2-Chloro-N6-cyclopentyladenosine

2-Chloro-N6-cyclopentyladenosine is a potent and selective agonist of adenosine A1 receptor [1].

The adenosine A1 receptor is a G protein-coupled receptor for adenosine and plays an important role in sleep promotion.

2-Chloro-N6-cyclopentyladenosine (CCPA) is a potent and selective agonist of adenosine A1 receptor. CCPA inhibited [3H]PIA binding to A1 receptors of rat brain membranes and [3H]NECA binding to A2 receptors of rat striatal membranes with Ki values of 0.4 and 3900 nM, respectively.

Also, CCPA inhibited adenylate cyclase in rat fat cell membranes with IC50 value of 33 nM and stimulated adenylate cyclase activity in human platelet membranes with EC50 value of 3500 nM [1]. In rat and bovine brain, CCPA exhibited high affinity for A1 receptors with Ki values of 1.3 and 0.5 nM, respectively. In spontaneously beating rat atria, CCPA inhibited chronotropic activity with EC50 value of 8.2 nM [2].

In ischemia/reperfusion rat model, CCPA significantly inhibited the rise of coronary perfusion pressure and diastolic pressure [2]. In rabbits, CCPA reduced mean blood pressure by 40-50% and also lowered heart rate [3]. In mice, CCPA (1.4-27.6 µmol/kg) increased [35S]TBPS binding in membranes from the substantia nigra, hippocampus, cerebral cortex and striatum mediated by A1 receptor. CCPA reduced GABA-coupled chloride channel function and induced anticonvulsant activity [4].

References:
[1].  Lohse MJ, Klotz KN, Schwabe U, et al. 2-Chloro-N6-cyclopentyladenosine: a highly selective agonist at A1 adenosine receptors. Naunyn Schmiedebergs Arch Pharmacol, 1988, 337(6): 687-689.
[2].  Monopoli A, Conti A, Dionisotti S, et al. Pharmacology of the highly selective A1 adenosine receptor agonist 2-chloro-N6-cyclopentyladenosine. Arzneimittelforschung, 1994, 44(12): 1305-1312.
[3].  Concas A, Santoro G, Mascia MP, et al. Anticonvulsant doses of 2-chloro-N6-cyclopentyladenosine, an adenosine A1 receptor agonist, reduce GABAergic transmission in different areas of the mouse brain. J Pharmacol Exp Ther, 1993, 267(2): 844-851.
[4].  Sandoli D, Chiu PJ, Chintala M, et al. In vivo and ex vivo effects of adenosine A1 and A2 receptor agonists on platelet aggregation in the rabbit. Eur J Pharmacol, 1994, 259(1): 43-49.

Pharmacology of the highly selective A1 adenosine receptor agonist 2-chloro-N6-cyclopentyladenosine.[Pubmed:7848348]

Arzneimittelforschung. 1994 Dec;44(12):1305-12.

The pharmacological profile of 2-Chloro-N6-cyclopentyladenosine (CCPA, CAS 37739-05-2), a highly selective A1 adenosine receptor agonist, was characterized. Its effects were compared with those of the non-selective adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA). In binding studies on both rat and bovine brain, CCPA was highly potent on A1 receptors (Ki = 1.3 and 0.5 nmol/l, respectively) and displayed good A1 vs A2a receptor selectivity (500- and 920-fold, respectively). In functional studies, CCPA showed marked negative chronotropic activity in spontaneously beating rat atria (EC50 = 8.2 nmol/l). This effect was antagonized dose-dependently by the A1 selective antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). In the rat Langendorff model, in which global ischemia was induced, CCPA (3 nmol/l) prevented significantly the rise of diastolic pressure and coronary perfusion pressure during postischemic reperfusion. In vascular preparations, a functional activity responsive to A2a adenosine receptor stimulation, CCPA did not show any vasodilating properties up to micromolar concentrations, whereas NECA had a good relaxing activity in bovine coronary arteries (EC50 = 167 nmol/l). In rabbit platelets, a model sensitive only to A2a-receptor stimulation, CCPA did not elicit any relevant antiaggregatory properties, whereas NECA was found to be effective (IC50 = 200 nmol/l). Likewise, in an in vivo model of platelet aggregation in the rabbit using a non-invasive radioisotopic technique, CCPA (100 micrograms/kg, 30 min i.v. infusion) did not influence platelet function, whereas NECA (10 micrograms/kg, 30 min i.v. infusion) decreased peak value for platelet accumulation by 35%.(ABSTRACT TRUNCATED AT 250 WORDS)

Highly selective A(1) -adenosine-agonist (2-chloro-N6-cyclopentyladenosine) and reduction of flap necrosis in adipocutaneous flaps in rats.[Pubmed:22038887]

Head Neck. 2012 Aug;34(8):1100-5.

