CC12, a high-affinity ligand for [3H]cimetidine binding, is an improgan antagonist
Introduction
Reports of antinociception following the injection of certain histamine H2 antagonists into the rodent CNS (Netti et al., 1984) led to the discovery and characterization of a family of analgesic drugs which act independently of the H2 receptor (Li et al., 1996, Hough et al., 1997, Hough, 2004). The prototype drug, named improgan (Fig. 1), was originally described as a cimetidine-like drug which lacked H2 receptor antagonist properties (Ganellin, 1982). When administered by intracerebroventricular (i.c.v.) injection to rats, improgan is highly effective in attenuating thermal (Li et al., 1996), mechanical (Li et al., 1997a) and neuropathic (in preparation) nociceptive responses at doses which do not produce toxicity, change locomotor activity, or impair rotorod performance (Li et al., 1997a). Thus, improgan-like drugs have a preclinical profile suggestive of highly effective analgesics. Significant impediments to the clinical development of improgan-like analgesics are the failure to identify the improgan antinociceptive target, and the lack of penetration of the blood-brain barrier by these drugs. Progress on the latter was recently reported (Hough et al., 2005).
Although information has been gained by mapping the relevant CNS sites and circuits underlying improgan antinociception (Hough et al., 2001b, Svokos et al., 2001, Nalwalk et al., 2004, Nalwalk et al., 2005), the mechanism of action of this compound remains unknown. Improgan shows no significant affinity at 60 ion channels or G protein-coupled receptors (Hough et al., 2001a). Experiments with pharmacological antagonists (Li et al., 1997b) and knock-out mice exclude roles for known histamine (Mobarakeh et al., 2003) and opioid (Hough et al., 2000a) receptors. The improgan target may be an unknown histamine receptor (Hough et al., 1999), but this has not been established. Improgan also lacks affinity at known cannabinoid receptors, although cannabinoid mechanisms may participate in improgan signaling (Hough et al., 2002, Nalwalk et al., 2006). The search for improgan's mechanism has been hampered by a lack of appropriate pharmacological tools. For example, although some structure-activity studies have been performed (Hough et al., 1997, Hough et al., 2000b, Hough et al., 2006), no pharmacological antagonist of improgan has yet been discovered.
The search by our laboratory for in vitro models of improgan antinociception led us recently to investigate the radioligand binding of [3H]cimetidine (3HCIM) to rat brain homogenates. Although many laboratories have used 3HCIM binding as an index of histamine H2 receptor affinity, it was shown many years ago that the H2 receptor is not responsible for this specific binding (Smith et al., 1980, Warrander et al., 1983). The identity of the brain's 3HCIM binding site was never established, and the effects of improgan on 3HCIM binding have not been reported. Because i.c.v.-administered cimetidine produces antinociception (Li et al., 1996), the 3HCIM binding site may be an antinociceptive target. If so, then drugs with high affinity for this binding site should be analgesics, or behave as analgesic antagonists. Presently, we describe for the first time the synthesis and pharmacological properties of 4(5)-((4-iodobenzyl)thiomethyl)-1H-imidazole (herein named CC12, Fig. 1). We report here that CC12 has high affinity for the 3HCIM binding site and that this drug behaves as an improgan antagonist.
Section snippets
Animals
Male Sprague–Dawley rats (175–230 g) and male albino Swiss–Webster mice (25–40 g, both from Taconic Farms, Germantown, NY) were maintained on a 12:12-h light/dark cycle (lights on from 07:00 to 19:00 h) and provided with food and water. Rats were housed in groups of 3–4 until the time of surgery and individually thereafter. Mice were housed in groups of 4–6. All animal experiments were approved by the Institutional Animal Care and Use Committee of Albany Medical College.
Drugs and solutions
Cimetidine (base, Tocris,
Results
Preliminary studies explored the possible relevance of 3HCIM binding to improgan action. Membrane fractions from rat brain homogenates exhibited 3HCIM specific binding with characteristics similar to those previously published (Smith et al., 1980, data not shown). Improgan produced concentration-dependent inhibition of 3HCIM binding (Fig. 2). Non-linear regression of the inhibitory curve yielded an estimated IC50 value of 1.4 μM (calculated Ki = 793 nM), with a Hill coefficient of −0.91.
Discussion
3HCIM has been used extensively as a radioligand for the H2 receptor (e.g. Miyamoto and Nishio, 1993, Rivera et al., 1994), but it is clear that the binding sites labeled with this ligand are not H2 receptors. Smith et al. (1980) showed that imidazole-containing H2 antagonists bind to this site, but H2 antagonists lacking imidazole do not. Furthermore, Warrander et al. (1983) reported the existence of compounds which lack H2 antagonist activity, but have high affinity for 3HCIM binding sites.
