Intracellular recording and staining of cat's lateral geniculate neurons

Intracellular staining with recording micropipettes filled with a Procion yellow solution was attempted on 11 lateral geniculate neurons of chloralose-anesthetized cats for the purpose of correlating electrophysiologically identified cell types with morphologically identified cell types. Five neurons were successfully stained: one was located in lamina A and the others in lamina A1. They were all identified as P-cells on the basis of their responsiveness to electrical stimulation of optic disc, optic chiasm and visual cortex. The conduction velocities and synaptic delays for specific optic nerve fibers concerned with these P-cells were estimated from the relationship between latency and conduction distance. Intracellular staining has revealed that a neuron located in lamina A and three of four neurons located in lamina A1 had multipolar configuration, with their main dendrites oriented parallel to the plane of the laminae; while one neuron located in lamina A1 had a configuration similar to that of a class II-type neuron described by Guillery in his Golgi preparations. In these experiments no neurons located in lamina B, central interlaminar nucleus and medial interlaminar nucleus were stained. No interneurons were obtained, either.