ANALYSIS OF THE HETEROGENEITY WITHIN BOVINE PINEAL-GLAND BY IMMUNOHISTOCHEMISTRY AND IN-SITU HYBRIDIZATION

In the present study, we demonstrate a cortical and medullary arrangem ent of parenchymal cells in the bovine pineal gland by using antibodie s for neuron-specific enolase, synaptophysin, and hydroxyindole O-meth yltransferase (HIOMT) as markers of pinealocytes, and glial fibrillary acidic protein (GFAP) as a marker of interstitial (glial) cells. Furt hermore, by means of probes specific for HIOMT mRNA, we have examined possible differences in melatonin synthesis between the cortex and the medulla. Immunoreactive pinealocytes for each antigen investigated ar e more densely distributed in the cortex than in the medulla. In the c ortex, GFAP-positive interstitial cells have large intenselystained so mata endowed with several long, thin cytoplasmic processes, whereas in the medulla, they display smaller, less intensely labeled perikarya f rom which numerous fine short processes emerge. Golgi staining has con firmed these morphological differences between the interstitial cells in the cortex and those in the medulla. An analysis using confocal las er microscopy together with in situ hybridization for HIOMT mRNA has s hown that the expression of mRNA transcripts in the cortex is more int ense than that in the medulla. The expression of the HIOMT gene in a c luster of cells in the medial habenular nucleus is lower than that in pinealocytes of the pineal organ proper.