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Characterization of Delta‐Sleep‐Inducing Peptide‐Evoked Release of Met‐Enkephalin from Brain Synaptosomes in Rats
Author(s) -
Nakamura Akihiro,
Sakai Kenji,
Takahashi Yukie,
Shiomi Hirohito
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb08251.x
Subject(s) - endocrinology , medicine , chemistry , met enkephalin , enkephalin , hypothalamus , thalamus , free nerve ending , striatum , brainstem , opioid , biology , neuroscience , dopamine , biochemistry , receptor
Delta‐sleep‐inducing peptide (DSIP) stimulates the release of Met‐enkephalin (Met‐ENK) from superfused slices of the rodent lower brainstem in vitro. In our present study, DSIP (10– 10– 10– 9 M ) induced a significant release of Met‐ENK from medullary synaptosomes of rats. This DSIP‐evoked release of Met‐ENK was Ca 2+ dependent and tetro‐dotoxin (TTX) insensitive. Furthermore, DSIP (10– 11– 10– 9 M ) significantly increased 45 Ca 2+ uptake in medullary synaptosomes. These results demonstrate that DSIP acts directly on the nerve endings of Met‐ENK‐containing neurons to release this pentapeptide by generating a Ca 2+ influx into these neurons. Effects of DSIP on Met‐ENK release in other discrete brain regions were also studied. Significant DSIP‐evoked Met‐ENK release from synaptosomes was observed in the cortex, hypothalamus, and midbrain (at concentrations of 10– 10 and 10– 9 M ) and in the hippocampus and thalamus (only at 10– 9 M ), but not in the striatum. In the hypothalamus, the release of Leu‐enkephalin from its synaptosomes was slightly, but not significantly, enhanced by DSIP (10– 10– 10– 8 M). Our findings demonstrate that DSIP triggered a Ca 2+ influx in nerve endings to induce a subsequent release of Met‐ENK from neurons in only certain brain regions.