Synaptic plasticity in the cerebral cortex of mice: effects of radiation and anesthesia.

In the neuropil of layers II and III of the frontal cortex of adult mice, as seen in the electron microscope, sodium pentobarbital anesthesia alone results in a significant decrease in synaptic profile length at 1 day after anesthetization, followed by a return to normal or above normal levels after 2-28 days, while the number of synaptic profiles per unit cross section (profile incidence) is not altered; irradiation with 5-500 rad plateau argon particles significantly inhibits the profile shortening effect of anesthesia at 1 day after exposure, but this inhibition is not dose related; an inverse dose relationship in profile incidence appears at 2 days following irradiation with argon particles; at 1 to 2 hours after 150 or 220 rad x-irradiation, profile incidence is significantly reduced while the length is increased, effects that appear to be dose related and unaffected by adrenalectomy.