Prenatal ethanol exposure causes a variety of cognitive deficits that have a persistent impact on quality of life, some of which may be explained by ethanol-induced alterations in interneuron function. Studies from several laboratories, including our own, have demonstrated that a single binge-like ethanol exposure during the third-trimester equivalent of human pregnancy leads to acute apoptosis and long-term loss of interneurons in the rodent retrosplenial cortex (RSC). The RSC is interconnected with the hippocampus, thalamus, and other neocortical regions and plays distinct roles in visuospatial processing and storage and retrieval of hippocampal-dependent episodic memories. Here we used slice electrophysiology to characterize the acute effects of ethanol on GABAergic neurotransmission in neonates, as well as the long-term effects of neonatal ethanol exposure on parvalbumin-interneuron mediated neurotransmission in adolescent mice. Mice were exposed to ethanol using vapor inhalation chambers. In postnatal day (P) 7 mouse pups, ethanol unexpectedly failed to potentiate GABA A receptor-mediated synaptic transmission. Binge-like ethanol exposure of P7 mice expressing channel rhodopsin in parvalbumin-positive interneurons enhanced the peak amplitudes, total charge, decays, and decreased rise-times of optically-evoked GABA A receptor-mediated inhibitory postsynaptic currents in adolescent animals. These effects could partially explain learning and memory deficits caused by developmental ethanol exposure.
Experiment 2
AnimalsMice expressing the channel rhodopsin-2 (ChR2) variant ChR2 H134R fused to tdTomato in PV-INs were generated by crossing female heterozygous B6.129P2-Pvalb tm1(cre)Arbr /J (B6 PV cre , Jackson Laboratory, Bar Harbor, ME; stock number 017320) and male heterozygous B6.Cg-Gt(ROSA)26Sor tm27.1(CAG-COP4*H134R/tdTomato)Hze /J (Ai27D, Jackson Laboratory; stock number 012567) mice. After weaning, the offspring (hereafter referred to as B6 PV cre -Ai27D mice) were ear-tagged and tail snips were collected under isoflurane anesthesia. Genotyping was performed by Transnetyx (Cordova, TN). Male and female mice aged between P40 and P60 were used for all subsequent experiments ( Figure 1b).
Ethanol vapor chamber exposurePups and dams were exposed to either air or vaporized ethanol (95%, Koptec, King of Prussia, PA) for 4 h (approximately 10 a.m. to 2 p.m.) at P7 in custom-built ethanol vapor chambers 25 . Ethanol vapor concentrations were determined using a breathalyzer (Intoximeters, St. Louis, MO) and were between 8-9 g/dl. This exposure paradigm produces peak BECs in pups near 80 mM and triggers apoptotic neurodegeneration in several brain regions, including the RSC 13,18 . Immunohistochemistry 1 0