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

The purpose of this study was to measure the effects that toxicosis had on the hamster's predatory behavior and to compare these results with those found in previous studies with grasshopper mice. A 0.15 M LiCl injection caused hamsters 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. 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. The differences in these inhibitory effects are attributed to inherent differences in the attack responses of the two rodents.     

Dexamethasone can prevent stress-related litter deficits in the golden hamster

This study was designed to examine the effects of social subordination during early pregnancy in the golden hamster (Mesocricetus auratus). Primiparous females were mated to proven breeders and stressed during early pregnancy. Females were housed singly throughout gestation except for Days 4, 5, and 6 when they were paired for 10-min intervals three times each day with another female matched for age, weight, and day of pregnancy. Within each of the pairs, one female was consistently dominant to the other. Controls were exposed to a novel area instead of a conspecific. At parturition, all pups were counted, sexed, and weighed. There were no significant differences between control and dominant females' litter sizes and sex ratios. Subordinate females produced significantly smaller litters than control or dominant dams and significantly lower sex ratios than control dams. Subordinates produced fewer males than control or dominant dams, but there were no differences in the number of females produced. The entire experiment was repeated exactly except that females received a small dosage of dexamethasone in their drinking water on Days 3-7 of pregnancy. In this second group, there were no significant reductions in mean litter size, sex ratio, or pup weights among litters born to subordinate dams. These results suggest that subordinate dams produce smaller litters via selective resorption of males in utero and that the typical adrenal response to stress mediates this response.     

Contrasting visuomotor functions of tectum and cortex in the golden hamster

Summary Visually-guided orientation (spatial localization) and visual discrimination were dissociated by means of brain lesions in the golden hamster. After ablation of visual cortex, hamsters failed to discriminate visual patterns, but showed nearly normal ability to localize an object in space by means of vision. Ablation of the superior colliculus produced opposite effects: these animals were completely unable to orient to the position of a visual stimulus, but nevertheless showed excellent pattern discrimination.

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Zusammenfassung Visuell gesteuerte Orientierung (räumliche Lokalisation) und visuelles Unterscheidungsvermögen beim Goldhamster werden durch Hirnläsionen funktionell getrennt. Nach Entfernung der Sehrinde können die Tiere keine visuellen Musterunterscheidungen, wohl aber noch in fast normaler Weise visuelle Objektlokalisationen vornehmen. Entfernung des Colliculus superior führt zu entgegengesetzten Effekten: die Tiere können sich nicht mehr nach der Position eines visuellen Reizes orientieren, zeigen aber trotzdem ausgezeichnete Musterunterscheidung.

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During the period of the reported research, the author was supported by a U.S. Public Health Service predoctoral fellowship. Additional support was received from the National Institute of General Medical Sciences under their Training Grant STl GM 1064-04 BHS.For a more detailed report of this work, and reports of further experiments, see Schneider (1966).     

Lactose ingestion in the adult golden hamster (Mesocricetus auratus)

Adult mammals generally demonstrate a lower preference for the disaccharide sugar lactose than for any other common sugar, and because adults typically have low levels of the intestinal enzyme lactase, lactose ingestion may cause gastrointestinal distress. The lactose intake of adult golden hamsters was examined in three experiments; the main findings were: (a) hamsters allowed to choose between tap water and lactose solutions (maximum concentration = 32% weight/volume) over a 20-day period showed a clear preference for lactose solutions and ingested substantial quantities of lactose (up to 3 g/100 g body weight/day) without noticeable adverse effects; (b) hamsters consuming a single diet with lactose added (maximum concentration = 50%) over a period of days ingested up to 3.42 g/100 g body weight/day of lactose without noticeable adverse effects; (c) both hamsters with prior exposure to lactose solutions and those without such exposure consumed similar amounts of 32% lactose solution over an 8-day period, suggesting that hamsters' lactose intake does not depend on the occurrence of adaptation. It is suggested that the fermentative capacity of the hamster's pregastric pouch may underlie this animal's unusual tolerance for lactose.     

Hoarding

This commentary highlights areas of research during my career that have been very positively influenced by Dr. Aaron T. Beck’s work on cognitive theory, assessment, and treatment of behavioral disorders. These include collaborative efforts to develop assessment of beliefs and interpretations, as well as cognitive therapy for obsessive-compulsive disorder, and especially recent work on assessing, understanding beliefs about possessions, and cognitive behavior therapy for hoarding disorder.     

Evidence for separate control of estrous and circadian periodicity in the golden hamster.

To study the relationship between estrous and circadian periodicity, we investigated the period of the estrous cycle in two types of female golden hamsters: normals (circadian period approximately 24 h) and tau mutants (circadian period approximately 20 h). Records of running wheel activity, general locomotor activity, body temperature, vaginal secretion, and sexual receptivity of hamsters kept under constant lighting conditions indicated an estrous period of approximately 96 h for both groups of animals. The fact that animals with different circadian periods have the same estrous period suggests the existence of separate mechanisms in the control of circadian and estrous periodicity. Circadian periodicity is determined by a pacemaker located in the suprachiasmatic nuclei, whereas estrous periodicity is determined by positive and negative feedback loops involving the hypothalamus, pituitary, and gonads. Coupling of the two mechanisms takes place under at least some conditions, but additional research is necessary to elucidate the mechanisms by which this is accomplished.     

