Individual Odors in Djungarian Hamsters (Phodopus campbelli)

The sources of scent in Djungarian hamsters (Phodopus campbelli) that may be individually discriminated were investigated using an habituation paradigm. Male Djungarian hamsters were exposed to five presentations of a particular scent from one individual, and then to the same scent from a novel individual. Increased investigation of the scent from the novel individual indicated discrimination of scents from different individuals. Male hamsters distinguished individual differences in scents of other males from the midventral gland, urine, feces, mouth, and the corner of the mouth, which includes the sacculi; they did not discriminate among odors of different individuals when the scents were from the genital region, hindfeet, fur from behind ears or fur from the back. The results indicate that Djungarian hamsters have a repertoire of individually distinctive scents that are located in specific places on the body; these scents are not actively distributed to, nor passively picked up on, other parts of the body. The fact that scents from some areas do not contain individually distinctive information suggests that some sources may be specialized for producing individually distinctive scents.     

Development of Species Preferences in Two Hamsters, Phodopus campbelli and Phodopus sungorus: Effects of Cross-Fostering

Experiments were conducted to investigate species-specific preferences in two closely related species of hamsters, Phodopus campbelli and Phodopus sungorus . Male hamsters that were raised with conspecifics spent more time investigating an anaesthetized conspecific male than a heterospecific male, and also spent more time investigating odours of conspecifics than those of heterospecifics (midventral gland, urine, and saccular secretion). Cross-fostered P. sungorus males reversed their normal preferences, spending more time investigating stimuli (anaesthetized males and all three odours) of the foster species. Cross-fostered P. campbelli males also investigated an anaesthetized male of the foster species more than a male of their own species, but did not show a preference for odours alone. Social experience during the 15 d immediately following weaning also influenced these preferences. If exposures during and after nesting were to heterospecifics the preference for heterospecifics was strengthened; if either period of experience was with a conspecific, this eliminated the preference for heterospecifics in P. sungorus but did not influence the lack of a preference in P. campbelli . Thus, early experience during both the nestling stage and the 15 d after weaning influenced responses to species-typical cues in both species, but it had a more pronounced effect in P. sungorus .     

Indicators of Postoperative Pain in Syrian Hamsters (Mesocricetus auratus)

Despite the use of Syrian hamsters (Mesocricetus auratus) in research, little is known about the evaluation of pain in this species. This study investigated whether the frequency of certain behaviors, a grimace scale, the treat-take-test proxy indicator, body weight, water consumption, and coat appearance could be monitored as signs of postoperative pain in hamsters in a research setting. Animals underwent no manipulation, anesthesia only or laparotomy under anesthesia. An ethogram was constructed and used to determine the frequencies of pain, active and passive behaviors by in-person and remote videorecording observation methods. The Syrian Hamster Grimace Scale (SHGS) was developed for evaluation of facial expressions before and after the surgery. The treat-take-test assessed whether surgery would affect the animals’ motivation to take a high-value food item from a handler. The hypothesis was that behavior frequency, grimace scale, treat-take-test score, body weight, water consumption, and coat appearance would change from baseline in the surgery group but not in the no-intervention and anesthesia-only groups. At several time points, pain and passive behaviors were higher than during baseline in the surgery group but not the anesthesia-only and no-intervention groups. The SHGS score increased from baseline scores in 3 of the 9 animals studied after surgery. The frequency of pain behaviors and SHGS scores were highly specific but poorly sensitive tools to identify animals with pain. Behaviors in the pain category were exhibited by chiefly, but not solely, animals that underwent the laparotomy. Also, many animals that underwent laparotomy did not show behaviors in the pain category. Treat-take-test scores, body weight, water consumption, and coat appearance did not change from baseline in any of the 3 groups. Overall, the methods we tested for identifying Syrian hamsters experiencing postoperative pain were not effective. More research is needed regarding clinically relevant strategies to assess pain in Syrian hamsters.

