Thalamic reticular nucleus parcellation delineated by VIP and TRH gene expression in the rat

The distribution of the mRNAs encoding VIP (vasoactive intestinal peptide) and TRH (thyrotropin releasing hormone) was examined in the thalamic reticular nucleus of the adult rat using hybridization histochemistry with S35-labeled oligoprobes. Low levels of TRH expression were found in a medial tier. High levels of VIP expression were found in neurons located in a lateral shell of the same portion. High levels of TRH expression were found in a tier located dorsally and in a tier located ventrally to the first one. In these regions no VIP expression could be detected. These data suggest a parcellation of this nucleus according to the differential expression patterns of TRH and VIP.