Juana Luis

PARENTAL BEHAVIOR OF THE VOLCANO MOUSE, NEOTOMODON ALSTONI (RODENTIA: MURIDAE), IN CAPTIVITY

Abstract Paternal behavior of the volcano mouse (Neotomodon alstoni) was studied and its role in the care of young compared with that of the female. Paternal behavior of this rodent under laboratory conditions consisted of direct and indirect activities, such as huddling, grooming, sniffing, and retrieving young as well as maintenance and vigilance of the nest. The male volcano mouse exhibited all components of parental behavior displayed by mothers, except suckling. However, the male participated significantly more than the female in huddling, grooming, and sniffing. The existence of paternal behavior in this rodent suggests that under natural conditions this species exhibits a monogamous mating system because monogamy in rodents is often associated with paternal care.

MALE INFLUENCE ON MATERNAL BEHAVIOR AND OFFSPRING OF CAPTIVE VOLCANO MICE (NEOTOMODON ALSTONI) FROM MEXICO

Abstract Captive male Neotomodon alstoni exhibit paternal care. We tested whether presence of the male in the nest during the postpartum and weaning periods affect maternal care and promoted survival and growth of the offspring. For captive N. alstoni pairs (n = 10) both parents were maintained in the nest until weaning of the young, and in another 10 pairs the male was removed shortly after birth of young. The presence of the male had a negative impact on the time spent by females in huddling with nursing young. In the presence of the male, females groomed and sniffed young less frequently than did females rearing young in the absence of the male. Survival of offspring (84%) and their growth (20.6 ± 4.7 g) was significantly higher when both parents reared their young. Males provide additional care of young, allowing a higher quality of care by the female during rearing.

Paternal behavior in the Mongolian gerbil (Meriones unguiculatus): Estrogenic and androgenic regulation.

Here, we analyzed the effects of testosterone (T) and its metabolites, estradiol (E2) and dihydrotestosterone (DHT), on the onset of paternal behavior in virgin male Mongolian gerbils (Meriones unguiculatus). We hypothesized that T and E2, but not DHT, would facilitate the onset of paternal behavior. Seventy males displaying aggression toward pups were selected through a paternal behavior screening test. Forty males were bilaterally castrated. Of them, 10 were implanted with T, 10 with E2, and 10 with DHT, and 10 received no treatment. Another 30 males underwent a sham procedure. In these gerbils, T, E2 and DHT were measured to obtain the basal levels of these hormones. After treatment, the paternal behavior test was conducted again. Blood samples were obtained immediately after the administration of the test for the quantification of T, E2 and DHT by radioimmunoassay. Surprisingly, 100% of the males that received T, E2 and DHT implants stopped being aggressive and became paternal. Castrated and sham-operated males displayed no changes in their aggressive behaviors. This is the first report that T and its metabolites are involved in neuroendocrine mechanisms that inhibit aggression toward pups and facilitate paternal behavior in virgin male Mongolian gerbils. In addition, this is the first report of regulation of paternal behavior in a rodent by estrogenic and androgenic pathways.

Effect of Larrea tridentata (creosote bush) on cholesterol gallstones and bile secretion in hamsters

Larrea tridentata (Sesse and Moc. ex DC.) Coville is used for the treatment of gallstones in traditional Mexican medicine. The possible prevention or elimination of gallstones by ethanolic and aqueous extracts of the leaves and twigs of L. tridentata was tested in hamsters fed a rich carbohydrate, fat‐free diet. In addition, the effects of the ethanolic extract and its main metabolite, nordihydroguaiaretic acid, on bile secretion in the perfused liver were tested. In the experiment on prevention of gallstones, the dry ethanolic extract at a level of 0.5% of diet completely inhibited gallstone formation, lowered biliary moles percent cholesterol and increased the proportion of chenodeoxycholic acid of hepatic bile. The dry aqueous extract at a level of 1% of diet did not affect gallstone frequency or biliary parameters. In the experiment on elimination of gallstones, the ethanolic extract significantly reduced gallstone frequency, gallbladder bile cholesterol concentration and moles percent cholesterol. Both the ethanolic extract and nordihydroguaiaretic acid had cholestatic effects in the perfused liver, with an EC50 of 34 and 28 mg dL−1, respectively, when perfused for 10 min. This effect was reversible with concentrations up to 40 mg dL−1. The results indicate that L. tridentata could be useful in the treatment of gallstone disease, however care must be taken due to its hepatotoxicity.

Hemipenes in females of the mexican viviparous lizard Barisia imbricata (Squamata: Anguidae): an example of heterochrony in sexual development

The sexual development of saurians follows a similar pattern to that described for other amniotes. Changes in the timing or sequence of development events are known as heterochrony. We describe the pattern of sexual development in the viviparous Mexican lizard Barisia imbricata and report heterochrony in the regression of hemipenes in this lizard. We collected gestating females; some lizards were subjected to partial hysterectomy and the embryos were processed using routine histological technique to assess gonadal development; the remaining embryos were used to assess the development of hemipenes. Other pregnant females were kept in captivity in individual terraria until the time of delivery. All neonates were sexed by eversion of hemipenes and some of their body characteristics were recorded. Several neonates were sacrificed and processed to establish gonadal histology and the young of the remaining litters were maintained in captivity to observe the fate of the hemipenes in both sexes. Gonadal development began at embryonic stage 33 and the hemipenes were visible at the same stage. In the neonates, the ovary contained oogonias and ovarian follicles, whereas the testicles showed testicular cords. All neonates had hemipenes and sex could only be established through direct observation of the reproductive ducts and gonadal histology. The hemipenes regression in the females begins after approximately 7 months of postnatal development and concludes at about 15 months of age. We think that the delayed regression of the hemipenes reflects evolutionary differences among reptiles and may be an indication of a stage in the evolutionary process of this species.

