The non‐peptide tachykinin antagonist, CP‐96,345, is a potent inhibitor of neurogenic inflammation

102

1 The effect of the calcitonin gene-related peptide antagonist (CGRP837, 400 nmol kg-', i.v.) on the increased blood flow induced by calcitonin gene related peptide (CGRP), vasodilator prostaglandins, and topical capsaicin was measured with a laser Doppler blood flow meter in rat abdominal skin.2 The saphenous nerve was electrically stimulated and the effect of CGRP8-37 (400 nmol kg-', i.v.) on the increased blood flow (measured by laser Doppler flowmetry) and oedema formation (measured by the extravascular accumulation of ['25f]-albumin) was investigated in the rat hind paw.3 CGRP8-37 (400 nmol kg-', i.v.) had no effect on basal cutaneous blood flow at uninjected sites and sites injected with Tyrode buffer, but acted selectively to inhibit the increased blood flow induced by intradermal CGRP (10 pmol/site, P< 0.05), but not that induced by prostaglandin E2 (PGE2, 300 pmol/ site) or carba-prostacyclin (cPGI2, 100 pmol/site). 4 Capsaicin (0.1-33 mM), applied topically, acted in a dose-related manner to increase blood flow. CGRP837 (400 nmol kg-', i.v.) almost totally inhibited blood flow induced by capsaicin (10 mM; P <0.05) but did not significantly inhibit blood flow induced by a higher dose of capsaicin (33 mM). 5 The increased blood flow induced by short stimulation of the saphenous nerve (10 V, 1 ms, 2 Hz for 30 s) was inhibited by 76%, 5 min after i.v. CGRP837 (400 nmol kg-', i.v., P<0.05). 6 A longer (5 min) electrical stimulation of the saphenous nerve caused oedema formation, in addition to increased blood flow. The oedema formation was significantly inhibited by CGRP8-37 (400 nmol kg-', i.v., P<0.05). 7 The results suggest that the potent microvascular vasodilator neuropeptide, CGRP, is responsible for the increased blood flow observed after short stimulation of the saphenous nerve and that endogenous CGRP contributes in a pro-inflammatory manner to neurogenic oedema formation in the rat hind paw.

Section: Discussionsupporting

confidence: 81%

Effect of a calcitonin gene‐related peptide antagonist (CGRP_8–37) on skin vasodilatation and oedema induced by stimulation of the rat saphenous nerve

Escott

Brain

1993

102

“…Further, Xu et al (1992b) (Yamamoto & Yaksh, 1991;Nagahisa et al, 1992a). Several (Miranda et al, 1992), the detection of non-specific activity of CP-96,345 at ion channels (Schmidt et al, 1992) and the report that the antinociceptive effects of CP-96,345 in several behavioural tests in the rat is not enantioselective (Nagahisa et al, 1992b (Garret et al, 1991;Nagahisa et al, 1992a;Lembeck et al, 1992;Shepheard et al, 1993). Thus the evidence for anti-nociceptive activity of NK, receptor antagonists in behavioural tests is equivocal.…”

Section: Pharmacokineticsmentioning

confidence: 99%

Effect of RP 67580, a non‐peptide neurokinin₁ receptor antagonist, on facilitation of a nociceptive spinal flexion reflex in the rat

Laird¹,

Hargreaves²,

Hill³

1993

1 In order to examine the contribution of neurokinin, (NKI) receptors to facilitation of a spinal nociceptive reflex in the rat, we have investigated the effects of RP 67580 ((3aR,7aR)-7,7-diphenyl-2(1-imino-2-(2-methoxyphenyl/ethyl)perhydroisoindole)), a non-peptide neurokinin, (NK,) receptor antagonist, selective for the rodent receptor sub-type, on the activity of individual motorunits. These results were compared with the effects of RP 68651, the inactive 3aS, 7aS enantiomer of RP 67580, as a control for non-specific activity. 2 Experiments were performed on 15 rats anaesthetized with a continuous i.v. infusion of alphaxalone/ alphadalone and spinalized at T9-10. Single unit recordings of motorunit activity from biceps femoris/ semitendinosus were made with a concentric needle electrode. In each experiment, a vehicle dose followed by 4 sequential rising doses of either RP 67580 or RP 68651 were given at 15 min intervals. High intensity electrical stimuli were applied to the hindlimb receptive field of the motorunit at a rate of 1 per 60 s throughout the experiment to establish a baseline. A conditioning stimulus (20 of these stimuli at 1 Hz) was delivered 5 min after each dose and the effect of the size of the baseline response examined. 3 The conditioning stimulus evoked a facilitation of the baseline at the start of all experiments (mean increase ± s.e.mean = 151 ± 20%). RP 67580 attenuated this facilitation, with an IDso (± s.e.mean) of 2.5 ± 4.2 fg kg-', i.v., whereas RP 68651 at doses of up to 3 mg kg', i.v. did not. There was no statistically significant effect of drug on the baseline reflex, nor on the response to the conditioning stimulus. Doses of 300 and 3000 Itg kg-' of both RP 67580 and RP 68651 evoked small depressor effects on systemic arterial blood pressure. 4 We conclude that the facilitation of a spinal flexor reflex by noxious conditioning stimuli in the rat is mediated by NK, receptors whereas the baseline reflex is not. The results suggest that brain penetrant NK, receptor antagonists may have central anti-nociceptive effects.

