Ultrastructural Organization of the Neurotransmitters in the Feline Lateral Posterior Nuclear Complex of the Thalamus : Immunohistochemical Study

The lateral posterior complex (LP) of the thalamus receives a variety of different inputs from cortical and subcortical areas. We have previously demonstrated four types of vesicle containing profiles in this complex, and have identified GABA-ergic terminals. In this study, we examined the features by the light and electron microscopy of the immunoreactivity with antibodies raised against aspartate (Asp), glutamate (Glu), GABA, choline acetyltransferase (ChAT) and substance P (SP) in the LP complex. The following observations were found：(1) Asp and Glu；immunolabeled neurons were medium sized. Immunolabeled terminals were medium sized containing round vesicles and making asymmetrical synaptic contacts with dendritic profiles. (2) GABA；immunolabeled neurons were small. Immunolabeled terminals were small, contained pleomorphic synaptic vesicles and forming symmetrical synaptic contacts with dendritic profiles. (3) ChAT；no ChAT immunolabeled neurons were found. Immunolabeled terminals were small, and contained round vesicles making en passant, symmetrical and asymmetrical synaptic contacts with dendritic profiles. (4) SP；immunolabeled neurons were medium sized. Immunolabeled terminals were small containing round vesicles, and asymmetrical synaptic contacts with dendritic profile