The novel analgesic, cizolirtine, inhibits the spinal release of substance P and CGRP in rats
Introduction
Previous studies have shown that cizolirtine (5-{[(N,N-dimethylaminoethoxy)phenyl]methyl}-1-methyl-1H-pyrazol citrate) is a potent analgesic in mice and rats, with an efficacy superior to that of aspirin and other non-steroid anti-inflammatory drugs (Farré et al., 1989, Puig et al., 1991, Alvarez et al., 2000). Indeed, this compound significantly reduces pain-induced behaviours in rodents subjected to various acute nociceptive stimuli (acetic acid-induced writhing in mice and rats; phenylbenzoquinone-induced writhing in mice; tail-pinch and tail-flick tests in mice; formalin test in mice) (Alvarez et al., 2000). However, its mechanism of action is essentially unknown to date. Cizolirtine is characterized by a complete lack of ulcerogenic potential and antiinflammatory properties and does not inhibit prostaglandin synthesis (Alvarez et al., 2000). On the other hand, experiments with a large series of antagonists demonstrated that opioid, serotonin, histamine and dopamine receptors, as well as nicotinic and muscarinic cholinoceptors, could be blocked without any reduction in the analgesic properties of cizolirtine (Farré et al., 1989, Puig et al., 1991). In contrast, blockade of α2-adrenoceptors significantly reduced cizolirtine-induced analgesia (Alvarez et al., 2000), suggesting the involvement of a “catecholamine-link” in the mechanism of action of this drug. However, extensive in vitro binding experiments showed that cizolirtine, up to 10 μM, does not interact with various neurotransmitter transporters, ion channels and any of the receptors mentioned above plus GABA and glutamate receptors as well as α- and β-adrenoceptors (A.J. Farré, unpublished observations), indicating that this putative “catecholamine-link” does not correspond to some direct activation of α2-adrenoceptors by the drug.
The involvement of substance P (SP) and calcitonin gene-related peptide (CGRP) in the processing of nociceptive information has been demonstrated in numerous behavioural, electrophysiological and biochemical studies in mammals (Wiesenfeld-Hallin et al., 1984, Jessell and Womack, 1985, Micevych and Kruger, 1992, Weihe, 1992, Mantyh et al., 1997, Millan, 1999). In the spinal cord, SP is located within the superficial layers of the dorsal horn (laminae I and II), more precisely in the terminals of small primary afferent fibres (of A∂ and C types; Pohl et al., 1990), in descending bulbo-spinal neurones (Bowker et al., 1981) and in spinal interneurones (Weihe, 1992). On the other hand, CGRP within the dorsal horn is only contained in terminals of primary afferent fibres, notably those of small diameter which convey nociceptive signals from the periphery to the spinal cord (Wiesenfeld-Hallin et al., 1984, Pohl et al., 1990).
Previous studies in our laboratory and by other groups have shown that several analgesic drugs act by exerting a negative influence on the release of SP and/or CGRP from the terminals of primary afferent fibres within the superficial layers of the dorsal horn (see Bourgoin et al., 1994). Thus, agonists acting at α2-adrenoceptors (Bourgoin et al., 1993, Collin et al., 1994), opioid (Pohl et al., 1989a, Pohl et al., 1989b), GABA B (Malcangio and Bowery, 1993), adenosine (Santicioli et al., 1992) and some serotonin receptors (Scott and Fone, 1994, Arvieu et al., 1996) have been shown to exert analgesic effects through a direct presynaptic inhibition of primary afferent fibres.
In order to investigate whether a similar mechanism may underlie the analgesic action of cizolirtine, we examined the possible effects of this drug on the K+-evoked release of SP-like material (SPLM) and CGRP-like material (CGRPLM) from slices of the dorsal part of the lumbar enlargement of the rat spinal cord. In addition, we also analyzed the possible effects of intrathecal (i.t.) and intraperitoneal (i.p.) administration of cizolirtine on the in vivo outflow of SPLM and CGRPLM from the subarachnoid space in halothane-anaesthetized rats. Finally, because behavioural studies suggested that α2-adrenoceptors may participate in the analgesic effects of cizolirtine (Alvarez et al., 2000), we also investigated whether an α2-adrenoceptor antagonist, idazoxan, could interfere with the effects of this potent analgesic on the spinal release of SPLM and/or CGRPLM.
