Delivery by cesarean section leads to heavier adult bodyweight in prairie voles (Microtus ochrogaster).

Delivery by cesarean section now makes up 32.1 % of all births in the United States. Meta-analyses have estimated that delivery by cesarean section is associated with a > 50 % increased risk for childhood obesity by 5 years of age. While this association is independent of maternal obesity, breastfeeding, and heritable factors, studies in humans have been unable to test for a causal role of cesarean delivery in this regard. Here, we set out to use an animal model to experimentally test whether delivery by cesarean section would increase offspring weight in adulthood. Delivery by cesarean section may exert neurodevelopmental consequences by impacting hormones that are important at birth as well as during metabolic regulation in later life, such as oxytocin and vasopressin. The prairie vole (Microtus ochrogaster) has long been studied to investigate the roles of oxytocin and vasopressin in brain development and social behavior. Here, we establish that prairie voles tolerate a range of ambient temperatures, including conventional 22° housing, which makes them translationally appropriate for studies of diet-induced obesity. We also studied vole offspring for their growth, sucrose preference, home cage locomotor activity, and food consumption after birth by either cesarean section or vaginal delivery. At sacrifice, we collected measures of weight, length, and adipose tissue to analyze body composition in adulthood. Voles delivered by cesarean section had consistently greater bodyweights than those born vaginally, despite having lower food consumption and greater locomotive activity. Cesarean-delivered animals were also longer, though this did not explain their greater body weights. While cesarean delivery had no effect on vasopressin, it resulted in less oxytocin immunoreactivity within the hypothalamus in adulthood. These results support the case that cesarean section delivery plays a causal role in increasing offspring body weight, potentially by affecting the oxytocin system.

Paternal absence and increased caregiving independently and interactively shape the development of male prairie voles at subadult and adult life stages.

The influence of maternal caregiving is a powerful force on offspring development. The absence of a father during early life in biparental species also has profound implications for offspring development, although it is far less studied than maternal influences. Moreover, we have limited understanding of the interactive forces that maternal and paternal caregiving impart on offspring. We investigated if behaviorally upregulating maternal care compensates for paternal absence on prairie vole (Microtus ochrogaster) pup development. We used an established handling manipulation to increase levels of caregiving in father-absent and biparental families, and later measured male offspring behavioral outcomes at sub-adulthood and adulthood. Male offspring raised without fathers were more prosocial (or possibly less socially anxious) than those raised biparentally. Defensive behavior and responses to contextual novelty were also influenced by the absence of fathers, but only in adulthood. Offensive aggression and movement in the open field test changed as a function of life-stage but not parental exposure. Notably, adult pair bonding was not impacted by our manipulations. Boosting parental care produced males that moved more in the open field test. Parental handling also increased oxytocin immunoreactive cells within the supraoptic nucleus of the hypothalamus (SON), and in the paraventricular nucleus (PVN) of biparentally-reared males. We found no differences in vasopressinergic cell groups. We conclude that male prairie voles are contextually sensitive to the absence of fathers and caregiving intensity. Our study highlights the importance of considering the ways early experiences synergistically shape offspring behavioral and neural phenotypes across the lifespan.

Effects of paternal deprivation on empathetic behavior and the involvement of oxytocin receptors in the anterior cingulate cortex.

Paternal deprivation (PD) impairs social cognition and sociality and increases levels of anxiety-like behavior. However, whether PD affects the levels of empathy in offspring and its underlying mechanisms remain unknown. The present study found that PD increased anxiety-like behavior in mandarin voles (Microtus mandarinus), impaired sociality, reduced the ability of emotional contagion, and the level of consolation behavior. Meanwhile, PD reduced OT neurons in the paraventricular nucleus (PVN) in both male and female mandarin voles. PD decreased the level of OT receptor (OTR) mRNA in the anterior cingulate cortex (ACC) of male and female mandarin voles. Besides, OTR overexpression in the ACC reversed the PD-induced changes in anxiety-like behavior, social preference, emotional contagion, and consolation behavior. Interference of OTR expression in the ACC increased levels of anxiety-like behaviors, while it reduced levels of sociality, emotional contagion, and consolation. These results revealed that the OTR in the ACC is involved in the effects of PD on empathetic behaviors, and provide mechanistic insight into how social experiences affect empathetic behaviors.

