Male Mongolian Gerbils Research Articles

Neuroprotective effects of FeTMPyP: A peroxynitrite decomposition catalyst in global cerebral ischemia model in gerbils

Peroxynitrite involvement has been implicated in the neuronal damage. In the present study, we have investigated the neuroprotective effects of peroxynitrite decomposition catalyst (FeTMPyP) on global cerebral ischemia. Global cerebral ischemia-reperfusion (IR) injury was produced by 5 min occlusion of both common carotid arteries followed by reperfusion of 96 h in the adult male Mongolian gerbils. The extent of injury was assessed behaviorally by measuring neurological functions, locomotor activity, passive avoidance test and by histopathological evaluation of extent of damage to CA1 hippocampal pyramidal region. FeTMPyP (1 and 3 mg kg −1, i.p., administered 30 min prior to ischemia) treatment improved the neurological functions, reduced the hyperlocomotion and memory impairment in IR challenged gerbils. The loss of neurons from the pyramidal layer of the CA1 region caused by global IR injury was attenuated with FeTMPyP. FeTMPyP also inhibited lipid peroxidation as evident from reduction in brain malondialdehyde levels. These results suggest that peroxynitrite decomposition catalyst may be effective neuroprotective agent for global cerebral ischemia.

Reproduction of wild Mongolian gerbils bred in the laboratory with respect to generation and season 1. Morphological changes and fertility lifespan

AbstractA new strain of wild Meriones unguiculatus (strain Ugoe:MU95, named WILD) with high genetic variability was recently established in Germany. A previous study showed that offspring (F-1) of WILD founders (F-0) showed reduced spermatogenesis and testosterone compared to domesticated gerbils (LAB) maintained under similar conditions. We investigated F-0 and subsequent generations in respect to sexual maturation, duration of fertility and gonadal weights of different seasons. Body and reproductive organ weights showed negligible seasonal fluctuations in both strains. Testis and epididymis weights in WILD covered a wide range, which indicates a high reproductive variability. Reproductive organ weights increased in F-3. Less variable and high reproductive organ weights (testis >900 mg, epididymis >200 mg) in almost all LAB illustrate their readiness to reproduce, even in small individuals. Prominent testis (T+) was found in 71% of adult males (F-1, F-2) reflecting the natural portion of T+(63%) found in wild gerbils investigated in Mongolia in 1995 and 2002. Testicular descent was accelerated and pronounced in WILD F-3 (T+, 88%) and LAB (T+, 91%). Time between mating and the first litter was significantly longer in wild F-0 than in their offspring or LAB. The average age in wild F-0 when the last litter was born was 27 months. Breeding went on for 2 to 32 months and was mostly terminated by the death of the females. Relative testis and epididymis weights correspond in young adults and in old males up to 6 years, the total life span of male wild Mongolian gerbils. In summary, the results suggest that laboratory conditions improve the reproductive fitness of wild gerbils.

Is the T‐maze a suitable tool for investigating the effects of protein‐energy malnutrition on functional outcome following global ischemia?

The T-maze is a sensitive behavioral test used to measure functional outcome in rodent models of global ischemia. As our laboratory is investigating the adverse effects of protein-energy malnutrition (PEM) on global ischemia, this study determined: 1) if a sunflower seed reward used with the T-maze would interfere with PEM, and 2) whether PEM impairs working memory prior to the induction of global ischemia. Male Mongolian gerbils (11–12 wks) were randomized for 6 wks to either modified AIN-93M control diet (12% protein; n=12) or PEM (2% protein; n=12). Gerbils were habituated in the T-maze for 5 days, followed by 10 win-shift trials/day for 10 days. A mean body weight loss of 20% and 17% lower food intake compared to that of controls suggests that PEM was achieved; this will be confirmed by serum albumin measurements. Gerbils on control diet required a mean (± SEM) of 7.3 ± 0.7 trials in the T-maze to meet criterion (≥90% correct on 3 consecutive days), compared to 5.4 ± 0.4 trials in the PEM group (p = 0.025; unpaired t-test). The number of animals reaching criterion was 8/12 in the control group, and 12/12 in the PEM group [χ2(n=24, df=1) = 4.800, p=0.028]. These results suggest that the reward does not interfere with the model of PEM, and that T-maze performance is not impaired, but rather may be enhanced by PEM prior to ischemia. Future studies will unravel the influence of both PEM and nutritional repletion on cognitive deficits produced by global ischemia. Funded by CIHR/RPP and Heart and Stroke Foundation of Saskatchewan.