Pain experienced by laboratory animals can affect both animal welfare and research results. Little is known about the evaluation of pain in Syrian hamsters (Mesocricetus auratus) in the laboratory setting. However, various research models using Syrian hamsters involve surgery and are presumed to cause pain.^16,47,49 In 2018 alone, the USDA reported that 35,695 hamsters were used for research studies involving painful procedures.⁴⁸ Previously published behaviors exhibited by hamsters in response to pain include hunched posture with head down, reluctance to move, increased depression or aggression, extended sleep periods, and weight loss.^7,8,10,16,21 How these behaviors are affected by factors such as the type of painful stimulus, anesthetic protocol, handling procedures, and environmental conditions is unclear. The practicality of observing these signs in the research environment is uncertain and likely complicated by the nocturnal nature of Syrian hamsters and an assumed propensity of this species to mask pain, much like other prey species.^8,14,16A significant need exists for published data investigating whether behavioral observations or other clinical indicators can help recognize, quantify, or monitor pain in hamsters in a research setting. Detailed behavioral observations and well-controlled studies are needed to develop a system to assess postoperative pain in laboratory animals.^8,33 Moreover, little information is available on the efficacy of analgesic agents in hamsters.¹ The few studies of analgesics in hamsters rely on the mitigation of evoked pain responses (such as using a hot plate), which has limited relevance to clinical situations such as postoperative pain.^8,32,36,51 To date, no published literature has evaluated the efficacy or safety of analgesics to treat postoperative pain in hamsters. Validated real-time and practical methods for evaluating pain in Syrian hamsters would support the evaluation of analgesic efficacy in this species.Various assessments have been developed to identify signs of pain in other species. Behavioral ethograms have been used to evaluate pain and analgesic efficacy in mice, rats, rabbits, and guinea pigs in the research environment.^{5,6,20,23,25,34,35,39-41,53} Another tool used to evaluate pain in animals is the grimace scale, which has been developed for mice, rats, rabbits, ferrets, cats, sheep, pigs, horses, and even harbor seals.^{3,4,9,11,13,15,19,22,26,30,37,45,50} The use of a proxy indicator, such as burrowing and time-to-integrate-to-nest in mice and time-to-consume in guinea pigs, can be used as an additional tool for the evaluation of pain.^{5,17,18,35,38}Because none of the previously mentioned assessment techniques were specific to hamsters, we here explored using these approaches to detect pain in Syrian hamsters that underwent laparotomy in a laboratory setting. We developed a species-specific ethogram and the Syrian Hamster Grimace Scale (SHGS). We also devised a novel proxy indicator of pain for use in Syrian hamsters, the treat-take-test (TTT), which is based on hamsters’ natural behavior to hoard food.^16,46,49,52 Although water intake, body weight, and coat appearance are non-specific indicators of pain, we also measured these parameters.^5,19,23,33 Furthermore, we analyzed the effects of the presence of an observer and time of day. We hypothesized that behavior frequency, grimace scale, treat-take-test score, body weight, water consumption, and coat appearance would change from baseline in the surgery group but not in the no-intervention and anesthesia-only groups.     

Behavioral and Physiological Analyses of Ultrasound Production by Female Hamsters (Mesocricetus auratus)

The results of behavioral studies suggest specific roles forhigh-frequency vocalizations (ultrasounds) in courtship andcopulatory interactions among golden hamsters. In addition,these results, and functional interpretations based on them,can help to guide studies of physiological mechanisms controllingultrasonic communication. For example, interpretations of rodentultrasounds as sexual or agonistic signals suggest that ultrasoundrates depend on gonadal hormones. This prediction has been verifiedfor several rodent species, including hamsters. Similar reasoningshould apply to the analysis of brain mechanisms for ultrasoundproduction. In particular, the consideration of hamster ultrasoundsas sexual behaviors and vocalizations, as well as hormone-dependentresponses, suggests several brain areas as especially likelyparticipants in neural circuits mediating hormonal effects onultrasonic communication. The preliminary results of a studyin which we lesioned one of these areas, the mesencephalic centralgrey, confirm this structure's involvement in the control ofhamster ultrasounds, and, more generally, support the utilityof behavioral data in physiological studies.     

光照周期对叙利亚地鼠生长发育和繁殖的影响

对离乳雄性叙利亚地鼠（Ｍｅｓｏｃｒｉｃｅｔｕｓａｕｒａｔｕｓ）和雌性叙利亚地鼠各３０只分别给以长光照（１６Ｌ：８Ｄ）、中光照（１２Ｌ：１２Ｄ）和短光照（８Ｌ：１６Ｄ）三种光周期处理,研究光周期对叙利亚地鼠生长发育和繁殖的影响。１３周龄时,短光照处理组雄性地鼠的体重显著（Ｐ＜０．０５）高于长光照和中光照组的体重;雌性地鼠９周龄时长光照组的体重显著（Ｐ＜０．０１）高于另外两个处理组的体重,较高的日食量可能是长光照组具有较大体重的原因之一,雄性地鼠的睾丸、副睾和肾上腺重量及雌性地鼠的卵巢、子宫和肾上腺重量表现了随着光照时间的延长而递增的趋势。长光照条件有利于雌性地鼠的正常发情和繁殖。每天１６ｈ的光照对繁殖地鼠是比较适宜的。     

