Developmental changes in electrophysiological properties of layer III pyramidal neurons in macaque visual cortices.
Maruyama, A., Ishikawa, A., Hosoyama, D., Yoshimura, Y., Tamura, H., Sato,
We studied developmental changes of intrinsic membrane properties of layer III pyramidal neurons in the striate (V1) and inferior temporal (TE) cortices of macaque monkeys. Whole-cell patch-clamp techniques were applied to slices prepared from animals of different ages (10 days, 7-8 months, adult). The membrane time constant decreased with age in both V1 and TE. In V1, the value at 7-8 months was already close to that in adults, while in TE it gradually decreased up to adulthood. Inward rectification in response to hyperpolarization became stronger with age, and this change was more evident in V1 than in TE. In both areas, the maximal rate of firing in response to depolarizing current injection increased with age, and the duration of individual action potentials shortened. The results demonstrate that electrophysiological properties of cortical neurons in monkeys become matured over a prolonged period after birth, which may contribute to refinement of visual responsiveness during development.