Investigating the effect of bilateral amygdala lesions on fear conditioning and social interaction in the male Mongolian gerbil

Identification of the selective neurokinin NK 1 receptor antagonist, 2-( R)-(1-( R)-3,5-Bis(trifluromethyl)phenylethoxy)-3-( S)-(4-fluoro)phenyl-4-(3-oxo-1,2,4-triazol-5yl)methylmor-phine (MK-869), as a novel therapeutic approach for anxiety/depression has led to increased use of the Mongolian gerbil in behavioural studies since the gerbil NK 1 receptor pharmacology is similar to human, but not rat or mouse. Within this species, foot tapping and immobility elicited by aversive conditioning, as well as social interaction have been shown to be sensitive to clinically used anxiolytic and antidepressant agents and also NK 1 receptor antagonists. The high levels of NK 1 receptor binding in the amygdala as well as preclinical studies demonstrating increased release of substance P and corresponding internalisation of NK 1 receptors in the basolateral amygdala in response to stressful stimuli suggest that the BLA may represent a potential site of action for NK 1 receptor antagonists in anxiety and/or depression. Therefore, in the current study, we assessed the effect of bilateral BLA lesions in male Mongolian gerbils on footshock-induced foot tapping and immobility, social interaction, and NK 1-agonist-induced foot tapping. Lesioned gerbils exhibited reduced immobility time during fear conditioning, a non-significant reduction in immobility time when re-exposed to the conditioned stimulus (CS) 24 h later, and increased social interaction in the gerbil social interaction task. In contrast, BLA lesions had no effect on NK 1-agonist-induced foot tapping. These data provide further support that the gerbil BLA is a potential site for NK 1 receptor antagonists to attenuate anxiety-related behaviours.

Gastric expression of inducible nitric oxide synthase and myeloperoxidase in relation to nitrotyrosine in Helicobacter pylori-infected Mongolian gerbils

Objective. For obscure reasons Helicobacter pylori infection of the gastric mucosa is maintained despite a pronounced host defence response. The present study elucidates possible H. pylori-related interference in the oxy- and nitro-radical formation pathways. Material and methods. Male Mongolian gerbils were infected with two different H. pylori strains, TN2GF4 and SS1. At 3, 6, 12 or 18 months after inoculation, gastric expressions of myeloperoxidase (MPO), inducible nitric oxide synthase (iNOS) and nitrotyrosine were assessed by Western blotting. Results. Expression of both iNOS and MPO was markedly up-regulated in the H. pylori-infected animals compared with non-infected controls. The TN2GF4-infected animals initially (at 3 and 6 months) demonstrated pronounced expression of both iNOS and MPO. The SSI-infected animals exhibited a slower onset with significantly increased iNOS after 12 and 18 months. Nitrotyrosine expression was slightly elevated in the infected groups at 3 and 6 months compared with that in the controls. Nitrotyrosine levels then decreased and were no longer significantly different from those of controls (TN2GF4-infected animals) or were lower (SS1-infected animals) than in the controls. Conclusions. The results indicate that peroxynitrite formation as reflected by nitrotyrosine expression is low or even inhibited in chronic H. pylori infection despite pronounced expression of enzymes representing both the oxy- and nitro-radical formation pathways. The results support the theory that H. pylori survival is related to functional inhibition of mucosal enzymatic NO and/or oxy-radical formation.

