naloxone and Blepharoptosis

The enhancement of GABAergic and monoaminergic neurotransmission has been the mainstay of pharmacotherapy and the focus of drug-discovery for anxiety and depressive disorders for several decades. However, the significant limitations of drugs used for these disorders underscores the need for novel therapeutic targets. Neuronal nicotinic acetylcholine receptors (nAChRs) may represent one such target. For example, mecamylamine, a non-competitive antagonist of nAChRs, displays positive effects in preclinical tests for anxiolytic and antidepressant activity in rodents. In addition, nicotine elicits similar effects in rodent models, possibly by receptor desensitization. Previous studies (Xiao et al., 2001) have identified two metabolites of methadone, EMDP (2-ethyl-5-methyl-3,3-diphenyl-1-pyrroline) and EDDP (2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine), which are considered to be inactive at opiate receptors, as relatively potent noncompetitive channel blockers of rat α3β4 nAChRs. Here, we show that these compounds are likewise highly effective blockers of human α3β4 and α4β2 nAChRs. Moreover, we show that they display relatively low affinity for opiate binding sites labeled by [(3)H]-naloxone. We then evaluated these compounds in rats and mice in preclinical behavioral models predictive of potential anxiolytic and antidepressant efficacy. We found that EMDP, but not EDDP, displayed robust effects predictive of anxiolytic and antidepressant efficacy without significant effects on locomotor activity. Moreover, EMDP at behaviorally active doses, unlike mecamylamine, did not produce eyelid ptosis, suggesting it may produce fewer autonomic side effects than mecamylamine. Thus, the methadone metabolite EMDP may represent a novel therapeutic avenue for the treatment of some affective disorders.

Topics: Animals; Anti-Anxiety Agents; Antidepressive Agents; Blepharoptosis; Disease Models, Animal; Dose-Response Relationship, Drug; Humans; Male; Maze Learning; Mice; Mice, Inbred C57BL; Motor Activity; Naloxone; Protein Binding; Pyrrolidines; Rats; Rats, Sprague-Dawley; Swimming; Time Factors; Tritium

The potential antidepressant effects of two pyridazine derivatives, 5-benzyl 6-methyl 2-[4-(3-trifluoro-methyl phenyl) piperazin-1-yl] methylpyridazin-3-one (PC4) and 5-benzyl 6-methyl 2-[4-(3-chlorophenyl) piperazin-1-yl] methylpyridazin-3-one (PC13), were evaluated using classical psychopharmacological tests in mice. The intraperitoneal LD50 values of PC4 and PC13 were respectively 1125.8 and 429.6 mg kg-1. Only at intraperitoneal doses of 100 mg kg-1 did PC4 or PC13 significantly decrease locomotor activity. Both compounds (5-20 mg kg-1, i.p.) reduced the duration of immobility of mice in the forces swimming test, antagonized reserpine (2.5 mg kg-1, i.p.)-induced ptosis, and potentiated reserpine (2.5 mg kg-1, i.p.)-induced hypothermia. PC4 and PC13 (20 mg kg-1, i.p.) partly reversed hypothermia induced by low dose apomorphine (5 mg kg-1, s.c.) but were less effective for higher doses of apomorphine (16 mg kg-1, s.c.). At 200 mg kg-1, intraperitoneal PC13 enhanced the toxic effects of yohimbine (30 mg kg-1, s.c.), while PC4 was inactive. Head twitches produced either by L-5-hydroxytryptophan (4 mg kg-1, i.p.) in mice pretreated with pargyline (100 mg kg-1, i.p.) or by 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (3 mg kg-1, i.p.) were antagonized by both pyridazine derivatives (20 mg kg-1, i.p.). PC4 and PC13 showed analgesic properties in the phenylbenzoquinone-induced abdominal constriction test (5.0 < ED50 < 5.5 mg kg-1, i.p.) and in the hot-plate test (10 to 37% of analgesia at 10 mg kg-1, i.p.).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 5-Hydroxytryptophan; Analgesia; Animals; Antidepressive Agents; Apomorphine; Behavior, Animal; Blepharoptosis; Citalopram; Clomipramine; Drug Interactions; Fluoxetine; Hypothermia; Imipramine; Injections, Intraperitoneal; Injections, Subcutaneous; Male; Mice; Models, Molecular; Motor Activity; Naloxone; Piperazines; Pyridazines; Reserpine; Structure-Activity Relationship; Swimming; Trazodone; Yohimbine

Clinical studies have suggested that patients who take morphine for pain relief do not show a high degree of dependence. The present study examined the development of naloxone-precipitated withdrawal in rats receiving morphine in the presence or absence of formalin-induced pain. Morphine (10 mg/kg, i.p.) or saline was administered for 4 consecutive days 10 min after a subcutaneous injection of 50 microliters of 2.5% formalin or saline into the hind-paw. On the 5th day, rats were injected with naloxone (1 mg/kg, i.p.) and observed for signs of precipitated withdrawal (ptosis, teeth chattering and excretion/diarrhea). Naloxone-precipitated withdrawal symptoms were significantly greater in rats that received morphine in the absence of pain than in rats that received morphine in the presence of pain.

