MAPPING OF PROSTAGLANDIN-E(2) BINDING-SITES IN RAT-BRAIN USING QUANTITATIVE AUTORADIOGRAPHY

The density of specific prostaglandin E2 (PGE2) binding sites was quantitatively mapped in the rat brain using in vitro autoradiography. The anterior wall of the third ventricle and the nucleus solitary tract were found to have a very high density of binding sites (greater than 15 fmol/mg tissue). Two thalamic nuclei (paraventricular and anteroventral nuclei) and the dorsal parabrachial nucleus contained a high density of binding sites (10-15 fmol/mg tissue). Entorhinal cortex, ventral hippocampus, amygdala, dorsomedial hypothalamus, mammillary complex, some thalamic nuclei, central gray, superior colliculus, raphe nuclei, locus coeruleus, spinal trigeminal nucleus (caudal part) and the dorsal horn of the spinal cord (laminae 1 and 2) had each a moderate density of binding sites (5-10 fmol/mg tissue). Binding tended to occur in brain regions rich in neuronal cell bodies or neuronal cell processes (dendrites and axon terminals). PGE1, whose central actions are very similar to those of PGE2, had essentially the same pattern of binding sites as did PGE2 throughout the entire brain, suggesting there are receptors common to these two PGEs. In addition to already known functions of PGE2 in the hypothalamus, which include fever genesis, promotion of wakefulness, cardiovascular control and LH-RH release, the unique distribution of extrahypothalamic PGE2 binding sites found in this study suggests its involvement in the processing or modulation of viscerosensory, somatosensory (nociceptive and possibly thermal) and visual inputs as well as in the central integration of autonomic and limbic functions. Our results provide an anatomic basis for further physiological investigation of the functions of prostaglandins of the E series in the central nervous system.