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R D Lisk

Publications and source records attributed to R D Lisk.

At least 55 records · Page 3Linked to original sources
PubMed1984

Changes in responsiveness to newborn pups in pregnant, nulliparous golden hamsters.

Virgin female hamsters were mated and tested once daily for maternal retrieving behavior beginning on days 0, 5, 9, 13, 15, of the 16 day gestation period to determine if responsiveness toward newborn pups changes as pregnancy proceeds. Upon initial exposure to 3 newborn pups, only a small percentage of early-to-mid-pregnant females exhibited maternal retrieving behavior spontaneously. In contrast, over half of the 15 day pregnant females displayed retrieving during the first test. Despite the high frequency of initial pup-directed aggression and cannibalism, maternal retrieval was induced in the majority of the females in all groups by repeated daily exposure to 3 newborn pups. However, no significant differences were observed in the number of pup exposure periods required to induce maternal retrieving in 0, 5, and 9 day pregnant females. It is concluded that the high level of maternal responsiveness observed in the parturient hamster develops somewhat abruptly during late pregnancy. In this respect, the pattern observed in the hamster differs from the more gradual increase in maternal responsiveness reported in mid-to-late-pregnant mice and rats.

Aggression↗
PubMed1984

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

Social interactions of cycling female golden hamsters paired with ovariectomized animals in large enclosures were primarily agonistic over the 4-day estrous cycle. These aggressive interactions were intense 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 females in sexual heat were capable of attacking and dominating their rivals. Furthermore, cycling females exhibited significantly more aggressive acts than ovariectomized opponents 1 day prior to sexual receptivity. No differences in fighting patterns were found between animals on the other 3 days of the estrous cycle. Additional analyses revealed clear differences in agonistic elements, including flank marking, between dominant and subordinate females regardless of whether they were gonadectomized or intact. These analyses also showed that dominant individuals frequently chased and bit opponents during encounters within their nesting area. The 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.

Aggression↗
PubMed1983

Organization and expression of agonistic and socio-sexual behavior in golden hamsters over the estrous cycle and after ovariectomy.

Pairs of hamsters were housed in large enclosures that contained separate male and female living areas and observed over the 4-day estrous cycle and after ovariectomy. Agonistic elements exhibited frequently by females included on-back, boxing, lateral posturing, and biting, whereas males engaged frequently in boxing and on-back patterns of behavior. Furthermore, on-back and boxing by females were significantly higher on estrus than on any other day of the estrous cycle. Agonistic acts performed after ovariectomy did not differ in occurrence from those shown by animals on diestrus and proestrus. Vaginal marking increased during diestrus and attained a peak 24 hr prior to sexual receptivity. Both vaginal marking and mating occurred more frequently in the female's than male's home area suggesting that vaginal marking and mating occurred serve to attract males to the nest of females. Males also organized their marking patterns by location as shown by more flank marking in their own than their partner's area, albeit the significance for this difference in location is not known. The results demonstrate that when heterosexual pairs of hamsters are tested in large and partially familiar habitats, a wide range of behavior is exhibited and organized in a manner that is not observed in small and unfamiliar cages.

Aggression↗
PubMed1983

Female-induced pregnancy block in the golden hamster.

Recently mated female golden hamsters (Mesocricetus auratus) were paired with 12-day pregnant animals for three 10-min periods on 3 consecutive days. Pregnancy success was significantly reduced among subordinate recently mated females whereas litter size was significantly reduced among subordinate 12-day pregnant females. Additional results indicated that physical contact--specifically, defeat by another female--was necessary for blocking to occur. The use of relatively short exposure periods suggests that this effect could occur in the wild.

Aggression↗
PubMed1983

Conditions necessary to the establishment of mating dominance by the male hamster.

We tested whether establishment of a dominance hierarchy among four males will ensure the dominant male preferential mating access to a single female. Establishment of the dominance hierarchy in the absence of a female did not result in any competitive mating advantage for the dominant male in terms of mating priority or total number of intromissions. However, establishment of the dominance hierarchy in the presence of a female, with interactions between the males and female occurring throughout the 4-day estrous cycle prior to the female becoming receptive resulted in the dominant male having a clear mating priority. Under these conditions the dominant male achieved more intromissions than the three subordinate males combined. Thus, male dominance status can affect mating success; however, it appears that interaction with the female as well as with other males prior to the onset of receptivity by the female is essential for assurance of a clear mating priority.

Animals↗
PubMed1983

Central plus peripheral stimulation by androgen is necessary for complete restoration of copulatory behavior in the male hamster.

Male golden hamsters were castrated and received a unilateral intrahypothalamic implant of either testosterone propionate (TP) or estradiol benzoate (EB). Half the animals from each group also received 5 alpha-dihydrotestosterone (DHT) via subcutaneous silastic capsule implants. The males were tested in a three-part design (intact, castrate, implant) to determine the effectiveness of intracerebral alone versus intracerebral plus systemic hormone regimens in restoring copulatory behavior following castration. All treatment regimens reinstated ectopic and normal mounting behavior to levels comparable to those seen in the intact animals. However, only those animals which received DHT systemically in addition to intracerebral implantation of TP or EB showed intromissions after castration. Both EB and TP groups with systemic DHT had intromission levels comparable to the controls by day 14 after implantation. The results point to a dual mechanism for the regulation of sexual behavior in the male hamster. A central hormone-sensitive mechanism is found in the anterior hypothalamic-preoptic region which is necessary for mounting behavior to be expressed. Androgen can affect stimulation at this level via conversion (aromatization) to estrogen. In addition, a peripheral hormone-sensitive mechanism which is necessary for intromission responses depends on the presence of nonaromatizable androgen for maintenance of its sensory feedback channels. The complete copulatory behavior pattern occurs only when both systems are hormone stimulated.

