Intact Females Research Articles

Flight Initiation by Male Rhodnius prolixus is Promoted by Female Odors

Several triatomine bug species utilize chemical cues for sexual communication. We tested whether female or male Rhodnius prolixus, a vector of Chagas disease, produce volatile chemicals that elicit flight responses from conspecifics, and then isolated the source of the chemical. Males confronted with an airstream containing female odors showed a significantly greater take-off frequency compared to a blank airstream or an airstream with male odors. In contrast, females exhibited similar take-off frequencies to male or female odor as to a clean airstream. Occlusion of female metasternal glands with paraffin wax resulted in a significant decrease in male take-off frequency compared to that of intact females. Additionally, excised female metasternal glands elicited a similar take-off frequency from males as did intact females, both significantly greater than the take-off frequency to clean air. These results show that R. prolixus females release a pheromone from their metasternal glands that causes upwind flight in conspecific males.

Acute effects of 2-methoxyestradiol on endothelial aortic No release in male and ovariectomized female rats

The endogenous metabolites of 17β-estradiol are thought to have protective vascular effects, especially in males and estrogen-deprived females. The present study evaluated the acute in vitro effects of the active metabolite 2-methoxyestradiol on endothelial NO release from ovariectomized female and intact male and female rat aortas. NO was measured electrochemically by differential normal pulse amperometry using carbon fiber microsensors, and also by fluorescence microscopy using 4,5-diaminofluorescein diacetate. 2-Methoxyestradiol alone induced a maintained increase in endothelial NO release in male and ovariectomized rats that was reduced by pretreatment with L-NAME. NO release induced by calcium ionophore alone ( A23187) was lower in aortas from ovariectomized rats than from intact females, indicating that estrogen deprivation induces endothelial dysfunction. Pretreatment of aortas with 2-methoxyestradiol potentiated significantly the A23187-induced-NO release in ovariectomized as well as in males, but not in intact females. This potentiation was reduced or abolished by L-NAME. 2-Methoxyestradiol potentiated the vasodilatory effect of A23187 on intestinal arterioles, and also increased intestinal tissular laser-Doppler blood flow signal. These results demonstrate that 17β-estradiol and its active metabolite 2-methoxyestradiol increase basal aortic endothelial NO production and also cause a potentiation of the calcium ionophore-stimulated NO release in male and ovariectomized, while it has no effects on intact females. 2-Methoxyestradiol appears to be a promising pharmacological agent capable of improving endothelial function in men and postmenopausal women.

PHYTOESTROGENS EFFECT ON SEXUAL HORMONES LEVEL AND FERTILITY OF RATS

The influence of 30-day application of phytoestrogens compound to postpubertal male and female rats on the level of sexual hormones, gametes maturation and fertilization capacity was experimentally studied. Long-term phytoestrogenes supplies into animal’s organism bring out substantial changes in the level of sexual hormones. In females different estradiol contents are levelled at the estrus-diestrus stages that is typical for intact females. In males there was a considerable increase of estradiol, in a lesser degree — testosterone. Hence, the testosterone-esrtadiol ratio is altered. Morphological structural changes in male and female gametes, decreased spermatozoa motility, impaired embryonic implantation, a high rate of embryonic mortality are observed.

Ultrasonographic and ecobiometric findings in the eyes of adult goats

The knowledge of the normal appearance and ocular dimensions of goat eyes facilitates the use of ultrasonography in the evaluation of ocular disease. The objective of the present study was to determine ultrasonographic and ecobiometric findings in the eyes of adult goats. B- and A-mode ultrasonography was performed in 30 healthy adult goats (60 eyes) (n=5 intact females and n=15 castrated males). Ultrasonography was performed after instillation of a topical anesthetic. Lubricating jelly was placed on the 20MHz transducer tip as a stand-off pad. The transducer was placed in a longitudinal position until optimal B-scan images, according to echoes of the A-mode images, were obtained. Statistical analysis was carried out to compare the ecobiometric readings among genders (P<0.05). Means and standard deviations of the ocular structures for male and female goats, respectively, were, 3.46±0.55, 3.33±0.46mm (anterior chamber depth); 8.60±0.34, 8.65±0.39mm (lens thickness); 11.34±0.61, 11.39±0.66mm (vitreous chamber depth); and 23.43±0.92, 23.39±0.86mm (axial globe length). Ocular measurements between right and left eyes, as well as between males and females were not significantly different (P>0.05). The ultrasonographic appearances of goat eyes were very similar to those of other domestic and wild species.

