GR 73632

Ava[L-Pro9,N-MeLeu10] substance P(7-11) (GR 73632) and Sar9, Met(O2)11 increase distention-induced peristalsis through activation of neurokinin-1 receptors on smooth muscle and interstitial cells of cajal.[Pubmed:16330493]

J Pharmacol Exp Ther. 2006 Apr;317(1):439-45.

Substance P is generally considered an excitatory neurotransmitter related to gut motor activity, although an inhibitory influence of neurokinin-1 (NK1) receptor activation on peristalsis has also been reported. With an optimized in vitro method to assess distention-induced peristalsis, our aim was to clarify the effect of NK1 receptor activation on peristaltic activity and to reveal the mechanisms by which NK1 activation alters peristalsis. Distention of the small intestine of the mouse and guinea pig induced periodic occurrence of rhythmic waves of propagating rings of circular muscle contraction, associated with slow waves and superimposed action potentials, that propelled intestinal contents aborally. Activation of NK1 receptors by Ava[l-Pro(9),N-MeLeu10] substance P(7-11) (GR 73632) and Sar(9), Met(O(2))(11) on smooth muscle cells resulted in prolongation of the activity periods and increased action potential generation occurring superimposed on the intestinal slow wave activity. Activation of NK1 receptors on interstitial cells of Cajal resulted in an increase in slow wave frequency. Slow wave amplitude increased, likely by increased cell-to-cell coupling. The NK1 antagonist (S)-1-(2-[3-(3,4-dichlorophenyl)-1-(3-isopropoxyphenylacetyl)piperidin-3-yl]ethyl )-4-phenyl-1-azoniabicyclo[2.2.2]octane chloride (SR 140333) induced a decrease in the slow wave frequency and duration of the activity periods evoked by distention, which makes it likely that NK1 receptor activation plays a role in the normal physiological distention-induced generation of peristaltic motor patterns. In summary, NK1 receptors play a role in normal development of peristalsis and NK1 receptor activation markedly increases propulsive peristaltic contractile activity.

GR 73,632 and [Glu(OBzl)11]substance P are selective agonists for the septide-sensitive tachykinin NK1 receptor in the rat urinary bladder.[Pubmed:7538205]

Neuropeptides. 1995 Feb;28(2):99-106.

The existence of a septide-sensitive subtype of the tachykinin NK1 receptor has been recently proposed. In the rat isolated urinary bladder, the non-peptide NK1 receptor antagonist RP 67,580 exhibits a higher affinity towards septide (pKB 7.57) than towards [Sar9]substance P sulfone (pKB 7.00). In this study we have investigated the pharmacological profile of the non-mammalian tachykinin physalaemin, of the synthetic NK1 receptor agonist GR 73,632 (delta-aminovaleryl[LPro9,NMeLeu10]substance P(7-11)) and of [Glu(OBzl)11]substance P in relation to the putative existence of a septide-sensitive receptor. The activity of [Glu(OBzl)11]substance P at the NK1, NK2 and NK3 receptor was assayed in the guinea-pig ileum NK1 receptor assay (EC50 26 nM), in the rabbit pulmonary artery NK2 receptor assay (weak agonist activity) and in the rat portal vein NK3 receptor assays (no appreciable activity up to 1 microM). GR 73,632, [Glu(OBzl)11]substance P and physalaemin, all produced concentration-dependent contractions of the rat isolated urinary bladder, with EC50 values of 17, 79, and 9 nM, respectively. The responses to the three agonists were very slightly or not modified by the NK2 receptor antagonist SR 48,968 (1 microM). RP 67,580 (0.3-3 microM) produced a concentration-dependent rightward shift of the curve to GR 73,632, [Glu(OBzl)11]substance P and physalaemin without producing depression of their maximal response. Schild plot analysis indicated the competitive nature of the antagonism. The affinity (pKB) of RP 67,580 towards physalaemin, GR 73,632 and [Glu(OBzl)11]substance P was 7.12, 7.56 and 7.95, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Spinal actions of GR73632, a novel tachykinin NK1 receptor agonist.[Pubmed:10422886]

Peptides. 1999;20(2):301-4.

Behavioral characterization of GR73632, a newly synthesized tachykinin NK1 receptor agonist, was examined in mice. Intrathecal (IT) injection of GR73632 in the spinal subarachnoid space of mice elicited a dose-dependent behavioral syndrome, consisting of scratching, biting and licking. The time course of the response to GR73632 was almost similar to that of substance P. GR73632 evoked much more licking and biting than did substance P, that in turn caused less scratching. GR73632 was approximately 200-fold more potent than substance P in inducing the characteristic behavioral response. The GR73632-induced behavioral response was inhibited by IT co-administration of CP-96,345, a non-peptide NK1 receptor antagonist, but not its inactive enantiomer CP-96,344. CP-96,345, co-injected IT with substance P, also inhibited the behavioral response to substance P. These results demonstrate that the scratching, biting and licking response induced by IT GR73632 may be mediated by the NK1 receptor in the spinal cord. These findings suggest that GR73632 may be useful as a tachykinin NK1 receptor agonist and also for evaluating spinal pharmacological activities of NK1 receptor antagonists.

GR-73632 is a novel tachykinin neurokinin 1 (NK-1) receptor agonist. GR-73632 acts directly on the peripheral terminals of primary sensory neurons through NK1 receptor which convey itch signals.

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