RESUMEN
To study the synaptic nerve endings on the adrenaline [A], noradrenaline [NA] and small granular Chromaffin [SGC] cells of the mouse before and after puberty and the possible functional relationship between these cells. Male albino mice bred at the animal house-Jordan University, which aged 5, 10 and 12 days and 5 weeks were used. After sacrifice, the adrenal glands were removed from the animals and processed for examination with a Philips 300 electron microscope. The percentage of SGC cells and the number of synaptic endings on A and NA cells were calculated. All the nerve endings observed are typical in appearance with the cholinergic-type synaptic endings. No evidence of an adrenergic innervation of Chromaffin tissue of the adrenal medulla has been obtained during the present work, though the elongated processes of small granular Chromaffin cell could readily be misinterpreted as adrenergic nerve fibres. The processes of these cells come close to other Chromaffin cells, both A, NA cell and form synapses. Frequent exocytotic figures related to these cells were observed. The present findings suggest that the SGS cells form an intrinsic system that regulates the activity of other chromaffin cells, particularly in the early postnatal period when the extrinsic innervation of the chromaffin cells is not yet fully developed