Sex Differences in the Serotonergic Influence on the Hypothalamic-Pituitary-Adrenal Stress Axis

Appropriate interactions between serotonin (5-HT) and stress pathways are critical for maintaining homeostasis. Dysregulation of hypothalamic-pituitary-adrenal (HPA) stress axis is a common feature in affective disorders in which an involvement of 5-HT neurocircuitry has been implicated in disease vulnerability and treatment responsiveness. Because there is a greater prevalence of affective disorders in women, sex differences in the 5-HTergic influence on stress pathways may contribute to disease disparity. Therefore, our studies compared stress or citalopram-induced corticosterone levels in male and female mice. To determine whether sex-dependent HPA axis responsiveness was mediated by the difference in testosterone levels, testosterone-treated females were also examined. Gene expression patterns in 5-HTergic and stress neurocircuitry were analyzed to determine sites of potential sex differences and mechanisms of testosterone action. As expected, restraint stress corticosterone levels were higher in intact females and were masculinized by testosterone. Interestingly, citalopram administration independent of stress resulted in a greater corticosterone response in females, which was also masculinized by testosterone. Analyses along the 5-HT-HPA axis revealed sex differences including greater pituitary 5-HT receptors and adrenal weights in females. Moreover, in stress-regulatory regions, we found sex differences in glucocorticoid receptor and glutamic acid decarboxylase expression supportive of greater inhibitory modulation and feedback potential in males. Taken together, these data suggest that multiple sites related to 5-HTergic stimulation, corticosterone production, and negative feedback of HPA neurocircuitry combine to produce higher female stress responsiveness. These studies support a potential for sex-specific involvement of 5-HT and stress pathways in the etiology of affective disorders.

Effect of Sex Hormones on Crystal Formation in a Stone-forming Rat Model

To evaluate the contribution of sex hormones in urolithiasis using a stone-forming rat model. Gender differences because of sex hormones are thought to influence the incidence of urolithiasis. We divided rats into 7 groups, such as intact males, orchidectomized males, intact males subcutaneously implanted with testosterone, intact males subcutaneously implanted with estradiol, intact females, ovariectomized females, and intact females subcutaneously implanted with testosterone. At 10 weeks old, the rats were fed 0.5% ethylene glycol in drinking water and given 0.5 microg of 1,25-dihydroxy vitamin D(3). Kidney crystal deposition and the degree of oxidative stress were examined in each group, and endogenous oxalate metabolism and antioxidant enzymes were compared among groups using real-time reverse transcription-polymerase chain reaction. Extensive crystal deposition was observed in intact males and testosterone-administered males, whereas few crystals were found in intact females. Crystal deposition was inhibited in orchiectomized males and in those administered estradiol, whereas ovariectomized females and testosterone-administered females had slightly enhanced and very enhanced crystal deposition, respectively. Increases in urinary oxalate excretion paralleled renal crystal deposition, which were both enhanced by testosterone treatment through increased glycolate oxidase expression. Oxidative stress increased in groups with extensive crystal deposition compared with those without. Antioxidant enzyme expression was enhanced by estradiol. Testosterone was a promoter and estradiol an inhibitor of kidney crystal deposition, likely because of their effects on oxalate synthesis and oxidative stress.

