Neonatal androgenic stimulation and adult sexual behavior in male and female golden hamsters.

In an experiment with 48 male and 48 female golden hamsters, neonatally and adult castrated males as well as neonatally androgenized and nonandrogenized females were tested for both mounting and lordosis behaviors during treatment with either testosterone or ovarian hormones. Neonatal androgenization facilitated mounting behavior in adult Ss administered either testosterone or ovarian hormones and suppressed lordosis behavior in adult ovarian-hormone-treated Ss. Early androgen effects on the display of lordosis behavior during adult testosterone treatment were complex and varied with the exact timing of perinatal endogenous or exogenous androgenization. Species differences in hormone-behavior relationships and the possible role of perinatal androgenization in the development of rodents' ability to aromatize androgens are discussed. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physical and behavioral aspects of sexual maturation in male golden hamsters.

Male golden hamsters ( Mesocricetus auratus ) were examined from 3 to 9 wks of age for morphological, physiological, and behavioral indices of sexual maturation. Although each of the 8 variables (e.g., testis weight, seminal vesicle fluid, and rear mounts) selected for measurement displayed a unique developmental profile, a principal-components analysis of these variables resulted in the extraction of 2 principal components, one tentatively labeled physical and gross behavioral maturation (accounting for 66% of the total variance) and the other designated perfection of mounting orientation (accounting for an additional 12% of the variance). This result indicates that puberty in the male hamster is best viewed as 2 independent processes, rather than as a unitary process or as an arbitrary term applied to a variety of unrelated developmental phenomena. Advantages of using multivariate composite scores and selected univariate measurements are discussed, as are methods of comparing developmental changes in different variables. A 2nd experiment confirmed an unexpectedly early onset of androgen secretion and an unusual pattern of body weight gain. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pup cannibalism: One aspect of maternal behavior in golden hamsters.

In 5 experiments with a total of 157 golden hamsters (Mesocricetus auratus), examination of the role of 6 factors (e.g., extreme litter size, illness of pups, and lack of maternal experience) generally held to affect incidence of litter cannibalism in the golden hamster revealed little influence of any of them on frequency of pup destruction. More than 75% of mothers in all conditions examined cannibalized a portion of their litters during the 1st few days postpartum. Termination of cannibalism was found to result both from reduction in litter size, consequent upon destruction of young, and from changes in the internal state of the mother following parturition. The outcome of additional studies indicated that mothers maintain litter size at an individually determined value, behaviorally compensating for experimental alterations in pup number. Results are interpreted as indicating that pup cannibalism in hamsters is an organized part of normal maternal behavior which allows an individual female to adjust her litter size in accord with her capacity to rear young in the environmental conditions prevailing at the time of her parturition. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anabolic-androgenic steroid exposure during adolescence and aggressive behavior in golden hamsters

Anabolic androgenic steroid (AAS) abuse by adolescents represents a significant health care risk due to the potential for long-term negative physical and psychological sequelae, including increased aggressive behavior. The current experiments examined the effects of AAS use in young male adolescent hamsters (Mesocricetus auratus) and their consequences on aggressive behavior. It was hypothesized that AAS administration during adolescence predisposes hamsters to heightened levels of aggressive behavior (i.e., offensive aggression). To test this hypothesis adolescent male hamsters were administered high doses of synthetic AAS to mimic a 'heavy use' self-administration regimen used by athletes. Immediately following the exposure to AAS hamsters were tested for aggressive behavior using a resident-intruder model. Animals treated with high doses of AAS during their adolescent development showed heightened measures of offensive aggression i.e., decreased latency to bite and increased total number of attacks and bites) during the test period, while measures of total activity (total contact time) between the animals remained unchanged. AAS-treated males did not differ in body weight from controls, suggesting that the increased aggression was not due to increased body mass. The results of this study show that exposure to AAS during adolescence facilitates aggressive response patterns, but does not alter body weight.     

Dietary self-selection in chronically insulin-treated golden hamsters.

24 adult male golden hamsters were maintained on either Purina Rat Chow (chow group) or a self-selection diet consisting of high-protein chow, pure carbohydrate, and pure fat (choice group). Ss were injected for 12 consecutive days with either long-acting insulin (20, 60, and 100 U/kg for 4 days each) or physiological saline. Insulin-injected Ss under both dietary conditions increased their total caloric consumption by up to 33% and gained significantly more weight than saline-injected controls. Choice Ss increased their fat intake in response to the 60 and 100 U/kg dose of insulin, but carbohydrate and protein consumption increased only in response to the 100 U/kg dose. Choice Ss derived approximately 65% of the excess calories ingested during insulin administration from fat but only 20% from carbohydrate and 15% from protein. Results are related to those previously observed in other species. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory sensitive periods in albino rats and golden hamsters.

