A microwave‐hyperthermia model of febrile convulsions

Abstract

While convulsions associated with fever represent a serious problem in pediatric medicine, conventional animal models of febrile convulsions suffer numerous technical limitations. A microwave-hyperthermia model that eliminates these problems was tested. Microwave energy was used to increase the core temperature of 13- and 17-day-old rats, resulting in convulsions similar to febrile convulsions in human infants. Rats were irradiated for 10 min in circularly polarized waveguides at 918 MHz, CW (average SAR = 9.4 W/kg at 13 days and 18.0 W/kg at 17 days as determined by twin-well calorimetry). Day 17 irradiated rats were less susceptible to convulsions that were day 13 irradiated rats, indicating an age-dependent decline in susceptibility. Contrary to findings of earlier models using infrared or hot-oven heating, convulsions induced with microwave hyperthermia impaired neither brain growth nor subsequent performance during behavioral testing. Simultaneous measurement of brain and rectal temperatures during microwave irradiation revealed differential heating rates that favor thermal homeostasis in brain tissue.

Origins of Temporal Lobe Epilepsy: Febrile Seizures and Febrile Status Epilepticus

“…FS-like seizures can be induced by hyperthermia [29][30][31][32][33][34][35][36][37][38] or hyperthermia coupled with lipopolysaccharide (LPS) and kainic acid (KA) [39,40]. Seizures typically arise in all hyperthermia-sustaining animals [41] suggesting that genetic susceptibility is not necessarily required for their generation.…”

“…However, creating such a model is hampered by the fact that immature rodents do not readily develop fever [28,52]. There have been several animal models used to approximate FSE [29][30][31][32][33][34][35][36][37][38][39][40]79]. Some strive to generate febrile convulsions (FC) in rats by injecting the bacterial endotoxin LPS accompanied by a usually subconvulsive dose of the pro-convulsant drug KA while maintaining animals in a warm room (30°C) [80].…”

Febrile Convulsions Induced by Microwaves and the Alteration in Behavior of Albino Mouse OF1

“…The activity of the animal during exposure and the post-ictal periods was re corded on video. To this end the floor of the oven was painted green-with black squares which enabled mea surement of the subject's activity in each of the peri ods of exposure, as well as making possible the classi fication of each of the convulsions according to the basic types used by Hejeresen et al [13], After this period the temperature of the animal (post-ictal tem perature, PIT) was taken again and it was returned to the cage. The whole process took 10 min per ani mal.…”

“…With these methods the temperature of the ani mal's body rises from the exterior inwards, producing painful sensations which would modify behavior and affect accurate evalua tion. A solution to this problem was pro vided using a microwave as the source of broadcast energy for the induction of hyper thermia, which could serve as a model for FCs [13,14], Using these techniques, a con nection between FCs and minimal brain dis function syndromes has been sought [8,15] by applying behavior tests to those animals submitted to convulsions [16,17].…”

Novel Etiological and Therapeutic Strategies for Neurodiseases: Mechanisms and Consequences of Febrile Seizures: Lessons From Animal Models

“…Hyperthermia is induced by several methods in postnatal rodents to evoke seizures, such as the hair dryer model (26 -29), heated chamber model (30,31), hot water model [which might also be categorized as a model for hot-water epilepsy (32 -34)], microwave model (35), and lipopolysaccharide model (36).…”