The Journal of pharmacology and experimental therapeutics
-
J. Pharmacol. Exp. Ther. · Feb 2001
Gabapentin antinociception in mice with acute herpetic pain induced by herpes simplex virus infection.
The effects of systemic and local injections of gabapentin, a novel anticonvulsant agent, were tested on nociceptive behaviors in mice with acute herpetic pain. Transdermal infection with herpes simplex virus type-1 (HSV-1) produced nociceptive hypersensitivity of the infected hind paw to innocuous (allodynia) and noxious mechanical stimulation (hyperalgesia) with von Frey filaments. Systemic administration of gabapentin (10-100 mg/kg, peroral) produced a dose-dependent inhibition of both allodynia and hyperalgesia; gabapentin (30-300 mg/kg) did not affect locomotor activity. ⋯ Pretreatment with naltrexone (1 mg/kg) inhibited antinociceptive effect of morphine (5 mg/kg), but not gabapentin (100 mg/kg). Repeated administration of morphine (5 mg/kg, four times) led to tolerance of antinociceptive action, whereas gabapentin (100 mg/kg, four times) had antinociceptive effect even after the forth administration. The present results suggest that gabapentin is effective in the treatment of acute herpetic pain without apparent adverse effects, and analgesic action of gabapentin is mainly mediated by actions on the spinal cord.
-
J. Pharmacol. Exp. Ther. · Feb 2001
Evidence of a functional alpha7-neuronal nicotinic receptor subtype located on motoneurons of the dorsal motor nucleus of the vagus.
In vitro autoradiography using 125I-alpha-bungarotoxin (alpha-BGTx) and anti-alpha7 immunohistochemistry were performed on the dorsal motor nucleus of the vagus (DMV) of sham and chronically vagotomized rats to determine whether the alpha7-nicotinic acetylcholine receptor (nAChR) is located postsynaptically on DMV neurons whose axons contribute to the vagus nerve. Intense bilateral 125I-alpha-BGTx binding and anti-alpha7 immunostaining were observed in coronal brain sections containing the DMV of sham-vagotomized animals. Unilateral cervical vagotomy resulted in ipsilateral losses of 125I-alpha-BGTx binding and anti-alpha7 immunostaining from the DMV. ⋯ To test whether the alpha7-nAChR is similar to the alpha7-homomeric nAChR, experiments were performed in anesthetized rats, and compounds were microinjected into the DMV while monitoring intragastric pressure (IGP). alpha-BGTx and strychnine antagonized nicotine-induced increases in IGP; no antagonism was observed with methyllycaconitine, a compound known to block the homomeric alpha7-nAChR subtype. Recovery from alpha-BGTx-induced antagonism of the nicotine response was observed. We conclude that there is a nAChR containing the alpha7-subunit in the DMV that is different from the homomeric alpha7-nAChR subtype.
-
J. Pharmacol. Exp. Ther. · Feb 2001
Effects of A-134974, a novel adenosine kinase inhibitor, on carrageenan-induced inflammatory hyperalgesia and locomotor activity in rats: evaluation of the sites of action.
The present study investigated 1) antihyperalgesic actions of a novel and selective adenosine kinase (AK) inhibitor, A-134974 (IC(50) = 60 pM), in the carrageenan model of thermal hyperalgesia; 2) effects of A-134974 on locomotor activity; and 3) relative contributions of supraspinal, spinal, and peripheral sites to the actions of A-134974. Systemic A-134974 (i.p.) dose dependently reduced hyperalgesia (ED(50) = 1 micromol/kg) and at higher doses, reduced locomotor activity (ED(50) = 16 micromol/kg). Administration of A-134974 intrathecally (i.t.) was more potent (ED(50) = 6 nmol) at producing antihyperalgesia than delivering the compound by intracerebralventricular (ED(50) = 100 nmol, i.c.v.) or intraplantar (ED(50) >300 nmol) routes. ⋯ In the locomotor assay, i.t.-injected THEO did not antagonize hypomobility caused by systemic or i.t. administration of A-134974. However, i.c.v. infusion of THEO did block the hypomotive actions of i.c.v.-, i.t.-, and i.p.-administered A-134974. These data demonstrate that the novel AK inhibitor A-134974 potently reduces thermal hyperalgesia primarily through interactions with spinal sites, whereas its ability to depress locomotor activity is predominantly mediated by supraspinal sites.
-
J. Pharmacol. Exp. Ther. · Feb 2001
In vitro and in vivo pharmacological characterization of JTE-907, a novel selective ligand for cannabinoid CB2 receptor.
JTE-907 [N-(benzo[1,3]dioxol-5-ylmethyl)-7-methoxy-2-oxo-8-pentyloxy-1,2-dihydroquinoline-3-carboxamide] was evaluated in vitro and in vivo as a novel selective ligand for cannabinoid receptor of peripheral type (CB2). The compound binds with high affinity to human CB2 or mouse CB2 expressed on CHO cell membrane and to rat CB2 on splenocytes. The K(i) affinities for human, mouse, and rat CB2 were 35.9, 1.55, and 0.38 nM, respectively. ⋯ JTE-907 dosed orally inhibited carrageenin-induced mouse paw edema dose dependently. The same in vivo effect was observed with other cannabinoid receptor ligands such as SR144528, Delta(9)-tetrahydrocannabinol (THC), and Win55212-2. This is the first report that a CB2-selective inverse agonist, JTE-907, has an anti-inflammatory effect in vivo, and how the inverse agonist showed the same effect as Win55212-2 and Delta(9)-THC is discussed.