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)     

Exploratory behavior and reaction to novelty in rats with hippocampal perforant path systems disrupted.

In this article, exploratory behavior and reaction to novelty were investigated in rats with either disruption of the total hippocampal perforant path projection (TPP), the medial perforant path (MPP), or lateral perforant path (LPP). All three experimental groups displayed increased locomotor activity, and the LPP group was even more active than the TPP and MPP groups. The TPP and LPP animals made more rearings than the control rats. The MPP and LPP groups exhibited less exploration of familiar objects than the TPP and control groups. TPP animals appeared unable to recognize novelty, LPP rats showed decreased preference for novelty, and MPP rats had only a slight deficit in recognition of novelty. It is suggested that perforant path disruptions reduce the hippocampal formation's access to sensory information of neocortical origin. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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.     

Decline of sexual behavior in castrated male rats: effects of female precopulatory behavior

Ventricle cells from neonatal rats were cultured in a medium preventing cell proliferation on a modified Roller apparatus with a defined pericellular oxygen partial pressure (pO2) of 38 or 0.6 mm Hg for about one week. The cells were harvested after the second and eighth day of culture (corresponding to one or seven days of culture under a defined pO2) and prepared for electron microscopy. Electron micrographs of this material were examined by stereologic techniques. The obtained results showed some deviations of mitochondrial fine structure of heart muscle cells depending on oxygen supply. During cultivation with a pO2 of 0.6 mm Hg (hypoxic conditions) we observed a proportional increase in mitochondria without cristae and an increase in size accompanied by a more irregular shape. On the contrary, the mitochondria of cells cultured with a pericellular pO2 of 28 mm Hg, which we consider to be a normoxic condition, did not show any deviation of inner membrane arrangement, but an increase in number and a decrease of size during cultivation was apparent. The mitochondria-myofibrils ratio decreased during cultivation in both conditions of oxygen supply. The ratio between sarcoplasmatic reticulum and myofibrils decreased markedly at a pO2 of 0.6 mm Hg.     

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)     

Effects of ibotenate hippocampal and extrahippocampal destruction on delayed-match and -nonmatch-to-sample behavior in rats

The effects of ibotenate lesions of the hippocampus (HIPP) or hippocampus plus collateral damage to extrahippocampal structures (HCX) were investigated in rats trained to criterion on spatial versions of either a delayed-match (DMS) or delayed-nonmatch-to-sample (DNMS) task. After recovery from surgery, animals were retrained at "0" sec delays, then assessed at 0-30 sec delays for 15 d, retrained again at 0 sec delays, and retested for another 25 d on 0-30 sec delays. Pretrained HIPP-lesioned animals showed marked delay-dependent deficits in both tasks that never recovered. Detailed examination of within- and between-trial performance factors, including changes in response preferences, length of previous trial delay, and sequential dependencies, revealed important factors operating in lesioned animals that were either absent or insignificant before the lesion. Pretrained HCX-lesioned animals showed deficits similar to those of HIPP animals, with the noticeable exception of a strong "recency" influence of the previous trial. Another group of HIPP- and HCX-lesioned animals trained on the tasks after the lesion showed reduced impairments of the type described above, suggesting that extrahippocampal structures trained after the lesion can assume the role of the hippocampus to some degree. The findings indicate that both the type of lesion and the previous history of the animal determine the postlesion DMS and DNMS performance of animals suffering damage to the hippocampus and/or related structures.     

Effects of losartan on the sexual behavior of male rats

Many commonly used antihypertensive drugs such as diuretics and beta-blockers can interfere with sexual function in both sexes, causing loss of libido, impairment of erectile function and ejaculation in men, and delay or prevent orgasm in women. Newly developed antihypertensive drugs should ideally not interfere with the patients' quality of life including sexual function. This study examined the effects of losartan, a nonpeptide, specific antagonist for type I angiotensin II receptors, on the male sexual behavior of rats. Spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats were treated with losartan 30 mg/ kg/day or saline control for 7, 30 and 90 days. Dark-cycle video recording was used to analyze the male sexual activities of the rats. No significant alteration in male sexual performance was observed after 7 and 30 days of treatment with losartan. In contrast, SHRs treated with propranolol 5 mg/kg/day showed increases in intromission latency, ejaculation latency and postejaculatory period indicating decreased libido and erectile and ejaculatory function. Upon completion of 90 days of losartan administration, the mount latency of the SHR was significantly increased, suggesting a decrease in libido although other parameters were unchanged and there was no effect in WKY rats. It is therefore concluded that losartan may have an advantage in preservation of sexual function when used clinically for the treatment of hypertensive disorders.     

