Anti-seizure effects of progesterone and 3alpha,5alpha-THP in kainic acid and perforant pathway models of epilepsy.
The mechanism by which progesterone has its anti-seizure effects is unknown. Progesterone has a high affinity for intracellular progestin receptors, but has weak actions at gamma-aminobutyric acid (GABA)(A) receptors complexes. The progesterone metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) is devoid of activity at intracellular progestin receptors but is a highly effective modulator of GABA(A) receptor complexes. Whether progesterones anti-seizure actions are due to effects of progesterone itself or its metabolite 3alpha,5alpha-THP was investigated. In experiment 1, 25 ovariectomized Long-Evans rats were subcutaneously (s.c.) injected with 0.0, 4.0 or 8.0 mg/kg progesterone or 3alpha,5alpha-THP, 10 min prior to systemic administration of 32 mg/kg kainic acid. Four and 8.0 mg/kg progesterone significantly reduced the duration of partial and full seizures, without influencing the latency to partial or full seizures, or the number of partial or full seizures. 3alpha, 5alpha-THP (4.0 mg/kg) significantly increased the latency to initial partial seizure, and decreased the number and duration of partial seizures. In experiment 2, 60 ovariectomized Long-Evans rats were stereotaxically implanted with bipolar electrodes into the perforant pathway. Prior to perforant pathway stimulation, rats were s.c. injected with either progesterone (4.0 mg/kg, n = 12), 3alpha, 5alpha-THP (4.0 mg/kg, n = 13), progesterone (4.0 mg/kg)+4MA (10.0 mg of a 5alpha-reductase inhibitor, 17b-N, N-diethylcarbamoyl-4-methyl-4-aza,5alpha-androstan-3-one, n = 12), 4MA+vehicle (n = 10), or sesame oil vehicle (n = 13). Administration of progesterone or 3alpha, 5alpha-THP, but not vehicle control, P+4MA, or 4MA, resulted in significant decreases in partial seizures. In experiment 3, whole brain progesterone and 3alpha,5alpha-THP were measured by radioimmunoassay in additional rats (n = 66) administered the hormonal milieu indicated in experiments 1 and 2. Data suggest anti-seizure effects of progesterone may be due, in part, to metabolism to 3alpha,5alpha-THP and subsequent actions at GABA(A) receptor complexes.
Frye
C A
CA
Department of Psychology, The University at Albany, SUNY, 1400 Washington Avenue, Albany, NY 12222, USA. cafrye@cnsunix.albany.edu
Scalise
T J
TJ
D000818:Animals; D000927:Anticonvulsants / Q000627:therapeutic use*; D004195:Disease Models, Animal; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004827:Epilepsy / Q000209:etiology / Q000517:prevention & control*; D005260:Female; D007608:Kainic Acid; D010052:Ovariectomy; D019580:Perforant Pathway / Q000502:physiology*; D011280:Pregnanolone / Q000627:therapeutic use*; D011374:Progesterone / Q000627:therapeutic use*; D051381:Rats; D020318:Rats, Long-Evans
D000927:Anticonvulsants; D011374:Progesterone; D011280:Pregnanolone; D007608:Kainic Acid