The study has a double blind, balanced crossover design. Randomized, half of the subjects will be given Papaverine (PDE10 inhibitor, 300 mg orally) in the first session followed by placebo in the second, and the other half will be treated in the reverse order. There is a minimum of one month between the two test-sessions. After each of the two treatments, the subjects will be tested with both a psychophysiological (the Copenhagen Psychophysiological Test-Battery) and neuropsychological test-battery (tests from the Cambridge Neuropsychological Test Automated Battery, or "CANTAB"). The project has three phases: In the first phase 10 healthy subjects will be included to determine the kinetics of Papaverine-contained release capsules ; in the second phase 30 schizophrenia patients and 30 healthy subjects will be included to determine the impact on cognitive and sensory gating related deficits; Finally 10 Healthy subjects will be included to determine the effect of Papaverine on hemodynamical parameters by the means magnetic resonance scannings.
