Stress constitutes a risk factor for psychiatric disorders. Females are more susceptible to stress-related disorders, including depression, than males. Although dopamine (DA) system downregulation is implicated in the pathophysiology of depression, little is known about the female DA system at baseline, post-stress and during life transitions involving increased susceptibility to depression (i.e. postpartum period).
To this end, I performed extracellular recordings in DA neurons within the ventral tegmental area (VTA) of female rats under a variety of conditions. First, I compared three parameters of VTA activity, the number of spontaneously active DA cells per electrode track (i.e. population activity), firing rate, and firing pattern in naive male and female rats. Naive male and female rats were comparable in all measures at baseline. However, following exposure to an acute uncontrollable stressor (i.e. forced swim) as well as chronic mild stress (i.e., CMS- a rodent model of stress-induced adaptations relevant to depression), females exhibited greater stress effects on VTA population activity (i.e. reduced number of active DA cells).
Given these data suggesting enhanced stress-induced DA downregulation in females, VTA activity was assessed during the postpartum, as it is a time of: i) HPA-axis dysregulation, ii) elevated risk for developing depression and iii) there is little data regarding the dopaminergic adaptations shortly after giving birth and during the postpartum. Compared to virgins, early postpartum females (1-3 days postpartum) exhibited social anhedonia and increased immobility in the forced swim test, which was associated with a dramatic attenuation of VTA population activity similar to that observed in CMS-exposed females. None of these changes were observed when comparing virgins and late postpartum females, suggesting that these normative changes are transient. Finally, postpartum changes in maternal affect and VTA activity are modulated (i.e. can be prolonged) by pup removal and/or postpartum stress exposure (i.e. environmental resource depletion).
Millie Rincón-Cortés, PhD, is a postdoctoral research associate in the laboratory of Dr. Anthony Grace at the University of Pittsburg currently working on normative and stress-induced changes in affect-related behavior and dopamine activity during the postpartum period in rodents. Here, she has been funded through a T32 and a Ruth L. Kirschstein National Research Service Award (NRSA) Individual Postdoctoral Fellowship from the National Institute of Mental Health (NIMH) to study stress-induced dopamine downregulation in animal models relevant for psychiatric disorders and how these effects may differ between the sexes. Prior to this, she received her B.S. in Biology from the University of Puerto Rico-Mayaguez (2009) before completing a PhD in Neuroscience and Physiology at the NYU Medical Center’s Sacker Institute for Graduate Biomedical Sciences (2015). Her dissertation work was conducted under the supervision of Dr. Regina Sullivan and funded by a National Science Foundation Graduate Research Fellowship. Here, Dr. Rincón-Cortés employed a combination of behavioral, pharmacological, and anatomical techniques to study how traumatic infant experiences within the context of the caregiver program affective behaviors and brain areas implicated in both depression and addiction during later life. Dr. Rincón-Cortés was awarded the Sackler Dissertation Prize by the NYU School of Medicine and the Dissertation Award by the International Society for Developmental Psychobiology (ISDP) for this work.
No need to book, just turn up!