Intrasexual interactions among female golden hamsters (Mesocricetus auratus) over the estrous cycle.

Examined social interactions of cycling female golden hamsters paired with ovariectomized animals (N?=?96) in large enclosures. Interactions were primarily agonistic and intense over the 4-day estrous cycle, as indicated by frequent occurrences of chase and flight behavior. Dominant and subordinate social ranks were established in the majority of pairs (96%) tested, and even Ss in sexual heat were capable of attacking and dominating their rivals. Furthermore, cycling Ss exhibited significantly more aggressive acts than ovariectomized opponents 1 day prior to sexual receptivity. No differences in fighting patterns were found between Ss on the other 3 days of the estrous cycle. Additional analyses revealed clear differences in agonistic elements, including flank marking, between dominant and subordinate Ss, regardless of whether they were gonadectomized or intact. Analyses also show that dominant Ss frequently chased and bit opponents during encounters within their nesting area. Data are examined for implications on the adaptive organization of female hamster agonistic behavior and the neuroendocrine regulation of species-typical behavior over the estrous cycle. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavior of attack-primed and attack-satiated female golden hamsters (Mesocricetus auratus).

In 3 experiments with 50 female hamsters, "priming" the S by allowing it one biting attack on a smaller, methotrimeprazine-treated target hamster significantly decreased its latency to attack a subsequently presented probe target. Conversely, the latency of attacks on the probe was increased, and the number of attacks decreased, if the S was first "satiated" by allowing it 1 hr of ad-lib access to a target followed by a series of briefer target presentations until a criterion of 3 successive presentations without attack was met. The respective aggression-increasing and aggression-decreasing effects of these manipulations were also demonstrated in more naturalistic, unrestrained encounters between pairs of Ss that had just been exposed to the same manipulation. Neither manipulation affected the nonaggressive behaviors of sunflower seed acceptance and wheel running, which suggests that the effects of attack priming and satiation may be specific to aggression. (39 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)     

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)     

How golden hamsters (Mesocricetus auratus) discriminate top from bottom flank scents in over-marks.

Using a habituation-discrimination paradigm, the authors investigated what cues male golden hamsters (Mesocricetus auratus) use to determine the top and bottom positions in flank gland over-marks. A difference in the ages of 2 hamsters' marks did not, by itself, produce differential memory or evaluation of the 2 scents. A spatial configuration of marks suggestive of an overlap was sufficient for the apparently overlapping scent to be remembered or valued more than the apparently underlying scent. Cues from the overlap of 2 hamsters' marks were also sufficient. These results, consistent with those previously found for responses to hamster vaginal scent over-marks, suggest that hamsters use similar cues to analyze scent over-marks that are different in chemical composition and in social functions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory for individual scent in hamsters (Mesocricetus auratus) as assessed by habituation methods.

The memory of hamsters (Mesocricetus auratus) for the flank scent of older male hamsters was investigated in a series of habituation experiments. In 2 types of habituation tasks (Exps 1 and 2), male hamsters habituated to the flank scent of 1 male and then increased their level of investigation to that of a novel male; similar results were obtained when the intervals between trials ranged from 1 sec to 2 days. When the test trial was 10 or 21 days after habituation (Exp 3), males discriminated between familiar and novel flank scents at 10 days but not at 21 days. The results demonstrate recognition of familiar and unfamiliar individual odors and excellent memory for these differences. Habituation techniques yield extremely robust results and may be useful for investigations of other aspects of individual signatures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of food deprivation on hunger motivation in golden hamsters (Mesocricetus auratus).

Unlike most other laboratory animals, golden hamsters do not typically increase their food intake following periods of food shortage. It is possible that the hamster feeding system may not be programmed to respond to the metabolic consequences of deprivation; expressed in motivational terms, deprived hamsters would not be hungrier than usual and therefore would not eat more than usual. However, because food consumption is influenced both by hunger motivation and by the motivation to stop eating, the amount of food eaten is not necessarily the best measure of hunger motivation. Four experiments were conducted, revealing that acute food deprivation has significant effects on latency to eat, speed of eating, consumption of a quinine-adulterated diet, open-field activity, and persistence of performance of an instrumental response during extinction. These results constitute convergent evidence that food deprivation increases the hunger motivation of golden hamsters, although deprivation does not lead to increases in the total food intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scent counter-marks: Specialized mechanisms of perception and response to individual odors in golden hamsters (Mesocricetus auaratus).

