Facilitation of the lordosis response of the female hamster (Mesocricetus auratus)

A series of experiments investigated the facilitative effects of stimulation from the male hamster on the lordosis response of the female. Experiments 1 and 2 demonstrated that repeated exposure to copulatory stimulation increased lordosis duration of both females in natural estrus and females in induced estrus. Experiment 3 compared the facilitative effects of mounts and intromissions. Both mounts and intromissions increased lordosis duration. Experiment 4 compared the effects on lordosis duration of (1) noncoital contact with a male (2) the sight of a male, and (3) exposure to an empty cage. Noncoital contact with a male increased the lordosis duration; the other conditions had no effect.     

Postnatal development of the electrocortical activity in the golden hamster (Mesocricetus auratus)

Electrical activity was recorded from the occipital and parietal cortices of the golden hamster at the ages of 1, 2, 5, 7, 10, 13, 15, 20, 25, 30, 45, days, and adult (1 yr). Additional animlas were used for determination of brain weight and for studies of neuronal development. In the golden hamster the ECoG activity appeared by Postnatal Day 2 as intermittent and slightly irregular low voltage activity. From 7 to 10 days the amount of fast activity (18 - 20 cps) increased as did the amplitude in the slow waves of 6 – 9 cps. By 15 days the ECoG pattern was essentially similar to that the adult hamster. However, an augmentation in voltage and a predominance of faster rhythms (18 - 25 cps) were observed as the animal matured. Neurohistological data revealed that the cortex approached the general anatomical pattern of the adult by the 13th to 15th postnatal day.     

Mating-induced inhibition of receptivity in the female golden hamster (Mesocricetus auratus): III. Stimuli mediating long-term effects

In the golden hamster, mating with an intact male results in both a reduction in receptivity shown toward a second male (short-term effect) as well as an absolute abbreviation of the receptive period (long-term effect). The present study examined the components of the mating situation responsible for the long-term effect. In experiment 1 we showed that the paradigm used to determine receptivity (i.e., brief hourly exposures to an intact male) did not affect the duration of receptivity whereas an ad lib mating early during the receptive period resulted in a 40% reduction in the length of behavioral estrus. In experiment 2 females received various types of mating stimuli, e.g., mounts from an apronned male, intromissions from a vasectomized male, a simulated copulatory plug, manually-induced lordosis, or several of these stimuli in combination. Only intromissions from an intact or vasectomized male significantly reduced the duration of behavioral estrus. Although as few as 10 intromissions from a vasectomized male were effective in significantly shortening the receptive period, higher levels of vaginocervical stimulation from a single male (experiment 3) or from additional males (experiment 4) effected significantly greater reductions in the length of behavioral estrus. Our results further demonstrated that only those females that subsequently became pseudopregnant showed significant abbreviations of behavioral estrus. The association of these two phenomena is of obvious adaptive value since it provides a mechanism to terminate a behavior once its function has been achieved.     

Histochemical study of glycoconjugates in active and photoperiodically-regressed testis of hamster (Mesocricetus auratus)

The objective of the present study was to characterize glycoconjugates of hamster testis in gonadally-active and -inactive states by lectin histochemical methods. Thirteen HRP- or digoxigenin-labeled lectins were used in samples obtained from fertile and photoinhibited hamsters. In gonadally-active hamsters, spermatozoa tails were stained with Con-A, HPA, PNA, UEA-I, LTA, AAA, WGA and LFA and weakly with GNA and RCA-I. Spermatozoa acrosomes were labeled with HPA, SBA, WGA and PNA. Spermatid acrosomes were labeled with SBA, RCA-I, PNA, and WGA. Staining with GNA and Con-A was found in the Golgi phase and HPA staining was found in the Golgi phase and maturated spermatids. Cytoplasm of spermatocytes was labeled with Con-A, GNA, LTA, AAA, RCA-I, HPA, WGA and LFA, whereas spermatocyte membranes were stained with Con-A, LTA and AAA. Spermatogonia were strongly labeled with Con-A and moderately labeled with AAA, WGA and LFA. Sertoli cells were positive after staining with Con-A, AAA, WGA, and LFA. The lamina propria was positive after staining with UEA-I, LTA, AAA and LFA. Leydig cells showed strong labeling with SBA, Con-A, GNA, SNA and MAA, moderate labeling with WGA, weak labeling with RCA-I, AAA and LFA. In gonadally-inactive hamsters, spermatocytes showed increased staining with HPA, PNA and AAA, whereas staining with Con-A, GNA and LTA had disappeared. Spermatogonia showed an increased labeling with AAA and WGA, but labeling with Con-A and LFA had disappeared. Sertoli cells were strongly labeled with GNA. Con-A and GNA staining was decreased in Leydig cells of gonadally-inactive hamsters but PNA and HPA staining was increased. The lamina propria in regressed testes showed intense labeling with PNA. These results suggest that histological, morphological and hormonal changes occurring in hamster testis during exposure to a short photoperiod are reflected in altered patterns of expression and distribution of N- and O-linked glycans.     

