THALAMIC-PROJECTING PREPROCHOLECYSTOKININ MESSENGER RNA-EXPRESSING NEURONS IN THE DORSAL COLUMN NUCLEI OF THE RAT

This study aimed at investigating the expression of preprocholecystoki nin messenger RNA among thalamic-projecting neurons in the dorsal colu mn nuclei of the rat. Thalamic-projecting neurons were identified by i njection of cholera toxin subunit b into the ventroposterolateral nucl eus. Following immunohistochemical detection of retrogradely transport ed tracer substance, the expression of preprocholecystokinin messenger RNA in the projection neurons of the dorsal column nuclei was detecte d by in situ hybridization, using autoradiographic visualization of a S-35-labeled RNA probe complementary to preprocholecystokinin messenge r RNA. Many preprocholecystokinin-expressing neurons were seen in the dorsal column nuclei. A large proportion of these neurons were also la beled with cholera toxin. The double-labeled neurons, as well as neuro ns single-labeled with preprocholecystokinin messenger RNA or cholera toxin, were preferentially found within the middle region of the dorsa l column nuclei, located just caudal to the obex. These findings demon strate that neurons in the dorsal column nuclei express preprocholecys tokinin messenger RNA, and show that these neurons provide a peptiderg ic projection from the dorsal column nuclei to the ventroposterolatera l nucleus of the thalamus. These observations suggest that cholecystok inin may be involved in the transmission of somatosensory (tactile) in formation from the dorsal column nuclei to the thalamus. (C) 1997 IBRO . Published by Elsevier Science Ltd.