Detection of oviposition-deterring larval tracks in Chrysopa oculata and Chrysopa perla (Neuroptera: Chrysopidae)

We investigated the ability of females of the aphidophagous chrysopids Chrysopa oculata and Chrysopa perla to distinguish clean substrates from substrates with tracks of chrysopid first instars after ablation of various sensory organs potentially involved in the detection of oviposition-deterring semiochemicals (ODSCs). Also studied were effects of storage time on the degree of oviposition deterrence of substrates contaminated by larvae and by extracts of ODSC in intact females. C. oculata and C. perla laid significantly fewer eggs on substrates with conspecific larval tracks than on simultaneously provided clean substrates. Females of both chrysopids could perceive ODSCs solely through sense organs on the head. The oviposition of each species was significantly lower on contaminated than on clean substrates when any kind of sense organ on the head was completely removed, i.e. antennae, maxillary palpi, or labial palpi. C. oculata could still effectively differentiate substrates after ablation of both maxillary and labial palpi, indicating possible detection of volatiles via the antennae during flight. Only if all three pairs of sensory appendages were removed did females lay similar numbers of eggs on both substrates. In contrast, C. perla laid similar numbers of eggs on clean substrates and substrates with either conspecific or C. oculata larval tracks when maxillary and labial palpi were removed. Substrates with tracks of first instars of C. perla deterred C. oculata from oviposition after one year and conspecific females after 1.5 years from contamination. Both species laid significantly fewer eggs on substrates with tracks of C. oculata first instars than on clean substrates even after three years. Tracks of C. oculata third instars did not deter conspecific females more than tracks of first instars. ODSCs from tracks were easily extracted with water. Thus, precipitation is likely to reduce deterrent effects of contaminated plants. Chloroform extract from C. oculata first instars strongly deterred conspecific females from oviposition. Even after 725 days of storage, we found no statistically significant decline in the effect. The extract could be used to redirect egg laying from constructional parts of rearing cages to exchangeable oviposition substrates in mass rearing of chrysopids used for biological control. The hexane extract of third instars was inactive.

Partner preference: Assessing the role of the female goat

For domestic ruminants, the male is thought to have the control over mate choice. The aim of this study was to assess the potential role the female goat plays in choosing a sexual partner. Approach frequency and proximity time to various social or sexual stimuli in a Y-maze apparatus were used as partner preference assessment parameters. Ovariectomized females were either induced into estrus ( n = 8) or induced into anestrus ( n = 8) and exposed to various goal stimuli — intact unfamiliar females (estrous and diestrous), intact males, and neutral (empty) in six separate trials. Total arm entries and time spent within one body length of the goal (proximity time — used to calculate preference scores) were recorded for subjects. With a male present, anestrous subjects had significantly more total arm entries than estrous subjects. Estrous subjects showed a significant preference for the male goal (M) versus the estrous female (ES), diestrous female (DS), and empty goals, respectively. Estrous subjects also showed a preference for the ES and DS goals when one goal was left empty. Anestrous subjects showed a preference for the goal containing ES, DS, and M compared to empty goals. They also showed a preference for ES vs. DS. The Y-maze is a tool that can be used to assess sexual and social partner preferences in female goats. The role the female plays in choosing a partner may be much greater than previously considered.

Estrogen Is Renoprotective via a Nonreceptor-dependent Mechanism after Cardiac Arrest In Vivo