Population Control in Confined Colonies of Golden Hamsters (Mesocricetus auratus Waterhouse)

The mechanisms by which confined colonies of Golden Hamsters regulate the density of their population were investigated. Six experimental populations were established with two ♂♂ and two ♀♀ each and allowed to grow freely for 3–8 months. At no time did any population exceed eight individuals. This appeared to be the result of a high rate of infant mortality due to failure of pregnant and parturient ♀♀ to isolate themselves from the others. Two other populations were then established allowing many more nesting areas and more room for dispersal, but animals continued to crowd together and infant survival did not improve. These results contrast sharply with the large ultimate populations and only slowly developing disturbances seen in rats and mice. This difference in population control appears to be the direct result of a species difference in the tolerance of adults for strange newborns. In two further short-term experiments, the effects of the number and sex of adults in the founding population were systematically examined. The critical density at which no pups survived past the first day was six or more animals; ♀♀ appeared to contribute more than ♂♂ to infant mortality.     

Post-natal patterns of plasma androgen-binding activity in Djungarian (Phodopus sungorus) and golden (Mesocricetus auratus) hamsters

The binding of sex steroids to plasma proteins was examined in post-natal Djungarian and golden hamsters. With dihydrotestosterone or testosterone as ligands, steady-state polyacrylamide gel electrophoresis revealed 2 androgen binding components in the plasma of young Djungarian hamsters of both sexes. The fast-moving component exhibited a low affinity and high capacity for androgens and corresponded to albumin in stained gels. In contrast, the slow moving component was a beta-globulin with high affinity (Ka = 10(9) M-1) and low capacity for androgens, and was identified as a specific sex steroid-binding protein (SBP; also SHBG). This SBP did not bind oestrogens or corticosteroids and was electrophoretically distinct from corticosteroid-binding globulin (CBG). In addition, this protein did not appear to be of testicular origin because it was present in immature females and in immature males that had been castrated for 8 days. Plasma concentrations of SBP in males as measured by a diethyl-aminoethyl-cellulose binding assay were low at birth, became significantly elevated shortly thereafter when plasma androgen values were also elevated, and subsequently fell to low levels during puberty. These changes follow the same general pattern that has been described for other mammals, including humans, during this period of reproductive development. Although the significance of elevated SBP concentrations during prepuberty has yet to be determined, it appears that the increased concentrations of high-affinity androgen binding in the plasma of Djungarian hamsters plays a role in the asynchronous pubertal development of the testes and accessory organs which occurs in this species. The post-natal SBP pattern in females was similar to that observed in males. Plasma SBP levels were low or undetectable in adults of both sexes. As previously described for adult golden hamsters, the plasma of post-natal male and female golden hamsters lacked a specific SBP: androgen binding in this species is apparently limited to albumin and CBG.     

Intranasal Vaccination with Leishmanial Antigens Protects Golden Hamsters (Mesocricetus auratus) Against Leishmania (Viannia) braziliensis Infection

Background

Previous results have shown that oral and intranasal administration of particulate Leishmania (Leishmania) amazonensis antigens (LaAg) partially protects mice against L. amazonensis infection. However, vaccination studies on species of the subgenus Viannia, the main causative agent of cutaneous and mucosal leishmaniasis in the Americas, have been hampered by the lack of easy-to-handle bio-models that accurately mimic the human disease. Recently, we demonstrated that the golden hamster is an appropriate model for studying the immunopathogenesis of cutaneous leishmaniasis caused by L. (Viannia) braziliensis. Using the golden hamster model, our current study investigated whether the protective effect of intranasal immunisation with LaAg can be extended to L. braziliensis infection.

Methodology/Principal Findings

Golden hamsters vaccinated with either two intranasal (IN) doses of LaAg (10 µg) or two intramuscular doses of LaAg (20 µg) were challenged 2 weeks post-vaccination with L. braziliensis. The results showed that IN immunisation with LaAg significantly reduced lesion growth and parasitic load as well as serum IgG and IgG2 levels. At the experimental endpoint on day 114 post-infection, IN-immunised hamsters that were considered protected expressed IFN-γ and IL10 mRNA levels that returned to uninfected skin levels. In contrast to the nasal route, intramuscular (IM) immunisation failed to provide protection.