Acknowledgements
We thank Dr. Mark Fleck, Albany Medical College for evaluation of CC12 on GABAA receptors. We also thank Konstantina Svokos and Amanda Carpenter for excellent technical assistance. Professor Rob Leurs (Vrije University, Amsterdam), Dr. Mary Heinricher (Oregon Health Sciences University), and Dr. Milt Teitler (Albany Medical College) provided valuable comments on the manuscript. This work was supported by grants from the National Institute on Drug Abuse (DA-03816, DA-015915, and DA-07307).
References (66)
- et al.
Antagonism of an indirectly acting agonist: block by propranolol and sotalol of the action of tyramine on rat heart
Eur. J. Pharmacol.
(1980) - et al.
Effects of cimetidine-like drugs on recombinant GABAA receptors
Life Sci.
(2004) - et al.
Simple cannula for repeated intracerebral drug administration in rats
Pharmacol. Biochem. Behav.
(1979) Chemistry and structure-activity relationships of drugs acting at histamine receptors
- et al.
Effects of N-hydroxyethyl-pyrrolidinium methiodide, a choline analogue, on passive avoidance behaviour in mice
Neuropharmacology
(1975) - et al.
Agonist-stimulated [35S]GTPgammaS autoradiography: optimization for high sensitivity
Eur. J. Pharmacol.
(2001) - et al.
Activation of brainstem N-methyl-d-aspartate receptors is required for the analgesic actions of morphine given systemically
Pain
(2001) - et al.
Improgan, a cimetidine analog, induces morphine-like antinociception in opioid receptor-knockout mice
Brain Res.
(2000) - et al.
Antinociceptive activity of derivatives of improgan and burimamide
Pharmacol. Biochem. Behav.
(2000) - et al.
Significance of GABAergic systems in the action of improgan, a non-opioid analgesic
Life Sci.
(2001)
Antinociceptive, brain-penetrating derivatives related to improgan, a non-opioid analgesic
Eur. J. Pharmacol.
Antinociceptive activity of chemical congeners of improgan: Optimization of side chain length leads to the discovery of a new, potent, non-opioid analgesic
Neuropharmacology
Effects of naltrexone and histamine antagonists on the antinociceptive activity of the cimetidine analog SKF92374 in rats
Brain Res.
The selective cannabinoid antagonist SR 141716A blocks cannabinoid-induced antinociception in rats
Pharmacol. Biochem. Behav.
Characterization of histamine receptors in isolated pig basilar artery by functional and radioligand binding studies
Life Sci.
Activation of brain stem nuclei by improgan, a non-opioid analgesic
Brain Res.
Absence of 5-HT3 and cholinergic mechanisms in improgan antinociception
Pharmacol. Biochem. Behav.
Cannabinoid-improgan cross-tolerance: Improgan is a cannabinomimetic analgesic lacking affinity at the cannabinoid CB(1) receptor
Eur. J. Pharmacol.
Nociceptive facilitating neurons in the rostral ventromedial medulla
Pain
Histamine receptors in an experimental mammary carcinoma
Biomed. Pharmacother.
Synthesis of radioiodine labeled dibenzyl disulfide for evaluation of tumor cell uptake
Bioorg. Med. Chem.
Analgesic effects of μ antagonists after naloxone non-reversible stress-induced analgesia
Brain Res.
In vitro opioid activity profiles of 6-amino acid substituted derivatives of 14-O-methyloxymorphone
Eur. J. Pharmacol.
Excitatory amino acid antagonists in the rostral ventromedial medulla inhibit mesencephalic morphine analgesia in rats
Pain
A role for spinal, but not supraspinal, alpha2 adrenergic receptors in the actions of improgan, a powerful, non-opioid analgesic
Brain Res.
3H-cimetidine and the H2-receptor
Life Sci.
Imidazole derivatives–a new class of microsomal enzyme inhibitors
Biochem. Pharmacol.
Substituted imidazoles as inhibitors of microsomal oxidation and insecticide synergists
Pesticide Biochem. Physiol.
[3H]-thioperamide as a radioligand for the histamine H3 receptor in rat cerebral cortex
British Journal of Pharmacology
Cannabinoid agonist signal transduction in rat brain: comparison of cannabinoid agonists in receptor binding, G-protein activation, and adenylyl cyclase inhibition
J. Pharmacol. Exp. Ther.
In vivo characterization of a specific cannabinoid receptor antagonist (SR141716A): inhibition of delta 9-tetrahydrocannabinol-induced responses and apparent agonist activity
J. Pharmacol. Exp. Ther.
A method for determining loss of pain sensation
J. Pharmacol. Exp. Ther.
Synthetic analgesics, II Dithienylbutenyl and dithienylbutylamines
J. Pharmacol. Exp. Ther.
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