EFFECTS OF CHRONIC AND ACUTE ESTROGEN-TREATMENT ON THE DEVELOPING NORADRENALINE-CONTAINING NERVES OF THE RAT UTERUS

The developing noradrenaline-contining (NA-C) sympathetic nerves of th e rat uterus were analyzed following acute and chronic treatment with oestrogen. Histochemical methods were used in association with nerve d ensity measurements and biochemical assays. For comparative purposes, noradrenaline (NA) levels were measured in the urinary bladder and rig ht auricle following chronic oestrogen treatment. Acute treatment was performed by s.c. administration of a single dose of 40-mu-g oestradio l cypionate on the 25th day of age. Chronic treatment consisted of fou r doses of 10-mu-g oestradiol on days 10, 15, 20 and 25 of postnatal d evelopment. Both acute- and chronic-treated animals were killed at 28 days of age. The main biochemical findings were the following: (a) bot h acute and chronic oestrogen treatment increased the weight of the ut erine horn, parametrial tissue and uterine cervix; (b) in the uterine horn, the total content of NA was reduded following both oestrogen tre atments. However, the degree of reduction was greater after chronic tr eatment; (c) in the parametrial tissue, the NA levels were reduced onl y after chronic treatment; (d) in the cervix, the NA total content was increased after both treatments; (e) in the urinary bladder, there wa s a parallel increase between organ growth and NA content following ch ronic oestrogen treatment; (e) in the auricle neither the tissue weigh t nor the total content of NA were changed by chronic estrogen treatme nt. Histochemical studies showed that: (a) acute treatment with one si ngle dose of oestradiol, provoked a marked reduction in the density of NA-C nerves associated with the myometrial and parametrial smooth mus cle without affecting the innervation of blood vessels; (b) following chronic treatment, the only fibers we were able to recognize were thos e associated with blood vessels. these fibers were thinner and less in tensely fluorescent than in controls. Results are interpreted consider ing the differential sensitivity of uterine nerves to sex hormones. A possible involvement of oestrogen in changes of noradrenergic innervat ion of the uterus following puberty is discussed.