Effective suppression of hippocampal seizures in rats by direct hippocampal cooling with a Peltier chip

Abstract

Object The use of focal brain cooling to eliminate epileptic discharges (EDs) has attracted increasing attention in the scientific community. In this study, the inhibitory effect of selective hippocampal cooling on experimental hippocampal seizures was investigated using a newly devised cooling system with a thermoelectric (Peltier) chip. Methods A copper needle coated with silicone and attached to the Peltier chip was used for the cooling device. The experiments were performed first in a phantom model with thermography and second in adult male Sprague–Dawley rats in a state of halothane anesthesia. The cooling needle, a thermocouple, and a needle electrode for electroencephalography recording were inserted into the right hippocampus. Kainic acid (KA) was injected into the right hippocampus to provoke the EDs. The animals were divided into hippocampal cooling (10 rats) and noncooling (control, 10 rats) groups. Results In the phantom study, the cooling effects (9°C) occurred in the spherical areas around the needle tip. In the rats the temperature of the cooled hippocampus decreased below 20°C within a 1.6-mm radius and below 25°C within a 2.4-mm radius from the cooling center. The temperature at the needle tip decreased below 20°C within 1 minute and was maintained at the same level until the end of the cooling process. The amplitude of the EDs was suppressed to 68.1 ± 4.8% of the precooling value and remained low thereafter. No histological damage due to cooling was observed in the rat hippocampus. Conclusions Selective hippocampal cooling effectively suppresses the KA-induced hippocampal EDs. Direct hippocampal cooling with a permanently implantable system is potentially useful as a minimally invasive therapy for temporal lobe epilepsy and therefore could be an alternative to the temporal lobectomy.