Topographical distribution of NADPH-diaphorase-positive neurons in the cat's claustrum.

The NADPH-diaphorase histochemical technique was used to visualize the morphological features of the NADPH-diaphorase positive cells and fibres, and their distribution in both parts of the cat's claustrum. Taking into account the size and form of the perikaryon and the dendritic and axonal characteristics, the neurons are grouped in different subclasses: large, medium-sized and small. The present data suggest the occurrence of two populations of NADPH-diaphorase neurons in the claustrum. One population consisting of large and medium-sized positive neurons represents the projection neurons while the other population of small positive neurons corresponds to the local circuit neurons.