BACKGROUND: The 2-Chloro-N6-cyclopentyladenosine (CCPA) was proven to be a protective factor in ischemic reperfusion injury in myocardium and to reduce the infarct size in the heart. The purpose of this study was to determine whether flap necrosis could be reduced by intravenous administration of CCPA. METHODS: Fifty-six male Wistar rats were divided into 4 experimental groups. An epigastric adipocutaneous flap was raised, and the area of flap necrosis was assessed for all groups on the fifth postoperative day with planimetry software. RESULTS: The control group had a significantly lower rate of flap necrosis than the ischemic control group (p < .05). The nonischemic CCPA group had a significantly lower rate of flap necrosis than the nonischemic control group (p < .05). The ischemic CCPA group had a highly significant (p < .0001) rate of lower flap necrosis than the ischemic control group. CONCLUSION: Our data show that reduction of flap necrosis can be achieved both with and without ischemic periods by intravenous administration of CCPA.

An adenosine A1 agonist 2-chloro-N6 cyclopentyladenosine inhibits the angiotensin II-induced cardiomyocyte hypertrophy through the calcineurin pathway.[Pubmed:25277512]

Cardiology. 2014;129(3):153-62.

OBJECTIVES: The aim of this investigation was to study the underlying mechanism of an adenosine A1 receptor agonist 2-chloro-N6 cyclopentyladenosine (CCPA) inhibiting cardiomyocyte hypertrophy induced by angiotensin II (AngII). METHODS: Neonatal rat cardiomyocytes were treated with AngII to generate a cardiomyocyte hypertrophy model. Cardiomyocyte cultures were randomized into 5 groups: control; AngII; AngII + cyclosporin A (CsA); AngII + CCPA, and AngII + CCPA + DPCPX. Cardiomyocyte viability was measured by MTT assay. Protein synthesis was assessed by the application of (3)H leucine ((3)H-Leu) incorporation into protein. The mRNA expressions of atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), beta-myosin heavy chain (beta-MHC) and calcineurin Abeta (CnAbeta) were measured by real-time quantitative PCR. The protein level of CnAbeta was dissected by Western blotting. RESULTS: AngII administration at lower concentrations increased the cardiomyocytes viabilities gradually. Surface area, mRNA expressions of ANP, BNP and beta-MHC, and (3)H-Leu incorporation of AngII-induced cardiomyocytes were increased in a dose-dependent manner. As a calcineurin-specific inhibitor, CsA inhibited (3)H-Leu incorporation, surface area, mRNA expressions of ANP, BNP, beta-MHC, CnAbeta and protein expression of CnAbeta of AngII-induced cardiomyocytes. CCPA also suppressed the mRNA and protein expressions of CnAbeta and exerted antihypertrophic effects to a greater degree than CsA. The inhibition of CCPA on cardiomyocyte hypertrophy was counteracted by the A1 receptor antagonist DPCPX. CONCLUSION: The A1 receptor agonist CCPA could significantly inhibit AngII-induced cardiomyocyte hypertrophy via the calcineurin signaling pathway.

2-Chloro-N6-cyclopentyladenosine enhances the anticonvulsant action of carbamazepine in the mouse maximal electroshock-induced seizure model.[Pubmed:16382198]

Pharmacol Rep. 2005 Nov-Dec;57(6):787-94.

This study examines the anticonvulsant profile of interactions between 2-Chloro-N6-cyclopentyladenosine (CCPA, a selective adenosine A1 receptor agonist) and four conventional antiepileptic drugs (AEDs: carbamazepine--CBZ, phenobarbital, phenytoin and valproate) in the mouse maximal electroshock seizure (MES) model. Acute adverse effects produced by AEDs in combination with CCPA were determined in the chimney test (motor performance) and passive avoidance task (long-term memory). Results indicate that CCPA administered alone at 0.25 and 0.5 mg/kg significantly elevated the electroconvulsive threshold in mice. Additionally, the agent at a sub-threshold dose of 0.125 mg/kg potentiated the anticonvulsant activity of CBZ by reducing its ED50 in the MES test from 11.2 to 7.7 mg/kg (p < 0.01). In contrast, 8-cyclopentyl-1,3-dimethylxanthine (DPCPX, a selective adenosine A1 receptor antagonist at 5 mg/kg) abolished the enhanced anticonvulsant effects offered by the combination of CBZ with CCPA (0.125 mg/kg). Moreover, CCPA (0.125 mg/kg) co-administered with other tested AEDs had no significant impact on their antiseizure properties in the MES test in mice. Neither CCPA (0.125 mg/kg) administered singly, nor in combinations with conventional AEDs (at their ED50s) affected motor performance in the chimney test and long-term memory in the passive avoidance task. No pharmacokinetic alterations in brain CBZ concentrations were observed after administration of CCPA at 0.125 mg/kg. It may be concluded that CCPA, acting selectively on adenosine A1 receptors, enhances pharmacodynamically the antiseizure effect of CBZ in the MES test.

