Long-term effects of low prenatal alcohol exposure on GABAergic interneurons of the murine posterior parietal cortex.

BACKGROUND: Fetal alcohol spectrum disorders (FASDs) are characterized by a wide range of physical, cognitive, and behavioral impairments that occur throughout the lifespan. Prenatal alcohol exposure (PAE) can lead to adult impairments in cognitive control behaviors mediated by the posterior parietal cortex (PPC). The PPC plays a fundamental role in the performance of response tasks in both primates and rodents, specifically when choices between similar target and nontarget stimuli are required. Furthermore, the PPC is reciprocally connected with other cortical areas. Despite the extensive literature investigating the molecular mechanisms underlying PAE impairments in cognitive functions mediated by cortical areas, little is known regarding the long-term effects of PAE on PPC development and function. Here, we examined changes in the cellular organization of GABAergic interneurons and their function in PPC using behaviorally naïve control and PAE mice.

METHODS: We used a limited access model of PAE in which C57BL/6J females were exposed to a solution of 10% (w/v) ethanol and 0.066% (w/V) saccharin for 4 h/day throughout gestation. Using high-throughput fluorescent microscopy, we quantified the levels of GABAergic interneurons in the PPC of adult PAE and control offspring. In a separate cohort, we recorded spontaneous inhibitory postsynaptic currents (sIPSCs) using whole-cell patch clamp recordings from PPC layer 5 pyramidal neurons.

RESULTS: PAE led to a significant overall reduction of parvalbumin-expressing GABAergic interneurons in PAE mice regardless of sex. Somatostatin- and calretinin-expressing GABAergic interneurons were not affected. Interestingly, PAE did not modulate sIPSC amplitude or frequency.

CONCLUSIONS: These results suggest that impairments in cognitive control observed in FASD may be due to the significant reduction of parvalbumin-expressing GABAergic interneurons in the PPC. PAE animals may show compensatory changes in GABAergic function following developmental reduction of these interneurons.