Play-fighting in the Syrian golden hamster Mesocricetus auratus Waterhouse, and its relationship to serious fighting during postweaning development

In the Syrian golden hamster Mesocricetus auratus, play-fighting precedes serious fighting during postweaning development, and so may be thought to be a developmental precursor to adult aggression. However, based on both the targets attacked--that is, the cheek pouches during play-fighting and the rump or flanks during serious fighting, and the behavior patterns employed to attack and defend these targets--these two forms of fighting are shown to remain distinct from each other throughout development, even during the ages where they overlap. The decline of play in post-sexually-mature animals is shown to result from an increasing intolerance to contact between animals, and hence greater difficulty in the maintenance of a "playful mood." Therefore, these data show that play-fighting does not grade into serious fighting, and thus does not serve as a developmental precursor to adult aggression.     

Temporal pattern of recovery from sexual satiety in male golden hamster (Mesocricetus auratus)

In male rodents, copulatory activity ad lib leads to a complete inhibition of sexual behaviour performance known as sexual satiety. On the other hand, male hamsters display a peculiar copulatory pattern known as Long Intromission (LI) after being exposed to repeated mating. In this study, the characteristics of the temporal recovery of sexual behaviour after a sexual satiety test and the possible relationship between the presence of LI and the inhibition of sexual behaviour were analysed. Fifty males were exposed to repeated mating until they reached a criterion for sexual satiety. Thereafter, they were divided in several groups and retested for sexual activity after a period of 24, 48, 72, and 96 h. During the sexual satiety test LI appeared after nine ejaculatory series, with a mean latency of 18 min. Twenty-four hours after the satiety test, all the subjects (Ss) displayed copulatory activity, and LI appeared after a mean of 2.5 ejaculations with a mean latency of 9.1 min, whereas at 48 h, only 20% of Ss displayed sexual activity. During the 72-h period, the results obtained show a clear trend towards normalisation, and finally, at 96 h, all the sexual parameters were fully restored. The data showed that there was a close relationship between sexual inhibition and the presence of LI, and demonstrated that full recovery of sexual behaviour was reached 96 h after the sexual satiety test.     

Hormone dependent sex dimorphisms in the golden hamster (Mesocricetus auratus).

Sex dimorphisms in the copulatory behavior of gonadectomized hamsters were studied following chronic daily administration of either 6 μg estradiol benzoate; 300 μg dihydrotestosterone propionate; 300 μg testosterone propionate; or oil vehicle. All animals were tested weekly for male behavior and female behavior and then tested for female behavior following the injection of varied doses of EB plus 0.5 mg progesterone (P). Male hamsters had higher total lordosis durations than females when tested following chronic EB administration but without P. When tested for female behavior after EB plus P, EB-treated males did not differ from EB-treated females. In comparison to the oil controls, chronic DHTP treatment reduced the proportion of males and females displaying lordosis following the injection of 3 μg EB plus P. Chronic TP administration increased the proportion of males and females displaying lordosis following 1 μg EB plus P. In males, but not in females, TP treatment reduced the total lordosis durations following administration of 3 μg or 6 μg EB plus P. When tested for male behavior, EB-treated males mounted without intromission as frequently as TP-treated males and more frequently than DHTP-treated males but did not intromit or ejaculate. DHTP-treated males intromitted, but ejaculated less frequently than TP-treated males. TP restored the full copulatory pattern in males.     

