LOCALIZATION OF D-1 AND D-2 DOPAMINE-RECEPTORS IN THE RAT MESENCEPHALIC TRIGEMINAL NUCLEUS BY IMMUNOCYTOCHEMISTRY AND IN-SITU HYBRIDIZATION

The rat mesencephalic trigeminal nucleus (MTN) receives a dopaminergic innervation. In order to identify and localize dopaminoceptive cells within this nucleus, expression of D-1 and D-2 dopamine (DA) receptors was examined by immunocytochemistry with subtype-specific antibodies and in situ hybridization with digoxigenin-labeled cRNA probes. Immuno cytochemical labeling was restricted to neuronal perikarya and proxima l processes whereas the hybridization signal was confined to MTN cell bodies. Cells immunopositive for D-1 were located throughout the entir e MTN whereas cells labeled with D-2 antibodies were concentrated in i ts caudal portion. D-1 receptor message was found in relatively low le vels. in contrast, high levels of mRNA for D-2 were seen in MTN neuron s. The distribution of DA receptor mRNA-containing cells were very sim ilar to those of DA receptor immunoreactivity. Neurons expressing the D-1 receptor gene were localized in both rostral and caudal portions, which receive inputs from masticatory muscle spindles and from spindle s and periodontal ligament receptors, respectively. D-2 receptors were limited to ventrocaudally located cells. These results suggest that p rocessing of proprioceptive information in the MTN is controlled by th e DAergic input through different postsynaptic mechanisms. (C) 1997 El sevier Science Ireland Ltd.