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Maternal care is a motivated behavior and in the rabbit it is restricted to the spontaneous return of the mother to nurse her pups for just a few minutes once a day. Previously we have reported neural activation of brain areas and neuroendocrine cells after nursing. However, this daily spontaneous return suggests that the mother is in a high motivational state to nurse her pups. Here we hypothesized that during anticipation of nursing there is an activation of dopaminergic neurons of the mesolimbic system and in their target areas. Then we explored, by the expression of FOS protein, possible activation of the mesolimbic system as well as dopaminergic cells of the A10 cell group before and after nursing and in control does. Additionally, we measured FOS expression in the preoptic area and lateral septum. We found a significant increase of FOS before nursing, and a further increase after nursing, in the mesolimbic system and dopaminergic cells as well as in the preoptic area and lateral septum. Interestingly, the medial prefrontal area shows an intense activation during anticipation of nursing, which remains after nursing. We conclude that the activation of the mesolimbic system before nursing is related to the high locomotor behavior prior to the next nursing bout and support the proposal that the mother is in a high motivational state at the time of returning to the nest. The additional activation after nursing can be related to the neuroendocrine and neural consequences of the milk ejection reflex by suckling.

Natural infection of wild mammals by protozoa parasites is quite common in nature. For Neotropical Primates different infections of parasites that are etiological agent of disease in human have been identified. In particular, infections by Trypanosoma cruzi and Leishmania sp., have been reported for some New World primate species, but there are no reports of infection with these parasites in any primate species in Mexico. A serological study was conducted on two howler monkey species (Alouatta pigra and A. palliata) from the Mexican states of Campeche and Tabasco. A total of 55 serum samples (20 samples from A. pigra, 20 samples from A. palliata, and 15 samples from semifree ranging A. palliata of Los Tuxtlas, Veracruz as negative controls) were analyzed for the detection of immunoglobulin G antibodies against T. cruzi and Leishmania mexicana through enzyme linked immunosorbent assay test, indirect immunofluorescence assay and Western blot. The overall prevalence of antibodies in howler monkeys was 17.5% for T. cruzi and 30% for L. mexicana. Our results also indicate that A. pigra is more susceptible to develop leishmaniasis than A. palliata. Finally, the finding of positive serology in these primates should be given serious consideration for public health, given the potential role of these primate species as wild reservoirs for these diseases and the increasing contact of monkeys with human populations due to habitat loss and fragmentation. Am. J. Primatol. 75:161-169, 2013. © 2012 Wiley Periodicals, Inc.

Rabbit pups represent a natural model of food anticipatory activity (FAA). FAA is the behavioral output of a putative food entrainable oscillator (FEO). It had been suggested that the FEO is comprised of a distributed system of clocks that work in concert in response to gastrointestinal input by food. Scheduled food intake synchronizes several nuclei in the brain, and the hypothalamus has received particular attention. On the contrary, brainstem nuclei, despite being among the brain structures to first receive food cues, have been scarcely studied. Here we analysed by immunohistochemistry possible oscillation of FOS and PER1 proteins through a complete 24-h cycle in the dorsal vagal complex (DVC) and parabrachial nucleus (PBN) of 7-8-day-old rabbit pups scheduled to nurse during the night (02:00 h) or day (10:00 h), and also in fasted subjects to explore the possible persistence of oscillations. We found a clear induction of FOS that peaks 1.5 h after nursing in all nuclei studied. PER1 was only synchronized in the PBN, reaching highest values 12 h after nursing. Only PER1 oscillations persisted, with a shift, in fasted subjects. We conclude that the DVC nuclei are probably more related to the transmission of food cues to other brain regions, but that the PBN participates in the integration of information essential for FAA. Our results support previous findings suggesting that the DVC nuclei, but not PBN, are not essential for FAA. We suggest that PBN is a key component of the proposed distributed system of clocks involved in FAA.

