The behavioral and molecular effects of estradiol and progesterone on a rat model of spinothalamic tract lesion

The spinal cord injury is temporary or permanent damage in the spinal cord that disturbs the motor and sensory functions. The neuroprotective effects of steroids has been reported previously. Therefore, we designed a study to investigate the effects of different doses of estradiol (Est) and progesterone (Prog) on unilateral lesion of the spinothalamic tract (STT).

The 77 male adult Wistar rats were under the anesthesia for dorsal laminectomy at the spinal segments T8–T9. A tungsten-electrode was targeted to the right STT and unilateral lesion was made by a brief current pulse (300μA, 90s). Rats were divided into 11 groups and Est or Prog (2, 4, 8 and 16mg/kg) were administered 30min post-injury. Mechanical allodynia and open field as assessed before, 14 and 28 days after the injection then the animals were sacrificed. The western blotting was performed on T8–9 spinal segments to evaluate protein expression of ERK, p-P38, JNK, Iba1 and GFAP at the lesion site.

Est but not Prog significantly increased the pain threshold and motor activity at the dose of 8mg/kg on post-surgery days 14 and 28. Est but not Prog significantly increased the protein expression of ERK while decreased JNK protein. Both Est and Prog significantly decreased protein expression of p-P38, Iba1 and GFAP.

These results show Est (8mg/kg) is able to decrease mechanical allodynia and improve motor activity 14 and 28 days after spinothalamic tract lesion. It seems ERK, p-P38, JNK, Iba1 and GFAP are involved.