Influence of vitamin E on gastric mucosal injury induced by Helicobacter pylori infection

We investigated the effect of vitamin E on gastric mucosal injury induced by Helicobacter pylori (H. pylori) infection. Male Mongolian gerbils were divided into 4 groups (normal group without H. pylori infection, vitamin E-deficient, -sufficient and -supplemented groups with H. pylori infection). Following oral inoculation with H. pylori (ATCC43504 2 x 10(8) CFU), animals were fed diets alpha-tocopherol 2 mg/100 g diet in the normal and vitamin E-sufficient groups and alpha-tocopherol 0.1 mg/100 g and 50 mg/100 g in the vitamin E-deficient and -supplemented groups, respectively, for 24 weeks. Chronic gastritis was detected in all gerbils inoculated H. pylori. Gastric ulcer was detected in 2 of 7 gerbils only in the vitamin E-deficient group. In the vitamin E-deficient group, myeloperoxidase activity and mouse keratinocyte derived chemokine (KC) in gastric mucosa was significantly higher than in the vitamin E supplemented group. Subsequently, in an in vitro study expression of CD11b/CD18 on neutrophils was enhanced by H. pylori water extract. This effect was suppressed in a dose dependent manner by the addition of alpha-tocopherol. These results suggest that vitamin E has a protective effect on gastric mucosal injury induced by H. pylori infection in gerbils, through the inhibition of accumulation of activated neutrophils.

Chronic administration of ethyl docosahexaenoate decreases mortality and cerebral edema in ischemic gerbils

Dietary docosahexaenoic acid (DHA) intake can decrease the level of membrane arachidonic acid (AA), which is liberated during cerebral ischemia and implicated in the pathogenesis of brain damage. Therefore, in the present study, we investigated the effects of chronic ethyl docosahexaenoate (E-DHA) administration on mortality and cerebral edema induced by transient forebrain ischemia in gerbils. Male Mongolian gerbils were orally pretreated with either E-DHA (100, 150 mg/kg) or vehicle, once a day, for 4 weeks and were subjected to transient forebrain ischemia by bilateral common carotid occlusion for 30 min. The content of brain lipid AA at the termination of treatment, the survival ratio, change of regional cerebral blood flow (rCBF), brain free AA level, thromboxane B 2 (TXB 2) production and cerebral edema formation following ischemia and reperfusion were evaluated. E-DHA (150 mg/kg) pretreatment significantly increased survival ratio, prevented post-ischemic hypoperfusion and attenuated cerebral edema after reperfusion compared with vehicle, which was well associated with the reduced levels of AA and TXB 2 in the E-DHA treated brain. These data suggest that the effects of E-DHA pretreatment on ischemic mortality and cerebral edema could be due to reduction of free AA liberation and accumulation, and its metabolite synthesis after ischemia and reperfusion by decreasing the content of membrane AA.

Induction of gastric intraepithelial neoplasia of glandular stomach of mongolian gerbils by elicobacter pylori

Objective: To setup an animal model of gastric carcinogenesis by Helicobacter pylori (Hp) for basic, prevention and therapeutic research of Hp-related diseases. Methods: 22 young male Mongolian gerbils were administrated with suspension of Hp strain TN2 by intragastric gavage for 5 consecutive times (4×108 CFU/time, 1 time/4 days). 10 male gerbils were used as negative control. Two infected gerbils were killed at 10, 20, and 30 weeks, respectively, after inoculation to monitor the development of gastric lesions. Other animals were killed at 40 experimental weeks. Pathological changes of glandular stomach were examined histologically. Results: Gastric intraepithelial neoplasias (GIN) and low-grade dysplasias were observed only in the pyloric antrum of Hp-treated gerbils (3 and 2 ones, respectively), but not in control group (5/13 vs. 0/10, P<0.04). High incidence of chronic active gastritis and chronic atrophic gastritis were observed in Hp-treated animals (10/13, 76.9%). Low incidence of chronic atrophic gastritis was also detected in negative control gerbils (3/10, 30%; P<0.04). Conclusion: Hp inoculation could induce chronic inflammation and malignant lesions of the glandular stomach of Mongolian gerbils conveniently.

