Eicosanoids in synaptic transmission.

Arachidonic acid is released from membrane phospholipids in a receptor-dependent manner when neurons or glial cells are stimulated with neurotransmitters, hormones, or growth factors. The released fatty acid can be metabolized in brain tissue by three enzymatic pathways--cyclooxygenase, lipoxygenase, and cytochrome P450--giving rise to a series of biologically active products, the eicosanoids. Intracellular actions of these lipids include regulation of membrane ion channels, protein kinases, and ion pumps, thus suggesting a role as neuronal second messengers. In addition, the eicosanoids may be released into the extracellular space and interact with high affinity, G protein-coupled receptors on neurons and glial cells. Acting through these two distinct and complementary modes of action, the eicosanoids may participate in several forms of neuromodulation and synaptic plasticity.