Topics: Animals; Behavior, Animal; Blepharoptosis; Diarrhea; Formaldehyde; Male; Morphine Dependence; Naloxone; Pain; Rats; Substance Withdrawal Syndrome

The purpose of the present study was to investigate the role of the locus coeruleus in the development of opiate dependence. Two groups of rats each were subjected to either a electrolytic lesion of the locus coeruleus or a sham lesion. All animals were implanted with an intracerebroventricular (i.c.v.) cannula, and made physically dependent by subcutaneous insertion of two 75-mg morphine (base) pellets. Abstinence was precipitated by i.c.v. administration of methylnaloxonium (31-1,000 ng) 72 h after pellet implantation. Methylnaloxonium administered intracerebroventricularly induced a withdrawal syndrome characterized by the appearance of teeth chattering, mastication, rearing, wet dog shakes, jumping, piloerection, hyperactivity, ptosis and eye twitch. Withdrawal observed in the electrolytic lesion groups was less severe than in sham group. The presence of mastication, rearing, piloerection, hyperactivity, ptosis and eye twitch was significantly lower. These results support the hypothesis that the locus coeruleus has an important role in the expression of the physical signs of opiate dependence.

Topics: Animals; Blepharoptosis; Body Weight; Brain Chemistry; Dose-Response Relationship, Drug; Eye Movements; Injections, Intraventricular; Locus Coeruleus; Male; Mastication; Morphine; Morphine Dependence; Motor Activity; Naloxone; Norepinephrine; Piloerection; Quaternary Ammonium Compounds; Rats; Rats, Wistar; Substance Withdrawal Syndrome

It is known that the CXBK inbred strain of mouse is deficient in mu1 opioid receptors, whereas the strain has a delta opioid receptor population that is less consistently altered. In the present study, we compared physical dependence on morphine between CXBK and C57BL/6 mice. Both strains of mice were treated with morphine-admixed food for 5 days. During the treatment, the two strains of mice showed no signs of toxicity. There was no significant difference in morphine intake during the treatment between CXBK and C57BL/6 mice. After the treatment, the withdrawal was precipitated by injecting naloxone (0.01-30 mg/kg, s.c.). CXBK mice showed weight loss, diarrhea and ptosis, but not jumping and body shakes after low dose of naloxone. Whereas, C57BL/6 mice showed weight loss, diarrhea, ptosis, body shakes and jumping. These results suggest that naloxone-precipitated weight loss, diarrhea and ptosis may be mediated by mu2 and/or delta opioid receptor, while naloxone-precipitated jumping and body shakes may be mediated by mu1 opioid receptors.

Topics: Animals; Blepharoptosis; Diarrhea; Male; Mice; Mice, Inbred C57BL; Mice, Inbred Strains; Morphine Dependence; Motor Activity; Naloxone; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, mu; Substance Withdrawal Syndrome; Weight Loss

The antinociceptive effect in mice (hot-plate test) of caerulein (0.15 mg/kg s.c.) was many times more resistant to naloxone than that of morphine (2 mg/kg s.c., equipotent with the caerulein dose). The ED50 (mg/kg s.c.) of naloxone (given simultaneously with an agonist) was with morphine 0.01 and with caerulein 0.07. When administered intravenously after the agonist, the ED50 (mg/kg i.v.) against morphine was 0.012 and that against caerulein was 0.62. In either type of experiment the dose-response lines of naloxone against caerulein were very shallow as compared with those against morphine. A caerulein dose of 5 micrograms/kg enhanced the antinociceptive effect of morphine only when given before morphine, but not when given after it. The limited additivity of the effects together with the different susceptibility to naloxone of the antinociceptive actions indirectly suggest that caerulein and morphine do not share the same mechanism of action. Palpebral ptosis occurred only after caerulein and was completely resistant to naloxone 8 mg/kg s.c.

Topics: Analgesics; Animals; Blepharoptosis; Ceruletide; Cholecystokinin; Hemodynamics; Male; Mice; Morphine; Naloxone; Rats; Rats, Inbred Strains

Topics: Animals; Blepharoptosis; Catalepsy; Drug Antagonism; Drug Synergism; Humans; Kinetics; Levodopa; Male; Mice; Naloxone; Naltrexone; Reserpine

Topics: Animals; Behavior, Animal; Blepharoptosis; Brain; Catalepsy; Catatonia; Electric Stimulation; Electrodes, Implanted; Exophthalmos; Haloperidol; Humans; Hypothalamus; Male; Morphine; Naloxone; Rats; Self Stimulation