Effects of food supplementation and helminth removal on space use and spatial overlap in wild rodent populations.

Animal space use and spatial overlap can have important consequences for population-level processes such as social interactions and pathogen transmission. Identifying how environmental variability and inter-individual variation affect spatial patterns and in turn influence interactions in animal populations is a priority for the study of animal behaviour and disease ecology. Environmental food availability and macroparasite infection are common drivers of variation, but there are few experimental studies investigating how they affect spatial patterns of wildlife. Bank voles (Clethrionomys glareolus) are a tractable study system to investigate spatial patterns of wildlife and are amenable to experimental manipulations. We conducted a replicated, factorial field experiment in which we provided supplementary food and removed helminths in vole populations in natural forest habitat and monitored vole space use and spatial overlap using capture-mark-recapture methods. Using network analysis, we quantified vole space use and spatial overlap. We compared the effects of food supplementation and helminth removal and investigated the impacts of season, sex and reproductive status on space use and spatial overlap. We found that food supplementation decreased vole space use while helminth removal increased space use. Space use also varied by sex, reproductive status and season. Spatial overlap was similar between treatments despite up to threefold differences in population size. By quantifying the spatial effects of food availability and macroparasite infection on wildlife populations, we demonstrate the potential for space use and population density to trade-off and maintain consistent spatial overlap in wildlife populations. This has important implications for spatial processes in wildlife including pathogen transmission.

The function of brown adipose tissue at different sites of the body in Brandt's voles during cold acclimation.

Ambient temperatures have great impacts on thermoregulation of small mammals. Brown adipose tissue (BAT), an obligative thermogenic tissue for small mammals, is localized not only in the interscapular depot (iBAT), but also in supraclavicular, infra/subscapular, cervical, paravertebral, and periaortic depots. The iBAT is known for its cold-induced thermogenesis, however, less has been paid attention to the function of BAT at other sites. Here, we investigated the function of BAT at different sites of the body during cold acclimation in a small rodent species. As expected, Brandt's voles (Lasiopodomys brandtii) consumed more food and reduced the body mass gain when they were exposed to cold. The voles increased resting metabolic rate and maintained a relatively lower body temperature in the cold (36.5 ± 0.27 °C) compared to those in the warm condition (37.1 ± 0.36 °C). During cold acclimation, the uncoupling protein 1 (UCP1) increased in aBAT (axillary), cBAT (anterior cervical), iBAT (interscapular), nBAT (supraclavicular), and sBAT (suprascapular). The levels of proliferating cell nuclear antigen (PCNA), a marker for cell proliferation, were higher in cBAT and iBAT in the cold than in the warm group. The pAMPK/AMPK and pCREB/CREB were increased in cBAT and iBAT during cold acclimation, respectively. These data indicate that these different sites of BAT play the cold-induced thermogenic function for small mammals.

Body temperature and locomotor activity of social subterranean mole voles (Ellobius talpinus) in winter.

To find out whether a social subterranean rodent-the northern mole vole (Ellobius talpinus)-hibernates in winter, nine individuals from Southern Siberia were captured in late autumn and implanted with loggers [that constantly recorded body temperature (Tb) and locomotor activity] and then released. Eight of them were recaptured the following spring. From October to April, the animals' Tb never dropped below 33 °C, although cosinor analysis revealed a decrease in mesor values and in the amplitude of daily fluctuations of Tb and activity in winter months. Spectral density of circadian rhythms of both indexes also diminished in winter. The magnitude of Tb and fluctuations of activity differed between the two studied familial groups, probably due to their unequal numbers of individuals, which could affect the total heat production. The levels and patterns of temperature and activity fluctuations observed in winter rule out the possibility of hibernation in this species.

