The postnatal development of monoamine-containing structures in the hypothalamo-hypophyseal system of the albino rat

The development of monoamine-containing structures in the hypothalamo-hypophyseal system was studied in two strains of albino rats. It was found that catecholamine-containing cell bodies in various hypothalamic areas and nerve terminals in the median eminence-neurohypophyseal region have a wholly postnatal development. Slight individual and strain differences were observed in the rate of development of formaldehyde-induced fluorescence in these structures. This fluorescence could be depleted by means of reserpine and a catecholamine-synthesis inhibitor from the earliest time it became detectable suggesting that the catecholamine was present in storage granules and that the neurones conducted impulses as soon as they acquired their first catecholamine content. The neurones were also capable of taking up exogenous l-dopa and l-noradrenaline. Fluorescent fibres in the pars intermedia were seen at one week and in the infundibular process by the second week. The cells of the pars intermedia also showed definite specific fluorescence by postnatal day 2-3. Fluorescent cells capable of taking up l-dopa and l-noradrenaline were observed in the pars distalis of the pituitary.