Locomotor activity causes a rapid up-regulation of vasoactive intestinal peptide in the rat hippocampus

Vasoactive intestinal peptide (VIP) expression is restricted to interneuron s in the hippocampus of normal adult rats. However, 3-6 hours after a 60-mi nute walk in an activity wheel, VIP was transiently expressed in most pyram idal and granular neurons of the hippocampus. Locomotion was also associate d with a dramatic increase in VIP immunoreactivity in the motor cortex, pri marily in bipolar cells. Reverse transcriptase-polymerase chain reaction an alysis indicated that VIP mRNA increases transiently by more than twofold, before the increases in peptide immunoreactivity in both the hippocampus an d motor cortex. By comparison, another marker of inhibitory interneurons, g lutamate decarboxylase, did not change its expression pattern after locomot ion. The calcium binding protein, calbindin-D28K, normally expressed in int erneurons, was now found also in glial cells of the hippocampus and motor c ortex. Another marker of enhanced electrical activity, the immediate early gene, c-Fos, was expressed in pyramidal and granular neurons at 3 hours but not at 3 hours after locomotion. These results suggest that mapping of pep tide expression in the brain of a docile, inactive rat may not reflect the real distribution and functions of a peptide in an active animal. (C) 1999 Wiley-Liss, Inc.