Hypothalamic neuronal loss and altered circadian rhythm of temperature in a rat model of mesial temporal lobe epilepsy

Purpose: Numerous dysfunctions in endogenous hypothalamic function have bee n associated with mesial temporal lobe epilepsy (MTLE). One endogenous acti vity is the circadian rhythm of temperature (CRT). In this study we examine d whether hypothalamically mediated function is altered in the electrically induced, self-sustained, limbic status epilepticus model of MTLE. We then wished to determine whether there was a structural basis for regulatory alt erations. Methods: We measured CRT with peritoneal temperature telemetry obtained in light-entrained (LD) and in free-running, constant-dark (DD) conditions. CR T from epileptic and controls of normal animals and kindled animals were qu antized by fast Fourier transform-nonlinear least squares analysis to deter mine rhythmic complexity. Results: The circadian component of CRT was preserved in all animals. In DD , CRTs of epileptic animals were more complex than those of normal animals. CRT of kindled animals showed no increased complexity after electrically i nduced seizures. Neuronal density was decreased in regions of the anterior and posterior hypothalamus but not in the suprachiasmatic nuclei from the e pileptic rats. Conclusions: Alterations in CRT due to the epileptic state were independent of isolated seizures. Altered circadian thermoregulation in epileptic rats corresponded to regional hypo thalamic neuronal loss. Structural changes o f the hypothalamus may explain alterations in endogenous rhythms in MTLE.