Exposure and isolation of the superior sagittal sinus elicits Fos in the trigeminal nucleus caudalis and dorsal horn of the cervical spinal cord: how long should you wait?

The immunohistochemical detection of the proto-oncogene Fos is widely used as a marker of cell activation in the central nervous system for mapping neurobiological pathways. This study examined the time course of Fos disappearance following surgery by studying neurons in the trigeminocervical complex after three different rest periods, 4, 8 and 24 h. The region of interest was the trigeminocervical complex (TCC) which extends from the caudal medulla to the caudal level of the C2 spinal cord. Animals in the 24 h group had a median of only 66 positive cells, more than six times less cells than in those animals left for only 4 h. This study shows the considerable benefit of waiting 24 h over the more convenient time frame posed by the 4 and 8 h intervals.