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Reduced Progesterone Metabolites Protect Rat Hippocampal Neurones From Kainic Acid Excitotoxicity In Vivo

Reduced Progesterone Metabolites Protect Rat Hippocampal Neurones From Kainic Acid Excitotoxicity... The ovarian hormone progesterone is neuroprotective in some animal models of neurodegeneration. Progesterone actions in the brain may partly be mediated by the locally produced metabolites 5α‐dihydroprogesterone and 3α,5α‐tetrahydroprogesterone. The neuroprotective effects of these two metabolites of progesterone were assessed in this study. Ovariectomized Wistar rats were injected with kainic acid, to induce excitotoxic neuronal death in the hippocampus, and with different doses of 5α‐dihydroprogesterone and 3α,5α‐tetrahydroprogesterone. The number of surviving neurones in the hilus of the dentate gyrus of the hippocampus was assessed with the optical disector method. The administration of kainic acid resulted in a significant decrease in the number of hilar neurones and in the induction of vimentin expression in reactive astrocytes, a sign of neural damage. Low doses of 5α‐dihydroprogesterone (0.25 and 0.5 mg/kg body weight, b.w.) prevented the loss of hilar neurones and the appearance of vimentin immunoreactivity in astrocytes. Higher doses (1–2 mg/kg b.w.) were not neuroprotective. By contrast, low doses of 3α,5α‐tetrahydroprogesterone (0.25–1 mg/kg b.w.) were unable to protect the hilus from kainic acid while higher doses (2–4 mg/kg b.w.) were protective. The different optimal neuroprotective doses of 5α‐dihydroprogesterone and 3α,5α‐tetrahydroprogesterone suggest that these two steroids may protect neurones using different mechanisms. The neuroprotective effects of 3α,5α‐tetrahydroprogesterone may be exerted by the inhibition of neuronal activity via the GABAA receptor. This latter possibility is supported by the observation that 3β,5α‐tetrahydroprogesterone, an isomer of 3α,5α‐tetrahydroprogesterone that does not bind to GABAA receptor, was not neuroprotective. In summary, our findings suggest that progesterone neuroprotective effects may be, at least in part, mediated by its reduced metabolites 5α‐dihydroprogesterone and 3α,5α‐tetrahydroprogesterone. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Neuroendocrinology Wiley

Reduced Progesterone Metabolites Protect Rat Hippocampal Neurones From Kainic Acid Excitotoxicity In Vivo

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References (75)

Publisher
Wiley
Copyright
Copyright © 2004 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0953-8194
eISSN
1365-2826
DOI
10.1111/j.1365-2826.2004.01121.x
Publisher site
See Article on Publisher Site

Abstract

The ovarian hormone progesterone is neuroprotective in some animal models of neurodegeneration. Progesterone actions in the brain may partly be mediated by the locally produced metabolites 5α‐dihydroprogesterone and 3α,5α‐tetrahydroprogesterone. The neuroprotective effects of these two metabolites of progesterone were assessed in this study. Ovariectomized Wistar rats were injected with kainic acid, to induce excitotoxic neuronal death in the hippocampus, and with different doses of 5α‐dihydroprogesterone and 3α,5α‐tetrahydroprogesterone. The number of surviving neurones in the hilus of the dentate gyrus of the hippocampus was assessed with the optical disector method. The administration of kainic acid resulted in a significant decrease in the number of hilar neurones and in the induction of vimentin expression in reactive astrocytes, a sign of neural damage. Low doses of 5α‐dihydroprogesterone (0.25 and 0.5 mg/kg body weight, b.w.) prevented the loss of hilar neurones and the appearance of vimentin immunoreactivity in astrocytes. Higher doses (1–2 mg/kg b.w.) were not neuroprotective. By contrast, low doses of 3α,5α‐tetrahydroprogesterone (0.25–1 mg/kg b.w.) were unable to protect the hilus from kainic acid while higher doses (2–4 mg/kg b.w.) were protective. The different optimal neuroprotective doses of 5α‐dihydroprogesterone and 3α,5α‐tetrahydroprogesterone suggest that these two steroids may protect neurones using different mechanisms. The neuroprotective effects of 3α,5α‐tetrahydroprogesterone may be exerted by the inhibition of neuronal activity via the GABAA receptor. This latter possibility is supported by the observation that 3β,5α‐tetrahydroprogesterone, an isomer of 3α,5α‐tetrahydroprogesterone that does not bind to GABAA receptor, was not neuroprotective. In summary, our findings suggest that progesterone neuroprotective effects may be, at least in part, mediated by its reduced metabolites 5α‐dihydroprogesterone and 3α,5α‐tetrahydroprogesterone.

Journal

Journal of Neuroendocrinology – Wiley

Published: Jan 1, 2004

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