CHOLECYSTOKININ, DOPAMINE D-2 AND N-METHYL-D-ASPARTATE BINDING-SITES IN THE NUCLEUS OF THE SOLITARY TRACT OF THE RAT - POSSIBLE RELATIONSHIP TO INGESTIVE BEHAVIOR

Receptor autoradiography was used to investigate the distribution of b rainstem binding sites for cholecystokinin. dopamine and N-methyl-D-as partate with particular reference to the nucleus of the solitary tract of the rat, an area involved in the control of ingestive behavior. Bi nding sites for the A and B subtypes of the cholecystokinin receptor, labeled with [I-125]cholecystokinin octapeptide sulfate in the presenc e or absence of antagonists for the devazepide (A) or L-365,260 (B) re ceptor, were present throughout the caudal-rostral extent of the nucle us of the solitary tract, the A type predominating in the commissural, medial and gelatinous part and the B type in the lateral part. In the most rostral part of the medial nucleus of the solitary tract, both A and B receptors were present. Dopamine D-2 receptors, labeled with [I -125]NCQ-298, were found in all parts of the nucleus of the solitary t ract. No binding to the dopamine D, receptor, labeled with [I-125]SCH- 23982, was found in the brainstem. N-Methyl-D-aspartate receptors, lab eled with [H-3]dizocilpine maleate, were also present in the entire ca udorostral extent of the nucleus of the solitary tract. Binding to cho lecystokinin A receptors was co-distributed with [I-125]NCQ-298 and [H -3]dizocilpine maleate binding in the caudal and rostral parts of the nucleus of the solitary tract, and binding to cholecystokinin B recept ors overlapped with [I-125]NCQ-298 and [H-3]dizocilpine maleate bindin g in the rostral nucleus of the solitary tract. These results are cons istent with the hypothesis that cholecystokinin, dopamine and glutamat e interact in the nucleus of the solitary tract in the control of inge stive behavior. (C) 1997 IBRO. Published by Elsevier Science Ltd.