Impact of Acute Ethanol Injections on Medial Prefrontal Cortex Neural Activity

Abstract

The medial prefrontal cortex (mPFC) is a cortical brain region involved in the evaluation and selection of motivationally relevant outcomes. mPFC-mediated cognitive functions are impaired following acute alcohol exposure. In rodent models, ethanol (EtOH) doses as low as 0.75 g/kg yield deficits in cognitive functions. These deficits following acute EtOH are thought to be mediated, at least in part, by decreases in mPFC firing rates. However, these data have been generated exclusively in anesthetized rodents. To eliminate the potentially confounding role of anesthesia on EtOH modulated mPFC activity, the present study investigated the effects of acute EtOH injections on mPFC neural activity in awake-behaving rodents. We utilized three groups: the first group received 2 saline injections during the recording. The second group received a saline injection followed 30 minutes later by a 1.0 g/kg EtOH injection. The last group received a saline injection followed 30 minutes later by a 2.0 g/kg EtOH injection. One week following the awake-behaving recording, an anesthetized recording was performed using one dose of saline followed 30 minutes later by one dose of 1.0 g/kg EtOH in order to replicate previous studies. Firing rates were normalized to a baseline period that occurred 5 minutes prior to each injection. A 5-minute time period 30 minutes following the injection was used to compare across groups. There were no significant differences across the awake-behaving saline-saline group, indicating no major effect on mPFC neural activity as a result of repeated injections. There was a significant main effect across treatment & behavioral groups in the saline-EtOH 1.0 g/kg group with reductions in the EtOH & Sleep condition. In the saline-EtOH 2.0 g/kg, mPFC neural activity was only reduced in lowered states of vigilance. This suggests that EtOH only causes gross changes on neural activity when the animal is not active and behaving. Ultimately this means that EtOH’s impact on decision making is not due to gross changes in mPFC neural activity and future work should investigate its mechanism.