Journal of Neuroscience, Vol 5, 1527-1544, Copyright © 1985 by Society for Neuroscience
The co-occurrence of a substance P-like peptide and cholecystokinin-8 in a fiber system of turtle cortex
A Reiner, WD Eldred, MC Beinfeld and JE Krause
Single-label and double-label immunohistochemical techniques were used to
demonstrate the coexistence of substance P-like immunoreactivity (SPLI) and
cholecystokinin-8-like immunoreactivity (CCK-8-LI) in an extensive fiber
system within the telencephalic cortex of turtle. All SPLI-containing
fibers and terminals of this system contain CCK-8-LI and vice versa. The
fibers of this system course from more medial cortical regions to more
lateral ones, originating either from neurons in the more medial cortices
or from extracortical neurons, the axons of which ascend the medial wall of
the cortex. The precise location of the neurons that give rise to this
cortical projection system is uncertain, but a hypothalamic location seems
most likely at present. The fibers and terminals of this system are found
throughout the entire mediolateral and rostrocaudal extent of the
telencephalic cortex of turtle and are largely confined to the cell body
layer of the cortex. Fewer SPLI/CCK-8-LI-containing fibers are found in
pyriform (olfactory) cortex than in the other cortices. Ultrastructural
studies indicate that SPLI/CCK-8-LI-containing terminals make asymmetric
synapses on cell bodies or their proximal dendrites. Both SPLI and CCK-8-LI
are found in large dense core vesicles in these labeled terminals. Labeled
terminals also contained numerous small, round, unlabeled vesicles
clustered near synaptic release sites and a number of unlabeled large dense
core vesicles. Quantification of the percentage of the large dense core
vesicles that were labeled in SP-labeled terminals, in CCK-8- labeled
terminals, and in terminals labeled for both SP and CCK-8 provided
suggestive evidence that SPLI and CCK-8-LI must be contained within the
same large dense core vesicles. Radioimmunoassay indicated that the
SP/CCK-8-containing system of turtle cortex contains 0.93 +/- 0.090 pg of
SP/microgram of cortical tissue protein and 0.31 +/- 0.11 pg of
CCK-8/micrograms of cortical tissue protein. The CCK-8-like material in
turtle cortex coelutes with CCK-8-sulfate, using gradient elution high
pressure liquid chromatography (HPLC). The SP-like material, although
immunologically highly similar to undecapeptide SP (Reiner, A., J. E.
Krause, K. T. Keyser, W. D. Eldred, and J. F. McKelvy (1984) J. Comp.
Neurol. 226: 50-75), does not coelute with undecapeptide SP using gradient
elution HPLC.(ABSTRACT TRUNCATED AT 400 WORDS)