Central progesterone induces female sexual behavior in estrogen-primed intact male rats.

Injection of progesterone induced high levels of female lordotic behavior in 10 of 47 intact, estrogen-primed male Sprague-Dawley rats when it was applied directly to the medial preoptic/anterior hypothalamic area. All 17 Ss previously had shown lordosis when the serotonergic antagonist methysergide was applied to the same central sites. Few Ss responded to systematic progesterone and none to intracranial cholesterol. Intradiencephalic Metycaine, a local anesthetic, induced lordosis in 8 Ss that previously had responded to central progesterone. These data indicate that estrogen and progesterone act synergistically to induce lordosis in male rats when progesterone is administered directly to sensitive brain sites. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of long-term food reduction on the hypothalamus-pituitary-thyroid axis in male and female rats

The reduced thyroid activity during short-term starvation is associated with a lowered hypothalamic synthesis and secretion of TRH. However, little is known about the cause of the reduced thyroid function during prolonged malnutrition. We have therefore studied the effects of food reduction to one-third of normal (FR33) on the hypothalamus-pituitary-thyroid axis of male and female Wistar rats. After 3 weeks body weights of FR33 rats were almost 50% lower than those of controls. In both sexes, FR33 caused marked increases in serum corticosterone, and decreases in serum TSH, thyroxine (T4), free T4, tri-iodothyronine (T3) and free T3. While the free T3 fraction (FFT3) in serum decreased, the free T4 fraction (FFT4) tended to increase. Electrophoretic analysis indicated that decreased FFT3 was correlated with an increased thyroxine-binding globulin, while the increase in FFT4 seemed due to a decreased thyroxine-binding prealbumin binding capacity. Total RNA and proTRH mRNA in the hypothalamus were not affected by FR33. Median eminence and posterior pituitary TRH content tended to increase in FR33 rats, suggesting that hypothalamic TRH release is reduced in FR33 rats. Anterior pituitary TSH content was decreased by FR33 in both sexes, but pituitary TSH beta mRNA and TRH receptor status were not affected except for increased pituitary TSH beta mRNA in female FR33 rats. Although FR33 had no effect on pituitary weight, pituitary RNA and membrane protein content in FR33 rats were 50-70% lower than values in controls. In conclusion, prolonged food reduction suppresses the pituitary-thyroid axis in rats. In contrast to short-term food deprivation, the mechanism whereby serum TSH is suppressed does not appear to involve decreases in proTRH gene expression, but may include effects on pituitary mRNA translation. Our results further support the hypothesis that TSH release may be lowered by increased corticosterone secretion, although the mechanism of this effect may differ between acute starvation and prolonged food reduction.     

Differential effects of restraint stress on hippocampal 5-HT metabolism and extracellular levels of 5-HT in streptozotocin-diabetic rats

A HPLC method was developed for determination of risperidone and its therapeutically active main metabolite 9-hydroxyrisperidone in serum. After a single-step liquid-liquid extraction the analytes were separated on a C18 column and measured by UV detection at 280 nm. Inter-day coefficient of variation was <7% for both compounds at serum levels occurring in patients treated with ordinary doses. Studies of analytical interference showed that the most commonly coadministered antidepressants and benzodiazepines did not interfere. Some conventional low dose neuroleptics and clozapine did interfere, but this is of minor importance, because risperidone is intended as an alternative to these drugs.     

Effects of hippocampal microinjections of d-amphetamine and scopolamine on active avoidance behavior in rats.

