Zaprinast and rolipram enhances spatial and emotional memory in the elevated plus maze and passive avoidance tests and diminishes exploratory activity in naive mice

Background: Phosphodiesterase (PDE) inhibitors in the central nervous system have been shown to stimulate neuronal functions and increase neurogenesis in Alzheimer disease (AD) patients.

Material/methods: The aim of this study was to investigate the effects of zaprinast, a PDE5 Inhibitor, and rolipram, a PDE4 Inhibitor, on learning and memory in elevated plus maze (EPM) and passive avoidance (PA) tests in naive mice. Male Balb-c mice received short-term treatment with zaprinast (3 and 10 mg/kg) and rolipram (0.05 and 0.1 mg/kg) before the acquisition trial of the EPM and PA tests. The exploratory activity of the Animals was also investigated in the Hughes box test.

Results: Both zaprinast (10 mg/kg) and rolipram (0.1 mg/kg) significantly decreased second-day latency compared to the control group in the EPM test, while only rolipram (0.1 mg/kg) significantly increased second-day latency in the PA test. Both zaprinast (10 mg/kg) and rolipram (0.1 mg/kg) significantly decreased the number of entries to new areas and time spent in new areas in the Hughes box test.

Conclusions: Our study revealed that both zaprinast and rolipram enhanced spatial memory in EPM, while rolipram seemed to have more emotional memory-enhancing effects in the PA test compared to zaprinast. Both zaprinast and rolipram diminished exploratory activity in the Hughes box test, which can be attributed to the drugs' anxiogenic effects.