Scent counter-marking is a widespread phenomenon among mammals that is not well understood. Using a habituation paradigm, it was found that male golden hamsters (Mesocricetus auratus) exposed to partially overlapping scents of 2 females behaved on test trials as if they remembered the top scent but not the bottom scent. If the 2 females' scents did not overlap during exposure trials, males remembered both of them. Thus, if 2 individual scents partially overlap, hamsters (1) perceive which of the 2 scents was deposited most recently and (2) either remember the top scent and forget the bottom scent or attach greater significance to the top scent. These results indicate the existence of specialized perceptual and cognitive or motivational mechanisms that are used for interpretation and response to complex arrays of social odors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social learning in the golden hamster (Mesocricetus auratus).

Investigates whether golden hamster (Mesocricetus auratus) pups can acquire a new behavior by interacting with an experienced adult conspecific. The behavior consisted of using teeth and forepaws to retrieve a piece of food dangling from a small chain. Instrumental learning techniques were used to train the demonstrators. Four groups of pups were exposed to different kinds of social experience. In the 1st group, the pups interacted with their skilled mother, in the 2nd group, they did the same with their inexperienced mother, in the 3rd group, they interacted with inexperienced littermates; and in the 4th group, the pups were tested individually. At the end of an acquisition period, the pups were tested individually to assess their performance. Results demonstrate that interacting with a skilled mother has a remarkable effect on the acquisition of a new feeding behavior by hamster pups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of putative satiety peptides on feeding and drinking behavior in golden hamsters (Mesocricetus auratus).

Intraperitoneal cholecystokinin octapeptide (CCK-8 [0.1–5 μg/kg]) reduced feeding in Syrian hamsters in a dose-related fashion, except for males tested during the light phase of the illumination cycle. Proglumide (200 or 400 mg/kg), a putative CCK receptor antagonist, did not alter spontaneous food intake and did not reverse the suppression of feeding resulting from CCK-8. Bombesin (BBS [0.5–20 μg/kg]), thyrotropin releasing hormone (TRH [5–200 μg/kg]), and calcitonin (CC [2–22 μg/kg]) produced a dose-related suppression of food intake. BBS appeared to do so specifically. In contrast, TRH appeared to reduce feeding by temporarily debilitating the Ss and CC by evoking behavior (increased locomotor activity) incompatible with feeding. Intracerebroventricular (icv) injections of CCK-8, BBS, and CC produced dose-related inhibition of feeding, but only CCK-8 appeared to affect feeding behavior selectively. Reduced feeding after icv BBS was associated with excessive grooming, and icv CC, like systemic CC, increased locomotor behavior. (72 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of the interintromission interval on lordotic response and attack latency in golden hamsters (Mesocricetus auratus).

After 12–25 ejaculatory series, each consisting of several short intromissions (2- to 3-s vaginal penetration) and an ejaculation, male golden hamsters adopt an altered copulatory pattern consisting of long intromissions (5- to 25-s penetration with intravaginal thrusting). Receptivity declines and the tendency for the female to attack the male increases at about the time of this shift in copulatory pattern. Because the mean interintromission interval (III) between short intromissions is about 8 s compared to 100 s between long intromissions, it is possible that females detect this difference and adjust their mating accordingly. When the III between short intromissions from a rested male experimentally increased to 100 s by use of a halter and lead device, the duration of lordosis was significantly less than that displayed by females paired with control males (8-s III) and virtually the same as that displayed by females paired with males that produced only long intromissions. This suggests that the female uses the temporal patterning of intravaginal stimulation as one criterion for terminating mating with a particular male. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flavor–calorie learning in the golden hamster (Mesocricetus auratus).