Severe ischemia induces renal injury less frequently in women than men. In this study, cardiac arrest and cardiopulmonary resuscitation were used to assess whether estradiol is renoprotective via an estrogen receptor (ER)-dependent mechanism. Male and female C57BL/6 and ER gene-deleted mice underwent 10 min of cardiac arrest followed by cardiopulmonary resuscitation. Serum chemistries and renal stereology were measured 24 h after arrest. Estrogen did not affect mean arterial pressure, regional renal cortical blood flow, and arterial blood gases. Hence, female kidneys were protected (mean +/- SEM: blood urea nitrogen, 65+/- 21 vs.149+/- 27 mg/dl, P = 0.04; creatinine, 0.14 +/- 0.05 vs. 0.73 +/- 0.16 mg/dl, P = 0.01; volume of necrotic tubules, 7 +/- 1% vs. 10 +/- 0%, P = 0.04). Estrogen also reduced renal injury. In intact females (n = 5), ovariectomized/vehicle-treated (n = 8), and ovariectomized/estrogen-treated (n = 8) animals, blood urea nitrogen was 65 +/- 21, 166 +/- 28, and 50 +/- 14 mg/dl (P = 0.002); creatinine was 0.14 +/- 0.05, 0.74 +/- 0.26, and 0.23 +/- 0.27 mg/dl (P = 0.014); necrotic tubules were 2.5 +/- 0.25%, 12.0 +/- 1.9%, and 5.0 +/- 1.6% (P = 0.004), respectively. In ER-[alpha] and ER-[beta] gene-deleted mice and controls estradiol-reduced functional injury (blood urea nitrogen: estradiol 117 +/- 71, vehicle 167 +/- 56, P = 0.007; creatinine: estradiol 0.5 +/- 0.5, vehicle 1.0 +/- 0.4, P = 0.013), but the effect of estradiol was not different between ER-[alpha] or ER-[beta] gene-deleted mice. Adding ICI 182,780 to estradiol did not alter injury. In women, kidneys were protected from cardiac arrest through estrogen. Estradiol-mediated renoprotection was not affected by ER deletion or blockade. Estradiol is renoprotective after cardiac arrest. The results indicate that estradiol renoprotection is ER-[alpha] and ER-[beta] independent.

Gender-associated modulation of inducible CYP1A1 expression by andrographolide in mouse liver

We previously observed a strong synergistic effect on polycyclic aromatic hydrocarbon (PAH)-induced CYP1A1 expression by andrographolide, a major constituent of an herbal medicine derived from the plant Andrographis paniculata, in mouse hepatocytes in primary culture. The present paper describes confirmation of an enhancing effect of andrographolide on the CYP1 family in vivo in the PAH-responsive C57BL/6 mouse. Andrographolide did not alter CYP1 expression in the PAH-nonresponsive DBA/2 mouse. The enhanced expression induced by andrographolide was observed in male C57BL/6 mice, but not in intact or ovariectomized females, or in orchiectomized male mice. However, treatment with testosterone restored the effect in both orchiectomized males and ovariectomized females. These observations indicate a male hormone-related system to be a crucial mediator of the modulation of CYP1 expression by andrographolide. Precautions should be taken regarding the use of A. paniculata as an alternative medication or health promotion, according to its distinctive characterization on sexually dimorphic modulation of CYP1A1 expression.

Evidence of a Parathyroid Hormone-independent Chronic Effect of Estrogen on Renal Phosphate Handling and Sodium-dependent Phosphate Cotransporter Type IIa Expression

The effects of estrogen on phosphate metabolism are not well understood. To better define the chronic effects of estrogen on phosphate balance and on renal phosphate handling, the following groups were examined: A. young male and female rats, age- and weight-matched (age 8-10 weeks, 1 (st) study), and B. ovariectomized female rats (OVX), 22 weeks old, ovariectomized aged-matched rats receiving estrogen replacement (15 micromol x 3/week) for 14 weeks (OVX+E), control female rats (intact ovaries), and male rats, both age matched to OVX and OVX+E (2 (nd) Study). In younger females (1 (st) study), plasma phosphate was lower, whereas the urinary excretion of phosphate was higher than in males. In adult intact females and in OVX+E urinary excretion of phosphate was higher than in males and OVX (2 (nd) Study). In these rats, a significant correlation between plasma phosphate and estrogen level was found. Sodium-dependent phosphate cotransporter (NaPiIIa) mRNA expression and protein abundance were higher in the renal cortex of younger male rats than in age- and weight-matched females. In adult rats, NaPiIIa mRNA and protein abundance were higher in OVX than in OVX+E, and in mature males as compared with age-matched females. These differences were not related to the parathyroid hormone (PTH) levels. Chronic estrogen administration was also associated with increased plasma calcium level and urinary calcium excretion. These results suggest that chronic estrogen treatment is associated with an inhibitory, PTH-independent effect on the expression of NaPiIIa in the kidney, leading to sex-related differences in phosphate balance.

