Neuropeptides in the rat corpus cavernosum and seminal vesicle: Effects of age and two types of diabetes

Aims: To observe the development of neuropathic changes in two types of experimental diabetes using changes in concentrations of NPY, CGRP and amines in the corpora cavernosa and seminal vesicles. Type I diabetes was studied in Wistar rats after 12 and 16 weeks of STZ-induced hyperglycaemia, and Type II diabetes was studied in prediabetic GK rats aged 52 weeks. Both were compared with age-matched normal Wistar rats. Methods: NPY and CGRP were estimated using radioimmunoassay, and amines using HPLC. Results: There were significant changes in [CGRP] in the normal corpus cavernosum and in [NPY] in the normal seminal vesicle with age. STZ-diabetes, induced at 10 weeks of age, resulted in significant elevation of [NPY] and [CGRP] in the corpora cavernosa and seminal vesicles after 12 and 16 weeks of hyperglycaemia, relative to age-matched control rats. The GK rats were intolerant of glucose at 52 weeks of age, but did not have raised fasting blood glucose levels. [NPY], [CGRP] and [noradrenaline] in corpora cavernosa were significantly increased in the prediabetic GK animals relative to age-matched Wistar control rats. The seminal vesicles of GK rats showed a significant increase in [NPY], a non-significant increase in [CGRP], and a fall in [noradrenaline] relative to the age-matched Wistar controls. Conclusions: The results indicate increased levels of NPY and noradrenaline in autonomic nerves, and of CGRP in sensory nerves, innervating the corpus cavernosum in Type I and in prediabetic Type II GK rats.