Golden hamsters (Mesocricetus auratus) were repeatedly exposed to conditioning diets differing in both caloric density (1.98 or 5.01 kcal/g) and flavor (anise or clove) to demonstrate flavor-calorie learning. During testing, hamsters were presented with 2 jars that both contained a test diet consisting of a mixture of equal amounts of the conditioning diets; the test diet in 1 cup contained the flavor previously associated with the high-calorie diet, and the test diet in the other cup contained the opposite flavor. Hamsters showed a strong preference for the test diet containing the flavor previously associated with the high-calorie diet during conditioning; however, the preference was not robust, disappearing after only 3 brief extinction trials. The learned flavor preference was specifically attributable to flavor-calorie learning and not to either flavor-flavor learning or the effects of mere exposure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of frontal cortex in social odor discrimination and scent-marking in female golden hamsters (Mesocricetus auratus).

Orbital/agranular insular (ORB/AI) cortex has been implicated in traditional olfactory learning tasks and social behavior but its precise role in discriminating-learning social odors is not known. Female golden hamsters received aspiration lesions of ORB/AI or dorsomedial (DM) frontal cortex and were tested for their ability to (a) discriminate between odors of individual males in a habituation-discrimination task, (b) show preferences for male over female odors, and (c) scent-mark in response to male odors. Lesioned females readily discriminated between scents of individual males. Neither lesion altered female preferences for male odors. Females with DM lesions showed increased levels of scent marking to male odors, but those with ORB/AI cortex lesions did not differ from controls. Thus, ORB/AI cortex does not appear to be critical for discrimination of odors of individuals or sex or for scent-marking responses based on these discriminations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contributions of endothermy to huddling behavior in infant Norway rats ( Rattus norvegicus) and Syrian golden hamsters ( Mesocricetus auratus).

Infant Syrian golden hamsters (Mesocricefus auratus) do not exhibit endogenous heat production before 3 weeks of age and do not huddle effectively during cold exposure, gaining little thermoregulatory benefit from the presence of multiple littermates. In contrast, infant Norway rats (Rattus norvegicus) produce heat endogenously and are effective at maintaining elevated body temperatures by huddling. Therefore, the ineffective huddling of infant hamsters may be due to the absence of endogenous heat production. The huddling behavior of infants in mixed huddles of 8-day-old hamsters and weight-matched 4-5-day-old rats was observed to explore this possibility. The results indicate that hamsters, even when cold, effectively gain access to heat-producing rats, supporting the idea that endothermy contributes to the behavior of huddling by providing heat to each individual and thermal stimuli to other infants to support aggregation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Causes of scent marking in female golden hamsters (Mesocricetus auratus): Specific signals or classes of information?

Odor-elicited scent marking is common among mammals, but the proximate causes of marking are not well understood. Scent marking by female hamsters in response to 8 different male odors was investigated. Two odors (flank, mouth) increased flank marking and 2 (flank, rump) increased vaginal marking; in the latter case the effects of flank and rump odors were additive. Two odors (feces, urine) decreased flank marking but did not affect vaginal marking; other odors (foot, ear, ano-genital) had no influence on either scent-marking behavior. Results show that scent marking by females is influenced by a limited number of male odors, suggesting specific effects of particular odors. Classes of information (such as sexual identity) were not relevant causes of scent marking, as some odors containing such information were effective but others were not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the hippocampal system in social odor discrimination and scent-marking in female golden hamsters (Mesocricetus auratus).

Female golden hamsters (Mesocricetus auratus) received aspiration lesions of the parahippocampal region (PARA) or electrolytic lesions of the fimbria-fornix (FNX) and were tested for their (a) discrimination between odors of individual males in a habituation-discrimination task, (b) preference for male over female odors, and (c) scent-marking in response to conspecific odors. Both lesion groups habituated to repeated presentations of a male's odor. However, only FNX females discriminated between scents of individual males, whereas PARA females did not. Neither lesion eliminated female preferences for male odors. Females with FNX lesions showed decreased levels of scent marking, but those with PARA lesions had more subtle deficits. Thus, the PARA, but not the subcortical connections of the hippocampus, is critical for discrimination of the odors of individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determinants of mating success in the golden hamster (Mesocricetus auratus): II. Pregnancy initiation.