100 male Sprague-Dawley rats received bilateral injections of 20 or 40 mg of dextroamphetamine or scopolamine into the dorsal or ventral hippocampus prior to each of 8 daily training sessions in a discriminated Y-maze active avoidance task. Scopolamine, but not dextroamphetamine, facilitated avoidance responding in both sites, with the effect being greatest following administration of 20 mg into the dorsal hippocampus. On Days 9 and 10, all Ss received saline injections and were tested for transfer of responding to the nondrug state. A decrement of performance occurred irrespective of whether the drug had facilitated avoidance responding. The performance changes were greater following termination of scopolamine than dextroamphetamine injections, and in no case were so great as those previously reported following peripheral injections of the drugs. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

Lordosis behaviour in male, female and androgenized female rats

Sex differences in the lordodis response of adult rats to ovarian hormones were studied in a series of experiments. Male rats were less sensitive to oestradiol benzoate (OB, a single injection of 10, 100 or 1000 mug/kg or seven daily injections of 2, 10, or 50mglkg)then were female rats. Oestradiol benzoate-primed (10 mglkg)female, but not male, rats showed dose-dependent responses to progesterone (0-4, 2-0 or 10-0 mg/kg/. male rats responded clearly to progesterone (2 mg/rat) only when primed with a high dose of OB (100 mug/rat). Display of the whole pattern of female sexual behaviour was induced in male rats by treatment with 100 mug OB and 2 mg progesterone. Female rats treated with 1 mg testosterone propionate (TP) on day 4 of life, ovariectomized as adults and tested under the same endocrine conditions as the rats described above, retained behavioural OB sensitivity but responded poorly to progesterone. Evidence is presented that ovarian secretions during development significantly modify the response of neonatally TP-treated and normal female rats to OB in adulthood.     

Effects of novelty on the reproductive behavior of male Japanese quail (Coturnix coturnix japonica).

In Exp I, 8 sexually deprived male Japanese quail were exposed to 1 of 7 female Japanese quail until they satisfied a 20-min sexual satiation criterion. The female was then replaced with a novel female or was allowed to remain in the test cage undisturbed. Introduction of the novel female did not reinvigorate sexual behavior above levels observed when the female was allowed to remain undisturbed. In Exp II, with 9 males and 15 females, males that were not sexually deprived were tested in the presence of 2 females. During experimental tests, 1 of the females was novel and the other was familiar. During control tests, both of the females were familiar. The presence of a novel female increased overall levels of male sexual behavior and also increased the number of males engaged in reproductive behavior. However, the enhanced sexual behavior was not differentially directed toward the novel or familiar female. Implications of these findings for the mating system of Japanese quail and for studies of the role of novelty in sexual behavior are discussed. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of gonadal steroid hormones on hypothalamic vasopressin mRNA level in male and female rats

Experiments were carried out in 10-11-week old gonadectomized male and female Sprague-Dawley rats. Dot-blot analysis and 3'-end digoxigenin-labeled 26 meroligonucleotide probe was used in detecting the mRNA level hypothalamic vasopressin (AVP). The basal hypothalamic AVP-mRNA level in the sham-operated intact males was 45% higher than that in the sham-operated intact females (P < 0.05). Plasma osmolality was also higher in the sham-operated intact males than in the sham-operated intact females (P < 0.05). The hypothalamic AVP-mRNA level in ovariectomized rats was 30% higher than that in sham-operated intact females (P < 0.05). Although the hypothalamic AVP mRNA level tended to be lower in castrated males than in sham-operated intact males, the difference was not statistically significant. The difference in plasma osmolality between gonadectomized males and females was statistically insignificant. In castrated males, hypothalamic AVP-mRNA level was decreased following sc injection of estradiol (P < 0.05), but testosterone, progesterone or a combination of estradiol and progesterone were without effect. In ovariectomized rats, sc injection of estradiol or a combination of estradiol and progesterone resulted in a decrease in hypothalamic AVP-mRNA level (P < 0.01), but progesterone or testosterone had no effect. The difference in plasma osmolality between gonadal steriod hormones-treated rats and vehicle-treated rats was not statistically significant. These findings indicate that gonadal steriod hormones can affect hypothalamic AVP-mRNA level in rats, through some central mechanism.     

Exploratory behavior and reaction to novelty in rats: Effects of medial and lateral septal lesions.

This study was carried out to investigate whether medial septal (MS) or lateral septal (LS) lesions may differentially affect rats' ability to react to novelty or environmental change. Three types of task were used based on various sets of stimuli: visual and tactile, olfactory only, and visual only. The results showed that MS and LS lesions reduced preference for novelty, with different effects. The MS group displayed decreased exploration of both neutral and novel objects, whereas the LS group exhibited increased exploration of the objects compared with the control group. A reduced level of locomotor and rearing activity was initially seen among the MS animals. These results were compared with previous findings of behavioral changes after regional hippocampal perforant path lesions in the same test as used in this study. The comparisons imply that disruption of septal input to the hippocampal formation produces cognitive deficits different from those seen after disruption of entorhinal input. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of progesterone on the reinstatement of cocaine-seeking behavior in female rats.