Parental care and sexual interactions in Mongolian gerbils (Meriones unguiculatus) during the postpartum estrus

The behavior of male and female Mongolian gerbils was continuously video-recorded from 24 h before the parturition to the end of postpartum estrus. We noted that the mean interval between the delivery of the last pup and the first mounting was 13 h and 32 min. Over the whole duration of the postpartum estrus (7 h and 41+/-57 min), females spent significantly more time in crouching over, pup licking, nest building and "digging" activities, and were more recipient of allogrooming than males. Maternal pup retrievals were not very frequent (14.0+/-5.6 episodes), but males never retrieved pups nor exhibited a full sequence of nest building activity. Males spent a longer mean time in bodily interactions with females, as compared to the time they spent with pups, and engaged in intense copulatory activity (592.8+/-40.5 mounts or 1 episode per 46.7s); even during the delivery process males attempted to force copulation, but females rejected mounting in all cases. We conclude that females exhibited higher levels of parental care than males, and our findings suggest that males compete with pups in attracting the female's attention, since they actively disrupt maternal care or persistently persecute the female in order to copulate.

Suppressive effect of rice extract on Helicobacter pylori infection in a Mongolian gerbil model

Rice extract has been shown to protect gastric mucosa from stress-induced damage. In this study, the antibiotic effect and the anti-inflammatory effect of orally administered aqueous rice extract on Helicobacter pylori infection and H. pylori-induced gastritis, respectively, in Mongolian gerbils were investigated. Fifty specific-pathogen-free male Mongolian gerbils, seven weeks old, were divided into four groups: uninfected, untreated animals (group A); uninfected, rice extract-treated animals (group B); H. pylori-infected, untreated animals (group C); and H. pylori-infected, rice extract-treated animals (group D). Group C and D animals were killed 12 weeks after H. pylori infection (i.e., at 19 weeks of age) and group A and B animals were also killed at age 19 weeks. The stomachs were removed for histopathological examination with hematoxylin-and-eosin staining and anti-5'-bromo-2'-deoxyuridine (BrdU) immunostaining, and to determine the bacterial burden. Serum anti-H. pylori antibody titers were also tested. In groups A and B, the gastric mucosa showed no inflammatory cell infiltration and a few BrdU-reactive cells. Group C animals developed marked chronic active gastritis in the gastric mucosa, and BrdU-labeled cells in the gastric mucosa markedly increased in number. In group D animals, a significant reduction occurred in the degree of neutrophilic polymorphonuclear cell infiltration into the gastric mucosa, in the BrdU-labeling indices of gastric epithelial cells, and in anti-H. pylori antibody titers in the serum (P < 0.01), compared with although H. pylori was not completely eradicated. The rice extract was effective in suppressing inflammation and epithelial cell proliferation in the gastric mucosa in H. pylori-infected Mongolian gerbils. The rice extract has potential to exhibit a protective effect on H. pylori-related gastric mucosal diseases.

Down‐regulation of a morphogen (sonic hedgehog) gradient in the gastric epithelium of Helicobacter pylori‐infected Mongolian gerbils

Sonic hedgehog (Shh) is a morphogen involved in many aspects of patterning of the gut during embryogenesis and in gastric fundic gland homeostasis in the adult. Intestinal metaplastic change of the gastric epithelium is associated with the loss of Shh expression, and mice that lack Shh expression show intestinal transformation of the gastric mucosa. The present study was designed to investigate the alteration of Shh expression in the stomach of an experimental model of Helicobacter pylori (H. pylori) colonization. Male Mongolian gerbils were inoculated with H. pylori and examined 4 and 51 weeks later. The level of Shh mRNA expression was determined by quantitative RT-PCR and in situ hybridization. Shh protein expression was determined by immunoblotting and immunohistochemistry. Shh was expressed in the parietal cells, zymogenic cells, and mucous neck cells of the gastric fundic glands of gerbils. Prolonged colonization by H. pylori led to extension of the inflammation from the antrum to the corpus of the stomach, with loss of Shh expression. Loss of Shh expression correlated with loss of parietal cells, disturbed maturation of the mucous neck cell-zymogenic cell lineage, and increased cellular proliferation. Shh expression is significantly reduced in H. pylori-associated gastritis. These data show for the first time that H. pylori infection leads to down-regulation of the expression of a morphogen with an established role (Shh) in gastric epithelial differentiation.

