Effects of anesthetic agents on seizure-induction with intra-cortical injection of convulsants.

RATIONALE: Studies of partial or generalized seizure pathophysiology often require the use of intact animals. Additionally, anesthesia may be required for ethical reasons or paralysis if instrumental measures require immobilization. We examined three commonly used injected anesthetic for their impact on seizures induced by three convulsant agents. METHODS: We prepared rats, under pentobarbitone anesthesia (65 mg/kg) with a catheter, electrodes and a dural window, for later non-noxious experimentation. Three to seven days later, kainic acid (1.25 μg), picrotoxin (225 ng) or fluorocitrate (0.8 nmol) were injected intra-cortically in animals paralysed with succinylcholine, or anesthetised with pentobarbitone, urethane or fentanyl plus droperidol. We recorded EEG activity, the latencies to seizure discharges, the occurrence of spreading depressions and the presence of movements in response to the convulsants. RESULTS: Fentanyl plus droperidol was the only anesthetic agent permissive for seizure-discharges and spreading depressions. No significant differences in the time for seizure onset for fentanyl plus droperidol compared to paralyzed unanesthetised rats were seen for any of the convulsants (Student's t-test p>0.20). Movements during seizures as well as other drug-induced behaviors continued to be expressed during anesthesia. CONCLUSION: Fentanyl plus droperidol has useful properties as an anesthetic agent in studies of seizure induction with different convulsants.