Fluorescence microscopy and electron microscopy of adrenergic nerves after constriction at two points

SYNOPSIS Guinea pig and cat adrenergic nerves have been constricted at two points and the effects studied with the fluorescence method for the localization of noradrenaline and with the electron microscope. After operation there was a rapid accumulation of fluorescent material proximal to the constrictions. This was greater above the proximal than the distal lesion and persisted for several days. The accumulation above the distal constriction disappeared between 24–48 hours after operation. Any accumulation of fluorescent material distal to the constrictions could almost invariably be correlated with the presence of ganglion cells situated more peripherally, or with an inadequate constriction of the nerves. Electron microscopy showed an accumulation of vesicles with an electron‐dense core, believed to carry noradrenaline, proximal to the constrictions. This corresponded closely to the accumulation of fluorescent material. The results suggested that the passage of noradrenaline in these nerves is from the nerve‐cell body to the periphery. There was no unequivocal evidence of a retrograde flow of the transmitter.