Direct visualization of cholecystokinin subtype2 receptors in rat central nervous system using anti-peptide antibodies

The cholecystokinin receptor, subtype 2 (CCK 2R), is considered, based on receptor autoradiography, to be the predominant receptor for this peptide transmitter in the mammalian central nervous system. To directly visualize the CCK 2R we utilized a convenient and sensitive immunohistochemical procedure using antipeptide receptor antibodies raised in rabbits against unique portions of the carboxyl tail and third intracellular loop of the CCK 2R. Antibodies were characterized by ELISA and Western blotting, and used for immunohistochemistry in rat brain sections. Studies with both antibodies revealed a widespread topographic distribution of CCK 2R-like immunoreactivity (CCK 2R-LI) in regions such as cortex, olfactory bulb, nucleus accumbens, septum, striatum, hippocampus, basolateral amygdala, habenula, hypothalamus, thalamus, ventral mesencephalon, inferior colliculus, parabrachial nucleus, pontine nucleus, supercolliculus, red nucleus, subcommisural and occulomotor nucleus, area postrema, solitary, olivary, cochlear, cuneate and trigeminal nuclei and spinal cord dorsal horn in agreement with the results of previous receptor autoradiography.