Inhibition of phoshodiesterase type 2 or type 10 reverses object memory deficits induced by scopolamine or MK-801.

The objective of this study was to assess the effects of phosphodiesterase type 2 (PDE2) and type 10 (PDE10) inhibition on memory function in the object recognition task using the scopolamine- and MK-801-induced memory deficit model. The effects of the PDE2 inhibitor BAY 60-7550 and the PDE10 inhibitor PQ-10 on object recognition performance were investigated in the scopolamine (0.1mg/kg, i.p.) or MK-801 (0.125 mg/kg, i.p.) model. BAY 60-7550 was tested at a dose of 0.3-3mg/kg (p.o.) in both models; PQ-10 was tested at doses of 0.1-1mg/kg (p.o.) in the scopolamine model and 0.3-3mg/kg in the MK-801 model. All compounds were injected 30 min before the learning trial. Both BAY 60-7550 (1mg/kg) and PQ-10 (0.3mg/kg) attenuated the scopolamine-induced memory deficit. The MK-801-induced memory deficit was reversed after treatment with each PDE inhibitor at a dose of 1mg/kg or higher. PQ10 was highly brain penetrant, whereas 60-7550 levels in the brain were very low after oral treatment. We concluded that since BAY 60-7550 and PQ10 reversed both scopolamine- and MK-801-induced memory deficits, this supports the notion that dual substrate PDE inhibitors might be suitable candidates for cognition enhancement.