Prolonged reversal of the phencyclidine-induced impairment in novel object recognition by a serotonin (5-HT)1A-dependent mechanism

• Subchronic tandospironeinduced prolonged reversalof PCP-induced NOR deficit.
• Subchronic lurasidone, an atypical APD, induced prolonged reversal of NOR deficit.
• WAY100635, a5-HT1A antagonist, blocked the prolonged reversal of NOR by lurasidone.
• The reversal of the NOR deficit by lurasidone and tandospirone lasts several weeks.
• Lurasidone and tandospirone may induce metaplastic synaptic changes.

Many acute treatments transiently reverse the deficit in novel object recognition (NOR) produced by subchronic treatment with the N-methyl-d-aspartate receptor non-competitive antagonist, phencyclidine (PCP), in rodents. Treatments which restore NOR for prolonged periods after subchronic PCP treatment may have greater relevance for treating the cognitive impairment in schizophrenia than those which restore NOR transiently. We examined the ability of post-PCP subchronic lurasidone, an atypical APD with potent serotonin (5-HT)1A partial agonism and subchronic tandospirone, a selective 5-HT1A partial agonist, to enable prolonged reversal of the subchronic PCP-induced NOR deficit. Rats treated with subchronic PCP (2 mg/kg, twice daily for 7 days) or vehicle, followed by a 7 day washout period were subsequently administered lurasidone or tandospirone twice daily for 7 days (day 15–21), and tested for NOR weekly for up to two additional weeks. Subchronic lurasidone (1, but not 0.1 mg/kg) or tandospirone (5, but not 0.6 mg/kg) significantly reversed the PCP-induced NOR deficit at 24 h and 7days after the last injection, respectively. The effect of lurasidone persisted for one more week (day 36, 14 days after the last lurasidone dose), while tandospirone-treated rats were able to perform NOR at 7, but not 14, days after the last tandospirone dose. Co-administration of WAY100635 (0.6 mg/kg), a 5-HT1A antagonist, with lurasidone, blocked the ability of lurasidone to restore NOR, suggesting that 5-HT1A receptor stimulation is necessary for lurasidone to reverse the effects of PCP. The role of dopamine, GABA and the MAPK/ERK signalling pathway in the persistent, but not indefinite, restoration of NOR is discussed.