Journal of Neuroscience, Vol 7, 2344-2351, Copyright © 1987 by Society for Neuroscience
Desensitization to substance P-induced vasodilation in vitro is not shared by endogenous tachykinin neurokinin A
MA Moskowitz, C Kuo, SE Leeman, ME Jessen and CK Derian
Two mammalian tachykinins, substance P (SP) and neurokinin A (NKA), were
measured by radioimmunoassay in canine cephalic blood vessels and tested
for their vasoactivity in vitro. Levels of immunoreactive SP were
approximately 2-3 times greater than those of immunoreactive NKA in common
carotid, basilar, and middle cerebral arteries. Both endogenous tachykinins
relaxed precontracted segments of common carotid and basilar arteries in a
dose-dependent manner with an EC50 of 8.9 X 10(-11) M and 7 X 10(-10) M,
respectively, when added cumulatively. Relaxation was endothelial dependent
for both substances and not blocked or enhanced by pretreatment with
indomethacin, propranolol, lithium chloride, or atropine. Neither SP nor
NKA released 3H-inositol phosphates from phospholipid membranes of canine
carotid segments after preincubation with 3H-inositol. SP but not NKA or
the C-terminal fragments SP(4-11) caused desensitization to subsequent
additions of itself but not to the relaxation induced by sodium
nitroprusside, calcitonin gene-related peptide, or bradykinin. These
studies demonstrate that at least 2 peptides derived from
beta-preprotachykinin are contained within cephalic blood vessels and that
these products share similar vasoactive properties but differ in their
ability to desensitize vascular tachykinin receptors.