Conclusions/Significance

These results demonstrate for the first time that the nasal route of immunisation can induce cross protection against L. braziliensis infection.     

Post-natal development of the pineal organ in the hamsters Phodopus sungorus and Mesocricetus auratus

Summary In Phodopus sungorus, as in other mammals, the pineal organ forms an important link in the transduction of photoperiodic information to the endocrine system. The sympathetic innervation, via the superior cervical ganglion, controls the metabolism of serotonin and melatonin in the pineal, which in turn is involved in the control of the gonads. In the present study, the post-natal development of this system was investigated. Specimens 1, 5, 10, and 15 days post partum (p.p.) and adults were treated with monoamine-oxidase-inhibitor and perfused under ether anesthesia via the aorta with a buffer containing glyoxylic acid, formaldehyde and Mg⁺⁺. The brains were then dissected out and treated according to Falck-Hillarp for fluorescence microscopy and microspectrofluorometry. Day 1: The nervi conarii had reached the pineal capsule, but only in a few cases was the pineal organ invaded and then only by a few fibers. Day 5: A rich green-fluorescing net of fibers was present in the entire organ, stalk and lamina intercalaris. No 5-HT fluorescence was observable. Day 10: Similar to the stage at 5 days a rich green-fluorescing nerve fiber net was observed throughout the pineal and a yellow fluorescence in the pineal perikarya. Day 15: The general appearance resembles the adult. The nerve fibers are masked by the intense yellow fluorescence of the pineal perikarya. Fading of the latter, however, allows the catecholamine fluorescence to be seen. Golden hamsters at an age of 15 days p.p. show a similar appearance to Phodopus at an age of 15 days. Microspectrofluorometric determinations indicated the catecholamine to be noradrenaline, and confirmed a 5-HT/5-HTP origin of the yellow fluorescence appearing between day 5 and day 10. The amount of 5-HT/5-HTP was considerably less at day 10 than at day 15 or in adults. Sympathectomy by extirpation of the superior cervical ganglion abolished the catecholamine fluorescence completely in the pineal body, stalk and lamina intercalaris.Supported by grants from the Swedish Natural Science Research Council (to P. Meurling and Th. van Veen), and the Royal Physiographic Society of Lund     

Individual Odours in Two Chromosomal Species of Blind,Subterranean Mole Rat (Spalax ehrenbergi): Conspecific and Cross-species Discrimination

Mole rats from two chromosomal species (2n = 58 and 2n = 60) of the Spalax ehrenbergi superspecies of Israel were tested to determine whether they were able to discriminate differences in the odour of urine from same-sex individuals of their own and of the other chromosomal species. An habituation-discrimination apparatus was designed for use with these solitary and blind subterranean rodents. Animals habituated to the odour of urine from one individual presented for 10 min at a centre sniffing area in the roof of a 50 cm long Perspex tunnel. The odour of urine from the original donor and from a second individual were presented at two other sniffing areas in the tunnel roof during a 5 min discrimination phase. Significant differences in the time spent investigating the two odours demonstrated successful discrimination between them. The results indicate that male and female mole rats of both species can discriminate between the individual-specific odour cues in urine from pairs of conspecifics and pairs of heterospecific mole rats.     

Intravenous injection of unanesthetized hamsters (Mesocricetus auratus)

A rubber band tourniquet was applied to the proximal portion of the foreleg of unanesthetized male and female golden hamsters followed by intravenous injection in the cephalic vein using a 25 gauge needle. Volumes up to 0.3 ml could be injected easily.     

Experimental paracoccidioidomycosis in hamsters ( Mesocricetus auratus): Gestational interactions

