Acquisition of amygdala-kindled seizures in female rats: relationship between the effect of estradiol and intra-amygdaloid electrode location.
Ovariectomized, adult female rats, with or without estradiol replacement, were kindled by daily amygdala stimulation. Kindling acquisition varied with the intra-amygdala site of stimulation. During stimulation of the medial (AME) or central (ACE) nucleus, the only effect of estradiol replacement (E), compared to non-replaced rats (nE), was to significantly decrease the number of trials with afterdischarge (AD) during early kindling (stage 0). In rats receiving stimulation of the cortical nucleus (ACO) or the baso-lateral group of nuclei (ABL), a similar effect of estradiol was extended through stage 1. In addition, nE rats with ACO or ABL electrodes required significantly more trials with AD and accumulated more than twice the sec of AD during the late stages of kindling, compared to E rats and regressed to lower stage responses between the first stage 4 and last stage 5 responses; regressed responses never occurred in E rats. Estradiol also significantly decreased the prekindling AD threshold of the AME and ACE. These results indicate that estradiol accelerates early stage kindling, likely by proconvulsive properties to increase excitability within immediate amygdala projections. During late kindling stages, estradiol may participate in reinforcing or sustaining the convulsive readiness of kindling circuits established during bilateral recruitment. The site of action for this latter effect of estradiol may reside within circuits accessed by stimulation of the ACO or ABL, and not the AME or ACE.
Department of Pharmacology and Toxicology, University of Maryland School of Pharmacy, Baltimore, 21201.
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Buterbaugh
D000679:Amygdala / Q000187:drug effects / Q000503:physiopathology*; D000818:Animals; D004558:Electric Stimulation; D004566:Electrodes; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D007696:Kindling, Neurologic / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D012640:Seizures / Q000503:physiopathology*
D004958:Estradiol