Time Dependent Effects Of Ethanol On Excitatory Junction Potentials In The Superficial Extensor Muscle Of The Crayfish Tail

Abstract

Ethanol (EtOH) is a general anesthetic agent as defined by its ability to abolish movement in response to a noxious stimulus. While the behavioral effects of EtOH are well documented, the underlying cellular mechanisms are less understood. Various models have been proposed to explain the observed behavioral effects of EtOH in particular excitatory and inhibitory neural pathways, but most are not generalizable. In order to further the understanding of EtOHs effects at the level of the neuron, we studied the short term effects of an intoxicating concentration of EtOH (434mM) in excitatory motor neurons of the tail neuromuscular junction (NMJ) in the crayfish. By stimulating the nerve which innervates the tail muscle, we recorded the excitatory junction potentials (EJP) of the crayfish muscle both during EtOH exposure and after the EtOH was removed. Although there were individual differences between the crayfish, we found that EtOH significantly reduced the amplitude of EJPs over time, and while there was significant recovery after washing, the amplitude remained significantly below control levels. Moreover, we found that the slope of the EJP was significantly increased during EtOH exposure. These results suggest that EtOH adversely affects the postsynaptic component of the NMJ, and that the time of EtOH exposure is important for predicting EtOHs long-term effects. Further investigation is necessary to uncover the particular mechanisms that allow these synaptic changes to occur.