Potentiation of morphine-induced antinociception and locomotion by citalopram is accompanied by anxiolytic-like effects

Synergistic effect between citalopram and muscimol upon induction of anxiolytic- and antidepressant-like effects in male mice: An isobologram analysis

Background

There is evidence that both the GABAergic system and serotonin reuptake inhibitor (SSRI) such as citalopram are involved in the modulation of anxiety and depression processes. In this research, we examined the effects of GABAA receptor agents and citalopram on anxiety- and depression-related behaviors and their interaction in male mice.

Methods

For intracerebroventricular (i.c.v.) infusion, a guide cannula was implanted in the left lateral ventricle. Anxiety and depression behaviors were evaluated using the elevated plus-maze (EPM) and forced swimming test (FST).

Results

The results revealed that i.c.v. microinjection of muscimol (1 µg/mouse) enhanced % OAT (open arm time) and % OAE (open arm entries) in the EPM test and decreased immobility time in the FST without affecting locomotor activity, presenting anxiolytic- and antidepressant-like behaviors in the EPM and FST, respectively. On the other hand, i.c.v. microinjection of bicuculline (1 µg/mouse) reduced % OAT and % OAE without affecting locomotor activity and immobility time, presenting an anxiogenic-like effect. Moreover, i.p. administration of citalopram (8 mg/kg) increased %OAT and %OAE and reduced immobility time with no effect on locomotor activity, showing anxiolytic- and antidepressant-like responses in male mice. Furthermore, i.c.v. infusion of an ineffective dosage of muscimol potentiated the anxiolytic- and antidepressant-like responses induced by i.p. injection of citalopram in male mice. When citalopram and bicuculline were co-injected, a non-significant dose of bicuculline reversed the anxiolytic-like effect of citalopram in male mice. Also, the data revealed synergistic anxiolytic- and antidepressant-like behaviors between citalopram and muscimol in male mice.

Conclusions

The results suggested an interaction between citalopram and GABAergic agents on the modulation of anxiety and depression behaviors in male mice.

Target enzymes in oxaliplatin-induced peripheral neuropathy in Swiss mice: A new acetylcholinesterase inhibitor as therapeutic strategy

In the present study it was hypothesized that 5-((4-methoxyphenyl)thio)benzo[c][1,2,5] thiodiazole (MTDZ), a new acetylcholinesterase inhibitor, exerts antinociceptive action and reduces the oxaliplatin (OXA)-induced peripheral neuropathy and its comorbidities (anxiety and cognitive deficits). Indeed, the acute antinociceptive activity of MTDZ (1 and 10 mg/kg; per oral route) was observed for the first time in male Swiss mice in formalin and hot plate tests and on mechanical withdrawal threshold induced by Complete Freund's Adjuvant (CFA). To evaluate the MTDZ effect on OXA-induced peripheral neuropathy and its comorbidities, male and female Swiss mice received OXA (10 mg/kg) or vehicle intraperitoneally, on days 0 and 2 of the experimental protocol. Oral administration of MTDZ (1 mg/kg) or vehicle was performed on days 2-14. OXA caused cognitive impairment, anxious-like behaviour, mechanical and thermal hypersensitivity in animals, with females more susceptible to thermal sensitivity. MTDZ reversed the hypersensitivity, cognitive impairment and anxious-like behaviour induced by OXA. Here, the negative correlation between the paw withdrawal threshold caused by OXA and acetylcholinesterase (AChE) activity was demonstrated in the cortex, hippocampus, and spinal cord. OXA inhibited the activity of total ATPase, Na⁺ K⁺ - ATPase, Ca²⁺ - ATPase and altered Mg²⁺ - ATPase in the cortex, hippocampus, and spinal cord. OXA exposure increased reactive species (RS) levels and superoxide dismutase (SOD) activity in the cortex, hippocampus, and spinal cord. MTDZ modulated ion pumps and reduced the oxidative stress induced by OXA. In conclusion, MTDZ is an antinociceptive molecule promising to treat OXA-induced neurotoxicity since it reduced nociceptive and anxious-like behaviours, and cognitive deficit in male and female mice.