Insight-Related Challenges in the Treatment of Hoarding

Compulsive hoarding is a chronic and debilitating condition that has proven difficult to treat. The cognitive behavioral approaches that have otherwise been successful for people suffering from obsessive-compulsive disorder do not work very well for hoarding (Abramowitz, Franklin, Schwartz, & Furr, 2003). Many have suggested that this is due to the ego-syntonic nature of the symptoms and the accompanying lack of insight. This paper describes several challenges related to insight that limit the effectiveness of traditional cognitive behavioral approaches for compulsive hoarding. Problems with anosognosia, overvalued ideation, and defensiveness that characterize hoarding are described and suggestions offered for dealing with them.     

Olfactory discrimination of estrous condition by the male golden hamster (Mesocricetus auratus)

After repeated exposure to receptive and nonreceptive females, male golden hamsters were tested for olfactory preferences in a four-choice olfactometer. Males discriminated between the odor of anesthetized females in different stages of their estrous cycle when the airstreams carrying the stimulus odors were diluted. Previous failures to demonstrate such an ability were probably due to ceiling effects resulting from laboratory testing. Males preferred the odor of females on the day before receptivity (a day coincident with maximal scent marking by the female) and least preferred the odor of females on diestrus-1 (the day on which females attacked and chased males during pretesting encounters). Detection and quick response to an impending estrus would be especially important for males of a solitary and promiscuous species in which there is a first male mating advantage.     

Mating-induced inhibition of receptivity in the female golden hamster. I. Short-term and long-term effects

Female golden hamsters (Mesocricetus auratus) which have actively terminated mating with one male will respond in succession to two or more novel males. However, mating with the first male results in a reduction in receptivity shown toward a second male, with the size of the decrease being proportional to the amount of copulatory stimuli provided by the first male. Furthermore, the decreased receptivity shown toward the second male results in his achieving fewer ejaculations. These effects are more pronounced when the second mating occurs 5 min or 8 h after the first mating than when it occurs 1 or 4 h later, suggesting both short-term and long-term inhibitory effects. Copulation with a single male also effects a 40% shortening of behavioral receptivity. In a promiscuous species such as the hamster, prolonged copulation by the male may enhance the short-term inhibition of female receptivity, thereby reducing the risk of subsequent sperm displacement. The long-term effect occurs too late to affect sperm competition and may, instead, function to reduce the risk of predation as a result of unnecessary further mating.     

Hoarding in a compulsive buying sample

Previous research has indicated that many compulsive buyers also suffer from compulsive hoarding. The present work specifically examined hoarding in a compulsive buying sample. Sixty-six treatment-seeking compulsive buyers were assessed prior to entering a group therapy for compulsive buying using the Compulsive Buying Scale (CBS), the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS)-Shopping Version, the Compulsive Acquisition Scale (CAS), the German-CBS, the Saving Inventory-Revised (SI-R), the Maudsley Obsessive Compulsive Inventory (MOCI), the Barratt Impulsiveness Scale (BIS-11), and the Structured Clinical Interview for DSM-IV Axis I (SCID). Inclusion criteria were current problems with compulsive buying according to the proposed diagnostic criteria for compulsive buying by McElroy, Keck, Pope, Smith, and Strakowski [(1994). Compulsive buying: A report of 20 cases. Journal of Clinical Psychiatry, 55, 242-248]. Our results support the assumption that many but not all compulsive buyers suffer from compulsive hoarding. A significant association between the SI-R and the compulsive buying measures CBS, Y-BOCS-SV, German-CBS, and the CAS-Buy subscale was found, which is mostly caused by the SI-R subscale acquisition. The SI-R subscales clutter and difficulty discarding were more closely associated with the CAS-Free subscale and with obsessive-compulsive symptoms. Hoarding compulsive buyers reported more severe buying symptoms and obsessive-compulsive symptoms and presented with a higher psychiatric co-morbidity, especially any current affective, anxiety and eating disorder. Specific therapeutic interventions for compulsive buyers who also report compulsive hoarding appear indicated.     

Ethical Considerations in the Treatment of Compulsive Hoarding

Although empirically supported treatment for compulsive hoarding is in its preliminary stages, some information has emerged regarding ethical challenges experienced in treating this population. Our aims are twofold: (a) to inform the clinical community of ethical complications when conducting treatment for hoarding clients, and (b) to provide a decision-making model for ensuring quality and ethical care of hoarding clients. The ethical challenges (boundary crossings, dual roles, privacy/confidentiality, record keeping, fees, and cultural competence in treatment) were discovered through multiple roundtable discussions, supervision, and in the course of delivering empirically supported treatment protocols. A literature search was conducted to identify research that addressed ethical concerns. A decision-making model addressing ethical challenges in treatment of compulsive hoarding was developed.     

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

Rested adult golden hamsters produced a mean of 13 ejaculations and then showed a modified copulatory pattern consisting of long intromissions (10-30 s of intravaginal thrusting) during which no sperm transfer occurs. When a second (fresh) female was introduced, 58% of the males produced at least one more ejaculation, and 17% of the males produced one further ejaculation when placed with a third female. In similar three-female tests conducted 24 hr later, all males ejaculated (M = 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 first females. Second and third females, however, received fewer ejaculations and subsequently showed reduced fertility and produced smaller litters. Most males showed high levels of long intromissions on all days and with all females. The physiological significance of these long intromissions may be to trigger the progestational response. Examination of the rate of recovery from sexual exhaustion indicated that 2 or 8 hr of rest resulted in fewer than 50% of the males being capable of one further ejaculation. However, most of these single ejaculations were accompanied by long intromissions and resulted in successful pregnancies. Four to eight days were required for full recovery of ejaculatory capacity. This study showed 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. Thus, the limits of male capacity appear to vary widely among species.