PLASTICITY OF AUTONOMIC NERVES - DIFFERENTIAL-EFFECTS OF LONG-TERM GUANETHIDINE SYMPATHECTOMY ON THE SENSORY INNERVATION OF THE RAT UTERUS DURING MATURATION

The sensory nerves, containing substance P and calcitonin gene-related peptide, and noradrenaline-containing sympathetic nerves of the rat u terus were analyzed following long-term sympathectomy with guanethidin e in prepubertal (four weeks), young adult (eight weeks) and fully adu lt animals (18 weeks). Immunohistochemical and histochemical methods w ere used in association with nerve density measurements and biochemica l assays. The main findings were as follows: (1) long-term guanethidin e treatment completely abolished the noradrenergic innervation of the uterine horn and parametrial tissue and markedly reduced the tissue le vels of noradrenaline in both regions at the three ages analysed; (2) in the uterine horn guanethidine treatment had no effect on the tissue levels of either calcitonin gene-related peptide or substance P or on the density of calcitonin gene-related peptide-containing nerves, at any of the three ages studied; (3) in the parametrial tissue increased levels of calcitonin gene-related peptide were observed at 8 and 18 w eeks of age, together with a significant increase in the density of ca lcitonin gene-related peptide-containing nerves. Substance P levels sh owed a transient increase in this tissue at eight weeks. In conclusion , long-term sympathectomy with guanethidine resulted in an increase in calcitonin gene-related peptide and substance P in sensory nerves in the parametrial tissue, but not in the uterine horn. The changes in th e parametrial tissue only occurred after puberty. It is suggested that sensory nerves in the uterine horn may be less responsive to sympathe tic denervation since loss of sympathetic nerves occurs as part of a n ormal physiological process during pregnancy in this region.