Elevated TRH levels in pyriform cortex after partial and fully generalized kindled seizures

Abstract

In a previous study we reported significant elevations of TRH in neocortex, hippocampus and combined amygdala/pyriform cortex in rats 48 h after the last of a series of stage 5 kindled seizures. In the present study, to determine whether the increases in TRH were proportional to the intensity of the convulsions, and the degree of development of the kindling process, we compared the effects of partially kindled (stage 2) vs fully kindled (stage 5) seizures. As a further refinement, we examined separately the TRH responses in the pyriform, cingulate and frontal cortices. The responses were especially marked in the pyriform cortex, where TRH increased 7-fold after stage 5 kindled convulsions, compared with 2-fold increases after stage 2-3 seizures. Increases were seen in other cortical regions, as well, but only after stage 5 seizures. These findings are consistent with reports suggesting that the increases in brain TRH occurring after convulsions are aftereffects of the seizures, possibly representing homeostatic anticonvulsant responses, and that the pyriform cortex is a site that is uniquely activated by convulsions.