Dendritic morphology of visual callosal neurons in the golden hamster

The visual callosal neurons and the connections between the two cerebral hemispheres in hamsters have been shown to be important for visual functions, but little is known about the detailed morphology of these neurons. In this study, we have used techniques based on retrograde transport of a fluorescent tracer, Granular Blue, and intracellular injection of Lucifer Yellow in fixed brain slices to identify the laminar distribution and dendritic morphology of the visual callosal neurons in the 17/18a border region of the adult golden hamster. The cells giving rise to the callosal projections were morphologically heterogeneous, although they were all spiny neurons. Most were pyramidal cells, but some were stellate cells. They were located in layers II-VI, with cells concentrating in three bands: (1) in the middle three fifths of layer II/III; (2) in layer IV, and (3) in the middle three fifths of layer V. In layer II/III and layer V, the great majority of the cells were pyramidal or star pyramidal neurons. In layer IV, about half were stellate neurons and the rest pyramidal or star pyramidal neurons. In layer VI, they consisted mostly of modified pyramidal cells. The soma areas of the pyramidal and star pyramidal neurons in all the layers ranged from 52 to 335 micron 2 with a mean of 148 micron 2 (n = 92; SD = 64.4). In general, these cells gave rise to 3-5 basal dendrites.(ABSTRACT TRUNCATED AT 250 WORDS)