Abstracts

Testosterone can undergo sequential A-ring reduction to 5[alpha]-androstane-3[alpha],17[beta]-diol (5[alpha],3[alpha]-diol) by a pathway analogous to that by which progesterone is converted to allopregnanolone. There is evidence that 5[alpha],3[alpha]-diol may have similar properties to allopregnanolone as a modulator of GABA[sub]A[/sub] receptors. In the present structure-activity study, we evaluated 5[alpha],3[alpha]-diol and its epimers 5[beta]-androstane-3[alpha],17[beta]-diol (5[beta],3[alpha]-diol) and 5[alpha]-androstane-3[beta],17[beta]-diol (5[alpha],3[beta]-diol) for anticonvulsant activity in a brain slice and whole animal seizure models.
[italic]In vitro [/italic]: Epileptiform discharges were induced in the rat hippocampal slice by perfusion with 55 [mu]M 4-aminopyridine (4-AP). Extracellular field potentials were recorded in CA3 region. [lt]A name=OLE_LINK1[gt]In some experiments, 5[alpha],3[alpha]-diol (10, 50 and 100 [mu]M), 5[beta],3[alpha]-diol (100 [lt]/A[gt]mM), or 5[alpha],3[beta]-diol (100 [mu]M) were perfused in combination with 4-AP. An automated system was used to determine the number of positive-going epileptiform discharges in 10 min epochs during 1 hr recording period.
[italic]In vivo [/italic]: Male NIH Swiss mice were injected s.c. with pentylenetetrazol (PTZ) at 80 mg/kg, a dose producing 100% of seizures in control animals. 5[alpha],3[alpha]-Diol and its epimers (30-300 mg/kg) were administered 15 min prior to PTZ; animals failing to show clonic seizure activity during a 30 min observation period were scored as protected. ED[sub]50[/sub] values were determined with the Litchfield-Wilcoxon procedure.
5[alpha],3[alpha]-Diol reduced the frequency of epileptiform discharges induced by 4-AP. The effect of 5[alpha],3[alpha]-diol was concentration-dependent, with maximal 67% reduction at 100 [mu]M. The epimers at the same concentration were less potent: 5[beta],3[alpha]-diol reduced the number of discharges by 31%, whereas 5[alpha],3[beta]-diol yielded only 27% reduction. 5[alpha],3[alpha]-Diol inhibited PTZ-induced seizures [italic]in vivo[/italic] in dose-dependent manner (ED[sub]50[/sub], 75.8 mg/kg). 5[beta],3[alpha]-Diol also was protective, but was less potent (ED[sub]50[/sub],146 mg/kg). 5[alpha],3[beta]-Diol was devoid of any anticonvulsant activity up to a dose of 300 mg/kg.
The A-ring reduced testosterone metabolites protected against seizures with a stereoselectivity comparable to that of other neuroactive steroids. These results support a role of neuroactive metabolites of testosterone in seizure regulation.
[Supported by: NIH]