Protein kinase signalling requirements for metabotropic action of kainate receptors in rat CA1 pyramidal neurones

Hippocampal pyramidal neurons display a Ca2+-dependent K+ current responsible for the slow afterhyperpolarization (IsAHP), a prominent regulator of excitability. There is considerable transmitter convergence onto IsAHP but little information about the interplay between the kinase-based transduction mechanisms underlying transmitter action. We have added to existing information about the role of PKC in kainate receptor actions by demonstrating that direct postsynaptic activation of PKC with either OAG or indolactam is sufficient to inhibit IsAHP. The physiological correlate of this action - activation of PKC by kainate receptors - requires GÑi/o proteins. The cAMP/PKA system is well documented to subserve the actions of monoamine transmitters. We have found an additional role for the cAMP/PKA system as a requirement for kainate receptor-mediated inhibition of IsAHP. Inhibition of adenylyl cyclase with dideoxyadenosine or PKA with either H-89 or RpcAMPs blocked kainate receptor-mediated actions but did not prevent the actions of direct PKC activation with either OAG or indolactam. We therefore propose that the PKA requirement is upstream from the actions of PKC. We additionally report a downstream link in the form of increased MAP kinase activity which may explain the long duration of metabotropic actions of kainate receptors on IsAHP. <br/