The antibiotic minocycline prevents methamphetamine-induced rewarding effects in mice

Repeated use of methamphetamine (METH) causes dependence in humans, and to date, there are no effective medication treatments for METH addiction. We previously reported that the antibiotic minocycline attenuated behavioral abnormalities (hyperactivity and behavioral sensitization) and dopaminergic neurotoxicity in mice and monkeys, after the administration of METH. In this study, we examined the effect of minocycline on METH-induced rewarding effects in mice using the conditioned place preference (CPP) paradigm. Minocycline (40 mg/kg, IP) significantly attenuated METH (1.0 mg/kg, SC)-induced place preference in mice. In vivo microdialysis experiments using free-moving mice, showed that minocycline (40 mg/kg, IP) significantly attenuated the increased extracellular dopamine (DA) levels within the nucleus accumbens, typically seen after the administration of METH (1.0 mg/kg, SC). These findings suggest that minocycline may block METH-induced rewarding effects by down regulating extracellular DA levels in the nucleus accumbens of mice. This would make minocycline a potential therapeutic drug for the treatment of METH induced disorders.

Phencyclidine-induced cognitive deficits in mice are ameliorated by subsequent subchronic administration of donepezil: role of sigma-1 receptors

This study was undertaken to examine the effects of two acetylcholinesterase inhibitors (donepezil and physostigmine) on cognitive deficits in mice after repeated administration of the NMDA receptor antagonist phencyclidine (PCP). In the novel object recognition test, PCP (10 mg/kg/day for 10 days)-induced cognitive deficits were significantly improved by subsequent subchronic (14 days) administration of donepezil (1.0 mg/kg/day), but not donepezil (0.1 mg/kg/day). Furthermore, the effect of donepezil (1.0 mg/kg/day) on PCP-induced cognitive deficits was significantly antagonized by co-administration of the selective sigma-1 receptor antagonist NE-100 (1.0 mg/kg/day), suggesting the role of sigma-1 receptors in the active mechanisms of donepezil. In contrast, PCP-induced cognitive deficits were not improved by subsequent subchronic (14 days) administration of physostigmine (0.25 mg/kg/day). Moreover, repeated administration of PCP significantly caused the reduction of sigma-1 receptors in the hippocampus. The present study suggests that agonistic activity of donepezil at sigma-1 receptors plays a role in the active mechanisms of donepezil on PCP-induced cognitive deficits in mice. Therefore, it is likely that donepezil would be potential therapeutic drugs for the treatment of the cognitive deficits in schizophrenia.

Co-administration of a D-amino acid oxidase inhibitor potentiates the efficacy of D-serine in attenuating prepulse inhibition deficits after administration of dizocilpine

BACKGROUND

D-Serine, an endogenous agonist of the N-methyl-D-aspartate (NMDA) receptors, is effective in the treatment of schizophrenia. However, orally administered D-serine is metabolized substantially by D-amino acid oxidase (DAAO), diminishing its oral bioavailability. In this study, we examined the effects of oral D-serine administration with or without a DAAO inhibitor, 5-chloro-benzo[d]isoxazol-3-ol (CBIO), on the prepulse inhibition (PPI) deficits after administration of the NMDA receptor antagonist dizocilpine.

METHODS

Vehicle or D-serine (30, 300, or 900 mg/kg) with or without CBIO (30 mg/kg) was orally administered to mice 1 hour before administration of dizocilpine (.1 mg/kg), and then the PPI of the acoustic startle response was measured. We measured the extracellular levels of D-serine in the frontal cortex after oral administration of D-serine with or without CBIO.

RESULTS

Coadministration of CBIO with D-serine (30 mg/kg), but not D-serine (30 mg/kg) alone, significantly attenuated dizocilpine-induced PPI deficits. Furthermore, coadministration of CBIO significantly increased the extracellular levels of D-serine in the frontal cortex after administration of D-serine.

CONCLUSIONS

These findings suggest that coadministration of CBIO significantly enhanced the efficacy of D-serine in attenuating PPI deficits by administration of dizocilpine. Therefore, coadministration of D-serine and a DAAO inhibitor has therapeutic potential for the treatment of schizophrenia.

Phencyclidine-induced cognitive deficits in mice are improved by subsequent subchronic administration of the antipsychotic drug perospirone: role of serotonin 5-HT1A receptors

Accumulating evidence suggests that the serotonin 5-HT(1A) receptor may play a role in the pathophysiology of schizophrenia. The present study was undertaken to examine the effects of perospirone, an atypical antipsychotic drug with 5-HT(1A) receptor agonism, on cognitive deficits in mice after repeated administration of the NMDA receptor antagonist phencyclidine (PCP). Subsequent subchronic (14 days) administration of perospirone (1.0, 3.0, or 10 mg/kg) significantly attenuated PCP (10 mg/kg)-induced cognitive deficits in mice, in a dose-dependent manner. The effects of perospirone (10 mg/kg) were significantly antagonized by co-administration of the selective 5-HT(1A) receptor antagonist WAY100635 (1.0 mg/kg). Furthermore, hypothermia by the 5-HT(1A) receptor agonist 8-OH DPAT (0.25 mg/kg) was significantly attenuated in mice treated with PCP. Moreover, a receptor binding assay using [(3)H]WAY100635 revealed that levels of 5-HT(1A) receptors in the hippocampus, but not in the frontal cortex, of PCP-treated mice were significantly lower than those of saline-treated mice. These findings suggest that repeated PCP administration alters 5-HT(1A) receptor function in the mouse brain, and that subsequent subchronic administration of perospirone ameliorates PCP-induced cognitive deficits via 5-HT(1A) receptors. Therefore, perospirone could be a potential therapy for the cognitive deficits observed in schizophrenic patients.

Phencyclidine-induced cognitive deficits in mice are improved by subsequent subchronic administration of the antibiotic drug minocycline

BACKGROUND

The N-methyl-d-aspartate (NMDA) receptor antagonist phencyclidine (PCP)-induced cognitive deficits have been used as an animal model for schizophrenia. This study was undertaken to determine whether the antibiotic drug minocycline could improve PCP-induced cognitive deficits in mice.

METHODS

Saline (10 ml/kg/day, s.c., once daily on day 1-5, 8-12) or PCP (10 mg/kg/day, s.c., once daily on day 1-5, 8-12) were administered to mice for 10 days. Subsequently, vehicle (10 ml/kg/day, i.p.) or minocycline (4.0 or 40 mg/kg/day, i.p.) was injected for 14 consecutive days. One day after the final injection, a novel object recognition test was performed.

RESULTS

PCP-induced cognitive deficits in mice were significantly improved by subsequent subchronic (14 days) administration of minocycline (40 mg/kg), but not minocycline (4.0 mg/kg).

CONCLUSIONS

This study suggests that minocycline could be a potential therapeutic drug for cognitive deficits in schizophrenic patients.