Neuroprotection by steroids after neurotrauma in organotypic spinal cord cultures: a key role for progesterone receptors and steroidal modulators of GABA(A) receptors

Neuropharmacology. 2013 Aug:71:46-55. doi: 10.1016/j.neuropharm.2013.03.010. Epub 2013 Mar 28.


Progesterone is neuroprotective after spinal cord injury, however its mechanism of action remains unexplored. Here we used organotypic spinal cord slice cultures from 3 weeks-old mice to evaluate the mechanisms of neuroprotection by progesterone and its 5α-reduced metabolites. In vitro spinal cord injury, using a weight drop model, induced a decrease in the number of motoneurons. This was correlated with an increase in the number of dying cells (PI⁺ cells) and in LDH release. Addition of 10 μM of progesterone, 5α-dihydroprogesterone (5α-DHP) or allopregnanolone (3α, 5α-tetrahydroprogesterone) to the medium at the time of injury rescued the spinal cord slices from the effects of damage. Progesterone prevented membrane cell damage, motoneuron loss and cell death. These effects were not due to its bioconversion to 5α-DHP nor to allopregnanolone, as supported by the finasteride, an inhibitor of 5α-reductase enzymes, and by the absence of 5α-reduced progesterone metabolites in the slices analyzed by gas chromatography-mass spectrometry. The neuroprotective effects of progesterone required PR as they could not be observed in slices from homozygous knockout PR(-/-) mice. Allopregnanolone treatment was also neuroprotective. Its effects were not due to its bioconversion back to 5α-DHP, which can activate gene transcription via PR, because they were still observed in slices from knockout PR(-/-) mice. Allopregnanolone effects involved GABA(A) receptors, as they were inhibited by the selective GABA(A) receptor antagonist Gabazine, in both PR(+/+) and PR(-/-) mice. Altogether, these findings identify both PR and GABA(A) receptors as important targets for neuroprotection by progestagens after spinal cord injury.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5-alpha-Dihydroprogesterone / metabolism
  • 5-alpha-Dihydroprogesterone / pharmacology
  • Animals
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Cell Membrane / pathology
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism
  • Cell Nucleus / pathology
  • Cell Survival / drug effects
  • GABA-A Receptor Antagonists / pharmacology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Motor Neurons / drug effects*
  • Motor Neurons / metabolism
  • Motor Neurons / pathology
  • Nerve Tissue Proteins / agonists
  • Nerve Tissue Proteins / metabolism
  • Neuroprotective Agents / antagonists & inhibitors
  • Neuroprotective Agents / chemistry
  • Neuroprotective Agents / metabolism
  • Neuroprotective Agents / pharmacology*
  • Pregnanolone / chemistry
  • Pregnanolone / metabolism
  • Pregnanolone / pharmacology
  • Progesterone / analogs & derivatives
  • Progesterone / metabolism
  • Progesterone / pharmacology*
  • Receptors, GABA-A / chemistry
  • Receptors, GABA-A / metabolism*
  • Receptors, Progesterone / agonists*
  • Receptors, Progesterone / genetics
  • Receptors, Progesterone / metabolism
  • Spinal Cord / drug effects*
  • Spinal Cord / metabolism
  • Spinal Cord / pathology
  • Spinal Cord Injuries / drug therapy*
  • Spinal Cord Injuries / metabolism
  • Spinal Cord Injuries / pathology
  • Tissue Culture Techniques


  • GABA-A Receptor Antagonists
  • Nerve Tissue Proteins
  • Neuroprotective Agents
  • Receptors, GABA-A
  • Receptors, Progesterone
  • Progesterone
  • 5-alpha-Dihydroprogesterone
  • Pregnanolone