The location of muscarinic type 2 receptors within the synaptic circuitry of the cat lateral posterior nucleus

The ultrastructural distribution of the muscarinic type 2 acetylcholine rec eptor (M2) was examined in the lateral division of the lateral posterior (L P) nucleus of the cat thalamus, using immunocytochemistry. Postembedding im munocytochemical staining for gamma-aminobutyric acid (GABA) further, chara cterized M2 stained profiles. M2 receptors were predominately found on smal l caliber (presumably distal) dendritic arbors of thalamocortical cells and interneurons in the lateral LP nucleus. While glomeruli were not abundant in the lateral LP:nucleus, occasionally they contained dendritic terminals of interneurons (F2 profiles) stained for M2 receptors, Some GABAergic term inals throughout the neuropil also stained for M2 receptors. The location o f M2 receptors correlates well with the cholinergic innervation of the late ral LP nucleus and suggests that muscarinic modulation of visual signals di ffers in the lateral LP nucleus as compared with the lateral geniculate and pulvinar nuclei. (C) 1999 Elsevier Science Ireland Ltd. All rights reserve d.