Morphology of layer III pyramidal neurons is altered following induction of LTP in sensorimotor cortex of the freely moving rat

The organization of specific cortical connections can be altered by sensory and motor experience. These changes are believed to result from activity-d ependent changes in synaptic connectivity, similar to those induced in the hippocampus by high-frequency stimulation in long-term potentiation (LTP) e xperiments. If similar mechanisms are involved, then neocortical LTP induct ion may induce some of the same morphological changes that are seen followi ng learning. We induced LTP in the contralateral sensorimotor cortex by rep eated, daily tetanization of the corpus callosum in chronically implanted, freely moving rats. Anatomical results showed that the LTP induction was as sociated with alterations in dendrite morphology and increased spine densit y. These changes are qualitatively and quantitatively similar to those comm only observed, in studies in which rats are housed in complex environments. The similarity of results following exposure to complex environments and a fter LTP induction in the neocortex may indicate a reliance on the same cel lular mechanisms in both situations. (C) 2000 Wiley-Liss, Inc.