Effects of Three Consecutive Days of Morphine or Methadone Administration on Analgesia and Open-Field Activity in Mice with Ehrlich Carcinoma

This study assessed the exploratory behavioral responses in BALB/c mice inoculated with Ehrlich ascitic carcinoma after 3 consecutive days of treatment with morphine or methadone. Fifty-three female mice, 60 ± 10 d old, were used. Seven days after intraperitoneal tumor inoculation (2 × 10⁶ cells), the animals were randomized into 7 groups: morphine 5 mg/kg (MO₅), morphine 7.5 mg/kg (MO_7.5), morphine 10 mg/kg (MO₁₀), methadone 2.85 mg/kg (ME_2.85), methadone 4.3 mg/kg (ME_4.3), methadone 5.7 mg/kg (ME_5.7), and 0.9% NaCl (Saline) (n = 7). Drug treatments were administered subcutaneously every 6 h for 3 d. The animals were evaluated for analgesia using the mouse grimace scale (MGS) and for general activity using the open field test. The MGS was performed before tumor inoculation (day 0), on day 7 at 40, 90, 150, 240, and 360 min after drug injection, and on days 8 and 9 at 40, 150, 240, and 360 min after drug injection. The open field test was performed before tumor inoculation (day 0), on day 7 after inoculation at 40, 90, 150, 240, and 360 min after drug injection, and on days 8 and 9 after inoculation at 40, 150, and 360 min after drug injection. MGS results indicated that administration of morphine promoted analgesia for up to 240 min. Conversely, methadone reduced MGS scores only at 40 min. All tested doses promoted a significant dose-dependent increase in the total distance traveled and the average speed, and increase that was markedly pronounced on days 8 and 9 as compared with day 7. The frequencies of rearing and self-grooming decreased significantly after morphine or methadone administration. Despite the difference in analgesia, both drugs increased locomotion and reduced the frequency of rearing and self-grooming as compared with the untreated control animals.

Psychopharmacological characterization of an emerging drug of abuse, a synthetic opioid U-47700, in adult zebrafish

3,4-Dichloro-N-[2-(dimethylamino)cyclohexyl]-N-methylbenzamide (U-47700) is a selective μ-opioid receptor agonist originally synthesized as a prospective analgesic drug. Several times more potent than morphine, U-47700 has high abuse potential and may cause clinical neurotoxicity, euphoria, respiratory depression and occasional mortality. U-47700 also evokes analgesia, sedation and euphoria-like states in both humans and rodents. Despite the growing use and abuse of U-47700, its psychopharmacological and toxicological profiles in vivo remain poorly understood. The zebrafish (Danio rerio) is rapidly becoming a popular aquatic model organism for central nervous system (CNS) disease modeling and drug discovery. Here, we examine acute (1, 5, 10, 25 and 50 mg/L for 20-min) and chronic (0.1, 0.5 and 1 mg/L for 14 days) effects of U-47700 in adult zebrafish. Overall, we found overt sedation evoked in fish by acute, and hyperlocomotion with an anxiolytic-like action by chronic, drug treatments. Acute treatment with 1 and 10 mg/L U-47700 also resulted in detectable amounts of this drug in the brain samples, supporting its permeability through the blood-brain barrier. Collectively, these findings emphasize complex dose- and treatment-dependent CNS effects of U-47700 following its acute and chronic administration. Our study also supports high sensitivity of zebrafish to U-47700, and suggests these aquatic models as promising in-vivo screens for probing potential CNS effects evoked by novel synthetic opioid drugs.

Synergistic effect between citalopram and citicoline on anxiolytic effect in non-sensitized and morphine-sensitized mice: An isobologram analysis

