Lauren Lederle

Genetic Strain Differences in Learned Fear Inhibition Associated with Variation in Neuroendocrine, Autonomic, and Amygdala Dendritic Phenotypes

Mood and anxiety disorders develop in some but not all individuals following exposure to stress and psychological trauma. However, the factors underlying individual differences in risk and resilience for these disorders, including genetic variation, remain to be determined. Isogenic inbred mouse strains provide a valuable approach to elucidating these factors. Here, we performed a comprehensive examination of the extinction-impaired 129S1/SvImJ (S1) inbred mouse strain for multiple behavioral, autonomic, neuroendocrine, and corticolimbic neuronal morphology phenotypes. We found that S1 exhibited fear overgeneralization to ambiguous contexts and cues, impaired context extinction and impaired safety learning, relative to the (good-extinguishing) C57BL/6J (B6) strain. Fear overgeneralization and impaired extinction was rescued by treatment with the front-line anxiety medication fluoxetine. Telemetric measurement of electrocardiogram signals demonstrated autonomic disturbances in S1 including poor recovery of fear-induced suppression of heart rate variability. S1 with a history of chronic restraint stress displayed an attenuated corticosterone (CORT) response to a novel, swim stressor. Conversely, previously stress-naive S1 showed exaggerated CORT responses to acute restraint stress or extinction training, insensitivity to dexamethasone challenge, and reduced hippocampal CA3 glucocorticoid receptor mRNA, suggesting downregulation of negative feedback control of the hypothalamic–pituitary–adrenal axis. Analysis of neuronal morphology in key neural nodes within the fear and extinction circuit revealed enlarged dendritic arbors in basolateral amygdala neurons in S1, but normal infralimbic cortex and prelimbic cortex dendritic arborization. Collectively, these data provide convergent support for the utility of the S1 strain as a tractable model for elucidating the neural, molecular and genetic basis of persistent, excessive fear.

Reward-Related Behavioral Paradigms for Addiction Research in the Mouse: Performance of Common Inbred Strains

The mouse has emerged as a uniquely valuable species for studying the molecular and genetic basis of complex behaviors and modeling neuropsychiatric disease states. While valid and reliable preclinical assays for reward-related behaviors are critical to understanding addiction-related processes, and various behavioral procedures have been developed and characterized in rats and primates, there have been relatively few studies using operant-based addiction-relevant behavioral paradigms in the mouse. Here we describe the performance of the C57BL/6J inbred mouse strain on three major reward-related paradigms, and replicate the same procedures in two other commonly used inbred strains (DBA/2J, BALB/cJ). We examined Pavlovian-instrumental transfer (PIT) by measuring the ability of an auditory cue associated with food reward to promote an instrumental (lever press) response. In a separate experiment, we assessed the acquisition and extinction of a simple stimulus-reward instrumental behavior on a touch screen based task. Reinstatement of this behavior was then examined following either continuous exposure to cues (conditioned reinforcers, CRs) associated with reward, brief reward and CR exposure, or brief reward exposure followed by continuous CR exposure. The third paradigm examined sensitivity of an instrumental (lever press) response to devaluation of food reward (a probe for outcome insensitive, habitual behavior) by repeated pairing with malaise. Results showed that C57BL/6J mice displayed robust PIT, as well as clear extinction and reinstatement, but were insensitive to reinforcer devaluation. DBA/2J mice showed good PIT and (rewarded) reinstatement, but were slow to extinguish and did not show reinforcer devaluation or significant CR-reinstatement. BALB/cJ mice also displayed good PIT, extinction and reinstatement, and retained instrumental responding following devaluation, but, unlike the other strains, demonstrated reduced Pavlovian approach behavior (food magazine head entries). Overall, these assays provide robust paradigms for future studies using the mouse to elucidate the neural, molecular and genetic factors underpinning reward-related behaviors relevant to addiction research.

Obesity as a Risk Factor for Complications After Second-Trimester Abortion by Dilation and Evacuation.

OBJECTIVE: To evaluate the association between obesity (body mass index [BMI] 30 or higher) and dilation and evacuation (D&E) complications. METHODS: We conducted a retrospective cohort study of women who underwent D&E abortion from February 2009 to April 2013 at a hospital-based abortion practice in California. We evaluated the association between obesity and risk of complication after D&E using logistic regression. We defined complications a priori as cervical laceration, hemorrhage, uterine atony, anesthesia complications, uterine perforation, disseminated intravascular coagulation, and retained products of conception. We defined major complications as those requiring hospitalization, transfusion, or further surgical intervention. RESULTS: Complications occurred in 442 of 4,520 D&Es (9.8%), with equal proportions in obese and nonobese women (9.8%). Major complications occurred in 78 (1.7%) patients. After adjustment for age, ethnicity, prior vaginal delivery, prior cesarean delivery, and gestational duration, there was no association between BMI and D&E complications. Any individual complication was associated with each additional week of gestation (odds ratio [OR] 1.3, 95% confidence interval [CI] 1.3–1.4), prior vaginal delivery (OR 1.5, 95% CI 1.2–1.9) and prior cesarean delivery (OR 1.8, 95% CI 1.4–2.3). Major complications were associated with each additional week of gestation (OR 1.3, 95% CI 1.1–1.4) and cesarean delivery (OR 1.8, 95% CI 1.1–3.1). CONCLUSION: We found no association between obesity and D&E complications. Our findings are consistent with previous studies demonstrating that later gestational duration is associated with an increased risk of complications. Obesity may not warrant referral to a high-risk abortion center, particularly because referral-associated delay might increase the risk of complications. LEVEL OF EVIDENCE: II

Identification of a novel gene regulating amygdala-mediated fear extinction

Recent years have seen advances in our understanding of the neural circuits associated with trauma-related disorders, and the development of relevant assays for these behaviors in rodents. Although inherited factors are known to influence individual differences in risk for these disorders, it has been difficult to identify specific genes that moderate circuit functions to affect trauma-related behaviors. Here, we exploited robust inbred mouse strain differences in Pavlovian fear extinction to uncover quantitative trait loci (QTL) associated with this trait. We found these strain differences to be resistant to developmental cross-fostering and associated with anatomical variation in basolateral amygdala (BLA) perineuronal nets, which are developmentally implicated in extinction. Next, by profiling extinction-driven BLA expression of QTL-linked genes, we nominated Ppid (peptidylprolyl isomerase D, a member of the tetratricopeptide repeat (TPR) protein family) as an extinction-related candidate gene. We then showed that Ppid was enriched in excitatory and inhibitory BLA neuronal populations, but at lower levels in the extinction-impaired mouse strain. Using a virus-based approach to directly regulate Ppid function, we demonstrated that downregulating BLA-Ppid impaired extinction, while upregulating BLA-Ppid facilitated extinction and altered in vivo neuronal extinction encoding. Next, we showed that Ppid colocalized with the glucocorticoid receptor (GR) in BLA neurons and found that the extinction-facilitating effects of Ppid upregulation were blocked by a GR antagonist. Collectively, our results identify Ppid as a novel gene involved in regulating extinction via functional actions in the BLA, with possible implications for understanding genetic and pathophysiological mechanisms underlying risk for trauma-related disorders.