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Biomedical subjects

B Svare

Publications and source records attributed to B Svare.

At least 19 recordsLinked to original sources
PubMed1993

Investigation of anabolic steroids in two taste aversion paradigms.

The aversive effects of estradiol have been studied in two different taste aversion paradigms. A similar investigation was undertaken for the anabolic-androgenic steroids, nandralone and testosterone cypionate, using Rockland-Swiss mice. Experiments 1 and 2 used the brief exposure of a novel saccharin solution as the conditioned stimulus for taste aversion learning, and showed that anabolic steroids (1 mg) do not induce taste aversions. Instead, these hormones induced a small non-contingent increase in saccharin preference. Experiment 3 showed that daily nandralone administration (1 mg/day) had a greater anabolic effect than the same dose of testosterone cypionate. Experiment 4 paired the continuous exposure to a novel diet with daily nandralone injections, and showed that steroid treatment increased intake of the novel diet. When the novel diet was subsequently presented with the familiar diet in a two-choice preference test, there was no indication that an aversion was conditioned to the novel target diet. On the contrary, nandralone treatment significantly increased the preference for the novel diet. These experiments show that anabolic-androgenic steroids do not have aversive effects in mice, and that they may have positive consequences.

Anabolic Agents↗
PubMed1988

Genotype modulates the aggression-promoting quality of progesterone in pregnant mice.

During late pregnancy, female mice of the DBA/2J inbred strain are more likely to exhibit aggressive behavior toward a standard stimulus intruder male than C57BL/6J females. This strain difference can not be accounted for by differences in circulating levels of progesterone (P) since pregnant DBA/2J and C57BL/6J females exhibit similar patterns of the steroid throughout pregnancy. Upon receiving subcutaneously implanted Silastic capsules containing P, virgin DBA/2J mice are more likely than virgin C57BL/6J to respond to the steroid by exhibiting aggression. Strain differences in the aggressive behavior exhibited by pregnant mice may be related to genotype-based variation in central neural tissue sensitivity to P.

Aggression↗
PubMed1988

Estradiol benzoate can function as an unconditioned stimulus in a conditioned taste aversion paradigm.

The extent to which gonadal steroid hormones can serve as unconditioned stimuli in a conditioned taste aversion paradigm was examined in Rockland-Swiss albino mice. With saccharin serving as the conditioned stimulus, subcutaneously injected estradiol benzoate, but not progesterone or testosterone propionate, was found to be a potent unconditioned stimulus in both male and female mice. Dose-response effects were also observed; increasing dosages of estradiol benzoate led to increasingly stronger conditioned aversions in both males and females. The aversion detected in males was more resistant to extinction than that seen in females. Prepubertal gonadectomy reversed the sex-dependent effects of estradiol benzoate in learned aversions in adulthood; castration of males promoted the extinction process, whereas ovariectomy of females retarded extinction. The results may be useful for our understanding of the mechanisms involved in conditioned taste aversion learning as well as a wide array of hormone-dependent behavioral responses.

Animals↗
PubMed1988

Suckling stimulation modulates the maintenance of postpartum aggression in mice.

Previous work in female mice has shown that suckling stimulation is essential for the initiation of male-directed aggression during the immediate postpartum period. The present work examined the importance of this stimulus for the maintenance of aggression during lactation. Surgical excision of nipples (thelectomy) on Postpartum Day 5 accelerates the decline in aggression that ordinarily occurs during the final third of lactation (Postpartum Days 15-21), but does not disrupt the behavior during the middle third of lactation (Postpartum Days 6-12). Thus, both the initiation of aggression during the early postpartum period and the maintenance of the behavior during late lactation are controlled by suckling from young.

Aggression↗
PubMed1988

Prenatal stress alters maternal aggression in mice.

Prenatal stress (heat and restraint) reduced pregnancy-induced and elevated postpartum aggression in Rockland-Swiss (R-S) albino female mice. Though prenatally-stressed females were indistinguishable from control animals with respect to parental behavior during the virgin state, the former displayed slightly lower levels of nestbuilding during early pregnancy, and delivered slightly more male offspring at parturition. The young born to prenatally-stressed females exhibited deficits in birth weights and body weight gain in contrast to pups delivered by control females. The anogenital distances of prenatally-stressed females were shorter than those of control females, suggesting that alterations in fetal testosterone exposure may be responsible for disruptions in behavior and reproduction.

Aggression↗
PubMed1987

Adrenal modulation of parental behavior in neonatally gonadectomized C57BL/6J male mice.

C57BL/6J male mice ordinarily kill neonatal mouse pups even if they are rendered androgen deficient by neonatal castration. Experiment 1 showed that adrenalectomy during adult life significantly decreased the tendency of neonatally gonadectomized males to kill newborns. Experiment 2 demonstrated that testosterone exposure (via silastic implants) during adult life prevented the effects of adrenalectomy in that killing was elevated and retrieving was reduced in neonatally gonadectomized males. Adrenal androgens may be responsible for maintaining killing behavior in neonatally castrated C57BL/6J male mice.

Adrenal Glands↗
PubMed1987

Genotype modulates prenatal stress effects on aggression in male and female mice.

