Ultrastructural analysis of substance P-immunoreactive nerve fibers in myenteric ganglia of guinea pig small intestine

Abstract

Electron microscopic immunocytochemistry has been used to study the distribution and synaptic relationships of substance P (SP)- immunoreactive nerve fibers in ultrathin sections from whole-mount preparations of myenteric ganglia from guinea pig small intestine. At the light microscopic level, myenteric ganglia stained for ultrastructural study contained dense arrays of SP-immunoreactive nerve fibers around and between the neuronal and glial cell bodies. At the electron microscopic level, SP-containing nerve fiber profiles occurred throughout the neuropil of the myenteric ganglia. Both vesicle- containing and nonvesiculated nerve fiber profiles were immunoreactive. The positive vesiculated profiles contained variable proportions of small clear and large granular vesicles. Two-thirds of the vesicle- containing nerve fiber profiles in myenteric ganglia were immunoreactive for SP. Many vesiculated SP-immunoreactive nerve fiber profiles were directly apposed to each myenteric neuron. However, only about 0.6% of these vesiculated profiles formed synapses that showed the ultrastructural specializations of vesicle clustering presynaptically and fuzzy electron-dense material on the postsynaptic membrane. On the other hand, morphologically identifiable synapses with SP-immunoreactivity comprised about half the total number of synapses in the ganglia. SP-immunoreactive synapses were observed on nonvesiculated nerve processes in the periphery of the ganglia and on nerve cell bodies. Most of the axosomatic SP synapses occurred on small neurons that lay either on the surfaces of the ganglia or near the fibers of the internodal strands where they traveled through the ganglia. Both SP-positive and SP-negative nerve cell bodies received SP synapses.(ABSTRACT TRUNCATED AT 250 WORDS)

Complete penetration of antibodies into vibratome sections after glutaraldehyde fixation and ethanol treatment: light and electron microscopy for neuropeptides.

“…Enk, and NPY nerve fibers suggests that high glutaraldehyde fixatives may retain these antigens somewhat better than fixatives with little or no glutaraldehyde. For example, the anti-SP antiserum used here at an optimal dilution of 1:60,000 on tissue fixed with 1% or 2.5% glutaraldehyde has an optimal dilution of 1:16,000 when used on tissue fixed in 0.05 % glutaraldehyde-formaldehyde-picric acid (Llewellyn-Smith et d.,1988,1989.…”

“…In a previous study (UewellynSmith et al, 1985), it was shown that immunoreagents could penetrate completely through intact myenteric ganglia from intestine that had been fixed with 0.05% glutaraldehyde, 4% formaldehyde, 0.2% picric acid, and then washed with 10% ethanol. Since all immunoreactive nerve fibers are stained after this treatment, it has been possible to quantify immunoreactive nerve fibers in wholemount preparations made from different layers of the gut d l (Llewellyn-Smith et al, 1988, 1989. The purpose of the present experiments was to adapt the ethanol washing protocol for use in the central nervous system so that we could carry out similar quantitative EM immunocytochemical studies in the brain and spinal cord.…”

The Enteric Nervous System and Its Extrinsic Connections

“…The latter nonspecialized association is the most common. Most enteric neurons receive both specialized and nonspecialized contacts [35][36][37].…”

Characterisation of substance P-induced endocytosis of NK1 receptors on enteric neurons

“…The high density of tachykinin fibres within enteric ganglia is suggestive of tachykinins also being transmitters at neuroneuronal synapses. These fibres form synapses on the cell bodies of enteric neurons (Llewellyn-Smith et al 1989) and tachykinins depolarise the majority of nerve cells (Katayama et al 1979).…”