methylatropine and Pain

The compound LXM-10 (2,4-dimethyl-9-beta-phenylethyl-3-oxo-6, 9-diazaspiro [5.5]undecane chloride) is a new spirocyclopiperazinium salt compound. This is the first article to evaluate its antinociceptive effect in the abdominal constriction test induced by acetic acid and the hot-plate test. In the abdominal constriction test, LXM-10 had a significant dose-response effect, and the maximal inhibition ratio was 79.2%. In the hot-plate test, LXM-10 had significant dose-response and time-response effects. The antinociceptive effect began at 1.0 h, peaked at 2.0 h, and persisted 3.0 h after s.c. administration. The hot-plate latency was increased by 126.8% at the dose of 12.0 mg/kg. The antinociceptive effect of LXM-10 was blocked by mecamylamine (a central and peripheral neuronal nicotinic acetylcholine receptor antagonist, 0.25, 0.5, 1.0 mg/kg, i.p.), hexamethonium (a peripheral neuronal nicotinic acetylcholine receptor antagonist, 0.2, 1.0, 5.0 mg/kg, i.p.), atropine (a central and peripheral muscarinic acetylcholine receptor antagonist, 0.2, 1.0, 5.0 mg/kg, i.p.), and atropine methylnitrate (a peripheral muscarinic acetylcholine receptor antagonist, 0.2, 1.0, 5.0 mg/kg, i.p.) in a dose-dependent fashion. In contrast, the effect was not blocked by naloxone (a non-selective opioid receptor antagonist, 2.0 mg/kg, i.p.) or yohimbine (a alpha(2)-adrenergic receptor antagonist, 1.0, 2.5, 5.0 mg/kg, i.p.) in the hot-plate test. Therefore, the antinociceptive effects of LXM-10 involve the peripheral neuronal nicotinic and muscarinic acetylcholine receptors; they are not related to opioid receptors or alpha(2)-adrenergic receptors. LXM-10 did not affect motor coordination, spontaneous activity, or body temperature. These findings with LXM-10 suggest that spirocyclopiperazinium derivatives could provide insight on new analgesics.

Topics: Analgesics; Animals; Atropine; Atropine Derivatives; Body Temperature; Drug Evaluation, Preclinical; Female; Hexamethonium; Male; Mecamylamine; Mice; Mice, Inbred ICR; Motor Activity; Naloxone; Pain; Pain Measurement; Piperazines; Psychomotor Performance; Receptors, Adrenergic, alpha-2; Receptors, Muscarinic; Receptors, Nicotinic; Receptors, Opioid; Yohimbine

The irreversible muscarinic agonist, BM123 (63 mu moles kg-1, IV), was shown to produce central and peripheral physiological signs characteristic of cholinergic agonists. It also induced hypothermia, elevated nociceptive thresholds, reduced locomotor activity and disrupted spontaneous alternation performance in rats. The centrally acting muscarinic antagonist, atropine (50 mu mole kg-1) prevented or reduced all the above effects of BM123 when given SC 40 min prior to the BM123 injection. In contrast, the peripherally acting muscarinic antagonist, N-methyl atropine, prevented only the peripheral effects and the elevated nociceptive thresholds. Habituation of activity during a 20 min session was observed in all groups despite different levels of general activity. These findings are consistent with a model in which atropine and N-methyl atropine compete with BM123 for reversible association with the muscarinic receptor. In the case of BM123 administered alone, the association results, first, in agonist effects and proceeds to form an irreversible complex. Our present results show that by competing with BM123 for mAChR sites during the initial, reversible state of the interaction, atropine blocks the cholinomimetic effects of the agonist during both this state and its otherwise subsequent irreversible state.

Topics: Animals; Atropine; Atropine Derivatives; Behavior, Animal; Body Temperature; Habituation, Psychophysiologic; Motor Activity; Pain; Parasympatholytics; Pyrrolidinones; Rats; Rats, Inbred Strains; Sensory Thresholds; Time Factors

Kojic amine [2-(aminomethyl)-5-hydroxy-4H-pyran-4-one], an analogue of gamma-aminobutyric acid (GABA), produced dose-related, but short-lived, antinociceptive activity in the 48 degrees C [ED50 = 9.2 (8.2-10.3) mg/kg i.p.] and 55 degrees C [ED50 = 13.8 (12.2-15.7) mg/kg i.p.] hot-plate tests in the mouse. The antinociceptive activity of kojic amine at 48 degrees C was found to be insensitive to bicuculline (1.0 mg/kg i.p.) and picrotoxin (0.5 mg/kg i.p.). At this temperature, antinociception was distinctly separate from the impairment of motor function (measured by a rotorod assay) and was not significantly affected by prior treatment with the cholinergic antagonist, atropine sulfate (10.0 mg/kg i.p.). However, at 55 degrees C, the antinociceptive effect of a large dose (20 mg/kg i.p.) of kojic amine was significantly attenuated by similar pretreatment with atropine sulfate, but not by the peripheral cholinergic antagonist, atropine methylnitrate (10.0 mg/kg i.p.). Kojic amine exhibited no significant interaction with haloperidol (0.5 mg/kg i.p.) at this temperature. In animals made tolerant to morphine, THIP or baclofen, there was analgesic cross-tolerance between kojic amine, morphine and baclofen but not between kojic amine and THIP. It is suggested that kojic amine-induced antinociception is similar to that produced by both THIP and baclofen. Thus, kojic amine represents a unique tool with which to study GABA-ergic antinociceptive processes.

Topics: Animals; Atropine; Atropine Derivatives; Baclofen; gamma-Aminobutyric Acid; Isoxazoles; Male; Mice; Morphine; Motor Activity; Pain; Pyrans; Pyrones