Adaptive responses to habitat change: Theory and tests with field experiments.

Habitat loss and change are often implicated as the primary causes of species extinction. Although any population can be instantly imperiled by catastrophe, most habitat loss occurs gradually, thus enabling affected individuals an adaptive advantage to occupy the best of their dwindling opportunities. I demonstrate how to infer the advantage between two habitats for any density and frequency-dependent strategy of habitat selection. I explore the concept of an Adaptive Dispersal Strategy Landscape to reveal the Evolutionarily Stable Strategy separately for ideal-free and ideal preemptive habitat selectors. Both solutions reveal an initially counterintuitive expectation that individuals living at high density gain insufficient adaptive advantage to disperse from a deteriorating habitat. Adaptive dispersal is constrained at high density because habitats of better quality are fully occupied. I test the theory with measures of movement and foraging in crossover experiments on a seminatural population of meadow voles. The experiment allowed the voles to choose among patches and between enclosures in which I differentially manipulated food and shelter. Although photographs from an infrared camera documented voles venturing from one habitat to the other, none became resident. Voles preferentially foraged in the richer of the two enclosures, even when I reversed treatments, and they foraged more in patches protected by mulched straw. The adaptive advantage of dispersal using a surrogate fitness proxy based on the voles' giving-up densities mirrored that generated by theory. The convergence between theory and experiment yields much-needed insight into our ability to test, predict, and hopefully resolve, the ecological, evolutionary, and conservation consequences of habitat loss.

Prairie voles as a model for adaptive reward remodeling following loss of a bonded partner.

Loss of a loved one is a painful event that substantially elevates the risk for physical and mental illness and impaired daily function. Socially monogamous prairie voles are laboratory-amenable rodents that form life-long pair bonds and exhibit distress upon partner separation, mirroring phenotypes seen in humans. These attributes make voles an excellent model for studying the biology of loss. In this review, we highlight parallels between humans and prairie voles, focusing on reward system engagement during pair bonding and loss. As yearning is a unique feature that differentiates loss from other negative mental states, we posit a model in which the homeostatic reward mechanisms that help to maintain bonds are disrupted upon loss, resulting in yearning and other negative impacts. Finally, we synthesize studies in humans and voles that delineate the remodeling of reward systems during loss adaptation. The stalling of these processes likely contributes to prolonged grief disorder, a diagnosis recently added to the Diagnostic and Statistical Manual for Psychiatry.

Maladaptive cardiac and behavioral reactivity to repeated vicarious stress exposure in socially bonded male prairie vole siblings.

Behaviors, emotions, and cardiovascular functions are influenced by stress. But these detrimental effects are not exclusive to an individual that directly experiences stress. Stress is also experienced vicariously through observation of another individual undergoing stress. The current study used the strong social bonds in socially monogamous prairie voles to determine effects of repeated vicarious stress on cardiac and behavioral outcomes. Male prairie voles were exposed to either a 5-minute open field chamber alone [separate (control)] or while concurrently witnessing their sibling undergo a tail-suspension stressor [concurrent (experimental)], repeated across 4 sessions. Cardiac responses in animals in the open field were evaluated for heart rate and heart rate variability prior to, during, and after each test session, and behaviors were evaluated for motion, exploration, stress reactivity, and anxiety-relevant behaviors during each test session. The concurrent condition (versus separate) displayed increased heart rate and reduced heart rate variability during repeated test sessions, and impaired recovery of these parameters following the test sessions. The pattern of disturbances suggests that both increased sympathetic and reduced parasympathetic influence contributed to the cardiac responses. Animals in the concurrent condition (versus separate) displayed disrupted rearing, grooming, and motion; reduced duration of center section exploration; and increased freezing responses across repeated test sessions. Collectively, cardiac and behavioral stress reactivity are increased as a function of vicarious stress in prairie voles, which are evident across repeated experiences of stress. These results inform our understanding of the experience of vicarious stress in social species, including humans.

