CHARACTERIZATION OF INDUCIBLE CYCLOOXYGENASE IN RAT-BRAIN

Considerable debate exists regarding the cellular source of prostaglan dins in the mammalian central nervous system (CNS). At least two forms of prostaglandin endoperoxide synthase, or cyclooxygenase (COX), the principal enzyme in the biosynthesis of these mediators, are known to exist. Both forms have been identified in the CNS, but only the distri bution of COX 1 has been mapped in detail. In this study, we used West ern blot analysis and immunohistochemistry to describe the biochemical characterization and anatomical distribution of the second, mitogen-i nducible form of this enzyme, COX 2 in the rat brain. COX 2-like immun oreactive (COX 2-ir) staining occurred in dendrites and cell bodies of neurons, structures that are typically postsynaptic. It was noted in distinct portions of specific cortical laminae and subcortical nuclei. The distribution in the CNS was quite different from COX 1. COX 2-ir neurons were primarily observed in the cortex and allocortical structu res, such as the hippocampal formation and amygdala. Within the amygda la, neurons were primarily observed in the caudal and posterior part o f the deep and cortical nuclei. In the diencephalon, COX 2-ir cells we re also observed in the paraventricular nucleus of the hypothalamus an d in the nuclei of the anteroventral region surrounding the third vent ricle, including the vascular organ of the lamina terminalis. COX 2-ir neurons were also observed in the subparafascicular nucleus, the medi al zona incerta, and pretectal area. In the brainstem, COX 2-ir neuron s were observed in the dorsal raphe nucleus, the nucleus of the brachi um of the inferior colliculus, and in the region of the subcoeruleus. The distribution of COX 2-ir neurons in the CNS suggests that COX 2 ma y be involved in processing and integration of visceral and special se nsory input and in elaboration of the autonomic, endocrine, and behavi oral responses. (C) 1995 Wiley-Liss, Inc.