Adenosine receptors and their ligands.[Pubmed:11111832]

Naunyn Schmiedebergs Arch Pharmacol. 2000 Nov;362(4-5):382-91.

The regulatory actions of adenosine are mediated via four subtypes of G protein-coupled receptors distinguished as A1, A2A, A2B and A3 receptors. Their presence on basically every cell makes them an interesting target for the pharmacological intervention in many pathophysiological situations. A large number of ligands have been synthesized over the last two decades and provide agonists and antagonists that are more or less selective for the known receptor subtypes. In addition, many radioligands are available in tritiated or radioiodinated form. The comparative pharmacological characterization of all four human adenosine receptor subtypes revealed that some of the compounds thought to be selective from data in other species have unexpected potencies at human receptors. As a result, compounds that exhibit high affinity to only one subtype are an exception. Although the selection of ligands is immense, it is less than satisfying for most subtypes of adenosine receptors.

Anticonvulsant doses of 2-chloro-N6-cyclopentyladenosine, an adenosine A1 receptor agonist, reduce GABAergic transmission in different areas of the mouse brain.[Pubmed:8246158]

J Pharmacol Exp Ther. 1993 Nov;267(2):844-51.

The possible relationship between A1 adenosine receptors and the gamma-aminobutyric acid (GABAA) receptor complex was evaluated in the mouse brain. We studied the effect of in vitro addition and in vivo administration of 2-Chloro-N6-cyclopentyladenosine (CCPA), the most selective ligand for A1 receptors, on the biochemical parameters used currently to evaluate GABAergic function. In vitro, CCPA (0.01-100 microM) failed to modify [3H] GABA binding, [3H]flunitrazepam binding, t-[35S]butylbicyclophosphorothionate ([35S]TBPS) binding and muscimol-stimulated 36Cl- uptake. On the contrary, in vivo, CCPA (1.4-27.6 mumol/kg i.p.) increased [35S]TBPS binding in membranes from the cerebral cortex, hippocampus, striatum and substantia nigra, but not from the cerebellum, thalamus, hypothalamus and olfactory tubercle. The specific A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxantine (9.8 mumol/kg i.p.) abolished the effect of CCPA on [35S]TBPS binding, indicating that the action of this compound is mediated by its interaction with A1 receptors. Diazepam (1.7 mumol/kg i.p.), a positive modulator of GABAergic transmission, antagonized the increase of [35S]TBPS binding induced by CCPA. CCPA (2.8-8.3 mumol/kg i.p.) antagonized convulsions induced by isoniazid, an inhibitor of GABA synthesis, but neither antagonized nor potentiated isoniazid-induced increase of [35S]TBPS binding. CCPA (2.8-8.3 mumol/kg i.p.) antagonized the convulsions induced by pentylenetetrazol (398 mumol/kg i.p.), methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (50 mumol/kg i.p.) and bicuculline methiodide (9.8 mumol/kg i.p.). The results show that, in spite of its anticonvulsant activity, CCPA reduces the function of the GABA-coupled chloride channel function. This finding suggests that the anticonvulsant target sites are different from those involved in the action of CCPA on GABAA receptors.

2-Chloro-N6-cyclopentyladenosine: a highly selective agonist at A1 adenosine receptors.[Pubmed:3216901]

Naunyn Schmiedebergs Arch Pharmacol. 1988 Jun;337(6):687-9.

2-Chloro-N6-cyclopentyladenosine (CCPA) was synthesized as a potential high affinity ligand for A1 adenosine receptors. Binding of [3H]PIA to A1 receptors of rat brain membranes was inhibited by CCPA with a Ki-value of 0.4 nM, compared to a Ki-value of 0.8 nM for the parent compound N6-cyclopentyladenosine (CPA). Binding of [3H]NECA to A2 receptors of rat striatal membranes was inhibited with a Ki-value of 3900 nM, demonstrating an almost 10,000-fold A1-selectivity of CCPA. CCPA inhibited the activity of rat fat cell membrane adenylate cyclase, a model for the A1 receptor, with an IC50-value of 33 nM, and it stimulated the adenylate cyclase activity of human platelet membranes with an EC50-value of 3500 nM. The more than 100-fold A1-selectivity compares favourably with a 38-fold selectivity of CPA. Thus, CCPA is an agonist at A1 adenosine receptors with a 4-fold higher selectivity and 2-fold higher affinity than CPA, and a considerably higher selectivity than the standard A1 receptor agonist R-N6-phenylisopropyladenosine (R-PIA). CCPA represents the agonist with the highest selectivity for A1 receptors reported so far.