Chronic MK-801 administration provokes persistent deficits in social memory in the prairie vole (Microtus ochrogaster): A potential animal model for social deficits of schizophrenia.

The prairie vole (Microtus ochrogaster) is a rodent species that has been used extensively to study biological aspects of human social bonding. Nevertheless, this species has not been studied in the context of modeling social deficits characteristic of schizophrenia. Building on studies in rodents that show that sub-chronic administration of an NMDA receptor antagonist induces persistent behavioral and neurological characteristics of schizophrenia, we administered MK-801 (0.2 mg/kg, daily, for 7 days) or physiological saline to young adult (45 days old) virgin male voles. At 69 days of age, we paired these males with virgin females. 24 h later, we assessed the males' social investigation of each female across the first 5 min of a three-hour preference test, and side-by-side contact with each female during the last hour of the test. Unlike saline-treated males, MK-801-treated males did not preferentially investigate the unfamiliar female, indicating a deficit in social memory. Although males of both groups preferentially spent time with their female partner, regression analysis revealed that deficits in social memory predicted lower partner preference in MK-801-treated males. We interpret these results in the context of recent studies of the natural history of the prairie vole as well as in the context of cognitive deficits in schizophrenia and propose that the social component of episodic memory might influence an individual's capacity to form and maintain long-term social bonds.

Habitat type modulates sharp body mass oscillations in cyclic common vole populations.

Cyclic rodent populations exhibit pronounced changes in body mass associated with the population cycle phase, long-known as Chitty effect. Although Chitty effect is a common epiphenomenon in both America and Europe, there is still incomplete evidence about the generality of these patterns across the entire range of most species. Moreover, despite decades of research, the underlying factors driving Chitty effect remains poorly understood. Here, we examined the influence of intrinsic and extrinsic factors that may underlie observed patterns in vole size variation in the Iberian common vole Microtus arvalis asturianus. We weighed and measured 2816 adult voles that were captured during 6 trapping periods. Vole numbers and body mass showed strong period- and phase-related variation both in females and males, demonstrating marked Chitty effect in the studied population. Body mass of adult males correlated with body length, evidencing that heavier males are also structurally larger. Statistical models showed that probability of occurrence of large-sized vole (> 37 g) was significantly more likely in reproductive males, during increase and peak phases, and it was modulated by habitat, with crop fields and field margins between crops showing an increased likelihood. We suggest an effect of the habitat on vole body mass mediated by predation.

Melanocortin agonism in a social context selectively activates nucleus accumbens in an oxytocin-dependent manner.

Social deficits are debilitating features of many psychiatric disorders, including autism. While time-intensive behavioral therapy is moderately effective, there are no pharmacological interventions for social deficits in autism. Many studies have attempted to treat social deficits using the neuropeptide oxytocin for its powerful neuromodulatory abilities and influence on social behaviors and cognition. However, clinical trials utilizing supplementation paradigms in which exogenous oxytocin is chronically administered independent of context have failed. An alternative treatment paradigm suggests pharmacologically activating the endogenous oxytocin system during behavioral therapy to enhance the efficacy of therapy by facilitating social learning. To this end, melanocortin receptor agonists like Melanotan II (MTII), which induces central oxytocin release and accelerates formation of partner preference, a form of social learning, in prairie voles, are promising pharmacological tools. To model pharmacological activation of the endogenous oxytocin system during behavioral therapy, we administered MTII prior to social interactions between male and female voles. We assessed its effect on oxytocin-dependent activity in brain regions subserving social learning using Fos expression as a proxy for neuronal activation. In non-social contexts, MTII only activated hypothalamic paraventricular nucleus, a primary site of oxytocin synthesis. However, during social interactions, MTII selectively increased oxytocin-dependent activation of nucleus accumbens, a site critical for social learning. These results suggest a mechanism for the MTII-induced acceleration of partner preference formation observed in previous studies. Moreover, they are consistent with the hypothesis that pharmacologically activating the endogenous oxytocin system with a melanocortin agonist during behavioral therapy has potential to facilitate social learning.