The effect of zinc diet on distribution of fatty acid in blood plasma chylomicrons

The effect of dietary zinc on the distribution of fatty acids in blood plasma chylomicrons was studied. The experiment was performed on male Mongolian Gerbils, fed ad libitum for 3 weeks with standard diet, containing 8 or 38 mg of Zn per kg of food (low zinc diet group, LZ, and saturated zinc diet group, SZ, respectivelly). At the 21st day gerbils were given sunflower oil by gavage. After 2.5 hours, blood was collected from abdominal vein, and samples were pooled (five animals per one sample). Chylomicron fractions were isolated by ultracentrifugation and mass of dried chylomicrons was measured. Fatty acid composition was analyzed by gas-liquid chromatography. Significantly higher amount of chylomicrons in blood plasma of SZ than in LZ group was found. In chylomicrons, following fatty acids were found: 16:0, 16:1, 17:0, 17:1, 18:0, 18:1, 18:2, 18:3, 20:0, 21:0 and 20:4. The amount of individual fatty acids in chylomicrons in both groups was similar, except 20:4 where lower amount in SZ group was found. Zinc diet did not affect fatty acid distribution in chylomicrons of both groups. Animals fed with zinc saturated diet had higher amount of fatty acids in blood plasma. Observed results suggest that dietary zinc influences the quantity of fatty acids absorption but not its distribution in chylomicrons.

Testis histology and plasma testosterone levels in the Mongolian gerbil (Meriones unguiculatus) after vasectomy

The Mongolian gerbil (Meriones unguiculatus) is a small rodent widely used in laboratory for biomedical and behavioural research. When the experimental protocol requires male contraception, vasectomy is one of the methods most used, although its effects on spermatogenesis in the Mongolian gerbil had never been investigated. In the present study, fertile male Mongolian gerbils were vasectomized for a histological survey of the testis and measurement of plasma testosterone levels. The main effects of vasectomy were: vacuolization and marked reduction of the germinal epithelium, increase in heterochromatin in some Sertoli cell nuclei, thickening of the tunica albuginea, widening of the interstitial space, appearance of macrophagic giant cells, and degeneration of the epithelium of the tubuli rectae. However, neither morphological changes in the Leydig cells nor alteration in the plasma testosterone levels were found. In conclusion, these preliminary results indicate that vasectomy, at least over a short time span, can impair spermatogenesis without affecting the production of plasma testosterone.

Sex differences in Mongolian gerbils in four tests of anxiety

Animal models or test paradigms for predominantly female disorders, such as anxiety, often use only male animals, with little or no investigation of sex differences. Thus, this study was conducted to compare the behaviour of males and females in four widely used tests of anxiety. The behaviour of male and female Mongolian gerbils was assessed in the elevated plus maze (EPM), black–white box (BWB), open-field and social interaction tests. In the elevated plus maze, females spent proportionally less time in the centre square and greater time in the closed arms compared with males. In the black–white box, they showed significantly greater entries into the black compartment, whilst in the open field, females spent less time sniffing the arena compared with males. Thus, in these three models, there are no conclusive sex differences in anxiety-like behaviour. However, in the social interaction test, females showed more exploratory/cage-orientated behaviour and less active social and aggressive behaviour. In addition, females terminated social contact more frequently. These results can be interpreted as true sex differences, as behaviour in the open-field and social interaction tests did not differ across the oestrous cycle. In conclusion, the results show that sex differences in anxiety-like behaviour in gerbils are best detected using the social interaction test, which suggests that females show a more anxious profile. It also further highlights the need for sex differences to be investigated in tests of anxiety.

