Effects of progesterone on the inflammatory response to brain injury in the rat.

The effects of progesterone on the cellular inflammatory response to frontal cortex injury were examined on postsurgical days 1, 3, 5, 7 and 9 in male rats treated with progesterone (4 mg/kg) and/or vehicle. Rats with bilateral contusions showed increased levels of edema on days 1, 3 and 5, more reactive astrocytes on days 3, 5, 7 and 9, and more macrophages/activated microglia on days 1, 3, 5 and 9 compared to shams. The number of neurons in the medial dorsal nucleus (MDN) of the thalamus reduced on days 5 and 9 after injury compared to shams. Progesterone reduced edema levels and increased the accumulation of macrophages/activated microglia compared to vehicle controls (p<0.025); however, these changes in the inflammatory response were not related to MDN neuronal survival. Our results confirm the possibility that one way progesterone mediates its neuroprotective effects following injury is through its actions on the inflammatory response.