CHOLECYSTOKININ-LIKE SYSTEMS IN THE CHAMELEON BRAIN

Immunohistochemical techniques were used to determine the distribution of cholecystokinin-8 (CCK8) immunoreactivity in the brain of the cham eleon. In the telencephalon, CCK8-immunopositive somata were sparse an d observed principally in the olfactory tubercle at the ventromedial e dge of the rostral telencephalon and in the medial septum. Immunoposit ive fibers were observed mainly in the medial septal region and the ve ntral telencephalon. In the diencephalon, numerous CCK8-reactive fiber s were densely concentrated in the periventricular region, the dorsola teral hypothalamus and the external zone of the median eminence. In th e thalamus, labelled fibers were restricted to the peri-rotundal nucle i and the lateral part of the habenula. Immunoreactive cell bodies wer e observed in the medial part of the dorsal lateral geniculate nucleus , in the periventricular, ventral and lateral regions of the hypothala mus. In the mesencephalon, the densest accumulations of immunopositive fibers were observed in the area pretectalis, the periventricular gra y matter, the medial tegmentum and the isthmus. Labelled neurons were observed in the deep, and occasionally intermediate, tectal layers and in the laminar nucleus of the torus semicircularis. In the rhombencep halon, labelled fibers were observed at the highest density in the cen tral gray matter and the locus coeruleus; labelled somata were observe d only in the nucleus of the tractus solitarius.