The vesicle content of catecholamine-containing axons in the rectum of the domestic fowl: effect of permanganate and chromaffin fixations.

The ultrastructural appearance of catecholamine-containing (CA) axon profiles in the rectum of the domestic fowl was compared following fixation using the chromaffin reaction or potassium permanganate. As described previously, after chromaffin fixation CA-axons in the perivascular plexuses contained many small granular vesicles (SGV) and variable numbers of large granular vesicles (LGV), whereas those in the non-vascular sites contained few small vesicles and were characterised by the presence of elongated LGV. Following fixation in potassium permanganate, CA-axons in both the non-vascular and vascular sites contained many SGV. The SGV were accompanied by variable numbers of large round vesicles which were often devoid of a core. Large vesicles comprised 16 and 26%, respectively, of total vesicles in the vascular and non-vascular axon profiles. The total number of vesicles per CA-axon profile in both the vascular and non-vascular site was not dependent on fixation procedure. It is concluded that the vesicle content of CA-axon profiles in the rectum of the domestic fowl is dependent on the fixative employed.