AN IMMUNOELECTRON MICROSCOPIC STUDY OF METHIONINE-ENKEPHALIN STRUCTURES IN CAT PREVERTEBRAL GANGLIA

Methionine-enkephalin-like immunoreactivity was detected in presynapti c nerve fibers and SIF cells in cat prevertebral ganglia. The immunore active nerve fibers contained a mixture of numerous small clear vesicl es and a few large vesicles; the immunoreactivity was only confined to the large vesicles. Most of the immunoreactive fibers were in apposit ion with non-immunoreactive neuronal profiles, without any detectable synaptic membrane specializations. The other immunoreactive fibers for med synaptic contacts mainly with non-immunostained dendrites and to a lesser extent with axons and neuronal soma. The characterization at t he ultrastructural level of the enkephalin-like immunoreactive structu res is discussed as regards the modalities whereby opiates may be invo lved in sympathetic ganglionic transmission.