Androgens↗
PubMed1982

Effects of septal lesions on lordosis in female hamsters.

The ovarian hormones, estradiol and progesterone, are believed to act at specific sites in the female brain to induce sexual receptivity. Septal lesions which have been comprehensively studied in the rat, were carried out on female hamsters. Lordosis behavior was quantified as an index of female sexual receptivity. Septal lesions were found to cause a significant increase in female sexual receptivity in hamsters primed with 3 or 9 micrograms estradiol benzoate (EB) and 200 micrograms progesterone (P), but low levels of lordosis were not enhanced in septal lesioned female hamsters primed with 1 microgram EB + 200 micrograms P. The facilitation of lordosis seen in septal lesioned hamsters is similar to that observed in female rats. However, our results do not confirm increases in sensitivity to estradiol in the hamster.

Animals↗
PubMed1981

Effect of neonatal intrahypothalamic testosterone implants on cyclicity and adult sexual behavior in the female hamster.

To localize the neural sites of hormone action for sexual differentiation in the hamster, pellets containing 3 microgram testosterone were implanted directly in the preoptic area-anterior hypothalamus (POA-AH) and the ventromedial hypothalamus-arcuate regions of the hypothalamus of 3-day-old female hamsters. The POA-AH implants strongly enhanced the potential for ectopic mounts, rear mounts, and intromission patterns after adult testosterone treatment. 50% of the females with neonatal POA-AH implants demonstrated vaginal acyclicity in adulthood, suggesting a significant disruption of normal gonadotropin release. Tests for female sexual behavior revealed that implants in both POA-AH and ventromedial arcuate had no significant effect on latency to lordosis or total lordosis duration with estrogen and progesterone priming, but did reduce the longest single bout of lordosis. In conjunction with other recent investigations, these findings suggest that in the hamster, as in other species, androgenization involves several independent processes in terms of both location and sensitivity to hormone exposure.

Animals↗
PubMed1980

Intrahypothalamic hormone implantation and activation of sexual behavior in the male hamster.

Intrahypothalamic implants of testosterone propionate (TP), 5 alpha-dihydrotestosterone (DHT) and estradiol (E) were compared for their effectiveness in reactivating sexual behavior of castrated male golden hamsters. Males tested preexperimentally and then observed for loss of sexual behavior responses after long-term castration were divided into four experimental treatment groups: anterior TP implants, DHT implants and E implants, and posterior TP implants. All animals were tested at 7 and 21 days postimplantation. On the day 7 implant test mount frequency, latency and duration per mount were significantly different from the castrate response for the TP implant groups. On the day 21 implant test both TP and E implant groups showed significant changes in mounting while intromission frequency, latency and duration per intromission were significantly different from the castrate only for the TP implant groups. DHT implants were not effective in reactivating any aspect of copulatory behavior in the castrate male hamster.

Animals↗
PubMed1980

Relative contributions of oestradiol and progesterone to the maintenance of sexual receptivity in mated female hamsters.

Sexual receptivity was measured as total lordosis duration (TLD) per 10 min test period with mating tests standardized across 24 h by giving the first test at the time when the lights were switched off (0 h) during a schedule of 14 h light : 10 h hardness and re-testing at intervals of 2 h. Long-term (14 days), high-level oestrogen treatment was necessary to achieve TLD scores similar to those found in female hamsters treated with oestrogen plus progesterone for 3 days. Mating of female animals treated with oestrogen only always resulted in a significant decrease in TLD scores at later tests (0 v. 2 h). If progesterone was given after the test at 0 h, a significant increase in TLD score was found at the test at 2 h and this increase was maintained across several tests. By 8 h TLD scores had decreased significantly in progesterone-treated mated female hamsters. Progesterone appeared to have, therefore, at least two roles in the regulation of sexual responsiveness in the female hamster: (a) under normal conditions of oestrogen exposure (1--3 days) progesterone was necessary for the induction of sexual receptivity and (b) progesterone was necessary for the maintenance of sexual responsiveness following short-term (10 min) mating in female hamsters treated with oestrogen only. In the oestrogen- and progesterone-treated female animal which is no longer receptive as a result of previous exposure to progesterone plus having been mated, sexual receptivity can be re-induced by treatment with a larger dose of progesterone. These findings have indicated that progesterone is the primary hormonal agent which regulates sexual receptivity in the mated female hamster. Furthermore, the eventual inhibitory effect of progesterone on sexual receptivity was not absolute even in the mated female animal but rather represent some form of habituation to that particular dosage of progesterone to which the animal had been previously exposed.

Animals↗