoproteins (VLDL), intermediate density lipoproteins (IDL), and the low density lipoproteins (LDL). These results further support the evidence that sex hormones influence lipoprotein metabolism in the rat.     

The role of sexually dimorphic medical preoptic area of the hypothalamus in the sexual behaviour of male and female rats

The human placental alkaline phosphatase (PLAP) gene was analysed for its utility as a histochemically detectable reporter gene in transgenic mice. A reporter gene was made by linking the PLAP structural gene to an enhancer-promoter element from the human beta-actin gene. This gene was inserted into the mouse genome by transfection of embryonic stem cells, and by microinjection of fertilized eggs. Histochemical staining showed that the transgene was uniformly expressed in four of four stable ES cell lines, and in all ten tissues examined from adult animals from five lines of transgenic mice. Non-transgenic cells did not stain. These results suggest that the human PLAP gene will be of utility in studies requiring phenotypic marking of cells in tissues of mice.     

Exogenous androgen activates female behavior in noncopulating, prenatally stressed male rats.

Male copulatory behavior was severely impaired in 39 male offspring of Sprague-Dawley female rats stressed during pregnancy. This deficiency persisted even after castration and prolonged treatment with testosterone propionate and after exposure to electric skin shock. However, androgen treatment effectively activated female lordotic behavior in a large percentage of prenatally stressed males but not in any controls and in only a negligible number of postnatally stressed males. Although prenatal stress demasculinizes and feminizes behavior, no modifications of reproductive morphology were detectable. It is suggested that prenatal stress alters normal sexual behavior differentiation by attenuating testosterone secretion from the fetal testes. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Competitive behavior in male, female, and pseudohermaphroditic female dogs.

Tested 36 male, spayed female, and pseudohermaphroditic female dogs in pairs for competition over a large bone. Pseudohermaphrodites had been exposed to testosterone propionate before and immediately after birth. In equal opportunity (EO) tests, both members of a pair had equal chance to seize the bone. Each EO test was followed by an established possession (EP) test. During an EP test, the loser of the preceding EO test was given possession of the bone before the former winner was returned to the test arena. Every S was tested against all other members of its own and the other groups. Males won 78 of 100 EO tests against normal females but only 61 of 100 against pseudohermaphrodites. Pseudohermaphrodites won 70 of 100 EO tests against normal females. When either normal or pseudohermaphroditic females were given possession of the bone in EP tests they were equally ineffective in defense against male challengers, losing 75 and 71% of their tests, respectively. Both types of females were more successful in defending possession during EP tests against each other. When normal and pseudohermaphroditic females were treated with testosterone, their performance in competition tests was not altered. Androgenic stimulation before and immediately after birth permanently modified the social behavior of pseudohermaphrodites as well as the behavior of males and normal females toward experimental Ss. (6 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pharmacokinetic evaluation of liposomal encapsulated ampicillin in male and female rats

The dispositions of free and liposomal entrapped ampicillin were compared in male and female rats after i.v. administration. Serial blood samples were collected for 2 h in the free drug study and 12 h for the liposomal formulation. Pharmacokinetic parameters obtained with free drug were not significantly different between genders. However, gender significantly influenced the disposition of liposomal encapsulated ampicillin. While no difference was observed in distribution t1/2 between genders, female rats had a shorter MRT, smaller Vss and Vt, and faster clearance as compared to male rats. In a second study, spleen, liver, kidney, heart, and lung were harvested post-injection of free and liposomal entrapped ampicillin. Free ampicillin did not distribute extensively into the tissue compartment and no gender difference was noted. In contrast, liposomal encapsulation resulted in a substantial tissue uptake. In general, female rats had higher concentrations in the spleen and lung as compared to male rats. In vitro plasma stability was not significantly different, suggesting that destabilization of the liposomes does not play a large role in the dispositional differences observed in these studies. However, in vivo interaction of liposomes and plasma lipoproteins may influence the disposition of encapsulated drug.     