Examined odor preferences of 72 infant, juvenile, and adult Sprague-Dawley rats and 119 Syrian hamsters in a 2-choice situation following 3–10 days of differential olfactory exposure. Exposure increased preferences for a simple botanical odor in infants and juveniles but not adults of both species. Preference differences between exposure groups were greatest for infants, moderate for juveniles, and insignificant for adults, suggesting that olfactory sensitive periods occur in these altricial rodent species. Age of exposure differentially influenced responses to combinations of conspecific and botanical odors. Results suggest that olfactory experience has a similar impact on responses of rats and hamsters to botanical but not conspecific odors. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential influence of stereoisomers of estradiol on sexual behavior of female hamsters.

Morphological and behavioral responses to estradiol-17β (E?-17β) and estradiol-17α (E?-17α) were examined in a series of 3 experiments with golden hamsters. The E?-17β augmented uterine growth to a greater extent than E?-17α. Lordosis in ovariectomized adults was elicited by treatment with E?-17β but not with E?-17α (each tested in combination with progesterone). When administered neonatally, only E?-17β disrupted estrous cyclicity in the intact female and induced the ability to mount in ovariectomized, androgen-treated adults. Results suggest the existence of a stereospecific response to estrogenic stimulation in neural tissue comparable with that occurring in the uterus. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preference for novel flavors in adult golden hamsters ( Mesocricetus auratus ).

Although animals generally prefer to eat foods with familiar rather than unfamiliar flavors, adult golden hamsters (Mesocricetus auratus) were found to do the opposite. After having prolonged exposure to a food with a particular flavor, hamsters were allowed to select between the food with the familiar flavor and the same food with a novel flavor. Hamsters consistently ate more of the food with the novel flavor, and this preference was long-lasting and resistant to extinction. Furthermore, the novelty effect was robust, being manifested in both sexes and under a variety of experimental circumstances. In contrast, rats tested under identical conditions consistently preferred the food with the familiar flavor. The origins of the novelty effect in hamsters remain to be determined. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flank-marking behavior and the neural distribution of vasopressin innervation in golden hamsters with suprachiasmatic lesions

In golden hamsters, microinjections of arginine-vasopressin (AVP) within the anterior hypothalamus trigger a stereotyped scent-marking behavior, flank marking. Our experiment was carried out to test the contribution of AVP neurons within the suprachiasmatic nucleus (SCN) in the control of this behavior. Our results suggest that the SCN does not contribute to flank-marking behavior. Whereas SCN lesions disrupted circadian rhythms of wheel running, the same lesions did not disrupt flank-marking. The results also suggest that neurons located outside the SCN contribute significantly to the vasopressinergic innervation of the brain and the expression of AVP-dependent behaviors, such as flank-marking behavior. Although AVP-immunoreactive fibers were severely (ca. 95%) depleted from several forebrain areas in SCN-lesioned hamsters, the effect of the lesions was much more limited within the forebrain areas involved in flank-marking behavior as well as within the midbrain and hindbrain.     

Shifting strategies for behavioral thermoregulation in developing golden hamsters.

Studied developmental changes in the golden hamster pup's capacity for behavioral temperature regulation. Groups of 3 pups aged 4-24 days were tested at room temperature (22°C), on a strong gradient (34-22°C), and on a mild gradient (30-22°C). The proportion of time engaged in the following behaviors was recorded: contact with the warm edge (thermotaxis), active huddling, and quiet huddling. Results show that Ss tested at 22° engaged in active huddling, and their temperature dropped rapidly. Only on Day 14 were they able to maintain their temperature constant with a combination of vigorous exploration and quiet huddling. On the strong gradient, Ss were able to regulate their temperature at all ages. Young Ss (4-5 days) depended on thermotaxis rather than huddling, separating when their temperature started to rise. With age, quiet huddling replaced thermotaxis as a dominant behavior. On the mild gradient, Ss combined active and quiet huddling with thermotaxis, so that their temperature dropped at a slow steady rate. It is concluded that hamster pups have a well-developed capacity for behavioral temperature regulation. Whether they attempt to keep their temperature constant or tolerate a slow rate of drop depends on the amount of exogenous heat available, which under natural conditions would be supplied predominantly by the mother. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of perinatal androstenedione on sexual differentiation in female rats.