Rodent disturbance reduces ecosystem stability through regulating plant and soil functions in Hulun Buir steppe.

Brandt's vole (Lasiopodomys brandtii), a typical rodent in the eastern Eurasian Steppe, has unclear impacts on ecosystem stability. In our field study in the Hulun Buir steppe, a multifunctional grazing ecosystem in this region, we used burrow entrance area and burrow density as alternative disturbance indices to derive a Disturbance Index (DI) for quantifying disturbance levels from rodents, and employed generalized linear mixed-effects model and the N-dimensional hypervolume framework to assess the influence of Brandt's vole disturbance on plant and soil functions, and then on the ecosystem functional stability. Our findings unequivocally illustrate that various plant functions including vegetation cover (Cover), aboveground biomass (ABG) and shoot carbon (ShootC) significantly declined with increasing disturbance, while shoot nitrogen (ShootN) and root nitrogen (RootN) show significantly positive responses. Soil functions such as soil nitrogen (SoilN), soil phosphorus (SoilP) and soil organic carbon (SoilC) showed significantly negative responses. Notably, the burrow entrance area exerts a more pronounced impact on both plant and soil functions in comparison to burrow density. Additionally, both disturbance indicators have a more significant influence on plant functions than on soil functions. Overall, the ecosystem functional stability progressively decreases with intensified disturbance, with varying response patterns for plant and soil functions, the former exhibited heightened stability as disturbance intensified, while the latter proved more stable at moderate disturbance levels. Our findings suggest that plant functions were more susceptible to disturbance by Brandt's vole compared to soils. Additionally, an ecosystem destabilization was synchronized with increasing Brandt's vole disturbance, although alterations in the functional stability of plants and soil show a different pattern.

Do fossorial water voles have a functional vomeronasal organ? A histological and immunohistochemical study.

The fossorial water vole, Arvicola scherman, is an herbivorous rodent that causes significant agricultural damages. The application of cairomones and alarm pheromones emerges as a promising sustainable method to improve its integrated management. These chemical signals would induce stress responses that could interfere with the species regular reproductive cycles and induce aversive reactions, steering them away from farmlands and meadows. However, there is a paucity of information regarding the water vole vomeronasal system, both in its morphological foundations and its functionality, making it imperative to understand the same for the application of chemical communication in pest control. This study fills the existing gaps in knowledge through a morphological and immunohistochemical analysis of the fossorial water vole vomeronasal organ. The study is primarily microscopic, employing two approaches: histological, using serial sections stained with various dyes (hematoxylin-eosin, Periodic acid-Schiff, Alcian blue, Nissl), and immunohistochemical, applying various markers that provide morphofunctional and structural information. These procedures have confirmed the presence of a functional vomeronasal system in fossorial water voles, characterized by a high degree of differentiation and a significant expression of cellular markers indicative of active chemical communication in this species.

Genetic admixture drives climate adaptation in the bank vole.

Genetic admixture introduces new variants at relatively high frequencies, potentially aiding rapid responses to environmental changes. Here, we evaluate its role in adaptive variation related to climatic conditions in bank voles (Clethrionomys glareolus) in Britain, using whole-genome data. Our results reveal loci showing excess ancestry from one of the two postglacial colonist populations inconsistent with overall admixture patterns. Notably, loci associated with climate adaptation exhibit disproportionate amounts of excess ancestry, highlighting the impact of admixture between colonist populations on local adaptation. The results suggest strong and localized selection on climate-adaptive loci, as indicated by steep clines and/or shifted cline centres, during population replacement. A subset, including a haemoglobin gene, is associated with oxidative stress responses, underscoring a role of oxidative stress in local adaptation. Our study highlights the important contribution of admixture during secondary contact between populations from distinct climatic refugia enriching adaptive diversity. Understanding these dynamics is crucial for predicting future adaptive capacity to anthropogenic climate change.

