Effect of Ganaxolone on Flurothyl Seizures in Developing Rats

Abstract

Summary:Purpose: To determine the effects of a newly synthesized epalon, ganaxolone (GNX), on primarily generalized seizures in rats of various ages during development. Epalons are classified as neuroactive steroids that interact at unique site of the GABA, receptor-CI-channel complex in the central nervous system.Methods: Sprague-Dawley male rats were used at 9, 15, 30, and 60 postnatal days (PN). GNX dissolved in 2-hydroxypropyl-P-cyclodextrine was administered intraperitoneally in different doses at various time points before flurothyl testing. The incidence and threshold of clonic and tonic-clonic flurothyl seizures were evaluated. Behavioral changes were also assessed.Results: In all age groups, the effects of GNX were dose dependent and more prominent 10 min after its administration.In PN 60 and PN 30 rats, GNX had dose-dependent anticonvulsant effects; tonic-clonic seizures were more sensitive to GNX treatment than clonic seizures. In PN 15 and PN 9 rats, GNX demonstrated dose-and time-dependent anticonvulsant effects against both types of flurothyl-induced seizures. GNX was more effective in PN 15 rats than in other age groups, but at doses that altered motor behavior.Conclusions: GNX has anticonvulsant effects against flurothylinduced seizures in all age groups tested. Its effects are more prominent in the two younger age groups, especially in PN 15 rats, but are associated with motor side effects. Key Wards: Ganaxolone-Seizures-Rats-Development-Flurothy I.Neurosteroids (also called neuroactive steroids) are steroid hormones that can be formed de novo in the central nervous system (CNS) (1). Neurosteroids can also be produced in brain tissues from the conversion of peripheral steroid hormones such as progesterone, deoxycorticosterone, and testosterone, which can cross the blood-brain barrier (2). Endogenous or synthetic neuroactive steroids' alter neuronal excitability by rapidly acting on the neuronal membrane within seconds to minutes (3,4).The endogenous metabolites of progesterone (501-pregnan-3a-ol-20-one and 5ci-pregnan-3rx,20c~-diol), deoxycorticosterone (5a-pregnan-301,2 1 -diol-20-one), and their synthetic analogue alphaxalone (501-pregnan-301-01-1 1,20-dione) are the best described neurosteroids (45).There is a class of neuroactive steroids called "epalons" that are devoid of hormonal effects with high specific activity for the GABA, receptor complex (4,6,7). Epalons interact as positive allosteric modulators at a unique receptor site of the GABA, receptor-C1-channel com- Ganaxolone (301-hydroxy-3P-methyl-Sol-pregnan-20-one; GNX) is a newly developed 3P-methylated synthetic epalon derived from the endogenous neuroactive steroid 3a-hydroxy-5a-pregnan-20-one (301,501-P) (11,12). In vitro studies show that GNX has a positive allosteric modulatory effect at the GABA, receptor-Clchannel complex (11). Data from in vivo studies demonstrate that GNX is a potent anticonvulsant against clonic pentylenetetrazol (PTZ)-, bicuculline-, t-butylbicyclophosphorothionate-, cocaine-, and aminophylline-induced s...

Pathogenesis and new candidate treatments for infantile spasms and early life epileptic encephalopathies: A view from preclinical studies

“…More recently, pretreatment with ganaxolone, a neuroactive steroid, delayed and reduced NMDA spasms in the prenatal betamethasone model (Yum et al 2014). The therapeutic relevance of ganaxolone in IS is currently unclear because the effect on spasms or flurothyl seizures was only observed with high doses that can produce motor impairment (Liptakova et al 2000; Yum et al 2014). In a multicenter open label, add-on clinical trial of ganaxolone in infants with refractory IS, 33% of the infants responded with at least 50% reduction in spasms but only one of the 15 patients became spasm-free (Kerrigan et al 2000).…”

Role of Anticonvulsant and Antiepileptogenic Neurosteroids in the Pathophysiology and Treatment of Epilepsy

“…Ganaxolone has similar pharmacological properties to the natural neurosteroids such as allopregnanolone (Reddy and Woodward, 2004). It has protective activity in diverse rodent seizure models, including clonic seizures induced by the chemoconvulsants pentylenetetrazol, bicuculline, flurothyl, aminophylline; limbic seizures in the 6-Hz model; amygdala and cocaine-kindled seizures; and corneal kindled seizures (Gasior et al, 2000; Liptáková et al, 2000; Reddy and Rogawski, 2000a, 2010b; Kaminski et al, 2003, 2004). During prolonged daily treatment, tolerance does not develop with the anticonvulsant activity of ganaxolone (Kokate et al, 1998; Reddy and Rogawski, 2000a).…”

JourANTI-CONVULSANT ACTIVITY OF GANAXOLONE ALONE AND IN COMPARISON WITH STANDARD ANTI-EPILEPTIC DRUGS IN RODENT MODELS

“…Electrophysiological recordings showed that nanomolar concentrations of GNX potentiated GABA-evoked chloride currents in Xenopus oocytes expressing human GABA-A receptor subunits α1, β2, γ2L, but direct activation of chloride flux occurred only at micromolar concentrations 14,15 .…”