An increase in estradiol facilitates the onset of paternal behavior in the dwarf hamster (Phodopus campbelli)

ABSTRACT In the dwarf hamster (Phodopus campbelli), activational effects of testosterone (T) and estradiol (E2) in the regulation of paternal behavior have been repeatedly rejected because peripheral concentrations of E2 do not change across the reproductive cycle of males. Further, castration no affected paternal behavior despite that both T and E2 concentrations decreased significantly. However, the role of these hormones has not been evaluated in models of castration and hormonal replacement in virgin males. Here, we analysed the effects of E2 and T in paternal behavior in virgin male dwarf hamster (Phodopus campbelli). Thirty paternal (PAT) males were bilaterally castrated; of them, 10 were implanted with T, 10 with E2 and 10 males received no treatment. Other 10 PAT males underwent sham‐castration. Seventeen aggressive (AGG) males were also bilaterally castrated; of these, 10 AGG received E2 replacement, 7 were not treated. Other 7 AGG males were submitted to sham‐castration. Following treatments, paternal behavior tests were conducted again. T and E2 levels in plasma were quantified by radioimmunoassay (RIA). The results showed that the treatments did not affect the paternal behavior of males that were initially paternal. Neither castration nor sham‐castration surgery affected the behavior of AGG males. However, when these males were treated with E2 and the concentrations of this hormone increase significantly they became paternal. Our data suggest that an increase in E2 levels shifted infanticidal behavior to paternal behavior in dwarf hamster. HighlightsAn increase in E2 facilitates transitions from aggressive males to paternal.Changes in T and E2 had no effect in paternal activities in paternal males from the beginning.Low concentrations of E2 may be the cause of infanticidal behavior.

Neuronal activation associated with paternal and aversive interactions toward pups in the Mongolian gerbils ( Meriones unguiculatus )

ABSTRACT Approach/avoid model is used to analyze the neural regulation of maternal behavior in the laboratory rat. This model proposes that the medial preoptic area (mPOA) and bed nucleus of stria terminalis (BNST) are brain regions involved in facilitating mechanisms. By contrast, anterior hypothalamic nucleus (AHN), ventromedial hypothalamic nucleus (VMH), and periaqueductal gray participate in the inhibiting mechanisms of neural regulation of maternal behavior. We hypothesized that there are also facilitating and inhibiting mechanisms in the neural regulation of paternal behavior. Here, we determined which neural areas are activated during paternal and aversive interactions with pups in the Mongolian gerbils (Meriones unguiculatus). By testing paternal behavior, we selected 40 males aggressive toward pups and 20 paternal males. These males were organized into six groups of 10 animals in each group: aggressive males that interacted with pups (AGG‐pups) or candy (AGG‐candy), paternal males that interacted with pups (PAT‐pups) or candy (PAT‐candy), and males with testosterone (T)‐induced paternal behavior that interacted with pups (IPAT‐pups) or candy (IPAT‐candy). After interacting with pups or candy, the brains were extracted and analyzed for immunoreactivity (ir) with c‐fos. Males that interacted with pups had significantly higher c‐fos‐ir in the mPOA/BNST than males that interacted with candy. Males that displayed aggression had significantly higher c‐fos‐ir in the AHN, VMH, and periaqueductal gray than aggressive males that interacted with candy. These results suggest that in the neural regulation of paternal behavior in the Mongolian gerbil underlie positive and negative mechanisms as occurs in maternal behavior. HIGHLIGHTSAnalyzing the neural regulation of paternal behavior with the approach/avoid model is novel.mPOA/BNST are part of the positive mechanism of neural regulation of paternal behavior.AHN/VMH are part of the negative mechanism of neural regulation of paternal behavior.A decrease in the testosterone level was observed in aggressive males that interacted with the pups.Neural regulation of paternal behavior is according to the approach/avoid model.

Does the conceptus of the viviparous lizard Barisia imbricata imbricata participates in the regulation of progesterone production and the control of luteolysis

It is generally accepted that progesterone is necessary to maintain gestation; however, the mechanisms that control the production of this steroid remain unknown. The corpus luteum has been assigned a central role in the maintenance of gestation based on its capacity to produce progesterone. A pseudopregnancy model was performed in a viviparous lizard, Barisia imbricata imbricata, to determine whether the absence of embryos would affect the pattern of progesterone production or the corpus luteum histology. Blood samples were obtained prior to ovulation and at 8, 16, and 24 weeks after ovulation (pseudopregnant and pregnant lizards), as well as one day after parturition (pregnant lizards) or 32 weeks after ovulation (pseudopregnant lizards). The corpus luteum was surgically removed one day after blood samples were obtained. Blood aliquots from nongravid females were obtained at similar timepoints. We found a significant reduction in plasma progesterone concentrations at 24 and 32 weeks post-ovulation in pseudopregnant lizards compared with those observed at similar times in intact pregnant lizards, whereas the progesterone levels in non-gestant lizards remained significantly lower than in either pseudopregnant or pregnant lizards. Moreover, we observed that the histological appearance of the corpus luteum from pseudogestational females (obtained 24 and 32 weeks post-ovulation) differed from the corpora lutea from lizards in late gestation and intact parturient lizards. These observations suggest that the conceptus participates in the regulation of progesterone production in late gestation and also in luteolysis control.