Testicular histomorphometric patterns and spermatogenesis dynamics of Oecomys bicolor tomes, 1860 (Rodentia: Cricetidae).

Although the order Rodentia does not present a high risk of extinction compared to mammals as a whole, several families demonstrate high levels of threat and/or data deficiency, therefore highlighting the need for targeted research and the application of ecological and reproductive data to the development of conservation actions. The order Rodentia, the largest among mammals, includes 9 families, and the family Cricetidae is the most diverse of the Brazilian rodents. In Brazil, 12 of the 16 genera of Oecomys are found. Oecomys bicolor is known in Brazil as the 'arboreal rat' and is, found in dry, deciduous and tropical forests. The mean body weight of Oecomys bicolor was 35.8 g and the gonadal, tubular and epithelial somatic indexes were, 0.53%, 0.47% and 0.37%, respectively. Seminiferous tubules volume density was 89.72% and the mitotic and meiotic indexes corresponded to 8.59 and 2.45 cells, respectively, and the yield of spermatogenesis was 23.83 cells. The intertubular compartment represented 10.28% of the testis parenchyma and around 5% of the interstitial space was occupied by Leydig cells, whose number per gram of testis was 11.10 × 107 cells. By evaluating the biometric and histomorphometric characteristics of the testis, there is evidence that this species has a high investment in reproduction. Due to the high contribution of the seminiferous epithelium and the intertubular compartment in this species, compared to the others of the same family, it is possible to infer that the species Oecomys bicolor has a promiscuous reproductive behaviour.

Intra-specific pelage color variation in a South American small rodent species / Variação intraespecífica da cor da pelagem de uma espécie de pequeno roedor sul-americano

Abstract Intra-specific color variation is often underestimated by researchers, and among mammals, intra-specific differences in coloration are poorly documented for most species. The main goal of this study was to apply an objective color measurement methodology to the study of a specific problem: the detection, if any, of patterns of changes in the fur color of specimens of Akodon budini in relation to biological (i.e., sex) and environmental (i.e., season) variables. We hypothesize that coat color will be more homogeneous in males than in females and that coat color will be darker in winter than in summer, the latter being orange. We measured the pelage color on five points over the dorsal surface of 26 A. budini museum specimens using a spectroradiometer and a diffuse illumination cabin. We used Principal Component Analysis to describe the association between the color variables, sex and season, and each of the observations. We then used general linear models of Analysis of Variance to examine relationships between color data, season, and sex. The results clearly confirm the hypothesis related to seasonal coat color change but do not directly confirm the hypothesis related to changes in coat color in relation to sex, and we show the complexity of the studied pattern. In conclusion, undoubtedly, the studied variables should accordingly be considered when studying the coloration of specimens for characterization, identification and discrimination of different taxonomic units based on color.

Resumo Variação de cor intra-específica é muitas vezes subestimada pelos pesquisadores, e entre espécies de mamíferos, as diferenças intra-específicas na coloração são pouco conhecidas para a maioria das espécies. O principal objetivo deste estudo foi aplicar uma metodologia objetiva de medição de cor para o estudo de um problema específico: a detecção de padrões de mudanças na cor da pele de espécimes de Akodon budini em relação a variáveis biológicas (i.e., sexo) e ambientais (i.e., temporada), se houver. Nossa hipótese é que a cor da pelagem do sexo masculino será mais homogênea do que a de fêmeas e que a cor da pelagem do inverno vai ser mais escura do que a de verão, sendo esta última mais laranja. Medimos a cor da pelagem em cinco pontos sobre a superfície dorsal de 26 espécimes de museu de A. budini usando um espectroradiômetro e uma cabine de iluminação difusa. Usamos Análise de Componentes Principais para descrever a associação entre as variáveis de cor, sexo e temporada, e cada uma das observações. Em seguida, usamos modelos lineares gerais da Análise de Variância para verificar as relações entre os dados de cor, temporada, e sexo. Os resultados confirmam claramente a hipótese relacionada à mudança sazonal de cor da pelagem, mas não confirmam diretamente a hipótese relacionada com alterações na cor da pelagem em relação ao sexo, e vamos mostrar a complexidade do modelo estudado. Em conclusão, sem dúvida, as variáveis estudadas devem consequentemente ser tidas em conta quando se estuda a coloração de amostras para caracterização, identificação e discriminação de diferentes unidades taxonômicas com base na cor.