Sex differences in Mongolian gerbils in four tests of anxiety

Animal models or test paradigms for predominantly female disorders, such as anxiety, often use only male animals, with little or no investigation of sex differences. Thus, this study was conducted to compare the behaviour of males and females in four widely used tests of anxiety. The behaviour of male and female Mongolian gerbils was assessed in the elevated plus maze (EPM), black–white box (BWB), open-field and social interaction tests. In the elevated plus maze, females spent proportionally less time in the centre square and greater time in the closed arms compared with males. In the black–white box, they showed significantly greater entries into the black compartment, whilst in the open field, females spent less time sniffing the arena compared with males. Thus, in these three models, there are no conclusive sex differences in anxiety-like behaviour. However, in the social interaction test, females showed more exploratory/cage-orientated behaviour and less active social and aggressive behaviour. In addition, females terminated social contact more frequently. These results can be interpreted as true sex differences, as behaviour in the open-field and social interaction tests did not differ across the oestrous cycle. In conclusion, the results show that sex differences in anxiety-like behaviour in gerbils are best detected using the social interaction test, which suggests that females show a more anxious profile. It also further highlights the need for sex differences to be investigated in tests of anxiety.

Regulation of ischemic cell death by the lipoic acid–palladium complex, Poly MVA, in gerbils

Modulation of ischemic cell death can be accomplished via a multitude of mechanisms, such as quenching radical species, providing alternative energy sources, or altering glutamate excitation. Transient cerebral ischemia will induce apoptotic cell death selectively to hippocampal cornus ammon's field 1 of the hippocampus (CA1) pyramidal cells, while neighboring CA3 and dentate neurons are spared. Poly MVA is a dietary supplement based on the nontoxic chemotherapeutic lipoic acid–palladium complex (LAPd). LAPd is a liquid crystal that works in cancer cells by transferring excess electrons from membrane fatty acids to DNA via the mitochondria. Therefore, by its structural nature and action as a redox shuttle, it can both quench radicals as well as provide energy to the mitochondria. To understand the role of LAPd in regulating ischemic cell death, we studied Poly MVA. Male Mongolian gerbils were subjected to 5 min of bilateral carotid artery occlusion under a controlled temperature environment (37.0–38.0°C). Animals were injected with physiological saline or either 30, 50, or 70 mg/kg of Poly MVA every 24 h beginning immediately after the occlusion until being sacrificed on experimental day 4. Damage was evaluated by analyzing nesting behavior and conducting blinded measures of viable CA1 lengths. All Poly MVA treatment dosages significantly ( p < 0.05) reduced hippocampal CA1 damage by 72 h. Nesting scores were significantly improved after 30 and 50 mg/kg treatment but not 70 mg/kg. While nesting is usually a very accurate indicator of morphological damage, the 70 mg/kg-treated animals demonstrated excessive energy, thus ignoring the nesting material. While numerous routes offer varying degrees of CA1 neuronal survival after transient global ischemia, only the LAPd complex, which quenches radicals and provides energy to stabilize the mitochondria, offers such significant protection. Thus, the administration of Poly MVA may be a potent neuroprotective agent for victims of transient ischemic attack (TIA), cardiac arrest, anesthetic accidents, or drowning.

Effect of duodenogastric reflux on N-methyl-N'-nitro-N-nitrosoguanidine-induced glandular stomach tumorigenesis in Helicobacter pylori-infected Mongolian gerbils

Both Helicobacter pylori (Hp) and bile acids are gastric carcinogens. An experimental model of duodenogastric reflux in Mongolian gerbils was developed and was used to study the effects of Hp infection and duodenogastric reflux on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced glandular stomach tumorigenesis independently and synergistically. Male Mongolian gerbils underwent both inoculation with Hp, and had duodenogastric reflux (DR) induced, or neither, followed by MNNG administration. Animals were sacrificed at week 40, and histopathological examination of their excised stomachs and serological investigation were performed. Glandular stomach adenocarcinomas were observed in animals that underwent Hp inoculation and/or induction of DR after MNNG administration, and glandular stomach adenomas were found in animals inoculated with Hp after MNNG administration. The incidence of glandular stomach tumors was significantly higher in animals inoculated with Hp after MNNG administration and in animals undergoing combined Hp inoculation, DR induction and MNNG administration than in animals only administered MNNG. These findings indicate that Hp infection has a stronger tumorigenic effect than the exposure to duodenal contents, and duodenal contents may attenuate the effect of Hp on glandular stomach tumorigenesis.

