Epinephrine proactive retardation of amygdala-kindled epileptogenesis

Recent findings indicate that a single injection (ip) of epinephrine can proactively retard the development of amygdala-kindled seizures. In these experiments, these findings were extended by examining the dose and temporal properties of this phenomenon. Rats were prepared with stimulating electrodes placed in the amygdala. At 30 min or 24, 48, or 72 hr before the first kindling trial, the animals received an epinephrine injection (0.01-1.0 mg/kg). The results indicate that the high epinephrine dose delayed the onset of kindling when injected within 24 hr before kindling, the intermediate dose delayed kindling when injected at 30 min before the first kindling trial, and the low dose was ineffective at all intervals. Injections administered after kindling had been established had no effect on later seizures, although injections during early kindling stages had a small effect on the further development of seizures. Examination of the time courses of increases in plasma catecholamine levels, blood pressure, and heart rate demonstrated that long-term changes in these measures cannot account for the retardation of kindling. The findings of these experiments indicate that although epinephrine does not directly affect seizure production with these procedures, the hormone does have long-lasting proactive effects on kindled epileptogenesis.