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)     

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)     

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)     

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)     

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)     

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)     

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)     

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)     

Role of learning in the selection of dietary protein in the golden hamster (Mesocricetus auratus).

Hamsters (Mesocricetus auratus) were kept for several weeks on maintenance diets (MDs) that were either nutritionally complete or protein deficient, and had periodic access to protein-free and high-protein conditioning diets (CDs) with marker flavors (anise and clove). In Experiment 1, protein-restricted hamsters came to prefer the flavor of high-protein CDs but did not prefer unflavored high-protein CD. Thus, hamsters learned to select dietary protein by attending to the flavor of the CD. In Experiment 2, a within-subjects design was used, and MDs also had marker flavors (garlic and sage). Hamsters came to prefer the flavor of high-protein CD when protein restricted, and they showed this preference even in the absence of protein restriction if reexposed for only 90 min to merely the flavor of a protein-deficient MD. Thus, learned associations between the flavor and the usual postingestional consequences of a recently ingested MD can affect short-term dietary protein selection. (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)     

Similarity in the qualities of individual odors among kin and species in Turkish (Mesocricetus brandti) and golden (Mesocricetus auratus) hamsters.

In this investigation, the authors used habituation techniques to explore similarities and differences in the qualities of individual odors from hamsters. In Experiment 1, male Turkish hamsters (Mesocricetus brandti) treated flank-gland odors of 2 males from 1 litter as similar compared with the odor of a male from another litter, whether the odor donors were familiar or unfamiliar. At the same time, the Turkish hamsters discriminated between the subtle differences in the individual odors of their familiar brothers. In Experiment 2, male Turkish and golden hamsters (Mesocricetus auratus) treated the flank-gland odors of 2 unfamiliar, unrelated conspecifics as similar compared with the flank odor of a heterospecific individual. The results suggest that similarities in individual odors are related to genetic similarity of the odor donors. These similarities could provide a basis for different types of social recognition, including kin and species recognition. (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)     

Decreased density of amygdaloid parvalbumin-positive interneurons and behavioral changes in dystonic hamsters (Mesocricetus auratus).

The dtsz hamster represents a model of primary paroxysmal nonkinesiogenic dyskinesia in which dystonic episodes can be induced by stress and anxious stimuli. This disease is regarded as a basal ganglia disorder. In fact, a deficit of striatal interneurons could play a key role in the pathophysiology in dystonic hamsters. Because the involvement of limbic structures cannot be excluded so far, the density of parvalbumin-immunoreactive (PV+) interneurons was determined in the basolateral amygdala in the present study. Compared with nondystonic hamsters, the density of PV+ interneurons was moderately decreased in the dtsz mutant. The functional consequence of this finding was examined by behavioral analyses. Examinations in the elevated plus maze and in a modified open field failed to disclose an enhanced anxiety-related behavior in dtsz hamsters (Mesocricetus auratus). A lower acoustic startle response and a stronger habituation in mutant hamsters than in controls correlated with a decreased body weight. Interestingly, prepulse inhibition was absent in mutant hamsters. The latter finding suggests a disturbed sensorimotor gating that can be related to alterations in both the basal ganglia nuclei and in limbic structures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of toxicosis on the predatory behavior of the golden hamster (Mesocricetus auratus).

Two experiments attempted to measure the effects that toxicosis had on the golden hamster's predatory behavior and to compare these results with those found in previous studies with grasshopper mice. In Exp I (n?=?17), a 0.15 M LiCl ip injection caused Ss to develop a greater aversion and to inhibit their feeding and attack responses more frequently toward a house cricket than did a similar injection of NaCl. In Exp II (n?=?13), the added presence of an almond coating on the cricket prolonged the number of days that a hamster exhibited an aversion toward the prey and an inhibition to attack. Essentially, the inhibitory effects from toxicosis in the hamster paralleled those found with the grasshopper mouse by W. M. Langley (see record 1982-20395-001) and Langley and K. Knapp (see record 1984-00491-001). The differences in these inhibitory effects are attributed to inherent differences in the attack responses of the 2 rodents. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maturational loss of thermotaxis prevented by olfactory lesions in golden hamster pups (Mesocricetus auratus).

5 day-old golden hamster pups preoperatively were tested on a thermal gradient, subjected to bilateral or unilateral olfactory bulbectomy or control dorsal cortical removal, and then tested on Days 6–25. Locomotion and rectal or belly temperature were monitored throughout the 2-min test. Controls became quiescent in the hot end of the gradient on Days 5–7 but after Day 8 chose cooler regions and increased their activity. Both unilaterally and bilaterally bulbectomized Ss spent more time in the heat throughout testing, were less active, and allowed their temperature to rise more rapidly than controls. Percentage of time in the heat was elevated in all bulbectomized Ss although some retained the ability to make an olfactory discrimination. Enhanced thermal behavior is apparently not due to anosmia per se. Altered thermal perception or responsitivity may result from loss of "nonspecific" olfactory projections that normally would mature at the beginning of the 2nd week. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Glutamate and the aggression neural circuit in adolescent anabolic steroid-treated Syrian hamsters (Mesocricetus auratus).

Adolescent exposure to anabolic androgenic steroids (AAS) alters the development and activity of the glutamate neural system in the latero-anterior hypothalamus (LAH) in hamsters (Mesocricetus auratus); that is, an important neural component of the adolescent AAS-induced aggressive response. In this article, we used retrograde tracing to investigate glutamate-specific alterations in the connections between the LAH and several other nuclei implicated in adolescent AAS-induced aggression. Briefly, hamsters were treated with AAS or sesame-oil control during adolescence and then microinjected with retrograde tracer into the medial amygdala (MeA), lateral septum (LS), or bed nucleus of the stria terminalis (BNST). Brains were then processed for vesicular glutamate transporter 2 (VGLUT2) and examined for AAS-induced changes in the number VGLUT2 cells containing retrograde tracer (VGLUT2/tracer) within the LAH. It is interesting to note that while aggressive AAS-treated hamsters injected retrograde tracer into the MeA showed a significant reduction in the number of VGLUT2/tracer cells in the LAH, aggressive AAS-treated hamsters injected tracer into the BNST showed a significant increase in the number of VGLUT2/tracer cells in the LAH when compared with controls. Last, AAS hamsters injected with tracer into the LS had a comparable number of LAH-VGLUT2/tracer cells to controls. The current results indicate that glutamate likely functions as the major aggression output system from the LAH and that adolescent AAS treatment significantly alters the neural circuitry modulating aggression. Moreover, increases in the number of glutamate projections from the LAH to the BNST in AAS hamsters identify the BNST as an area particularly important for the regulation of AAS-induced aggression. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effects of diet on feeding and body weight regulation during pregnancy and lactation in the golden hamster (Mesocricetus auratus).

Conducted 3 experiments with 90 female golden hamsters to test the hypothesis that the weight loss shown by lactating hamsters constitutes a regulated weight loss. Results support the hypothesis, showing that prefattened overweight Ss lost more weight from the time of mating to the end of lactation than did unmanipulated controls. However, the weight loss during lactation was reduced by giving Ss access to a high-fat diet, a result indicating that a portion of the lactational weight loss may also be regulated by the diet provided. When lactating Ss were given access to a fractionated diet consisting of pure fat, pure carbohydrate, or 45% protein, they increased their proportional intake of both protein and fat but not of carbohydrate. Studies show that hamsters differ from rats in their pattern of energy regulation during pregnancy, lactation, and the postsuckling period. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)