Receptor activation and inositol lipid hydrolysis in neural tissues.

Recent advances in our knowledge of the biochemistry, pharmacology, and cell biology of ligand-induced, stimulated turnover of inositol lipids in such diverse tissues as insect salivary glands, platelets, lymphocytes, and a number of exocrine glands have greatly altered our understanding of intracellular events leading to secretion, contraction, chemotaxis, and other cellular responses. Much of what has been learned regarding ligand-stimulated turnover of inosito1 lipids has come from nonneural systems, so that the presumption that signal transduction via this mechanism mediates significant steps in neural function must still be considered inferential. This reservation has been a major theme of a recent comprehensive review (Hawthorne, 1986). Nevertheless, that the brain contains large amounts of the substrates and enzymes of inositol lipid turnover and its associated second messenger systems and, further, that it is enriched with receptors that are linked to stimulated inositol lipid turnover argue strongly that the phosphoinositides indeed play an important role in brain function. There exist several general reviews on stimulated inositol lipid turnover (Bemidge, 1984; Bemdge and Irvine, 1984; Nishizuka, 1984, 1986; Hokin, 1985; Abdel-Latif, 1986; Downes, 1986; Williamson, 1986), including several that emphasize the nervous system (Downes, 1982, 1983; Fisher and Agranoff, 1986; Hawthorne, 1986; Nahorski et al., 1986). The present contribution emphasizes developments of neurochemical relevance since a review on the subject in this journal 8 years ago (Hawthorne and Pickard, 1979).