Immunocytochemical analysis of [Met5]enkephalin-Arg6-Gly7-Leu8 immunoreactive structures in the rat superior cervical ganglion.
Indirect immunofluorescence and immunoelectron microscopy were employed to analyze the enkephalinergic systems in the rat superior cervical ganglion (SCG). These systems were identified using specific antiserum against [Met5]Enkephalin-Arg6-Gly7-Leu8 (ENK-8), a peptide which is derived only from proenkephalin A. Abundant ENK-8 like immunoreactive (ENK-8-LI) neurons and fibers were observed in the SCG, but their distribution patterns were heterogenous; ENK-8-LI neurons were localized preferentially in the caudal two-thirds of the SCG, while immunoreactive fibers were found to be distributed more densely in the rostral one-third than in the remaining part of the SCG. Most of the ENK-8-LI neurons were large and had ultrastructural features resembling those of principal cells, some were identified electron microscopically as small intensely fluorescent (SIF) cells. ENK-8-LI fibers were varicose in appearance and surrounded the perikarya of neurons. Since most of these fibers were not detected after experimental decentralization of the SCG and since ENK-8-LI terminals were seen to contain small lucent vesicles, most of the former were thought to be preganglionic fibers. Immunoreactive fibers mainly formed synaptic contacts with the dendrites of non-immunoreactive principal cells, but a small proportion of ENK-8-LI principal cells also received synaptic input from them. Occasionally, immunoreactive fibers formed synapses with the processes or the soma of both ENK-8-LI and non-immunoreactive SIF cells. On the basis of these findings, we conclude that: (1) preganglionic ENK-8-LI fibers terminate mainly on the principal cells, which are devoid of ENK-8-LI structures; (2) the majority of ENK-8-LI neurons are principal cells, while the remainder are SIF cells; (3) inputs to these cells mainly involve structures lacking ENK-8 immunoreactivity; and (4) there are, however, a small number of ENK-8-LI preganglionic fibers which terminate on ENK-8-LI principal cells and SIF cells.
First Department of Internal Medicine, Osaka University Medical School, Japan.
Y
Y
Kanagawa-Terayama
A
A
Wanaka
H
H
Yamasaki
T
T
Matsuyama
M
M
Matsumoto
T
T
Kamada
C
C
Yanaihara
M
M
Tohyama
D000818:Animals; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000378:metabolism; D005728:Ganglia, Sympathetic / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D051381:Rats; D011919:Rats, Inbred Strains; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure
D004744:Enkephalin, Methionine; C033453:enkephalin-Met, Arg(6)-Gly(7)-Leu(8)-