Androstenedione was administered prenatally, postnatally, or both pre- and postnatally to female Sprague-Dawley rats. The extent to which reproductive morphology, ovarian functioning, and adult sexual behavior were masculinized and defeminized depended on the dosage, timing, and duration of the hormone treatment. The combined pre- and postnatal treatment resulted in the greatest degree of modification in that such females were anatomically masculinized and did not ovulate. When tested in adulthood, they showed a high potential for the male copulatory pattern and little lordotic behavior. It is concluded that androstenedione, while not as potent an androgen as testosterone propionate, nevertheless has the potential to participate in the process of sexual differentiation. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste aversions to food flavors and vaginal secretion in golden hamsters.

Although rodents readily associate virtually any distinctive flavor with gastrointestinal illness when the flavor and illness have been paired, experience with a flavor can provide information that interferes with later attempts to produce aversions to the familiar taste. The vaginal secretion of female hamsters carries sexual information for males, which does not depend on previous experience; it was studied, in the present 3 experiments, whether that built-in information might interfere with associations between flavor of the excretion and illness. Surprisingly, the Ss, 32 male Syrian hamsters, showed dramatic changes in behavior toward the vaginal secretion when its presentation was followed by lithium chloride poisoning. Results suggest that mammalian responses to sex pheromones are far more easily modified by experience than has been supposed. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intraspecific sexual preferences of female hamsters.

Studied the sexual preference behavior of 32 estrous females of 3 species of hamsters of the genus Mesocricetus by introducing individual females into an arena with a pair of males from 2 different species. When 1 male of the pair was a conspecific, females of all 3 species spent significantly more time investigating the conspecific male. When neither male was a conspecific, female Turkish hamsters (M. brandti) strongly preferred male Romanian hamsters (M. neutoni) to male Syrian hamsters (M. auratus), and female Romanian hamsters preferred male Turkish hamsters to male Syrian hamsters. Female Turkish hamsters displayed significantly more presentation behavior than did Romanian females, and Syrian females rarely presented. Female Turkish hamsters also displayed a stronger degree of preference behavior to a conspecific male than did females of either of the other species. The relatively stronger sexual preferences and greater amount of presentation displayed by Turkish hamsters may relate to the greater opportunity for sympatry with closely related forms and the polymorphic state of this species in the wild. The similarity of Turkish and Romanian hamsters on several characteristics may explain the preference of these species for each other when the alternative was a Syrian hamster. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serotonin regulation of aggressive behavior in male golden hamsters (Mesocricetus auratus).

These studies examined the neurochemistry and neuroanatomy of the serotonin (5-HT) system innervating the anterior hypothalamus (AH) and the interaction of 5-HT receptor agonists with arginine vasopressin (AVP) in the regulation of offensive aggression in golden hamsters. Because specific 5-HT1A, 5-HT1B, and AVP V1A binding sites were observed within the AH by in vitro autoradiography, the hamsters were tested for offensive aggression after microinjections of AVP in combination with either the 5-HT1A agonist 8-hydroxy-2-(di-n-propylarnino) tetraline (DPAT) or the 5-HT1B agonist CGS-12066A (CGS) directly within the AH. Though treatment with DPAT resulted in a dose-dependent inhibition of AVP-facilitated offensive aggression, CGS was ineffective. In addition, a retrograde tracer was injected within the AH to localize the distribution of 5-HT neurons projecting to the area. Retrogradely labeled 5-HT neurons were found within the dorsal, median, and caudal linear raphe nuclei and are suspected to inhibit AVP-facilitated offensive aggression by an activation of 5-HT1A receptors in the AH. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Forebrain sites of estradiol-17!b action on sexual behavior and aggression in female Syrian hamsters.

The effects of intracranial implants of estradiol in the ventromedial hypothalamus (VMH), the anterior hypothalamus (AH), or the medial amygdala (AMG) on aggression, sexual behavior, and serum estradiol were examined in female Syrian hamsters. Estradiol implants in the VMH, followed by systemic progesterone, stimulated sexual behavior and inhibited aggression. Estradiol implants in other intracranial sites activated sexual behavior but did not reliably inhibit aggression. Intracranially implanted and systemically treated animals had equivalent peripheral estradiol concentrations at sacrifice. Results suggest that (1) the VMH is an important neural site for estradiol actions on sexual and aggressive behavior, (2) the caudal AH and AMG may also be sites of estradiol action on sexual behavior, and (3) intracranial implants may only be effective given systemic estradiol exposure or the concurrent stimulation of multiple brain areas. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distribution of small vasopressinergic neurons in golden hamsters