Estradiol benzoate (EB) facilitates the acquisition and reinstatement of cocaine-seeking behavior when administered to ovariectomized (OVX) rats. In contrast, progesterone (P) decreases acquisition of cocaine self-administration, but the effects of P on the reinstatement of drug seeking are not known. The purpose of the present study was to compare the effects of EB and P on the reinstatement of cocaine-seeking behavior in female rats. Rats received either OVX or sham surgery (SH) and were trained to lever press for intravenous cocaine infusions (0.4 mg/kg) under a fixed ratio 1, 20-s time-out schedule during daily 2-hr sessions. After 14 days of stable responding, saline replaced cocaine, and a 21-day extinction period began. After extinction, rats were separated into 5 treatment groups (OVX+EB, OVX+EB+P, OVX+vehicle [VEH], SH+P, or SH+VEH), and VEH, EB, or EB+P was administered 30 min prior to each session for 5 days. After 3 days of hormone treatment, rats received a saline or cocaine (10 mg/kg) injection, and reinstatement of lever responding was assessed. Reinstatement responding in the OVX+EB group was greater relative to the OVX+EB+P, SH+P, and OVX+VEH groups, which had low levels of cocaine-primed responding. The SH+VEH and OVX+EB groups displayed similar high levels of cocaine-elicited reinstatement. The suppression of cocaine-induced reinstatement following P treatment suggests a role for P in the prevention of relapse to cocaine self-administration in female cocaine users. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual behavior increases dopamine transmission in the nucleus accumbens and striatum of male rats: Comparison with novelty and locomotion.

Extracellular concentrations of dopamine (DA) and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were examined concurrently, using in vivo microdialysis, in the nucleus accumbens and dorsal striatum of sexually active male rats during tests of locomotor activity, exposure to a novel chamber, exposure to sex odors, the presentation of a sexually receptive female, and copulation. DA increased significantly in the nucleus accumbens when the males were presented with a sexually receptive female behind a screen and increased further during copulation. Although DA also increased significantly in the dorsal striatum during copulation, the magnitude of the effect was significantly lower than that observed in the nucleus accumbens. In contrast, forced locomotion on a rotating drum, exposure to a novel chamber, and exposure to sex odors did not increase DA significantly in either region. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

8-OH-DPAT influences extracellular levels of serotonin and dopamine in the medial preoptic area of male rats

The effect of phospholipase C treatment on cardiolipin biosynthesis was investigated in intact H9c2 cardiac myoblasts. Treatment of cells with phosphatidylcholine-specific Clostridium welchii phospholipase C reduced the pool size of phosphatidylcholine compared with controls whereas the pool size of cardiolipin and phosphatidylglycerol were unaffected. Pulse labeling experiments with [1,3-3H]glycerol and pulse-chase labeling experiments with [1,3-3H]glycerol were performed in cells incubated or pre-incubated in the absence or presence of phospholipase C. In all experiments, radioactivity incorporated into cardiolipin and phosphatidylglycerol were reduced in phospholipase C-treated cells with time compared with controls indicating attenuated de novo biosynthesis of these phospholipids. Addition of 1,2-dioctanoyl-sn-glycerol, a cell permeable 1,2-diacyl-sn-glycerol analog, to cells mimicked the inhibitory effect of phospholipase C on cardiolipin and phosphatidylglycerol biosynthesis from [1,3-3H]glycerol indicating the involvement of 1,2-diacyl-sn glycerol. The mechanism for the reduction in cardiolipin and phosphatidylglycerol biosynthesis in phospholipase C-treated cells appeared to be a decrease in the activities of phosphatidic acid:cytidine-5'triphosphate cytidylyltransferase and phosphatidylglycerolphosphate synthase, mediated by elevated 1,2-diacylsn-glycerol levels. Upon removal of phospholipase C from the incubation medium, phosphatidylcholine biosynthesis from [methyl-3H]choline was markedly stimulated. These data suggest that de novo phosphatidylglycerol and cardiolipin biosynthesis may be regulated by 1,2-diacyl-sn-glycerol and support the notion that phosphatidylglycerol and cardiolipin biosynthesis may be coordinated with phosphatidylcholine biosynthesis in H9c2 cardiac myoblast cells.