The Effect of Adolescent Alcohol on Dopaminergic and Gabaergic Neurotransmission in the Adult Prefrontal Cortex

The prefrontal cortex (PFC) is thought to play an important role in cognitive processes that are negatively impacted by alcohol exposure. Compared to other brain regions, the neuronal connections of the PFC undergo a critical period of reorganization and refinement during adolescence that coincides with improvements in cognitive control and decision-making. Environmental insults that occur during this period may be particularly damaging to the PFC, resulting in aberrant neurodevelopment along with long-lasting effects on cognitive functioning that negatively impacts decision-making and behavioral control. Experimentation with alcohol typically begins during adolescence when it is often consumed in excessive binge-like episodes resulting in high levels of intoxication followed by a short period of abstinence. This dissertation addresses the hypothesis that binge-like adolescent alcohol (AIE) exposure alters the development of neurotransmitter systems in the prelimbic PFC (PrL-C) and as a result, PFC-dependent cognitive functions are compromised in adulthood. First, the effect of adolescent alcohol abuse on dopaminergic neurotransmission in the adult PrL-C was examined. AIE compromised adult protein expression of the dopamine-related enzymes tyrosine hydroxylase and catechol-O-methyl transferase. Electrophysiology studies revealed a loss of D1 receptor modulation of pyramidal neuron evoked firing in adult layer V PrL-C. The next part of this dissertation focuses on the effect of AIE on development of the PrL-C GABA system. AIE produced marked reductions in GABAA receptor-mediated tonic currents in pyramidal neurons in layer V PrL-C. This effect appears to be largely mediated by developmental alterations specifically in GABAA receptors containing the δ-subunit. The dissertation concludes by assessing the effect of AIE on risky decision-making in adulthood. Furthermore, given the role of GABA in decision-making, exploratory studies sought to enhance tonic GABA currents using the novel δ-GABAA receptor positive allosteric modulator AA29504 and testing the effect of the drug on risk/reward decision-making. The results suggest that AIE did not alter risk/reward decision-making in adulthood. Moreover, AA29504 administration did not alter decision-making on the probabilistic discounting task. Taken together, this dissertation reveals that AIE exposure results in persistent deficits in both dopaminergic and GABAergic neurotransmission in the adult PrL-C that may contribute to deficits in PFC-dependent behavioral control in adulthood

Binge-Like Alcohol Exposure During Adolescence Disrupts Dopaminergic Neurotransmission in the Adult Prelimbic Cortex

Repeated binge-like exposure to alcohol during adolescence has been reported to perturb prefrontal cortical development, yet the mechanisms underlying these effects are unknown. Here we report that adolescent intermittent ethanol exposure induces cellular and dopaminergic abnormalities in the adult prelimbic cortex (PrL-C). Exposing rats to alcohol during early-mid adolescence (PD28–42) increased the density of long/thin dendritic spines of layer 5 pyramidal neurons in the adult PrL-C. Interestingly, although AIE exposure did not alter the expression of glutamatergic proteins in the adult PrL-C, there was a pronounced reduction in dopamine (DA) D1 receptor modulation of both intrinsic firing and evoked NMDA currents in pyramidal cells, whereas D2 receptor function was unaltered. Recordings from fast-spiking interneurons also revealed that AIE reduced intrinsic excitability, glutamatergic signaling, and D1 receptor modulation of these cells. Analysis of PrL-C tissue of AIE-exposed rats further revealed persistent changes in the expression of DA-related proteins, including reductions in the expression of tyrosine hydroxylase and catechol-O-methyltransferase (COMT). AIE exposure was associated with hypermethylation of the COMT promoter at a conserved CpG site in exon II. Taken together, these findings demonstrate that AIE exposure disrupts DA and GABAergic transmission in the adult medial prefrontal cortex (mPFC). As DA and GABA work in concert to shape and synchronize neuronal ensembles in the PFC, these alterations could contribute to deficits in behavioral control and decision-making in adults who abused alcohol during adolescence

PiRATeMC: A highly flexible, scalable, and low-cost system for obtaining high quality video recordings for behavioral neuroscience

With the rapidly accelerating adoption of machine-learning based rodent behavioral tracking tools, there is an unmet need for a method of acquiring high quality video data that is scalable, flexible, and relatively low-cost. Many experimenters use webcams, GoPros, or other commercially available cameras that can be expensive, offer minimal flexibility of recording parameters, and not optimized for recording rodent behavior, leading to suboptimal and inconsistent video quality. Furthermore, commercially available products are not conducive for synchronizing multiple cameras, or interfacing with third-party equipment to allow time-locking of video to other equipment such as microcontrollers for closed-loop experiments. We present a low-cost, customizable ecosystem of behavioral recording equipment, PiRATeMC (Pi-based Remote Acquisition Technology for Motion Capture) based on Raspberry Pi Camera Boards with the ability to acquire high quality recordings in bright/low light, or dark conditions under infrared light. PiRATeMC offers users control over nearly every recording parameter, and can be fine-tuned to produce optimal videos in any behavioral apparatus. This setup can be scaled up for synchronous control of any number of cameras via a self-contained network without burdening institutional network infrastructure. The Raspberry Pi is an excellent platform with a large online community designed for novice and inexperienced programmers interested in using an open-source recording system. Importantly, PiRATeMC supports TTL and serial communication, allowing for synchronization and interfacing of video recording with behavioral or other third-party equipment. In sum, PiRATeMC minimizes the cost-prohibitive nature of conducting and analyzing high quality behavioral neuroscience studies, thereby increasing accessibility to behavioral neuroscience

Delineation of an insula-BNST circuit engaged by struggling behavior that regulates avoidance in mice

Active responses to stressors involve motor planning, execution, and feedback. The authors identify a neuronal projection from the insular cortex to the bed nucleus of the stria terminalis that is activated during motor struggling in response to restraint stress as a potential active coping response

Dorsal BNST α 2A -Adrenergic Receptors Produce HCN-Dependent Excitatory Actions That Initiate Anxiogenic Behaviors

Stress is a precipitating agent in neuropsychiatric disease and initiates relapse to drug-seeking behavior in addicted patients. Targeting the stress system in protracted abstinence from drugs of abuse with anxiolytics may be an effective treatment modality for substance use disorders. α2A-adrenergic receptors (α2A-ARs) in extended amygdala structures play key roles in dampening stress responses. Contrary to early thinking, α2A-ARs are expressed at non-noradrenergic sites in the brain. These non-noradrenergic α2A-ARs play important roles in stress responses, but their cellular mechanisms of action are unclear. In humans, the α2A-AR agonist guanfacine reduces overall craving and uncouples craving from stress, yet minimally affects relapse, potentially due to competing actions in the brain. Here, we show that heteroceptor α2A-ARs postsynaptically enhance dorsal bed nucleus of the stria terminalis (dBNST) neuronal activity in mice of both sexes. This effect is mediated by hyperpolarization-activated cyclic nucleotide-gated cation channels because inhibition of these channels is necessary and sufficient for excitatory actions. Finally, this excitatory action is mimicked by clozapine-N-oxide activation of the Gi-coupled DREADD hM4Di in dBNST neurons and its activation elicits anxiety-like behavior in the elevated plus maze. Together, these data provide a framework for elucidating cell-specific actions of GPCR signaling and provide a potential mechanism whereby competing anxiogenic and anxiolytic actions of guanfacine may affect its clinical utility in the treatment of addiction