Study of the social hierarchy and territoriality of Calomys callosus Rengger, 1830 (Rodentia: Cricetidae)

The genus Calomys comprises a lot of species distributed throughout South America. The species C. callosus Rengger, 1830 occur in Brazil, been often used in laboratory experiments. This work involved a study of aggressive behavior and dominance, which are aspects related to hierarchy and territoriality, among C. callosus males kept in a laboratory. The establishment of a hierarchy was observed, with the dominant animals controlling the space, food and water, while the remaining animals were confined to a restricted space. The intensity of aggression and variations in the number of attacks declined over time as a result of the formation of the hierarchy. No wounds were observed, probably due to the ritualistic nature of the attacks.

O genêro Calomys inclui várias espécies encontradas na América do Sul. A espécie C. callosus Rengger, 1830 ocorre no Brasil, sendo freqüentemente utilizada em experimentos de laboratório. Neste trabalho foram estudados, em machos mantidos em laboratório, o comportamento agressivo e a dominância, aspectos relacionados à hierarquia e territorialidade. Foi observado o estabelecimento de hierarquia, com os animais dominantes controlando o espaço, o alimento e a água, ficando os demais confinados em um espaço restrito. A intensidade das agressões e as variações no número de ataques diminuiram com o tempo, uma conseqüência da formação de hierarquia. Não foram observados ferimentos, devido provavelmente à ritualização dos ataques.

Hemodinâmica glomerular renal no roedor Calomys callosus / Kidney glomerular hemodynamics in the rodent Calomys callosus

A funçäo renal do roedor Calomys callosus, envolvido no ciclo de transmissäo de diversos agentes patogênicos para o homem foi avaliada no animal intacto, através da técnica de depuraçäo e micropunçäo renal. Os resultados mostraram que este roedor apresenta níveis pressóricos, hematócrito e proteínas plasmáticas semelhantes aos dos ratos submetidos ao mesmo procedimento experimental. Os pesos corporal e renal, bem como a filtraçäo glomerular global e por nefro assemelham-se aops do camundngo. Surpreendentemente estes roedores apresentaram significante número de glomérulos superficiais por rim, permitindo a avaliaçäo da hemodinâmica glomerular. Apesar da pressäo arterial semelhante à dos ratos Munich-Wistar (MW), a pressäo hidr[aulica intraglomerular no Calomys callosus foi interiro. Esyta reduçäo foi conseqüente à menor risistência pós-glomerular quando comparada à dos ratos MW. O fluxo plasmático glomerular atingiu valor bastante elevado em relaçäo à filtraçäo glomerular por nefro, fato que näo só compensaria a reduzida pressäo intraglomerular, como também seria suficiente para elevar a filtraçäo (por g/rim) a níveis superiores neste roedor, pois o coeficiente de ultrafiltraçäo glomerular (Kf) foi semelhante ao do rato MW. O presente trabalho sugere que apesar das dificuldades técnicas que este animal impöe devido ao seu reduzido tamanho, o estudo da funçäo renal global bem como da hemodinâmica glomerular é factível, podendo portanto ser utilizado como modelo para estudo da funçäo...