The N-terminal 1-16, but not C-terminal 17-29, galanin fragment affects the flexor reflex in rats.
The biological activity of two galanin (GAL) fragments, GAL-(1-16) and GAL-(17-29), was tested in vivo by using a spinal nociceptive flexor reflex model in the rat. Intrathecal (i.t.) GAL-(1-16) had a similar biphasic effect on the flexor reflex, with facilitation at lower doses and facilitation followed by depression at higher doses, as the full length peptide GAL-(1-29). GAL-(1-16) also effectively depressed the facilitation of the flexor reflex caused by i.t. substance P (SP) or C-fiber conditioning stimulation (CS) and potentiated the depressive effect of i.t. morphine on the reflex, both actions that have been reported earlier with GAL-(1-29). In contrast, i.t. GAL-(17-29), even at high doses, did not induce changes in the amplitude of the flexor reflex, nor did it interact with the effects of i.t. SP, morphine or C-fiber CS. It is concluded that the N-terminal portion of GAL-(1-29) is critical for the biological activity of the intact peptide in the dorsal horn of the rat spinal cord. The similarity between the effects of GAL-(1-16) and GAL-(1-29) indicates that they probably act on the same GAL receptor.
Department of Clinical Physiology, Karolinska Institute, Huddinge, Sweden.
X J
XJ
Xu
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Wiesenfeld-Hallin
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G
Fisone
T
T
Bartfai
T
T
Hökfelt
D000818:Animals; D005260:Female; D019004:Galanin; D009020:Morphine / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009186:Myelin Sheath / Q000502:physiology; D009475:Neurons, Afferent / Q000187:drug effects; D010446:Peptide Fragments / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012018:Reflex / Q000187:drug effects*; D013373:Substance P / Q000494:pharmacology; D013552:Swine
D010446:Peptide Fragments; D010455:Peptides; D013373:Substance P; D009020:Morphine; D019004:Galanin