Differences in the number of oxytocin, vasopressin, and tyrosine hydroxylase cells in brain regions associated with mating among great, midday, and Mongolian gerbils.

Neurotransmitters, such as oxytocin (OT), vasopressin (AVP), and dopamine (DA), within the mesolimbic system have deeply conserved roles in regulating mating-related behaviors. However, comparative studies among monogamous and polygamous animals focus mainly on Microtus; very little research has been done in gerbils. Here, we measured body weight, body length, tail length, serum hormone concentrations, and the immunoreactive (ir)-cells of OT, AVP, and tyrosine hydroxylase (TH) in the brain of the polygamous great gerbil (Rhombomys opimus), midday gerbil (Meriones meridianus), and monogamous Mongolian gerbil (Meriones unguiculatus). Body weight, body length, tail length, and serum AVP concentrations were greater in the great gerbil than in the midday gerbil and Mongolian gerbil. The number of OT and AVP cells in the para ventricular nucleus (PVN) and supra optic nucleus (SON) of the hypothalamus were greater in the Mongolian gerbil than in the great gerbil and midday gerbil. Similarly, the number of TH cells in the PVN, medial preoptic area (MPOA), and ventral tegmental area (VTA) was greater in the Mongolian gerbil than in the great gerbil and midday gerbil. To summarize, the number of OT and AVP cells in the PVN and SON and TH cells in the PVN, MPOA, and VTA in the monogamous Mongolian gerbil are greater than those in the great gerbil and midday gerbil.

Characteristics of pup ultrasonic vocalizations and parental behavior responses in midday gerbils (Meriones meridianus).

Ultrasonic vocalizations (USVs) play an important role in parent-infant interactions during the neonatal period of rodents because of the pups' need to be suckled and protected by their parents. However, studies on the effects of USVs on parental care are focused on maternal behavior, and little data on paternal care are available, with especially few investigations in midday gerbils. In this study, we examined the effects of early social deprivation (ED) on offspring due to USVs and parental behavior responses in midday gerbils (Meriones meridianus). The results indicated that the number of USVs in ED gerbils increased on postnatal day nine (40 calls/minute), whereas the number of gerbils in the parental care (PC) group remained high for up to 2 weeks (46.6 calls/minute), before decreasing. The number of USVs and duration of single syllables from postnatal day 3 to 21 in ED pups were significantly lower than those in PC pups. ED increased maternal licking, grooming behavior, and nest-building, but decreased huddling and exploring behavior. Similarly, ED increased paternal behavior, like nest-building, but reduced exploring and self-grooming. Overall, gerbil pups displayed high levels of USVs and various syllable types before weaning. ED significantly reduced the number of USVs and syllable types, but increased maternal licking, grooming, and paternal nest-building behavior.

Exposure to quinestrol and levonorgestrel affects maternal behavior and offspring development in midday gerbil (Meriones meridianus).

Quinestrol and levonorgestrel (EP-1, at a ratio of 1:2) are often used as anti-fertility compounds (sterilants) in rodents. As most of the research has focused on the sterility and damage caused in parental reproductive organs, there is little research on the effect of these contraceptive hormones on maternal behavior and offspring's early development. In this study, we examined maternal behavior after treatment with different doses of EP-1 (10 ml/kg) at postnatal days 3 and 10, separately. Various parameters were measured after treatment, including oxytocin expression, serum levels of estradiol and luteinizing hormone (LH), ovary damage after weaning of offspring, as well as the development and ultrasonic vocalizations (USVs) of midday gerbil (Meriones meridianus) offspring. At postnatal days 5 and 12, the EP-1 increased maternal licking, grooming, and retrieving behavior, while reducing contacting behavior. Oxytocin expression in the hypothalamic paraventricular and supraoptic nuclei increased, while the levels of estradiol and LH decreased. The ovaries and the development of follicles were clearly affected by the treatment. The EP-1 significantly reduced the pups' body weight, the amount and pulse duration of USVs, whereas the frequency range variation of USVs was increased. Overall, treatment with EP-1 during lactation significantly affected maternal behavior and impaired offspring early development in the midday gerbil.

Differences in cocaine- and morphine-induced cognitive impairments and serum corticosterone between C57BL/6J and BALB/cJ mice.

Addictive drug exposure is associated with impairments in various cognitive domains. Murine models of drug-induced cognitive impairment have helped to inform research on interventions to attenuate such cognitive diminishment; however, while differences between the drug-induced cognitive impairments exhibited by C57BL/6J and BALB/cJ mice have been observed, they remain unclear. This study measured differences in cognitive behavior performance on the object recognition test (ORT) and social recognition test (SRT) and serum levels of corticosterone (CORT) between C57BL/6J and BALB/cJ mice after 14-day chronic exposure to either cocaine (5 mg/kg) or morphine (3 mg/kg) at a dosage of 10 ml/kg/day. The ORT revealed that cocaine and morphine exposure significantly reduced the discrimination ratio in both C57BL/6J and BALB/cJ mice, exploration time was only reduced in C57BL/6J mice: the exploration times of C57BL/6J mice from the control (p < 0.05), cocaine (p < 0.05), and morphine (p < 0.01) administration groups were significantly less than those of BALB/cJ mice. The SRT demonstrated that drug exposure significantly reduced exploration time (cocaine, p < 0.01; morphine, p < 0.01) and impaired social recognition in C57BL/6J mice. No significant effect in BALB/cJ mice was observed. Serum CORT levels were lower in control C57BL/6J mice than in control BALB/cJ mice (p < 0.05), but no difference was observed after drug administration. In conclusion, changes in object and social learning recognition indicate that C57BL/6J mice are more sensitive than BALB/cJ mice to chronic drug exposure, especially to cocaine; concomitant changes in serum CORT may mediate these effects.