In the present study, the effects of intraperitoneal (i.p.) injections of citalopram and citicoline on morphine-induced anxiolytic effects were investigated in non-sensitized and morphine-sensitized mice using elevated plus-maze (EPM). Subcutaneous (s.c.) administration morphine (5 mg/kg) increased the percentage of open arm time (%OAT, in morphine-sensitized mice), and open arm entries (%OAE, in non-sensitized mice), but not a locomotor activity, indicating an anxiolytic response to morphine. On the other hand, i.p. administration of naloxone decreased %OAT (morphine-sensitized mice), and %OAE (non-sensitized and morphine-sensitized mice), but not a locomotor activity, showing an anxiogenic effect to naloxone. Moreover, i.p.co-administration of citalopram (5 and 10 mg/kg) and citicoline (75 mg/kg) induced the anxiolytic effect. Interestingly, i.p. co-administration of low doses of citalopram (0.5, 1 and 2.5 mg/kg) and citicoline (25 mg/kg) significantly increased %OAT and %OAE in non-sensitized as well as %OAT in morphine-sensitized mice, indicating an anxiolytic effect. An isobolographic analysis of data was performed, presenting a synergistic interaction between citalopram and citicoline upon the production of anxiolytic effect in non-sensitized and morphine-sensitized mice. In conclusion, it seems that (1) morphine sensitization affects the anxiety behavior in the EPM, (2) μ-opioid receptors play an important role in morphine anxiolytic effect, (3) citalopram and citicoline induced anti-anxiety effect, (4) a synergistic effect of citalopram and citicoline upon induction of anti-anxiety behavior in non-sensitized and morphine-sensitized mice.

Disulfiram attenuates morphine or methadone withdrawal syndrome in mice

Taking opioids is often accompanied by the development of dependence. Unfortunately, treatment of opioid dependence is difficult, particularly because of codependence - for example, on alcohol or other drugs of abuse. In the presented study, we analyzed the potential influence of disulfiram, a drug used to aid the management of alcoholism, on opioid abstinence syndrome, which occurs as a result of opioid withdrawal. Opioid dependence in mice was induced by subcutaneous administration of either morphine or methadone at a dose of 48 mg/kg for 10 consecutive days. To trigger a withdrawal syndrome, the opioid receptor antagonist, naloxone, was administered at a dose of 1 mg/kg (subcutaneous), and the severity of withdrawal signs was assessed individually. Interruption of chronic treatment with morphine or methadone by naloxone has led to the occurrence of opioid abstinence signs such as jumping, paw tremor, wet-dog shakes, diarrhea, teeth chattering, ptosis, and piloerection. Importantly, pretreatment with disulfiram (25, 50, and 100 mg/kg) reduced the intensity of withdrawal signs induced by naloxone in morphine or methadone-treated mice. These findings show the effectiveness of disulfiram in reducing opioid abstinence signs.

Tetrabenazine, a vesicular monoamine transporter-2 inhibitor, attenuates morphine-induced hyperlocomotion in mice through alteration of dopamine and 5-hydroxytryptamine turnover in the cerebral cortex

A single administration with morphine (30 mg/kg, i.p.) induced long-lasting hyperlocomotion in male ICR mice. Pretreatment of mice with a benzoquinolizine derivative tetrabenazine (TBZ; a reversible vesicular monoamine transporter-2 inhibitor) (1 mg/kg, i.p.) for 30 min significantly attenuated the hyperlocomotion induced by morphine, as compared with vehicle (saline)-pretreated mice. No significant change in locomotion was observed in mice pretreated with TBZ (1 mg/kg) alone. Mice treated with TBZ (1 mg/kg) showed an increase in immobility time in a tail suspension test, as compared with saline-treated mice. Pretreatment with TBZ (1 mg/kg) had no effect on morphine (1-30 mg/kg)-induced antinociception. TBZ at a dose of 1 mg/kg inhibited dopamine turnover (the ratio of 3,4-dihydroxyphenylacetic acid/dopamine) and 5-hydroxytryptamine turnover (the ratio of 5-hydroxyindoleacetic acid/5-hydroxytryptamine) in the cerebral cortex of mice challenged with morphine, as compared with saline-pretreated mice challenged with morphine. No stereotypic behavior was observed in mice treated with morphine (30 mg/kg) in combination with TBZ (1 mg/kg), so the reduction in observed locomotion did not result from induction of stereotypical behavior. Moreover, TBZ (1 and 2 mg/kg) pretreatment had no effect on stereotyped behaviors observed in mice challenged with 10 mg/kg methamphetamine. These data support the potential antagonistic actions of TBZ on some opiate actions, and encourage further exploration of potential effects on morphine reinforcement.