Sex differences in the steroidogenic systems in the rat hippocampus

Sex differences, laterality, and hormonal regulation of androgen receptor (AR) immunoreactivity in rat hippocampal CA1 pyramidal cells were examined using the PG21 antibody. Adult male rats were either castrated or sham-operated at least 2 weeks prior to sacrifice. Gonadally intact females were sacrificed on the day of proestrus. Animals received an injection of either testosterone propionate (TP) or vehicle 2 h prior to sacrifice. Within CA1, both the intensity of staining and the number of AR+ cells were assessed. AR immunostaining was detected in all the groups with marked variation among them. The overall ranking of staining intensity was: gonadally intact males > females given TP > castrated males given TP > females > castrated males given vehicle. The number of AR+cells within subregions of CA1 showed the same basic pattern: among control-treated animals, gonadally intact males have more than females, but castrated males have the least, and acute TP treatment increases the number in both sexes. The increased level of AR immunoreactivity in CA1 of castrated males following acute TP treatment suggests that testicular androgens in adulthood normally increase AR immunoreactivity there, producing a sex difference favoring males in gonadally intact animals. We also found a higher number of AR+ CA1 cells on the left than on the right, but only in gonadally intact males and in females given TP. These results suggest that a laterality of AR distribution in the rat hippocampus may lead to lateralities in hippocampal structure and function.

Male pigeons react differentially to altered facial features of female pigeons

Male pigeons exhibit robust courtship to the head of a female, but not so much to the body. The specific features in the female head which are critical for triggering courtship from males remain unclear. We examined this issue by studying preference behaviour of male pigeons between a pair of photographic images of female conspecifics: a series of normal female faces and a series of digitally altered facial features. Preference was determined by measuring the duration of male courtship 'coo' responses near each of these images. Males preferred intact females compared to those missing the eyes and beak. They also responded less when only the eyes and beak were visible without the head, suggesting that these local features were important, yet more effective when embedded in the context of the head than when they were not. Enlarging or removing the beak had a significant impact on preference, whereas manipulating the eyes had a weaker effect. Finally, males exhibited no preference between normal females and those that had spatially rearranged eyes and beak. These results suggest that pigeons naturally attend to the local features of the head, but not to the spatial configuration, for conspecific recognition.

The Role of Oestradiol in Sexually Dimorphic Hypothalamic‐Pituitary‐Adrena Axis Responses to Intracerebroventricular Ethanol Administration in the Rat

Systemic ethanol (EtOH) administration activates the hypothalamic-pituitary-adrenal (HPA) axis of rats in a sexually dimorphic manner. The present studies tested the role played by the central nervous system (CNS) in this phenomenon. To localise the effects of the drug to the brain, we utilised an experimental paradigm whereby a small, nontoxic amount of the drug was delivered via intracerebroventricular (i.c.v.) injection. EtoH administered i.c.v. rapidly diffuses throughout the cerebrospinal fluid and brain, and does not cause neuronal damage or have any long-term physiological or behavioural effects. Experimental groups included intact males, intact cycling females, and ovariectomised (OVX) animals with or without replacement oestradiol (E(2)). Intracerebroventricular EtOH-induced HPA hormonal activation was determined by measuring plasma adrenocorticotrophin (ACTH) levels. Activation of brain areas that both regulate HPA function and are responsive to gonadal hormones was determined using expression of the transcription factor c-fos (Fos) as a marker of neuronal activity. We observed sex- and oestrous cycle- dependent differences in HPA activation by EtOH as measured by both these parameters. ACTH secretion was highest in females in pro-oestrus or oestrus, just prior to or after the endogenous peak of E(2), as was Fos expression in the paraventricular nucleus of the hypothalamus (PVN) and the locus coreuleus (LC) of the brainstem. In OVX animals, E(2) replacement caused an increase in PVN and LC Fos expression in response to i.c.v. EtOH compared to OVX controls, but a decrease in ACTH secretion. Taken together, these results indicate that at the level of the CNS, EtOH stimulates HPA activity more robustly at times when the effects of E(2) are high, but that E(2) alone is not responsible for this effect. The data further suggest that the LC plays an important role in the circuitry, which appears to be different from that activated following the systemic administration of EtOH.

