Hyperthermia sensitizes rats to cocaine's proconvulsive effects and unmasks EEG evidence of kindling after chronic cocaine.

In phase I, 64 male and female Sprague-Dawley rat siblings from 8 litters were divided equally among 4 treatment groups; saline plus normothermia (S37), saline plus hyperthermia (S45), cocaine (30 mg/kg) plus normothermia (C37), and cocaine plus hyperthermia (C45) and treated daily from 45-60 days of age. Cocaine plus hyperthermia produced protracted, intense and often fatal convulsions, whereas animals from either treatment alone did not convulse. Subsequently, 12 males, representing all phase I treatment groups equally, were implanted with telemetric transmitters to monitor the EEG and core body temperature in phase II. Survivors of this second phase were exposed to one trial each of saline plus hyperthermia, cocaine plus normothermia, and cocaine plus hyperthermia, in that order. The data obtained suggests that 1) the telemetered EEG and temperature can be used to detect changes reflecting sensitization/kindling in the absence of behavioral expression (convulsions), 2) analysis of EEG power spectral bands and body temperature curves showed that a history of daily cocaine exposure seems to have contributed more than daily hyperthermia to subsequently observed seizure patterns and thermic responses, and, finally, 3) cocaine plus hyperthermia resulted in a shorter latency to convulse and a lower maximal EEG seizure voltage, while increasing the variety, severity and duration of its behavioral expression (convulsion).