Postnatal development of noradrenaline-containing nerves of the rat uterus

The postnatal development of noradrenaline (NA)-containing nerves of the rat uterus and its associated blood vessels was investigated using histochemical and biochemical methods. These studies were carried out in conjunction with examination of the morphology of the uterus and the density of blood vessels at the prepubertal, peripubertal and adult stages. It was demonstrated that: (1) the rat uterus is innervated at birth; (2) the innervation of blood vessels develops earlier than that of the myometrium and the density of NA-containing perivascular nerves is not affected by puberty; (3) between birth and day 30 (prepubertal) there was a progressive increase in the innervation of the myometrium which was accompanied by a progressive increase in the total NA content of the organ; (4) at the first oestrus there was a marked increase in the weight of the uterus and isolated myometrial and parametrial tissue. Both muscle cell size and number were also increased. The density of myometrial innervation by NA-containing nerves was markedly reduced, although the total NA content did not change at this stage. This indicates a 'dilution' of myometrial NA-containing nerves in a greater amount of non-neuronal tissue; and (5) between the peripubertal and adult stages there was a further increase in uterine weight together with an increase in the number of smooth muscle cells and a reduction in the density of myometrial NA-containing nerves. Although the density of perivascular nerves was unaffected by puberty, the number of blood vessels supplying the uterus increased during the transition to the adult stage. This was reflected by a significant increase in the total NA content of the uterine horn and of isolated myometrial and parametrial preparations.