Sex differences in cytosolic androgen receptors in gonadectomized male and female rats

OBJECTIVE: To assess the impact of the introduction of the laparoscopic cholecystectomy on surgical training, and the outcome of laparoscopic cholecystectomies performed by residents compared with those of surgeons. DESIGN: Retrospective analysis. SETTING: University hospital, The Netherlands. SUBJECTS: 943 Patients who underwent cholecystectomies from January 1987-December 1993 by residents and surgeons. In 527 patients the cholecystectomy was open and in 416 laparoscopic. MAIN OUTCOME MEASURES: The percentage of cholecystectomies done by residents in the period 1987-1993. The outcome of laparoscopic cholecystectomies done by surgeons and residents in terms of duration of operation, conversion rate, postoperative complications, and hospital stay. RESULTS: Before the laparoscopic era about 70% of all cholecystectomies were done by residents. After its introduction in 1990, the residents did 38% of the laparoscopic cholecystectomies in 1991, 39% in 1992, and 64% in 1993. There were no differences in outcome of laparoscopic cholecystectomy in terms of duration of operation, conversion rate, postoperative complications and hospital stay between surgeons and residents. CONCLUSIONS: The introduction of laparoscopic cholecystectomy caused a temporary decline in the number of cholecystectomies done by residents. Laparoscopic cholecystectomy was integrated as a standard surgical procedure in the residents' training programme within two years of its introduction. The outcome of laparoscopic cholecystectomies done by supervised residents and surgeons was similar, and so laparoscopic cholecystectomy should be part of residents' training.     

Prolactin-releasing effect of buspirone in developing and adult male and female rats

The prolactin-releasing effects of buspirone, an azaspirodecanedione anxiolytic drug unrelated to the benzodiazepines in structure and pharmacologic properties, was examined in developing and adult male and female rats. The possibility that effects of this drug on hormone release could be modulated by neonatal brain sexual differentiation was also evaluated. A single injection of buspirone, 2 or 10 mg/kg body wt, increased serum prolactin (PRL) levels in both sexes; the increase was significant from Day 12 onward. The PRL-releasing effect increased with age. No significant sexual differences were observed in younger rats, but in peripubertal and adult animals, the hyperprolactinemic response was higher in the female. Neonatal androgenization of females or orchidectomy of males failed to modify the PRL-releasing action of buspirone. Serum titers of luteinizing hormone and follicle-stimulating hormone were not modified by buspirone at any age. The present results show for the first time the ontogeny of the PRL-releasing effect of buspirone in male and female rats, and provide evidence that the response is higher in the female and that the effect does not depend on brain sexual differentiation.     

Effects of environmental conditions on food consumption in female and male rats

The present experiment examined food and water consumption under different housing conditions in 20 female and 20 male Wistar rats. Food and water consumption were measured for 6 h a day following an 18-h same-sex crowded or individual housing period for each of 6 days. All subjects were individually housed during the 6-h measurement period and had access to food and water. Female rats consumed more food and water than did male rats during the 6-h period, regardless of their 18-h housing condition. In addition, previously crowded rats consumed more food and water during the 6-h period than did rats that were previously individually housed. During the 18-h period, when subjects were differentially housed, males consumed more food and water than did females; crowded rats ate less than did individually housed rats; and crowded rats drank more water than did individually housed rats. Based on plasma corticosterone data, the female and male rats were differentially affected by housing conditions. The present results are discussed with regard to housing conditions per se and sex differences in stress responses to housing.     

Functional lateralization for auditory temporal processing in male and female rats.

