Protein kinase C (PKC) is present in high concentrations in neuronal tissues and has been implicated in a broad spectrum of neuronal functions. Nerve cells can transmit signals over long distances by means of electrical impulses. Opening of voltage-gated Ca2+ channels following depolarization of the presynaptic membrane by an action potential, normally translates the electrical signal into several chemical messages. The influx of Ca2+ triggers an exocytotic release of a variety of neurotransmitters from synaptic vesicles. The chemical messages are then reverted back to electrical form through channel-linked receptors such as nicotinic, glutamate, and GABAA receptors located on postsynaptic membranes. Many proteins related to these processes of synaptic transmission may be the prime targets of PKC action. Activation of this enzyme in nerve cells is frequently associated with the modulation of ion channels (Shearman et al 1989), desensitization of receptors (Huganir & Greengard 1990), and enhancement of neurotransmitter release (Robinson 1992). The PKC pathway may modulate the efficacy of synaptic transmission, thus providing a basis for some forms of memory. On the other hand, non-channel-linked receptors respond to agonists, thereby initiating a cascade of enzymatic reactions. The first step in this cascade is activation of G protein, which may either interact directly with ion channels or control the production of intracellular second messengers. When phospholipases are activated via G protein-linked receptors, PKC is activated by increased amounts of diacylglycerol (DAG) in membranes, as a result of