Parasagittal zonation of GABA-B receptors in molecular layer of rat cerebellum.

Two distinct receptors mediate the effects of ~,-aminobutyric acid (GABA) in the central nervous system. GABA-A receptors, which are linked to the modulatory benzodiazepine site and chloride ion channels, are the predominant mediators of inhibitory neurotransmission in the brain. GABA-B receptors are linked to potassium and calcium channels and may act by regulation of adenylate cyclase (Bowery et al., 1988). GABA-A and GABA-B receptors differ in their anatomic distributions. In the cerebellar cortex, GABA-A receptors are located mainly in the granule cell layer while GABA-B are receptors found predominantly in the molecular layer. We have found that molecular layer GABA-B receptors are distributed in parasagittal zones of high and low ligand binding. This is the first documentation of parasagittal zonation of any known receptor type in cerebellar cortex. GABA-B receptor autoradiography was performed as previously described (Chu et al., 1987). Six male Sprague-Dawley rats (weight = 175-200 g) were decapitated and the brains were rapidly extracted from the cranial vault and frozen in crushed dry ice. Twenty micron sections were cut on a cryostat in a coronal plane and thaw mounted onto gelatin coated slides. Triplicate sections from each brain were run. Slides were prewashed in 50 mM Tris-C1 buffer (pH 7.4) containing 2.5 mM