In 3 studies, adult male rats showed significantly better discrimination of tone sequences with the right ear than with the left ear. This result parallels similar findings of left-hemisphere specialization for auditory temporal processing in humans and nonhuman primates. Furthermore, because clinical evidence supports a link between specialization of the left hemisphere for auditory temporal processing and for speech processing, these results may reflect evolutionary precursors to left-hemisphere language specialization. Because male rats showed a stronger ear advantage than female rats, the findings may relate to evidence of a stronger right ear advantage in men than in women. Finally, results suggest that neonatal handling enhances lateralization for auditory temporal processing in both sexes. Combined results implicate neuroendocrine mechanisms as important factors in the development of lateralization for auditory temporal processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of olfactory stimuli during copulation in male and female rats.

Describes 3 experiments with a total of 74 gonadally-normal male and 29 ovariectomized female Long-Evans rats. Male and female reactions toward odors from novel and original partners were observed prior to the male's attaining his 1st or 2nd ejaculation. The male's reaction depended upon the sexual condition of the female. Only prior to their initial ejaculation did the males prefer their original partner's odors to those of novel females and only if the odors were collected from the females prior to copulation. This finding corresponded with observations of the male's random choice of partner during copulation. Females responded nonpreferentially if they had copulated prior to testing and showed a marked decrease in responsiveness as copulation continued. Prior to copulation females preferred the odors from males which had not copulated to those of males which had. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Creatine kinase-B mRNA levels in brain regions from male and female rats

The creatine kinase-B (CKB) enzyme is proposed to have a pivotal role in the regeneration of ATP in the nervous system. In the present study, the steady-state levels of CKB mRNA were determined by RNase protection assay in seventeen separate brain regions obtained from rats during the initial interval of the light period or period of inactivity in rats. The antisense probe used specifically hybridizes to CKB mRNA and discriminates CKB from CKM mRNA. The results show that brain regions from Wistar rats differ in CKB mRNA content. Highest levels of CKB mRNA were detected in the male and female cerebellum. High levels of CKB mRNA were observed in the spinal cord, brain stem and its structures (medulla, pons and midbrain) and olfactory bulb of the male rats. Female rats also contained high levels of CKB mRNA in the brain stem. In both male and female rats, the frontal cortex, occipital cortex, hippocampus and striatum exhibited lower levels of CKB mRNA relative to the complete brain. Statistical analyses demonstrated a significant difference between the male and female CKB mRNA profiles. However, CKB mRNA levels in brain regions with estrogen receptors (hypothalamus, hippocampus) were similar in male and female rats. Differential CKB mRNA levels in various brain regions may suggest diverse physiological significance of the CKB system in the regulation of brain energy metabolism.     

Open-field and avoidance behavior after neostriatal lesions in male and female rats.

The behavioral effects of lesions of the anterodorsal or posteroventral parts of the caudate-putamen were studied in 2 experiments with a total of 115 male and 101 female adult albino Holtzman rats that were gonadectomized or left untreated prior to brain surgery. Anterodorsal (ADC) lesions consistently impaired acquisition of 1-way avoidance behavior and tended to interfere with the development of a 2-way avoidance response; comparable effects were observed in gonadectomized and intact Ss of both sexes. By contrast, ADC lesions increased activity in the open field only in intact females and increased rearing only in ovariectomized females. Posteroventral caudate (PVC) lesions caused transient aphagia and adipsia in both sexes but did not consistently affect open-field activity or the acquisition of 1-way avoidance responses by either sex. These lesions profoundly impaired acquisition of shuttle box avoidance responses by intact males. By contrast, castrated males and intact and ovariectomized females with PVC lesions avoided normally in the shuttle box. Results suggest that localization of behavioral functions within the striatum differs with the sex of the S, in part because of activational effects of gonadal hormones. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selection of phenytoin responders and nonresponders in male and female amygdala-kindled Sprague-Dawley rats

