The acceleration of amygdala kindling epileptogenesis by chronic low-dose corticosterone involves both mineralocorticoid and glucocorticoid receptors

Kumar, Gaurav; Couper, Abbie; O’Brien, Terence J.; Salzberg, Michael R.; Jones, Nigel C.; Rees, Sandra M.; Morris, Margaret J.

doi:10.1016/j.psyneuen.2007.05.011

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Volume 32, Issue 7 , Pages 834-842, August 2007

The acceleration of amygdala kindling epileptogenesis by chronic low-dose corticosterone involves both mineralocorticoid and glucocorticoid receptors

Gaurav Kumar
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Melbourne, Vic, Australia
- Co-first authors.
Abbie Couper
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Melbourne, Vic, Australia
- Co-first authors.
Terence J. O’Brien
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Melbourne, Vic, Australia
- Department of Neurology, Royal Melbourne Hospital, University of Melbourne, Melbourne, Vic, Australia
Michael R. Salzberg
- Department of Psychiatry, St. Vincent's Hospital, University of Melbourne, Melbourne, Vic, Australia
Nigel C. Jones
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Melbourne, Vic, Australia
- Corresponding author. Tel.: +61383443273; fax: +61393471863.
Sandra M. Rees
- Department of Anatomy and Cell Biology, University of Melbourne, Melbourne, Vic, Australia
Margaret J. Morris
- Department of Physiology and Pharmacology, University of New South Wales, Sydney, NSW, Australia

Received 23 January 2007; received in revised form 24 April 2007; accepted 24 May 2007.

Summary

We have previously demonstrated that low-dose corticosterone (CS) administration, used as a model of the effect of chronic stress, accelerates epileptogenesis in the electrical amygdala kindling rat model of temporal lobe epilepsy (TLE). This current study examined the relative contributions to this effect of mineralocorticoid (MR) and glucocorticoid (GR) subtypes of glucocorticoid receptors. Female non-epileptic wistar rats 10–13 weeks of age were implanted with a bipolar electrode into the left amygdala. Five treatment groups were subjected to rapid amygdala kindling: water-control (n=9), CS treated (6mg/100ml added to drinking water; n=9), CS+spironolactone (MR antagonist, 50mg/kgsc; n=9), CS+mifepristone (GR antagonist, 25mg/kgsc; n=9), and CS+both antagonists (n=7). Rats were injected with vehicle or the relevant antagonist twice daily for the entire kindling period. Experimental groups differed significantly in the number of stimulations required to reach the ‘fully kindled state’ (Racine, 1972) ANOVA, F_(4,38)=2.73, p=0.04). Amygdala kindling was accelerated in the CS-treated group compared with water controls (mean stimulations for full kindling: 45.2 vs. 86.5, p<0.01). This acceleration was inhibited by both the MR and GR antagonist treatments (mean stimulations: 69.6 and 70.4, p=0.04 and 0.04 vs. CS group, respectively), with the kindling rates in these groups not significantly different from water-treated subjects (p=0.26 and 0.29, respectively). The kindling rates in the MR and GR antagonist treatment groups did not significantly differ from each other (p=0.93), nor from the combined treatment group (mean stimulations: 62.8, p=0.59 and 0.54, respectively). This study demonstrates that activation of both high-affinity (MR) and low-affinity (GR) glucocorticoid receptors are involved in mediating CS-induced acceleration of amygdala kindling epileptogenesis.