Nursing in the rabbit is under circadian control, and pups have a daily anticipatory behavioral arousal synchronized to this unique event, but it is not known which signal is the main entraining cue. In the present study, we hypothesized that food is the main entraining signal. Using mother-deprived pups, we tested the effects of artificial feeding on the synchronization of locomotor behavior, plasma glucose, corticosterone, c-Fos (FOS) and PERIOD1 (PER1) rhythms in suprachiasmatic, supraoptic, paraventricular and tuberomammillary nuclei. At postnatal day 1, an intragastric tube was placed by gastrostomy. The next day and for the rest of the experiment, pups were fed with a milk formula through the cannula at either 02:00 h or 10:00 h [feeding time = zeitgeber time (ZT)0]. At postnatal days 5‐7, pups exhibited behavioral arousal, with a significant increase in locomotor behavior 60 min before feeding. Glucose levels increased after feeding, peaking at ZT4‐ZT12 and then declining. Corticosterone levels were highest around the time of feeding, and then decreased to trough concentrations at ZT12‐ZT16, increasing again in anticipation of the next feeding bout. In the brain, the suprachiasmatic nucleus had a rhythm of FOS and PER1 that was not significantly affected by the feeding schedule. Conversely, the supraoptic, paraventricular and tuberomammillary nuclei had rhythms of both FOS and PER1 induced by the time of scheduled feeding. We conclude that the nursing rabbit pup is a natural model of food entrainment, as food, in this case milk formula, is a strong synchronizing signal for behavioral, hormonal, metabolic and neural parameters.

Rabbit does nurse their pups once a day with circadian periodicity and pups ingest up to 35% of their body weight in milk in < 5 min. In the doe, there is a massive release of prolactin. We hypothesised that periodic suckling synchronises dopaminergic populations that control prolactin secretion. We explored this by immunohistochemical colocalisation of PER1 protein, the product of the clock gene Per1 on tyrosine hydroxylase (TH) cells in three dopaminergic populations: tuberoinfundibular dopaminergic (TIDA), periventricular hypophyseal dopaminergic (PHDA) and incertohypothalamic dopaminergic (IHDA) cells. PER1/TH colocalisation was explored every 4 h through a complete 24-h cycle at postpartum day 7 in does that nursed their pups either at 10.00 h (ZT03) or at 02.00 h (ZT19; ZTO = 07.00 h, time of lights on). Nonpregnant, nonlactating females were used as controls. In control females, there was a rhythm of PER1 that peaks at ZT15. By contrast, in nursed does, the PER1 peak shifted in parallel to scheduled nursing in TIDA and PHDA cells but not in IHDA cells, which are not related to the control of prolactin. Next, we determined that the absence of suckling for 48 h significantly decreases the number of PER1/TH colocalised cells in PHDA but not TIDA cells. Locomotor behaviour in control subjects was maximal at around the time of lights on but, in nursed females, shifted at around the time of scheduled nursing. Finally, in the suprachiasmatic nucleus, there is a maximal expression of PER1 at ZT11 in the three groups. However, this maximal expression was significantly lower in the nursed groups in relation to the control group and in the groups deprived of nursing for 48 h. We conclude that suckling synchronises dopaminergic cells related to the control of prolactin and appears to be a nonphotic stimulus for the suprachiasmatic nucleus.

Background Ketamine hydrochloride is an anesthetic commonly utilized to obtain biological samples in various non-human primates. Its application alters individual hematologic and biochemical values. The aim of this study was to analyze its effect on blood parameters of Alouatta pigra. Method We collected blood samples at 10 and 40 minutes after the application of ketamine in 12 adult female A. pigra living in free-ranging conditions. Results The analysis showed that 40 minutes after application of ketamine, the number of platelets, lymphocytes and concentration of phosphorus decreased; however, creatinine, cholesterol, triglycerides, and potassium values increased. Conclusions Our results suggest that ketamine appears to have little effect on the hematology and blood biochemistry of Alouatta pigra females with respect to those reported for other non-human primates. It is also important to consider the elapsed time after their application when taking blood samples for proper interpretation of the hemogram of Alouatta pigra females.

Mother rabbits nurse their young once a day with circadian periodicity. Nursing bouts are brief (ca. 3 min) and occur inside the maternal burrow. Despite this limited contact mother rabbits and their pups are tuned to each other to ensure that the capacities of each party are used efficiently to ensure the weaning of a healthy litter. In this review we present behavioral, metabolic and hormonal correlates of this phenomenon in mother rabbits and their pups. Research is revealing that the circadian rhythm of locomotion shifts in parallel to the timing of nursing in both parties. In pups corticosterone has a circadian rhythm with highest levels at the time of nursing. Other metabolic and hormonal parameters follow an exogenous or endogenous rhythm which is affected by the time of nursing. In the brain, clock genes and their proteins (e.g. Per1) are differentially expressed in specific brain regions (e.g. suprachiasmatic nucleus, paraventricular nucleus) in relation to providing or ingesting milk in mothers and young, respectively. These findings suggest that circadian activities are modulated, in the mothers, by suckling stimulation and, in the young, by the ingestion of milk and/or the perception of the mammary pheromone. In conclusion, the rabbit pup is an extraordinary model for studying the entraining by a single daily food pulse with minimal manipulations. The mother offers the possibility of studying nursing as a non-photic synchronizer, also with minimal manipulation, as suckling stimulation from the litter occurs only once daily.

