SPROUTING OF NON-SYMPATHETIC MYELINATED AND UNMYELINATED FIBERS IN RESPONSE TO CHRONIC SYMPATHETIC DENERVATION IN THE PINEAL-GLAND OF THE CHINESE-HAMSTER, CRICETULUS-GRISEUS

We have examined the effects of chronic sympathetic denervation on non -sympathetic myelinated and unmyelinated fibres in the superficial pin eal gland of the Chinese hamster (Cricetulus griseus), using LM, EM an d immunohistochemistry. The results suggest that non-sympathetic, myel inated and unmyelinated fibres enter the superficial pineal gland at i ts distal portion by way of the nervi conarii, and that these fibres a re immunoreactive for calcitonin gene-related peptide or substance P. Non-sympathetic, myelinated and unmyelinated fibres in the superficial pineal gland increased in number following chronic superior cervical ganglionectomy. The number of unmyelinated fibres in the nervi conarii also increased in ganglionectomized animals. Thus, the numerical incr ease of calcitonin gene-related peptide or substance P fibres found in the superficial pineal gland after long-term sympathectomy may be due to sprouting of these fibres. It is speculated that the growth of non -sympathetic, myelinated and unmyelinated fibres and myelination of th e former fibres occurring after sympathectomy are caused by nerve grow th factor-related mechanisms.