Protein Kinase C Enhances Serotonergic and Non-Serotonergic Synaptic Transmission

Abstract

Serotonin (5-HT) is an excitatory neurotransmitter found in the CNS that regulates brain activities such as sleep, mood, and learning. Protein kinase C (PKC) is a G-protein-activated second-messenger enzyme that is responsible for the closing of potassium (K+) channels and the subsequent broadening of action potentials resulting in the release of neurotransmitters. While several previous studies have examined the role of PKC in vertebrate serotonergic transmission, practically no research has been conducted involving the functioning of 5-HT and PKC in invertebrate synaptic transmission. Thus, we devised an experiment utilizing the crayfish neuromuscular junction and intracellular recording techniques to determine the role of PKC in invertebrate serotonergic synaptic transmission. Through the application of 5-HT, the PKC inhibitor chelerythrine, and the 5-HT(2) receptor antagonist ketanserin, we found chelerythrine considerably reduced the heightened responses resulting from serotonin. This suggests that PKC plays a role in excitatory serotonergic synaptic transmission, and further results indicate PKC is also active in enhancement of nonserotonergic EPSPs.