In rats, small (diameter: ca. 10 micrograms) vasopressinergic neurons have been localized in the forebrain, including extrahypothalamic sites, such as the bed nucleus of the stria terminalis (BST) and the medial amygdala (MeA). In golden hamsters, no such neurons have ever been described in extrahypothalamic sites, while their presence in some hypothalamic sites, such as the paraventricular nucleus (PVN), remains controversial. The present studies were carried out to confirm the existence of small vasopressinergic neurons in the forebrain of golden hamsters, using rats as a positive control. The presence of small vasopressinergic neurons in these sites was first tested by immunocytochemistry in colchicine-treated animals. The resulting distribution was corroborated by in situ hybridization for vasopressin (AVP) mRNA. While a large number of small AVP-immunoreactive (AVP-ir) neurons was found in the BST and MeA of colchicine-treated rats, none was found in the same locations in hamsters. Interestingly, as a few large (diameter: 20-25 micrograms) AVP-ir neurons were found in the BST just medial to the small neurons in rats, the same area contained a few large and small AVP-ir neurons in hamsters. In the PVN, large and small AVP-ir neurons were found in rats and hamsters. However, three to four times more neurons were counted in rats. These data were confirmed by in situ hybridization. Indeed, in hamsters, no labelling for AVP mRNA was detected in small neurons within the BST and MeA. Furthermore, the PVN of rats contained more labelling for AVP mRNA, as compared to hamsters. These results confirm that the distribution of vasopressinergic neurons in rats cannot be generalized to other species without a detailed analysis.     

Effects of castration and replacement therapy on sexual behavior of adult male rhesuses.

Observed the sexual behavior of 10 male rhesus monkeys before and after castration and during replacement therapy with testosterone propionate. In 10 tests before castration, all of the Ss ejaculated at least once, and in Weeks 21-25 and 51-55 after castration, 50 and 30%, respectively, ejaculated at least once. In the 35 postcastration tests given over a 55-wk period, 2 males did not ejaculate. 50% of the Ss achieved intromission 1 yr after castration. The percentage of castrated Ss showing intromission and ejaculation and the frequency of these responses were higher than those reported for most nonprimate species but did not differ greatly from those reported for the dog. Within 1 wk testosterone propionate restored whatever aspects of behavior were affected to precastration levels. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pancreatic neoplasms induced in Syrian golden hamsters. I. Scanning electron microscopic observations

Pancreases from Syrian golden hamsters treated with N-nitrosobis(2-hydroxy-proply)amine for 10 to 25 weeks were examined under scanning electron microscopy (SEM). Findings indicate that the neoplasms originated from the ductal epithelium and developed progressively. Adenomas were lined by epithelium of differing cells types, ranging from a flat singly ciliated form to cuboidal-columnar types, or to mixed cell populations. The epithelial lining of the ductal carcinomas exhibited tubular and papillary cystic spaces, and cell surfaces were similar to the cuboidal and columnar epithelium of adenomas and of ductal epithelial hyperplasia. However, microvilli were dense and of varied lengths. The SEM observations correlated with patterns seen in routine histologic preparations.     

Appetitive sexual behavior in male rats: 2. sexual reward and level-changing behavior

The immunodeficiency of patients with chronic renal failure (CRF) is related to multiple and complex alterations of the cytokine network and of its target cells such as T or B lymphocytes, monocytes, fibroblasts or endothelial cells. Chronic activation of monocytic functions is recognized as a key factor in these immunological disorders. Since macrophage colony stimulating factor (M-CSF) is essential for the activation of several functions of monocytes and macrophages and their production of cytokines such as interleukin-1, interleukin-6, and tumor necrosis factor alpha, we investigated its involvement in patients with CRF. When measured by ELISA, M-CSF serum levels were significantly higher in patients with progressive CRF and those on hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) than in controls. M-CSF serum levels did not correlate with the degree of renal insufficiency and were probably related to complex alterations in its production and/or degradation by the specific M-CSF receptors of macrophages. In HD patients the M-CSF serum concentrations inversely correlated with the number of circulating lymphocytes and were significantly higher in anemic patients requiring treatment with erythropoietin. Our results suggest that M-CSF may play a role in altering the immune system in uremic patients by maintaining in the circulation and tissues permanently primed monocytes and/or macrophages that can then be triggered to an activated state by secondary stimuli such as endotoxins, complement components, other cytokines or contact with foreign surfaces.