Nursing in the rabbit is a circadian event during which mother and pups interact for a period of < 5 min every day. Here we explored behavioral and neuronal changes in the mother by analyzing the suprachiasmatic nucleus (SCN), and oxytocinergic (OT) neurons in the paraventricular nucleus (PVN) and the supraoptic nucleus (SON). We maintained lactating does in a light-dark cycle (lights on at 07 : 00 hours; ZT0); they were scheduled to nurse during either the day (ZT03) or the night (ZT19). Groups of intact and nursing females was perfused, one at each 4-h point through a 24-h cycle. We explored, by immunohistochemistry, the PER1 expression and double-labeling, with OT antibody, of neurons in the PVN and SON at lactation on day 7. In the SCN, intact and lactating groups had peak PER1 expression at ZT11; however, there was a reduction in PER1 at peak time in the nursing groups. There was a locomotor activity rhythm with increased activity around the time of lights-on in intact subjects and around the time of suckling in lactating does. There was an induction of PER1 in OT cells in the PVN and SON that shifted in phase with timing of nursing. We further explored the maintenance of the PER1 expression in OT cells in nursing-deprived does and found a significant decrease at 24 and 48 h after the last nursing. We conclude that suckling induced PER1 in the PVN and SON, but not in the SCN, in nursing does, and also shifted their locomotor behavior.

In nature and under laboratory conditions, dams nurse rabbit pups once daily for a duration of fewer than 5 min. The present study explored neural mechanisms mediating the timing of nursing in this natural model of food anticipatory activity, focussing on the suprachiasmatic nucleus (SCN), the locus of the master circadian clock and on the dorsomedial hypothalamic nucleus (DMH), a region implicated in timing of food-entrained behavior. Rabbit pups are born in the dark, with eyelids closed. Nursing visits to the litters also occurs during the dark phase. To explore the effect of the timing of feeding, pups were maintained in constant darkness, while females housed in a light-dark cycle were permitted to nurse their pups either during the night (night-fed group) or day (day-fed group). All pups exhibited anticipatory locomotor activity before daily nursing. In the SCN, PER1 and FOS peaked during the night in both groups, with a longer duration of elevated protein expression in the night-fed group. In contrast, DMH peak PER1 expression occurred 8 h after pups were fed, corresponding to the shift in timing of nursing. Comparison of nursed and 48 h fasted pups indicates that the timing of PER1 expression was similar in the SCN and DMH, with fewer PER1-positive cells in the latter group. The results indicate that rabbit pups show food anticipatory activity, and that timing of nursing differentially affects PER1 expression in the SCN and DMH.

There is no information on the neuroanatomical distribution of the progesterone receptor (PR) in the rabbit. Therefore, we mapped the distribution of PR-immunoreactive cells in the forebrain of ovariectomized female rabbits. Vehicle-injected ovariectomized rabbits showed PR-immunoreactive cells only in the infundibular nucleus (IN) and nucleus X (lateral to the ventromedial hypothalamic nucleus). The injection of oestradiol benzoate (EB; 5 micro g/day for 5 days) increased the number of PR-immunoreactive cells in the IN and in three nuclei of the preoptic region (periventricular, medial, and principal). Abundant PR were also found in the paraventricular nucleus and nucleus X. Administration of progesterone (10 mg/day) for 3 days to EB-treated rabbits (a treatment that induces digging behaviour for the maternal nest and suppresses sexual receptivity and scent-marking) eliminated PR-immunoreactivity from all brain areas analysed except the IN. Thus, one-third of the number of cells seen in the ovariectomized + EB condition persisted in this region despite progesterone injections. Withdrawal of progesterone (and continuation of EB) for 5 (but not for 2) days (in a schedule similar to the one that induces straw-carrying and hair-pulling for the maternal nest) increased the number of PR-immunoreactive cells in all regions analysed. These results show that restricted regions of the female rabbit forebrain express abundant PR which are either: (i). up-regulated by oestradiol and down-regulated by progesterone; (ii). oestradiol-insensitive and down-regulated by progesterone; or (iii). insensitive to both oestradiol and progesterone.