Section snippets
Animals
Male Sprague–Dawley rats (Centre d'Elevage Charles River, 76410 Saint-Aubin-lès-Elbeuf, France), weighing 250–300 g, were housed under controlled environmental conditions (12 h alternate light–dark cycles, 21±1°C ambient temperature, 60% relative humidity, food and water available ad libitum) for at least 7 days before being used for the experiments. Procedures involving animals and their care conformed to the institutional guidelines that are in compliance with national and international laws
Effects of cizolirtine on the K+-evoked release of SPLM and CGRPLM from rat spinal cord slices
Under basal non-depolarizing conditions (i.e. [K+]=5.4 mM, in the absence of drugs), the spontaneous outflow of both SPLM (2.25±0.06 pg SP equivalents/ fraction, mean±SEM, n=8 separate experiments) and CGRPLM (18.80±0.60 pg CGRP equivalents/fraction, mean±SEM, n=8) from superfused slices of the dorsal half of the rat lumbar enlargement remained stable throughout the whole superfusion experiments (15 fractions, 60 min). At all the concentrations tested (10 nM–0.1 mM), cizolirtine did not
Discussion
The characteristics of the in vitro and in vivo release of SPLM and CGRPLM from the rat spinal cord presently observed were identical to those previously found under the same experimental conditions (Mauborgne et al., 1987, Pohl et al., 1989a, Pohl et al., 1989b, Bourgoin et al., 1993, Collin et al., 1994). Chromatographic analyses indicated that the immunoreactive materials released from the spinal cord under both in vitro and in vivo conditions corresponded mainly to authentic SP and CGRP (
Acknowledgements
This research was supported by grants from Institut National de la Santé et de la Recherche Médicale (INSERM) and Laboratorios Dr Esteve S.A. S. Ballet was recipient of a fellowship from the Ministère de l'Education Nationale, de la Recherche et de la Technologie (MENRT) during performance of this work.
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2022, Regulatory Toxicology and PharmacologyCitation Excerpt :Cizolirtine [(±)-5-{α-[2-(dimethylamino)ethoxy]benzyl}-1-methyl-1H-pyrazol] is a drug that was developed as candidate for the treatment of pain and urinary incontinence secondary to overactive bladder. The analgesic activity of cizolirtine is considered related to its inhibitory influence on the release of the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) by primary afferent fibres at the spinal cord level, via α2-adrenoceptor-dependent presynaptic inhibition (Aubel et al., 2004; Ballet et al., 2001). Further to its involvement in the transmission of nociceptive signals from the periphery to the central nervous system, SP and CGRP have also been proposed to participate as sensory neurotransmitters in the regulation of the bladder physiology playing a role in the sensory neuron plasticity in the development of detrusor overactivity (Arms and Vizzard, 2011; Montier et al., 1994; Smet et al., 1997).
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2021, Regulatory Toxicology and PharmacologyCitation Excerpt :Cizolirtine was shown to dose-dependently decrease pain in response to thermal and electrical stimuli in human volunteers (Farre and Frigola, 2002), alleviate post-operative pain caused by third molar extraction (Matthew et al., 2000), and produce a relevant pain reduction in patients with primary skin allodynia under conditions of post-traumatic/post-herpetic neuropathy (Shembalkar et al., 2001), renal colic pain (Pavlik et al., 2004), cancer pain and diabetic neuropathy (Farre and Frigola, 2002). The analgesic activity of cizolirtine is considered related to its inhibitory influence, via an α2-adrenoceptor-dependent presynaptic inhibition, on the release by primary afferent fibres at the spinal cord level of substance P (SP) and calcitonin gene-related peptide (CGRP), two neuropeptides involved in the transmission of nociceptive signals from the periphery to the central nervous system (Aubel et al., 2004; Ballet et al., 2001). In vivo microdialysis studies have demonstrated that cizolirtine administration increases the release of noradrenaline and serotonin in the rat prefrontal cortex in coincidence with the duration of its analgesic activity (Farre and Frigola, 2002).
Cizolirtine Citrate, an Effective Treatment for Symptomatic Patients with Urinary Incontinence Secondary to Overactive Bladder: A Pilot Dose-Finding Study
2009, European UrologyCitation Excerpt :Most of the AEs reported with C400 were gastrointestinal, particularly dry mouth, nausea, and vomiting. It is well-known that antimuscarinic drugs produce nausea, vomiting, and especially dry mouth [6–13,14,15,20,21]. This has not been evidenced in the case of cizolirtine, given the no-interaction of this drug with muscarinic receptors [22–26].
Evidence for adenosine- and serotonin-mediated antihyperalgesic effects of cizolirtine in rats suffering from diabetic neuropathy
2007, NeuropharmacologyCitation Excerpt :Within the spinal cord, 5-HT1B receptors are mainly confined within the superficial layers of the dorsal horn, where a relatively high proportion of these receptors are located on the terminals of primary afferent fibres (Laporte et al., 1995). Furthermore, stimulation of these receptors inhibits the Ca2+-dependent release of both SP and CGRP from the spinal terminals of primary afferent fibres (Arvieu et al., 1996), like that found with cizolirtine (Ballet et al., 2001). Accordingly, since cizolirtine does not bind to 5-HT1B receptors (Alvarez et al., 2000), it can be proposed that this drug promotes 5-HT release, which, in turn, activates 5-HT1B receptors on primary afferent terminals.