Morphological changes in presynaptic terminals of the chick ciliary ganglion after stimulation in vivo. A stereological study showing a net loss of total membrane.

The Edinger-Westphal nucleus of one day old chicks was stimulated in vivo. This nucleus projects via the oculomotor nerve to the ciliary ganglion. The stimulation produces morphological changes in the calyciform endings located in the ciliary ganglion. There is a significant reduction of the numerical density on area of the clear and the dense core vesicles. The numerical density of the coated vesicles is low compared to that of the clear vesicles. Their density is however almost doubled by the stimulation. The vesicles, the vacuoles and the plasma membrane were quantified using stereological procedures. A net loss of total membrane was found due to the loss of organelle membrane not compensated for by an equivalent increase of the plasma membrane. These observations are discussed in terms of the theory of vesicular membrane recycling as proposed by Heuser and Reese (1973).