Synapse
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The distribution of enkephalin (ENK)-like immunoreactivity (LI) in spinal cord and medulla oblongata of cat and gray monkey (Macaca fascicularis) was studied by use of immunofluorescence and peroxidase antiperoxidase (PAP) techniques. Possible coexistence between ENK- and 5-hydroxytryptamine (5-HT)-LI was also analyzed with double labeling immunofluorescence. Furthermore, in situ hybridization was used to demonstrate cell bodies in the brain stem expressing mRNA encoding for ENK. ⋯ In the monkey brain stem without colchicine treatment, using the PAP technique, heavily stained ENK-IR cell bodies could be seen in the lateral reticular nucleus whereas, as in the cat, only a few, weakly stained ENK-IR cell bodies could be seen in the midline raphe nuclei. Using in situ hybridization technique, ENK mRNA expressing cells were demonstrated in the lateral reticular nucleus while no convincing mRNA signal could be found over cell bodies in the raphe nuclei. It is concluded that part of the ENKergic innervation of the cord in both species derives from supraspinal or suprasegmental levels.(ABSTRACT TRUNCATED AT 400 WORDS)