MICRODIALYSIS REVEALS CHANGES IN EXTRACELLULAR OPIOID PEPTIDE LEVELS IN THE AMYGDALA INDUCED BY AMYGDALOID KINDLING STIMULATION

Enkephalins released in basolateral nucleus of the amygdala in respons e to electrical stimulation were determined in amygdala kindled and no nkindled freely moving rats using microdialysis. Enkephalin release wa s enhanced after a single and repetitive electrical stimulation (233 a nd 130% above control levels, respectively) in nonkindled rats. In ful ly kindled rats, the extracellular enkephalin levels decreased (35% be low the control levels) within the first 20 min after onset of stage V kindled seizures, reaching baseline level 40 to 60 min following the generalized seizure activity. HPLC analysis identified the majority of recovered immunoreactive material from the amygdala as Met-enkephalin . On the basis of our results it is suggested that the enhanced enkeph alin release in the amygdala during the early kindling stages might ha ve a suppressive effect which may represent a homeostatic mechanism to avoid the spread of the afterdischarge to other structures. The decre ased extracellular level of enkephalin in the amygdala after stage V k indled seizures could reflect a general impairment of inhibitory mecha nisms in this structure with subsequent production of seizure activity . (C) 1994 Academic Press, Inc.