In situ hybridization studies on mRNAs for cholecystokinin, calcitonin gene-related peptide and choline acetyltransferase in the lower brain stem, spinal cord and dorsal root ganglia of rat and guinea pig with special reference to motoneurons.

In situ hybridization techniques were used to analyse the distribution of cholecystokinin (CCK) mRNA in the lower brain stem, spinal cord and dorsal root ganglia of the rat and guinea pig, in comparison with that of mRNAs for calcitonin gene-related peptide (CGRP) and choline acetyltransferase. In the rat, CCK mRNA was found in numerous motoneurons in the spinal cord as well as in the motor trigeminal, facial and hypoglossal nuclei. Coexistence of CCK mRNA and CGRP mRNA could be established in spinal and brain stem motoneurons. Conversely, in the guinea pig CCK mRNA could only be detected in few motoneurons in the spinal cord. In both species, CCK mRNA was present in the spinal trigeminal nucleus and in the dorsal horn of the spinal cord, in numerous small cells located in the outer laminae (mainly II-IV), and in the rat was also found in large cells in laminae IV and V. Few small cells in laminae VI-VIII and X of the spinal cord and cells in several brain stem nuclei, such as the solitary tract, gracile and cuneate nuclei, also showed CCK mRNA in the rat. In the guinea pig brain stem CCK mRNA was found, among others, in the solitary tract nucleus, pontine reticular formation and pontine periventricular grey. In dorsal root ganglia CCK mRNA was abundant in the guinea pig, but almost absent in the rat, where only single cells were found that expressed low levels of this mRNA.