PENICILLIN-G INDUCED INTERICTAL ACTIVITY INCREASES BOTH OPIOID PEPTIDE TISSUE CONTENT AND IN-VITRO RELEASE IN THE RAT-BRAIN

Penicillin-G has been used as a common agent to produce epileptic foci and interictal activity. The development of the interictal spikes has been associated with enhanced inhibitory effects. There is evidence t hat the opioid peptides play an important role in the production of so me transient postictal behaviors. In order to test whether enkephalins are involved during the interictal activity, we analyzed immunoreacti ve met- and leu-enkephalin content and their release in vitro, after t he injection of 50 IU of penicillin-G into the left amygdala. Male Wis tar rats were injected once daily for 5 days, and sacrificed by decapi tation (15 min after the penicillin-G infusion) on the fifth day. The rats were divided into two groups: 1. In one group we analyzed the tis sue content of enkephalins in hypothalamus, hippocampus, amygdala, str iatum and cerebral cortext. 2. The second group was used for the asses sment of the in vitro release of enkephalins from amygdala slices. In the amygdala, the drug treatment produced an increase in the tissue co ntent of IR-ME. No changes occurred in the other structures. The conte nt of IR-Leu-enkephalin increased in all structures analyzed except th e cerebral cortex. In vitro release of both enkephalins increased in d rug treated animals. These results suggest that the enkephalins could be involved in postictal mechanisms, as a result of repetitive interic tal spiking.