Investigated the initiation of pregnancy and the physiological significance of long intromissions (10–30 sec of intravaginal thrusting), in 4 experiments with 425 virgin and 808 multiparous female LVG golden hamsters and 102 stud males. Results show that virgin females required significantly less copulatory stimulation to induce pregnancy and maximize litter size. Ss receiving only long intromissions showed a 100% pseudopregnancy rate, suggesting that long intromissions can initiate the neuroendocrine response necessary to maintain pregnancy. When the male delivered only 1 or a few ejaculations, the inclusion of long intromissions significantly increased the percentage of both virgin and multiparous females that became pregnant. Order of ejaculations did not affect the proportion of multiparous females that delivered litters. However, litter size of females receiving the 1st or 5th ejaculation was significantly larger than that of females receiving the 10th or 15th ejaculation. Multiple-male matings did not augment pregnancy rates or litter sizes compared with matings with a single, rested male. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determinants of mating success in the golden hamster (Mesocricetus auratus): I. Male capacity.

Studied the maximum copulatory capacity of 102 male golden hamsters to determine what effect a steady state of copulatory activity would have on the chronic fertility of the male, and to determine the rate of recovery from copulatory recovery. Rested Ss produced a mean of 13 ejaculations and then showed a modified copulatory pattern consisting of long intromissions (10–30 sec of intravaginal thrusting) during which no sperm transfer occurred. When a 2nd (fresh) female was introduced, 58% of the Ss produced at least 1 more ejaculation, and 17% of the Ss produced 1 further ejaculation when placed with a 3rd female. In similar 3-female tests conducted 24 hrs later, all Ss ejaculated (mean 4 ejaculations); this level of ejaculatory output was maintained over a subsequent 10-day period of daily testing. Four ejaculations ensured a nearly 100% pregnancy rate and maximum litter size in the 1st females. Second and 3rd females, however, received fewer ejaculations and subsequently showed reduced fertility. Two or 8 hrs of rest resulted in fewer than 50% of the Ss being capable of 1 further ejaculation. However, most of these single ejaculations were accompanied by long intromissions and resulted in successful pregnancies. Findings show that the male golden hamster has a higher ejaculatory output and more rapid recovery from sexual exhaustion than other small rodents that have been studied. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hoarding-induced lever pressing in golden hamsters (Mesocricetus auratus): Illumination, time of day, and shock as motivating operations.

Assessed the effects of illumination, time of day, and shock on the hoarding-induced lever pressing of 42 male golden hamsters. Results of Exp I show that Ss pouched the pellets instead of eating them when there was illumination. It was also observed that the Ss stopped lever pressing in the absence of chamber illumination. When chamber illumination and time-of-day variables were manipulated systematically, this was especially prominent in Ss tested during their night cycle. In Exp II, it was observed that the presence of mild shock, but not pure tone, could also alleviate the need for food deprivation in maintaining a food-reinforced lever press response. Data are discussed in terms of the potential for using illumination and mild shock as alternative sources of establishing motivation for food-reinforced behaviors. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feeding differences in pubertal and aged golden hamsters (Mesocricetus auratus) are related to specific cerebral expression pattern of histamine subtype 3 receptor.

The hibernating golden hamster (Mesocricetus auratus) is becoming a useful rodent model to study the neurophysiological role of some neuromediators on vital behaviors such as sleep and thermoregulation. Recent works have shown that the histamine neuroreceptor subtypes (H1-3R) are able to modulate such behaviors. Here, specific subtype(s) and cerebral nuclei that were actively operating on feeding behaviors in pubertal and adult hamsters were identified. Of the subtypes assessed, H?R antagonist (thioperamide) provoked significant ( p