Playback of rat 22-kHz ultrasonic vocalizations as a translational assay of negative affective states: An analysis of evoked behavior and brain activity

Sex differences in offspring risk and resilience following 11β-hydroxylase antagonism in a rodent model of maternal immune activation

Maternal immune activation (MIA) puts offspring at greater risk for neurodevelopmental disorders associated with impaired social behavior. While it is known that immune signaling through maternal, placental, and fetal compartments contributes to these phenotypical changes, it is unknown to what extent the stress response to illness is involved and how it can be harnessed for potential interventions. To this end, on gestational day 15, pregnant rat dams were administered the bacterial mimetic lipopolysaccharide (LPS; to induce MIA) alongside metyrapone, a clinically available 11β-hydroxylase (11βHSD) inhibitor used to treat hypercortisolism in pregnant, lactating, and neonatal populations. Maternal, placental, and fetal brain levels of corticosterone and placental 11βHSD enzymes type 1 and 2 were measured 3-hrs post treatment. Offspring social behaviors were evaluated across critical phases of development. MIA was associated with increased maternal, placental, and fetal brain corticosterone concentrations that were diminished with metyrapone exposure. Metyrapone protected against reductions in placental 11βHSD2 in males only, suggesting that less corticosterone was inactivated in female placentas. Behaviorally, metyrapone-exposure attenuated MIA-induced social disruptions in juvenile, adolescent, and adult males, while females were unaffected or performed worse. Metyrapone-exposure reversed MIA-induced transcriptional changes in monoamine-, glutamate-, and GABA-related genes in adult male ventral hippocampus, but not in females. Taken together, these findings illustrate that MIA-induced HPA responses act alongside the immune system to produce behavioral deficits. As a clinically available drug, the sex-specific benefits and constraints of metyrapone should be investigated further as a potential means of reducing neurodevelopmental risks due to gestational MIA.

Decoding the language of fear: Unveiling objective and subjective indicators in rodent models through a systematic review and meta-analysis

While rodent models are vital for studying mental disorders, the underestimation of construct validity of fear indicators has led to limitations in translating to effective clinical treatments. Addressing this gap, we systematically reviewed 5054 articles from the 1960 s, understanding underlying theoretical advancement, and selected 68 articles with at least two fear indicators for a three-level meta-analysis. We hypothesized correlations between different indicators would elucidate similar functions, while magnitude differences could reveal distinct neural or behavioral mechanisms. Our findings reveal a shift towards using freezing behavior as the primary fear indicator in rodent models, and strong, moderate, and weak correlations between freezing and conditioned suppression ratios, 22-kHz ultrasonic vocalizations, and autonomic nervous system responses, respectively. Using freezing as a reference, moderator analysis shows treatment types and fear stages significantly influenced differences in magnitudes between two indicators. Our analysis supports a two-system model of fear in rodents, where objective and subjective fears could operate on a threshold-based mechanism.