Explanation of the embryonic rat superior cervical ganglion initiated a retrograde response in noradrenergic neurons. By the 4th day of explanation, tyrosine hydroxylase activity per cell decreased to 62% of the day 0 control value. The rate of neurite outgrowth during the same period increased by 66%. By the 6th day both tyrosine hydroxylase activity and rate of neurite outgrowth returned to initial values. This inverse relationship is consistent with a proposed reordering of synthetic priorities that occurs in the parental cell body during axonal regeneration.