Prenatal stress (heat and restraint) significantly increased postpartum aggression (proportion of animals fighting and/or the intensity of the behavior) in C57BL/6J female mice and reduced the behavior in DBA/2J females. For intermale aggression, prenatal stress increased the behavior (intensity of aggression) in C57BL/6J males but did not affect aggressive behavior in DBA/2J animals. Infanticidal behavior (the killing of young) exhibited by male mice was not influenced by prenatal stress in either strain. Relative anogenital distance measurements in neonates at birth did not serve as a reliable predictor of strain variation in prenatal stress effects. Prenatal stress did not influence this measure of prenatal androgen exposure in DBA/2J or C57BL/6J females. For males, prenatal stress elevated relative anogenital distance in C57BL/6J mice and decreased this measure in DBA/2J animals. Prenatal stress effects on aggressive behavior in male and female mice therefore depend upon genotype. Strain-dependent differences may be modulated by differences in endocrine reactivity to prenatal stress/and or differential central neural tissue sensitivity to hormones.

Aggression↗
PubMed1986

Mice: progesterone stimulates aggression in pregnancy-terminated females.

Three experiments were conducted in order to assess the role of progesterone (P) in the aggressive behavior displayed by late pregnant Rockland-Swiss mice toward adult male intruders. In Experiment 1, hysterectomy on the 15th day of gestation reduced the aggressive behavior normally displayed by pregnant mice toward male intruders. In Experiment 2, Silastic implants of P stimulated aggression in hysterectomized mice but did not fully restore the behavior to the level of fighting normally observed in pregnant animals. In Experiment 3, aggressive behavior in P-treated hysterectomized animals was inhibited by simultaneous exposure to estradiol (E). Also, treatment with E alone did not stimulate aggression in hysterectomized mice. While pregnancy-induced aggression is promoted by P, other neuroendocrine factors may act in concert with the steroid to fully stimulate aggression in gravid mice.

Abortion, Induced↗
PubMed1986

Prior intrauterine position influences body weight in male and female mice.

In two longitudinal studies, intrauterine location of male and female Rockland-Swiss mice relative to fetuses of the same and opposite sex dramatically influenced body weight. In one study, body weight of males and females that were located in utero between two female fetuses (OM animals) or between two male fetuses (2M animals) was assessed from birth to the time of weaning (25 days of age). The body weights of 2M females were indistinguishable from those of OM and 2M males on all but a few of the 25 postnatal days of life. Also, 2M females were significantly heavier than OM females from Postnatal Day 6 onward, and 2M males weighed significantly more than OM males from Postnatal Day 19 onward. In a second study, food intake and body weight of animals from different intrauterine locations were examined from 25 to 120 days of age. Regardless of prior intrauterine position, males were always heavier than females. However, prior in utero location modulated body weight in that 2M females were significantly heavier than OM females and 2M males were reliably heavier than OM males. Intrauterine position effects were observed in the absence of any appreciable influence of this variable on levels of food intake. Taken together, the results suggest that prior in utero location may influence metabolic set points involved in the regulation of body weight and fat storage.

Age Factors↗
PubMed1986

Mice: postpartum aggression is elevated following prenatal progesterone exposure.

Pregnant Rockland-Swiss (R-S) mice were injected with sesame oil or 250 or 500 micrograms of progesterone (P) on Days 12 through 16 of gestation and the postpartum aggressive behavior of their female offspring was examined in adulthood. Both doses of P significantly increased the intensity of aggression (number of attacks) exhibited by the female offspring toward an adult male intruder. The low dose of P also produced significant increases in relative anogenital distance. These effects were seen in the absence of any effects on body weight at birth or in adulthood, or on reproductive performance. The findings support previous research, in both animals and humans, showing that prenatal brain differentiation and subsequent behavior are masculinized by prenatal exposure to progesterone.

Aggression↗
PubMed1986

Intrauterine contiguity influences regulatory activity in adult female and male mice.

Female mice located in utero between two female fetuses exhibited higher levels of locomotor activity in adulthood than did females located between two male fetuses. Male mice, which were less active than females, also were influenced by intrauterine contiguity. Males located in utero between two female fetuses were more active than males which resided between two male fetuses. These results indicate that intrauterine position influences behaviors involved in the maintenance of metabolic homeostasis.

Animals↗
PubMed1986

Postpubertal isolation decreases infanticide and elevates parental care in C57BL/6J male mice.

Postpubertal (60 days of age) but not prepubertal (21 days of age) isolation reduced the normal tendency of C57BL/6J male mice to kill newborn pups (infanticide) and instead dramatically elevated their exhibition of parental care (retrieving of young). These effects were time-dependent in that longer durations of isolation (60 days) were more effective than shorter durations (20 days) of individual housing. Postpubertal isolation of male mice with previous killing experience also resulted in a reduction in infanticide and an elevation in parental care, but these effects were not as dramatic as those observed in naive, nonexperienced animals. The findings are discussed in terms of endocrine and neurochemical changes known to accompany isolation in mice.

Age Factors↗
PubMed1986

Prenatal stress reduces intermale aggression in mice.

Prenatal stress (heat and restraint) significantly reduced intermale aggression (percentage of animals fighting and the number of attacks and lunges) in Rockland-Swiss Albino mice. These data, in combination with previous reports showing deficits in male copulatory responses, suggest that a wide array of androgen-dependent social behaviors may be influenced by prenatal stress.

Aggression↗
PubMed1986

Prenatal stress effects: are they mediated by reductions in maternal food and water intake and body weight gain?

Heat and restraint stress reduced maternal food and water intake as well as body weight gain in pregnant Rockland-Swiss (R-S) Albino mice. Because maternal undernutrition during pregnancy has been reported to disrupt sociosexual behavior in male and female rodent offspring, prenatal stress effects may be modulated, in part, by alterations in essential regulatory behaviors of pregnant animals.

Animals↗