“…The assumption that bradykinin releases tachykinins which then act on NK,-receptors is further supported by our findings that CP-96,345 not only significantly reduced the collagenase-induced paw oedema but also caused a similar reduction of rat paw oedema induced by an equipotent dose of BK. Nonspecific effects of CP-96,345, reported to appear when it is used in high doses Donnerer et al, 1992;Griesbacher et al, 1992;Lembeck et al, 1992a), can be ruled out since the inactive enantiomer, CP-96,344, did not affect the oedema induced by collagenase or BK. In addition, CP-96,345 did not affect collagenase-induced paw oedema in rats which had been pretreated with capsaicin.…”

Section: Discussionmentioning

confidence: 99%

Mediation by bradykinin of rat paw oedema induced by collagenase from Clostridium histolyticum

Legat

Griesbacher

Lembeck

1994

1 Collagenases are thought to play a major role in the pathology of gas gangrene caused by Clostridium histolyticum, because they can destroy the connective tissue barriers. We investigated possible mediators involved in the oedema formation and plasma protein extravasation which follow the injection of a collagenase (EC 3.4.24.3) from Clostridium histolyticum into one hind paw of anaesthetized rats. 2 The magnitude of the oedema following a subplantar injection was dependent on the dose of collagenase (30, 100 and 300 Lg) injected. It reached its maximum within 30 min and remained unchanged for at least 5 h. Plasma protein extravasation into the paw was most pronounced within 20min of the injection. Heat-inactivated collagenase was ineffective. named Hoe-140) reduced oedema formation in a dose-dependent manner with a maximal reduction of around 65% at a dose of 100 nmol kg-' (s.c.). A significant effect could already be observed at a dose of 10 nmol kg-. The duration of the effect of icatibant (100 nmol kg-1) was found to be at least 3 h. These results demonstrate the high potency and long duration of action of icatibant. Pretreatment of rats with the bradykinin B, antagonist, des-Arg9-[Leu8]-BK did not affect collagenase-induced paw oedema. Thus, the observed collagenase-induced effects are mainly mediated by BK through activation of B2 receptors. 4 Pretreatment of adult rats with capsaicin (125 mg kg-', s.c.) three weeks before the collagenase injection caused a significant attenuation of the paw oedema and of plasma extravasation but was significantly less effective than icatibant (100 nmol kg-', s.c.). The non-peptide substance P antagonist, CP-96,345 (10 ltmol kg', i.v.) significantly reduced collagenase-induced oedema formation to a degree comparable with that seen after capsaicin pretreatment. The inhibition by the substance P antagonist was significantly smaller than that seen after icatibant. The inhibitory effect of icatibant in capsaicinpretreated rats, or of icatibant together with CP-96,345 in untreated rats, was not greater than that of significantly reduced the bradykinin-induced paw oedema. These findings indicate that collagenase leads to the release of bradykinin; bradykinin then stimulates afferent C-fibre terminals and causes the release of substance P and probably also neurokinin A, which augment the oedema-inducing effect of bradykinin. 5 Indomethacin or mepyramine plus cimetidine failed to inhibit collagenase-induced paw oedema. Thus, prostaglandins and histamine do not seem to be involved in collagenase-induced paw oedema. 6 After subplantar injection of collagenase, the sensitivity scores in a modified formalin-test rapidly increased during the first 10 min. This increase was abolished by pretreatment with icatibant (100 nmol kg '-, s.c.) indicating that the stimulation of nociceptive afferent neurones following injection of collagenase is due to the action of released kinins.7 In conclusion, bradykinin appears to be the main mediator of inflammation induced by a collagenase from Clost...