MATURATIONAL CHANGES IN SYMPATHETIC AND SENSORY INNERVATION OF THE RAT UTERUS - EFFECTS OF NEONATAL CAPSAICIN TREATMENT

The plasticity of the sympathetic and sensory innervation of the rat u terus was examined, before and after puberty, in controls and in anima ls where primary sensory nerves had been destroyed by neonatal capsaic in treatment. Immunohistochemical and histochemical methods were used in association with nerve density measurements and biochemical assays. The main findings were as follows: (1) Puberty was associated with a marked increase in the weight of the uterine horn, uterine cervix and parametrial tissue. This was unaffected by capsaicin treatment. (2) Th e sympathetic innervation of the uterine horn and parametrial tissue w as reduced following puberty as revealed by a decrease in the density of noradrenaline-containing nerves and a marked decrease in the tissue concentration of noradrenaline. Sympathetic nerves supplying the uter ine cervix and the blood vessels of the uterus appeared to be unaffect ed by puberty. (3) In contrast, the sensory supply of the uterus by su bstance P and calcitonin gene-related peptide-containing nerves increa sed in parallel with uterine growth during puberty resulting In no cha nge in nerve density and only a slight reduction in peptide concentrat ion. (4) Neonatal capsaicin treatment caused a long-lasting depletion of substance P- and calcitonin gene-related peptide-containing nerves. In the uterine horn and parametrial tissue, capsaicin-resistant calci tonin gene-related peptide, but not substance P, still increased with tissue weight during puberty, indeed, in the uterine horn, the relativ e increase was greater than in controls. (5) Sensory denervation resul ted in an increase in the non-vascular sympathetic supply of the uteru s, although there was a regional variation in the time course of the r esponse. Perivascular sympathetic nerves were unaffected by capsaicin treatment. The pattern of change in non-vascular noradrenaline-contain ing nerves associated with puberty was similar in nature to controls. Thus, there is considerable plasticity in the innervation of the uteru s both during puberty and following sensory denervation. A complex pat tern of change occurs with differential responses in vascular and nonv ascular nerves and in different regions of the uterus. Such difference s may be due in part to the different origins of individual nerve popu lations and/or to their relative sensitivities to sex hormones.