Olfactory Perception of Oviposition-Deterring Fatty Acids and Their Methyl Esters by the Asian Corn Borer,Ostrinia furnacalis

Olfactory perception of myristic, palmitic, stearic and oleic acids and their corresponding methyl esters by Asian corn borer moths, Ostrinia furnacalis (Guenée) (Lepidoptera: Crambidae) was investigated. It was found that mated females with both antennae amputated, in contrast to intact females and females with one antenna removed, could not discriminate between simultaneously provided control filter papers and filters treated with a blend of oviposition-deterring fatty acids. Oviposition by mated females exhibited a very marked periodicity, with all egg masses deposited during the scotophase and most egg masses laid before midnight. According to the peak and trough period of oviposition, electroantennogram (EAG) responses from both mated females and males to the four fatty acids and four methyl esters were tested within two two-hour periods from 3 to 5 hours after the start of darkness and from 1 to 3 hours after light onset, respectively. Significant EAG responses above solvent and background were elicited by all test chemicals from females, and by most of the test compounds from males. EAG values of all test chemicals from mated females were not statistically different between the two test periods except for methyl myristate. Conversely, EAG responses from mated males to myristic acid, stearic acid and their methyl esters significantly differed between the two test periods.

Cortisol levels and aggression in neutered and intact free-roaming female cats living in urban social groups

Free-roaming domestic cats in urban areas often live in defined social groups, and the breeding females in these groups tend to form structures of a matrilineal nature. In recent years, resulting from the growing populations of free-roaming cats in many cities worldwide, these cats are being managed using the Trap–Neuter–Return (TNR) method. The aims of this study were to explore the hypotheses that (a) neutering reduces aggression in the females living in such social groups; and (b) if such reduction does occur, that it might be accompanied by a reduction in cortisol levels. The study was conducted on eight cat feeding groups in residential neighbourhoods in Tel Aviv, Israel. The municipal veterinary department offers TNR services upon request. Cats are collected from the feeding group and returned to their original group after neutering. We found that neutered females showed reduced aggressiveness as well as reduced cortisol levels compared to the intact females. In addition, those intact females that displayed more aggression had higher cortisol levels compared to the less aggressive intact females. Based on the results of this study it is possible to suggest for the first time a possible relationship between cortisol levels and aggression in free-roaming female domestic cats. This study is an initial step in assessing the long-term effects of Trap–Neuter–Return (TNR) on the welfare of the individual cat. If cortisol levels in female cats are reduced after neutering, partly as a result of reduced social and reproductive pressures (as expressed by lower aggression of the neutered females), it is possible that TNR has an added beneficial role in cat welfare in addition to that of control of population size.

Rhythmic Supplementation of 17β-Estradiol According to the Physiological Estrous Cycle: Effect on Blood Pressure in Female Ovariectomized Rats

Female Wistar-Kyoto rats (WKY) show a 4-day estrous cycle. The aim of this study was to examine the impact of 17beta-estradiol supplementation every fourth day to ovariectomized rats - mimicking the physiological estrous cycle - on regulation of blood pressure. We monitored blood pressure telemetrically in intact females, ovariectomized (OVX), and ovariectomized WKY injected subcutaneously with 17beta-estradiol (OVX (E2)) in a 4-day rhythm for 24 weeks. Blood pressure decreased both in intact females and OVX (E2), whereas that of OVX persisted at constant levels. The underlying mechanisms studied include the nitric oxide pathway, the rennin-angiotensin system as well as the endothelin system. Serum and urinary nitrate/nitrite (NOx) as well as aortic eNOS decreased in OVX and were restored to normal in OVX (E2). Conversely, caveolin-1 was higher in OVX than in intact females and OVX (E2) while Hsp90 did not differ among groups. Plasma angiotensin II and aortic AT (1) receptor expression increased in OVX and were normalized in OVX (E2). AT (2) receptor expression was regulated reciprocally. Serum endothelin-1 was significantly elevated in OVX and OVX (E2). There was no difference in aortic ET (A) receptor expression between groups whereas ET (B) receptor expression was higher in intact females and OVX (E2) than in OVX. The study suggests that supplementation of 17beta-estradiol in female WKY according to the natural estrous cycle maintains the physiological blood pressure encompassing vasorelaxing and vasoconstricting pathways. The physiological estrous cycle should be kept in mind when cardiovascular data are to be collected/interpreted under estrogen supplementation.

