Alcohol use disorders are chronic debilitating diseases characterized by severe withdrawal symptoms that contribute to morbidity and relapse. GABA receptor (GABAR) adaptations have long been implicated in the chronic effects of alcohol and contribute to many withdrawal symptoms associated with alcohol dependence. In rodents, GABAR hypofunction results from decreases in Gabra1 expression, although the underlying mechanism controlling Gabra1 expression after chronic ethanol exposure is still unknown. We found that chronic ethanol exposure using either ethanol gavage or two-bottle choice voluntary access paradigms decreased Gabra1 expression and increased Hdac2 and Hdac3 expression. Administration of the HDAC inhibitor trichostatin A (TSA) after chronic ethanol exposure prevents the decrease in Gabra1 expression and function as well as the increase in Hdac2 and Hdac3 expression in both the cortex and the medial prefrontal cortex (mPFC). Chronic ethanol exposure and withdrawal, but not acute ethanol exposure or acute withdrawal, cause a selective upregulation of HDAC2 and HDAC3 associated with the Gabra1 promoter that accompanies a decrease in H3 acetylation of the Gabra1 promoter and the reduction in GABAR α1 subunit expression. TSA administration prevented each of these molecular events as well as behavioral manifestations of ethanol dependence, including tolerance to zolpidem-induced loss of righting reflex, reduced open-arm time in the elevated plus maze, reduced center-time and locomotor activity in the open-field assay, and TSA reduced voluntary ethanol consumption. The results show how chronic ethanol exposure regulates the highly prominent GABAR α1 subunit by an epigenetic mechanism that represents a potential treatment modality for alcohol dependence.

Maternal smoking during pregnancy is associated with enduring psychopathology, such as increased likelihood of substance use, in offspring. Various animal models demonstrate that continuous nicotine exposure produces teratogenic effects in offspring, as well. In the present experiment, a novel intravenous (IV) exposure model was utilized to determine if gestational nicotine (GN) treatment produced alterations in methamphetamine-induced sensitization and the expression of brain derived neurotrophic factor (BDNF) in the mesocorticolimbic dopamine system of adolescent offspring. Dams were injected with IV saline or nicotine (0.05 mg/kg/injection) 3x/day on gestational days 8–21. Habituation was measured on postnatal day (PND) 25–27 and baseline activity on PND 28. On PND 29–35, offspring were injected with saline or methamphetamine (0.3 mg/kg) and locomotor activity was measured after the first and seventh injections. On PND 36, brains were removed, flash frozen, and BDNF protein levels in the nucleus accumbens (NAcc), dorsal striatum (Str), frontal cortex (FC), and hippocampus (Hipp) were analyzed. GN did not affect habituation or the induction of methamphetamine-induced sensitization. Interestingly, GN, but not adolescent methamphetamine treatment, elevated levels of BDNF in the NAcc and Str; however, the GN-induced increase in BDNF in the FC was attenuated by adolescent methamphetamine treatment. Both GN and adolescent methamphetamine treatment increased BDNF in the Hipp. These findings indicate that GN exposure will result in increased levels of BDNF protein throughout the mesocorticolimbic dopamine system during adolescent development, and suggests that methamphetamine abuse will modulate the expression of BDNF in motivational circuitries of adolescent offspring exposed to GN.

BACKGROUND: The prefrontal cortex (PFC) acts as an integrative hub for the processing of cortical and sub-cortical input into meaningful efferent signaling, permitting complex associative behaviors. PFC dysfunction is consistently observed with ethanol dependence and is a core component of the pathology of alcohol use disorders in current models of addiction. While intracortical GABAergic neurotransmission is understood to be essential for maintaining coordinated network activity within the cortex, relatively little is known regarding functional GABAergic adaptations in PFC during ethanol dependence. METHODS: In the present study, male and female (>PN60) Sprague-Dawley rats were administered ethanol (5.0 g/kg; intragastric gavage) for 14-15 consecutive days. 24 hours after the final administration, animals were sacrificed and brains extracted for electrophysiological recordings of isolated GABA A receptor-mediated currents or analysis of GABA A receptor subunit protein expression in deep layer prefrontal cortical neurons. RESULTS: Chronic ethanol exposure significantly attenuated activity-dependent spontaneous GABA A receptor-mediated inhibitory post-synaptic current (IPSC) frequency with no effect on amplitude. Furthermore, analysis of IPSC decay kinetics revealed a significant enhancement of IPSC decay time that was associated with decrements in expression of the α1 GABA A receptor subunit, indicative of further impaired phasic inhibition. These phenomena occurred irrespective of neuron projection destination and sex. Based on previous observations by our laboratory of an epigenetic mechanism for ethanol-induced changes in cortical GABA A receptor subunit

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The granule cell layer of the cerebellum functions in spatio-temporal encoding of information. Granule cells (GCs) are tonically inhibited by spillover of GABA released from Golgi cells and this tonic inhibition is facilitated by acute ethanol. Recently, it was demonstrated that a specialized Ca2+-activated anion-channel, bestrophin1 (Best1), found on glial cells, can release GABA that contributes up to 50–75% of the tonic GABAergic current. However, it is unknown if ethanol has any actions on Best1 function. Using whole-cell electrophysiology, we found that recombinant Best1 channels expressed in HEK-293 cells were insensitive to 40 and 80 mM ethanol. We attempted to measure the Best1-mediated component of the tonic current in slices using 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). We confirmed that this agent blocks recombinant Best1 channels. Unexpectedly, we found that NPPB significantly potentiated the tonic current and the area and decay of GABAA-mediated spontaneous inhibitory post-synaptic currents (IPSCs) in GCs in rodent slices under two different recording conditions. To better isolate the Best1-dependent tonic current component, we blocked the Golgi cell component of the tonic current with tetrodotoxin and found that NPPB similarly and significantly potentiated the tonic current amplitude and decay time of miniature IPSCs. Two other Cl−-channel blockers were also tested: 4′-diisothiocyanatostilbene-2,2′-disulfonic acid disodium salt hydrate (DIDS) showed no effect on GABAergic transmission, while niflumic acid (NFA) significantly suppressed the tonic current noise, as well as the mIPSC frequency, amplitude, and area. These data suggest that acute ethanol exposure does not modulate Best1 channels and these findings serve to challenge recent data indicating that these channels participate in the generation of tonic GABAergic currents in cerebellar GCs.