Evidence for differential storage of calcitonin gene-related peptide, substance P and serotonin in synaptosomal vesicles of rat spinal cord.
Homogenates of rat ventral and dorsal spinal cords were subjected to differential and gradient centrifugation on linear sucrose gradients following lysis of a synaptosomal fraction. The distribution of calcitonin gene-related peptide (CGRP) and substance P (SP) in dorsal spinal cord as well as the distribution of serotonin (5-HT) and SP in ventral spinal cord was determined, using radioimmunoassay (RIA) for CGRP and SP and high-performance liquid chromatography for 5-HT. In dorsal spinal cord. CGRP and SP had an almost identical distribution, with one peak in an intermediate density fraction which according to electron microscopy contained i.a. large dense-cored vesicles, and a second peak in a heavy fraction enriched in synaptosome-like structures. In ventral spinal cord, 5-HT and SP had different distribution patterns; 5-HT peaked in a light fraction containing many small synaptic vesicles, whereas SP peaked in an intermediate density fraction similar to the one in dorsal spinal cord. Both 5-HT and SP had second peaks in high density fractions containing synaptosome-like structures. The study demonstrates that the peptides CGRP and SP, partly coexisting in dorsal spinal cord, both seem to be stored in large vesicles inside synaptosomes, whereas the amine 5-HT and the peptide SP, coexisting in ventral spinal cord, appear to have a differential storage with 5-HT mainly in small vesicles and SP in large vesicles, both inside synaptosomes.
Fried
G
G
Department of Physiology, Karolinska Institutet, Stockholm, Sweden.
Franck
J
J
Brodin
E
E
Born
W
W
Fischer
J A
JA
Hiort
W
W
Hökfelt
T
T
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D013116:Spinal Cord / Q000378:metabolism* / Q000648:ultrastructure; D013373:Substance P / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism*
D012701:Serotonin; D013373:Substance P; D015740:Calcitonin Gene-Related Peptide