Biological Sex Differences in the Monodelphis Domestica: Investigating Behavioral Responses in Environmental Enrichment and Conditioned Place Preference Paradigms

The Monodelphis domestica, commonly known as the grey short-tailed opossum, has become an increasingly frequented animal model for areas of psychological study, including comparative psychology. Despite the growing interest in utilizing the Monodelphis as an animal model, several areas of research remain limited in what has been studied. This includes associative learning and the effects of environmental enrichment on the Monodelphis. This study novelly incorporates the two using environmental enrichment with the conditioned place preference (CPP) paradigm to both diversify associative learning literature and expand existing knowledge on the Monodelphis domestica. The CPP paradigm included interactive objects as environmental enrichment to investigate biological sex differences in Monodelphis behavioral responses

Sex differences in stress reactivity and responses to novelty in the gray short-tailed opossum (Monodelphis domestica)

Introduction: Investigating how exposures to stress and novel environments influence behavior is important for translational research that aims to improve mental health. Previous studies have focused on reactions to novelty and revealed changes in defense reactions and exploratory behavior. (Pisula et al., 2012). Objective: The focus of the present study is to investigate sex differences in behavioral responses to novel environments and restraint stress in the gray short-tailed opossums (Monodelphis domestica). Using the Monodelphis is innovative because it is a non-traditional animal model that is ideal for developmental research. Methods: Using AnyMaze video tracking software, animals’ behaviors (6 males, 6 females) in the restraint stress task (3 min) and open field task (10 min) were recorded. AnyMaze and JWatcher were used to quantify movements, both locomotor and non-locomotor, and finally the data collected analyzed using SPSS. Restraint was used to inflict stress in the subjects, and the reactions were movements in paw, tail, and head. Reactions to a novel environment were assessed via exploratory and locomotor behaviors in an open field. Results: The results of a t-test revealed that the movement of the head was significantly different between sexes when considering p\u3c0.05 cutoff, with the female showing higher reactivity than their male counterparts (t(10)= 2.278, p\u3c 0.05). There were no sex differences in the other behaviors. To further compare the results, an open field paradigm was used, where subjects were introduced to a new environment and their reactions were reviewed. Our preliminary observations indicate that males were more prone to vast exploration of the new environment and at a faster pace, while females exhibit slower movements and limited exploration, mainly focusing in the areas closer to the walls. Discussion: We are currently conducting additional experiments with more subjects to determine if the behavior exhibited by females are a consequence of them feeling stressed by the novelty of the environment. If the results favor our hypothesis, then we could conclude that females are more susceptible to experiencing stress. To further analyze the data collected from both experiments, we are taking into consideration the age of the subjects, as considering this variable can help understand their behavior and stress reactivity at different stages of life. Conclusions: Clinical and epidemiological research have identified major gender/sex differences in neuropsychiatric disorders, and stress is a major contributor to mental health problems. Our results support the hypothesis that sex differences in stress reactivity and responses to novelty are present in Monodelphis, suggesting that sex differences have a biological component and that animal models can be used to study mechanisms that underlie sex differences in stress responses

The impact of biological sex on motor function and responses to novel environments in the gray short-tailed opossum (Monodelphis domestica)

Background: Understanding the different stress reactions in different environments can help us understand stress factors. Studying animal behavior is important for translational research for mental health improvement. Previous literature has shown that stress is a risk factor for higher cancer incidence and poorer cancer survival. (Klejbor & Turlejski., 2012), as well as mental health outcomes. Understanding of how stress is related to cancer can help improve therapeutic outcomes as preventive measures (Glaser et al., 1987). Methods: Using the Rota Rod apparatus, 12 animals (3 males, 9 females) were tested at 36 rpm for a maximum of 400 seconds (Madroñal et al., 2010). Open field apparatus was used to test 8 animals (4males, 4 females), their locomotor and non-locomotor behaviors were recorded using AnyMaze. Data collected from both experiments were analyzed with SPSS software. Results: The preliminary results showed sex differences, female’s average number of revolutions (44.54) was higher than their male counterparts (26.15). Results from the open field showed females exhibit less immobile episodes (f(1)=6.000. p Conclusions: Previous literature has shown stress is a risk factor and a major contributor to mental and physical health problems. Preliminary results support the hypothesis that there is a biological component in stress reactivity to novel environments in the Monodelphis, and that animal models are a good alternative to study sex differences in stress responses and motor function. Further research is needed to test housing effects in the short-tailed opossums