Christina co-organized the 2020 Michigan Regional Postdoctoral Symposium. She also presented her research demonstrating important differences between two common laboratory species (rats and mice) in the choice seeking social interaction versus food, demonstrating that rats are more socially driven and mice are more food driven. These differences may help to reveal potentially distinct underlying brain mechanisms.
Christina Reppucci published a paper in the journal Physiology & Behavior entitled Wistar rats and C57BL/6 mice differ in their motivation to seek social interaction versus food in the Social versus Food Preference Test. Christina and co-authors Leigha Brown, Ashley Chambers and Alexa Veenema characterized the Social versus Food Preference Test, a behavioral paradigm designed to investigate the competition between the choice to seek social interaction and the choice to seek food. Social and feeding behaviors have in common that they are both highly motivated behaviors and are regulated by overlapping systems in the brain. This study assessed how this competition was modulated by internal cues (social isolation, food deprivation), external cues (familiar or novel social stimulus), sex (males, females), age (adolescents, adults), and rodent model (Wistar rats, C57BL/6 mice). Social over food preference scores were reduced by food deprivation and social familiarly (both anticipated) while social isolation did not have an effect. The degree of food deprivation-induced changes in stimulus investigation patterns were greater in adolescents compared to adults, which likely reflect their higher need for food. Adolescent Wistar rats spent more time investigating the social and food stimuli than adult Wistar rats, probably indicating their overall higher motivation. Strikingly, baseline stimulus preference and investigation times varied greatly between rodent models: Wistar rats were generally more social-preferring and C57BL/6 mice were generally more food-preferring. These results indicate that age and rodent model need to be taken into account when using the Social versus Food Preference Test for future studies investigating the peripheral and central systems that can coordinate the expression of stimulus preference related to multiple motivated behaviors. This publication is accompanied by a corresponding methods paper published in the journal MethodsX entitled The social versus food preference test: A behavioral paradigm for studying competing motivated behaviors in rodents.
Leigha Brown, Valerie Khaykin and Haley Velisek presented their research posters in virtual format at the MSU Undergraduate Research and Arts Forum. Check out the youtube presentation by Leigha and Valerie and the youtube presentation by Haley! Congrats to Leigha, Valerie, and Haley on a fantastic job as well as Christina and Katie for excellent mentoring.
Christina, Jessica, and Katie presented posters on their research at the International Behavior Neuroscience Society 2020 Online Poster Sessions.
We are very happy to re-open the lab and continue our research during the ongoing pandemic.
Congratulations to Jessica Lee for being awarded with a highly competitive 3-year NSF graduate research program fellowship! Well deserved! Jessica will study the role of the brain reward system in social play behavior by focusing on how projections from the nucleus accumbens to the ventral pallidum regulate social play in male and female juvenile rats.
Christina Reppucci published a paper in the International Journal of Play entitled Involvement of orexin/hypocretin in the expression of social play behaviour in juvenile rats. Christina and co-authors Cassandra Gergely, Remco Bredewold, and Alexa Veenema demonstrated that the orexin/hypocretin-synthesizing neurons in the brain are activated in response to social play in juvenile rats. Blocking orexin signaling in the brain increasing social play in low baseline social play individuals and decreasing social play in high baseline social play individuals. Furthermore, increasing orexin signaling decreased social play irrespective of baseline social play levels. The neuropeptide orexin/hypocretin is well known for its role in arousal, wakefulness, and appetite. Our results demonstrate a broader involvement of orexin/hypocretin including motivated social behaviors such as social play.
Brett DiBenedictis published a paper in the journal Psychoneuroendocrinology entitled Involvement of ventral pallidal vasopressin in the sex-specific regulation of sociosexual motivation in rats. Brett and co-authors Harry Cheung, Elizabeth Nussbaum, and Alexa Veenema demonstrated that the ventral pallidum, which is a brain region that is part of the mesocorticolimbic reward circuit, is involved in the regulation of sociosexual motivation through vasopressin V1A receptor signaling. Interestingly, this regulation occurs in a sex-specific way. In detail, compared to female rats, male rats have more vasopressin fibers in the ventral pallidum and a higher percentage of vasopressin cell bodies in the bed nucleus of the stria terminalis and medial amygdala that project to the ventral pallidum. Antagonizing vasopressin signaling in the ventral pallidum decreased males’ opposite sex preference, while enhancing females’ opposite sex preference. Thus, sociosexual motivation requires high vasopressin signaling in males but low vasopressin signaling in females. This is an important finding because it will help us understand the functional significance of sex differences in the brain (in this case in the vasopressin system) for the regulation of behavior. This, in turn, may have implications for sex-specific drug treatment aimed to restore social functioning in humans.