PURPOSE: We recently described that, by repeated testing of the anticonvulsant phenytoin (PHT), it is possible to select responders and nonresponders from large populations of amygdala-kindled Wistar rats. Whereas responders show marked and reproducible increases of focal seizure threshold (afterdischarge threshold: ADT) on repeated testing of PHT, 75 mg/kg i.p., nonresponders do not show any significant ADT increase after this dose, thus allowing use of these subgroups in the search for mechanisms of pharmacoresistance in temporal lobe epilepsy. In this study, we examined whether PHT responders and nonresponders can also be selected from large groups of kindled rats of the Sprague-Dawley strain. METHODS: Male and female Sprague-Dawley rats were amygdala kindled, followed by once weekly i.p. testing of PHT. RESULTS: In contrast to recent experiments in Wistar rats, 75 mg/kg PHT did not induce significant ADT increases in Sprague-Dawley rats, indicating strain differences in response to this drug after kindling. When the dose was lowered to 50 or 25 mg/kg, significant and reproducible ADT increases were obtained in Sprague-Dawley rats of both genders. Therefore these doses were used for selection of responders and nonresponders in a total of 42 rats. Almost 50% of the rats were PHT responders, whereas no rat was a nonresponder when tested in up to six subsequent drug trials. Many rats were variable responders (i.e., showed ADT increases in some but not all trials), which was not due to low or variable drug absorption after i.p. injection. CONCLUSIONS: The data indicate that, in contrast to Wistar rats, Sprague-Dawley rats are not suited for selection of PHT nonresponders, but rather are quite responsive to this drug. A further difference to the Wistar strain is the truncated dose-response with loss of anticonvulsant efficacy at 75 mg/kg in kindled Sprague-Dawley rats, which may, at least in part, explain the inconsistent results reported on the anticonvulsant efficacy of PHT in this strain in the literature. The lack of anticonvulsant activity after administration of 75 mg/kg may be a result of kindling, because administration of this dose before kindling causes a significant ADT increase in this strain. This kindling-induced alteration of the anticonvulsant activity of PHT is a phenomenon that contrasts Sprague-Dawley with Wistar rats and deserves further investigation.     

Localization and quantity of hyaluronan in urogenital organs of male and female rats

Inhibition of red cell carbonic anhydrase (CA) activity resulted in the rapid development of a respiratory acidosis (0.25 pH depression within 15 min post-injection) in the blood of trout. In the lamprey, however, the onset of the respiratory acidosis was delayed and its magnitude was less (0.18 pH depression at 6 h post-injection). Erythrocyte pH of both species decreased by about 0.12 units by 1 h after CA inhibition. These data, combined with the lack of rapid anion (Cl-/HCO3-) exchange in the red cells of agnathans but not in other lower vertebrates, support the hypotheses that (1) the majority of total CO2 in lamprey is transported within the erythrocyte, and (2) the limiting step in the evolution of a functioning Jacobs-Stewart cycle, and thus the evolution of the common mechanism of systemic CO2 transport in vertebrate blood, was the incorporation of the band-3 anion exchange protein into the membrane of the red cell.     

Lordosis in the male golden hamster elicited by manual stimulation: characteristics and hormonal sensitivity

The lordosis response was regularly elicited from 24 of 31 intact, adult male hamsters, using manual somatosensory stimulation of the dorsal rear body. In these males there was no correlation between measures of male-typical behavior and lordosis. Castration had no effect on male lordosis duration scores even when intromissions were eliminated. Combined treatment with estradiol benzoate and progesterone significantly increased male lordosis duration scores. The body surface was mapped with a standardized brush stimulus. For eliciting lordosis, effectiveness of stimulation increased in an almost identical manner for hormone-primed males and females from the anterior to the posterior part of the body, with the stimulation of flanks, rump, and perineum the most effective. Within each skin zone, absolute effectiveness was greater in females than in males. Various types of somato-sensory stimulation were compared for their effectiveness in eliciting lordosis. Females were more responsive to these stimuli than males, even when males were hormonally primed. These behavioral data have implications for concepts of the neural organization of male- and female-typical mating responses existing within the same individual.