Adam12 plays a role during uterine decidualization in mice

In mouse, decidualization is characterized by the proliferation of stromal cells and their differentiation into specialized type of cells (decidual cells) with polyploidy, surrounding the implanting blastocyst. However, the mechanisms involved in these processes remain poorly understood. Using multiple approaches, we have examined the role of Adam12 in decidualization during early pregnancy in mice. Adam12 is spatiotemporally expressed in decidualizing stromal cells in intact pregnant females and in pseudopregnant mice undergoing artificially induced decidualization. In the ovariectomized mouse uterus, the expression of Adam12 is upregulated after progesterone treatment, which is primarily mediated by nuclear progesterone receptor. In a stromal cell culture model, the expression of Adam12 gradually rises with the progression of stromal decidualization, whereas the attenuated expression of Adam12 after siRNA knockdown significantly blocks the progression of decidualization. Our study suggests that Adam12 is involved in promoting uterine decidualization during pregnancy.

Effects of estradiol on food intake and meal patterns for diets that differ in flavor and fat content

Apart from the well known inhibitory effects of estradiol on food intake, meal size, and body weight in female rats that have been documented over the past thirty years, a more recent report presents the opposite finding; that a large dose of estradiol can increase food intake and weight gain in gonadally intact female rats presented with a palatable diet. The purpose of the present experiment was to further examine this hypothesis by evaluating the ability of estradiol to influence feeding behavior in ovariectomized rats presented with diets that differ in flavor and fat content. Female rats were given a cyclic regimen of estradiol benzoate treatment (5.0 or 20.0 µg) or the oil vehicle and were presented with the standard chow diet or a diet with a higher fat content and chocolate flavor. Food intake, meal size, and meal number were monitored three days after the first injection of estradiol or oil. Compared to the chow diet, food intake increased when animals had access to the chocolate/fat diet during the vehicle treatment condition. Both doses of estradiol significantly decreased food intake, meal size, and body weight gain when animals were presented with either the standard chow diet or the chocolate/fat diet. These findings indicate that estradiol does not stimulate the intake of a palatable diet in ovariectomized rats, and suggest that previous results showing that estradiol enhanced eating and weight gain stemmed from a disruption of the hypothalamic–pituitary–gonadal axis when intact females received a large dose of exogenous estradiol.

Potential risk factors associated with feline behaviour problems

A retrospective study was carried out on feline behaviour problems presented at the Animal Behaviour Clinic at the Barcelona School of Veterinary Medicine to identify the main risk factors. Three hundred thirty six cats presented for a behaviour problem between 1998 and 2006 were included in the study group. A total of 189 presented at the Hospital of the Barcelona School of Veterinary Medicine for problems other than behavioural and having no record of behaviour problems were used as control group. The main owner's complaint was aggression (47%) followed by inappropriate elimination (39%). 64% of aggression cases involved conflicts between cats and 36% of cases were aggression towards people, owners being the most common target of aggression (78% of all cases of aggression were directed towards people). Play-related aggression and petting-related aggression were the main causes of aggressive behaviour towards people (43.1 and 39.6% of cases respectively). Most housesoiling problems involved urination (59%), followed by urination and defecation (32%) and defecation (9%), and the most common diagnosis was aversion to the litterbox (63.4%). Persian cats were presented more frequently for elimination problems than other breeds ( χ 2 = 6.40; p < 0.01). Cats with behaviour problems came from pet shops more frequently than control cats ( χ 2 = 10.39; p < 0.001). Cats without outdoor access showed significantly more behaviour problems than those with outdoor access ( χ 2 = 31.85; p < 0.001) and aggression problems were more common in single cat households than in multicat households ( χ 2 = 25.47; p < 0.001). Intact females were presented more frequently for aggression problems than neutered females ( χ 2 = 7.74; p < 0.01).