Sexual motivation suppresses paternal behaviour of male gerbils during their mates' postpartum oestrus

Adult male Mongolian gerbils, Meriones unguiculatus, avoid contact with their young on the day that the young are born. However, on succeeding days, fathers spend nearly as much time in contact with their offspring as do mothers. We undertook a series of studies to investigate the causes of the day-to-day change in male parental behaviour. In experiment 1, we tested males' response to pups before, after and on the day of their mates' parturition, and found that males were more parental both before and after the day of birth of their young than on that day. In experiment 2, we compared the parental behaviour of males paired either with intact or with ovariectomized dams (which do not come into postpartum oestrus) and found that males that were mated to intact females were less attentive to pups on the day of their birth than were the males mated to ovariectomized females. In experiment 3, we compared the parental responses of castrated and intact males to newborn pups and found that castrated males were more parental than intact males. In experiment 4, we compared the parental responses of males that were exposed to postpartum oestrous females but prevented from mating for 24 h. Extending the period of male sexual arousal to 24 h inhibited paternal responsiveness to neonates for 24 h. We interpret these results as being consistent with the hypothesis that on the day of birth of a litter, a male's parental behaviour is inhibited by the motivation to mate during his partner's postpartum oestrus.

Mongolian gerbil fathers avoid newborn male pups, but not newborn female pups: olfactory control of early paternal behaviour

We examined effects on the parental behaviour of male Mongolian gerbils, Meriones unguiculatus, of the sex and number of pups in a litter. Recent fathers interacting with foster litters consisting entirely of newborn males decreased the time that they spent in contact with a litter the greater the number of pups it contained. However, fathers that interacted with litters composed entirely of newborn females showed no change in the time they spent in contact with a litter as a function of its size. Fathers responded similarly to litters of 1- and 3-day-old female pups, but their responses to male pups changed from avoidance to approach as the age of males increased from 1 day to 3 days, and fathers made anosmic by intranasal administration of zinc-sulfate solution did not avoid neonatal litters. Results of a correlational study revealed that the more time males spent with newborn young during a 30-min test, the greater their latency to mate with their partners in postpartum oestrus and the shorter the duration of their mating effort during the 24 h immediately after parturition. We discuss these findings as consistent with the view that androgen-mediated olfactory stimuli produced by newborn male Mongolian gerbils make them unattractive to fathers, possibly functioning to increase the time that recent fathers mate-guard while their partners are in postpartum oestrus.

Effects of FK506 on the translocation of protein kinase C and CaM kinase II in the gerbil hippocampal CA1 neurons

To explore biochemical basis for cerebroprotective effect of immunosuppressant FK506, we studied changes in subcellular distribution of protein kinase Cγ (PKCγ) as well as calcium/calmodulin-dependent protein kinase II (CaMKII) after ischemia. Male Mongolian gerbils were subjected to 5 min forebrain ischemia. FK506 (1 or 3 mg kg-1) was administered at 1 min after recirculation, which was confirmed to be cerebroprotective by histological examination at seven days after ischemia. At the designated time points (before ischemia, 5 min ischemia, 1 and 24 h recovery), heads were frozen and samples were taken from CA1 subfield of hippocampus. Western blot analysis was carried out. Persistent translocations of PKCγ and CaMKII to synaptosomal P2 fraction were observed in vehicle-treated group. FK506 significantly decreased levels of PKCγ and CaMKII in P2 fraction at 24 h of recovery. The present results suggest FK506 downregulates translocated PKCγ and CaMKII, which may contribute to its survival promoting effect after cerebral ischemia.