Paracoccidioides brasiliensis is a dimorphic fungus presenting specific steroid hormone receptors, both in the yeast and mycelial forms and estrogen inhibits the transition from mycelium to yeast. In the acute phase, the disease occurs with equal frequency in both sexes but in adults, females are spared. Placental fungal infection has been reported, but references to fetal infection have not been confirmed. We used 78 Syrian female hamsters divided into 3 groups: GI consisted of 30 infected mated females, GII of 20 infected unmated females and GIII of 28 uninfected mated females. Animals of group I were mated 4 weeks after infection and half of them were submitted to cesarean section on day 15 after successful mating; the other half was maintained and submitted to cesarean section and sacrificed 14 weeks after infection. Half of the animals of group II were sacrificed seven weeks and the other half 14 weeks after infection. Uninfected animals of group III were treated the same as the animals of group I. The animals were infected with strain 18 of P. brasiliensis by the intracardiac route. We evaluated the disease by the volume of granulomas in different organs, number of fungi in liver and spleen and the immunologic responses [ ELISA, Double Immunodifusion ( DID), Delayed Hypersensitivity Skin Test ( DHT) and Macrophage Migration Inhibition ( MMI)]. We studied the infection through the gestation by evaluation of the abortions, morphologic and clinic examinations of the fetuses. Our results showed that the infection did not transfer to the fetus through the placenta, but the number of abortions was larger among infected females. The newborns of GI females were smaller, weighed less and showed little vitality. The disease was more severe and disseminated in infected mated females, especially in the second sacrifice 14 weeks after inoculation, when the total volume of granulomas in them (56.3 mm) was much greater than in the infected unmated females (12 mm). This revised version was published online in June 2006 with corrections to the Cover Date.     

Studies on sex chromosomes of four hamster species: Cricetus cricetus, Cricetulus griseus, Mesocricetus auratus, and Phodopus sungorus.

In this paper, we present an analysis of the sex chromosomes of four hamster species after application of different staining techniques. The mitotic X chromosomes show a striking similarity in G-banding pattern but rather great differences in their C-banding patterns. A presumably homologous euchromatic segment that exhibits two distinct G-bands appears in the X chromosome of each species. The Y chromosome of Cricetus cricetus is in contrast to those of the other species, because it reveals a relatively well-differentiated G- and C-banding pattern. In meiotic metaphase I, interstitial chiasmata can be found in the sex bivalents of Cricetus cricetus and Cricetulus griseus, whereas the gonosomes of Mesocricetus auratus and Phodopus sungorus sungorus are terminally associated. The regions that are involved in pairing or association are always heterochromatic.     

Scent Marking by Male Golden Hamsters (Mesocricetus auratus) II. The role of the flank gland scent in the causation of marking

Investigated the role of the odor of the flank gland in the stimulation of flank marking by male hamsters, Mesocricetus auratus. In the first experiment it was shown that a ♂ has customary marking posts and that a second ♂ introduced into the first ♂'s area will mark in the same places. In experiment 2 nine test ♂♂ flank marked less in the home cages of flank glandectomized ♂♂ than in the cages of normal ♂♂. In experiment 3 it was shown that flank glandectomized ♂♂ marked at within the range of frequencies for normal ♂♂.     

Paternal responsiveness in biparental dwarf hamsters (Phodopus campbelli) does not require estradiol

Males of the biparental hamster species Phodopus campbelli act as midwives and are responsive to an experimentally displaced pup. Males also have peripheral estradiol concentrations that are similar to conspecific females. Castration reduces peripheral estradiol, yet does not affect paternal responsiveness despite the known role of estradiol in maternal behavior. Synthesis of estradiol within the central nervous system, however, might not be affected by castration. Males received implants of osmotic pumps containing the aromatase inhibitor letrozole to reduce both peripheral and central estradiol concentrations. Though estradiol was effectively reduced, it had no effect on paternal responsiveness or reproductive success. Neither testosterone nor aggression directed towards an intruder was altered. Results support the emerging conclusion that estradiol is not required for the exceptional paternal behavior of male P. campbelli.     

Mitochondria-targeted antioxidant SkQ1 accelerates maturation in Campbell dwarf hamsters (Phodopus campbelli)

We tested two hypotheses. 1) SkQ1 positively affects postnatal development of hamsters in litters born to parents receiving long-term SkQ1 treatment. 2) SkQ1 accelerates maturation of juvenile females receiving the antioxidant treatment from 10 days of age. Parental pairs were kept in an outdoor vivarium under conditions close to natural. At the age of 25 days, juvenile males in litters born to parents treated daily with SkQ1 (50 nmol/kg per os) had higher epididymis mass. Both the size of a litter and SkQ1 affected epididymis mass in young males. Both the litter size and SkQ1 affected uterus mass in 25-day-old females. Juvenile females who received SkQ1 treatment from 10 days of age demonstrated earlier opening of the vagina. This experiment was replicated with the same result. At the age of 2.5 months, virgin females treated with SkQ1 from the early age demonstrated higher ovary mass.