Dopaminergic Modulation Of Excitatory Junction Potentials At The Crayfish Neuromuscular Junction

Abstract

Dopamine (DA), a neurotransmitter found throughout the body, has been found to have modulatory effects on synaptic transmission in both the peripheral and central nervous systems. Modulatory effects take place through dopamine receptor subtypes, which respond in a variety of different ways to the binding of dopamine. This study attempted to first identify the modulatory effects of dopamine at the neuromuscular junction (NMJ) of crayfish, and then quantify the relative contribution of the D2/D3 receptor subtype(s) to overall modulation using sulpiride, a D2/D3-specific antagonist. We placed crayfish preparations in three different solutions: ringers solution, ringers solution with dopamine, and ringers solution with dopamine and sulpiride. While bathed in solution, the preparations were stimulated at increasing voltage levels and the corresponding excitatory junction potential (EJP) amplitudes were recorded. With the addition of dopamine to the ringers solution, we found a decrease in maximum EJP amplitude and an increase in the voltage level required to stimulate this amplitude. These differences, however, were not statistically significant. The addition of sulpiride to ringers solution containing dopamine showed a decrease in EJP amplitude and an increase in required stimulatory voltage. These differences were also not statistically significant. Our results may support previous research finding an inhibitory effect of dopamine on synaptic transmission.