Effect of chronic ethanol treatment on hippocampal CA3 neurons

Bursting is an important property of certain mammalian neurons, related to long-term potentiation and oscillatory interactions in small networks. Abnormalities in bursting may underlie neurological and psychiatric disorders. Chronic ethanol exposure increases the number of calcium channels in several animal tissues (Dolin et al 1987) including rat hippocampus (Docherty & Brown 1986). Since calcium channels are intimately related to inherent bursting in neurons, chronic ethanol exposure may affect this behavior. Such a change would have implications for theories of reinforcement and learning in persons with alcohol use disorders (Charness 1992). The objective of this study was to decide whether ethanol-related increases in calcium channels affect bursting in CA3 hippocampal neurons. A neural model of the mammalian CA3 hippocampal neuron was previously developed. Chronic ethanol exposure increases calcium conductances by 50 to 100 percent, and calcium conductances in the model were increased by 50 percent throughout the neuron to simulate this effect. Changes in calcium conductance profoundly affected the neuronʹs behavior. Action potentials related to calcium conductances were prolonged and had greater amplitudes. Bursting was prolonged. These results show that changes in calcium conductances induced by chronic ethanol exposure have important effects on the behavior of the CA3 hippocampal neuron. These findings have implications for the role of the hippocampus in epileptogenesis. The inherent rhythmicity of the neuron is disrupted as well, a change that may affect the behavior of both the small and larger networks comprising the hippocampus. Disruption of these networks may have implications for other neuropsychiatric phenomena, including learning, memory, and the regulation of level of consciousness.