Ovarian hormones influence odor stimulated flank marking behavior in the hamster (Mesocricetus auratus)

The effect of ovarian hormones on the frequency of female flank marking in response to the odors of male hamsters was examined. The amount of flank marking differed significantly (p less than 0.01) among the days of the estrous cycle, with the lowest levels of flank marking occurring on estrus. Ovariectomy (OVX) eliminated the 4 day rhythm, and significantly (p less than 0.01) reduced the total amount of flank marking. Implantation of Silastic capsules containing estradiol benzoate (EB) in OVX hamsters increased flank marking by approximately two-fold when compared to hamsters implanted with blank Silastic capsules. In a second series of experiments, OVX hamsters given EB flank marked significantly (p less than 0.01) more than those with blank capsules. Subcutaneous injection of progesterone (P) into OVX-EB treated hamsters 6 hr prior to testing significantly reduced flank marking when compared to OVX-EB treated hamsters given oil. No differences were observed in flank marking between groups of OVX hamsters with blank capsules and injected with P or oil. In summary, these data indicate that the four day rhythm of odor stimulated flank marking in intact female hamsters may be the result of the 4 day fluctuations of estrogen and progesterone that occur during the estrous cycle.     

Absence of post-fast food compensation in the golden hamster (Mesocricetus auratus).

Ad lib food intakes and body weights were measured for hamsters fed one of 4 different diets. Animals were then placed on an intermittent starvation (IS) schedule in which food was available ad lib on alternate days only. Hamsters of both sexes showed little or no post-fast food compensation, i.e., after 24 hr of food deprivation their daily food intake was no greater than their daily intake during baseline testing. These animals lost a large percentage of their initial body weight and many of them died. Other hamsters restricted daily to half-day feeding periods that nearly coincided with the light (L) or dark (D) phases of the illumination cycle also failed to show food compensation; they generally ate no more during D- or L-periods that followed a half day of food deprivation than during D- or L-periods that succeeded a half day of ad lib feeding. These animals lost substantial portions of their initial body weight and many died. Hamsters refed after a 96-hr fast and an 18% loss in body weight also did not increase their food intake substantially above baseline values. In each of these experiments substantial portions of the body weight lost during starvation were not regained during extended ad lib refeeding regimens. These findings contrast strikingly with the behavior of rats tested concurrently; rats showed a dramatic post-fast hyperphagia, rapid recovery of body weight lost during starvation, and a reversal of the normal nocturnal feeding pattern when refeeding began during L-periods. Hamsters' nocturnal rhythms of eating and drinking were remarkably stable in the face of all the experimental manipulations. However, hamsters, as well as rats, were quite effective in compensating for changes in diet density; a 1:1 dilution of a liquid diet produced a prompt doubling in the volume of diet ingested. Impressive but less complete compensation was recorded when solid diets were diluted with inert substances (kaolin, cellulose). Hoarding and perhaps hibernation rather than compensation may have evolved as adaptations to periods of food scarcity. Noncompensation may be related to hamsters' nonresponsiveness to some signal of energy depletion. The possibility of lipogenesis being a rate-limiting step is considered. The desirability of adequate field data as a prerequisite to laboratory analysis of feeding behavior is emphasized.     

Enteropathogenicity of Escherichia coli isolated from hamsters (Mesocricetus auratus) with hamster enteritis.

Escherichia coli isolated from ilea of hamsters with hamster enteritis were tested for enteropathogenicity in intestinal loops prepared in both adult and weanling hamsters. E. coli isolated from hamsters with hamster enteritis caused dilatation of loops in weanling hamsters but not in adult hamsters.     

Operant responding for dietary protein in the golden hamster (Mesocricetus auratus).

Golden hamsters housed in operant chambers over a period of weeks had ad lib access to a maintenance diet that was either nutritionally complete (NCMD) or protein-free (PFMD), and they were required to press a lever on a fixed-ratio (FR) schedule to obtain 20-mg high-protein pellets. As the FR requirement increased, hamsters maintained on the NCMD made fewer lever presses and ate fewer pellets, and at the highest FR levels, they earned very few pellets. In contrast, hamsters maintained on PFMD increased the number of lever presses as the FR requirement increased, and they only slightly reduced the number of pellets eaten. Even at the highest FR requirement levels, PFMD hamsters still derived an average of 11-12% of total calories from protein, a level of intake that is either adequate for adult hamsters, or very nearly so. Previous research has shown that hamsters make adaptive behavioural adjustments in response to time-restricted access to dietary protein, and the present findings demonstrate that protein-restricted hamsters that must press a lever to obtain protein-rich pellets also make adaptive behavioural adjustments when challenged with increases in the FR requirement.