Antipsychotic profile of rolipram: efficacy in rats and reduced sensitivity in mice deficient in the phosphodiesterase-4B (PDE4B) enzyme.

RATIONALE: Recent studies provide evidence for reduced phosphodiesterase-4B (PDE4B) as a genetic susceptibility factor as well as suggesting an association of several single nucleotide polymorphisms (SNPs) in PDE4B that are associated with an increased incidence of schizophrenia.
OBJECTIVES: The aim of the current study was to assess the activity of rolipram, a nonsubtype-selective PDE4 inhibitor, in several animal models predictive of antipsychotic-like efficacy and side-effect liability and to use PDE4B wild-type and knockout mice to begin to understand the subtypes involved in the activity of rolipram.
RESULTS: In rats, rolipram antagonized both phencyclidine hydrochloride- and D-amphetamine-induced hyperactivity and inhibited conditioned avoidance responding (CAR). In PDE4B wild-type mice, rolipram dose-dependently suppressed CAR (ED(50) = 2.4 mg/kg); however, in knockout mice, their sensitivity to rolipram at the higher doses (1.0 and 3.2 mg/kg) was reduced, resulting in a threefold shift in the ED(50) (7.3 mg/kg), suggesting PDE4B is involved, at least in part, with the activity of rolipram. Only the highest dose of rolipram (3.2 mg/kg) produced a modest but significant degree of catalepsy.
CONCLUSIONS: Rolipram has a pharmacologic profile similar to that of the atypical antipsychotics and has low extrapyramidal symptom liability. These results suggest that PDE4B mediates the antipsychotic effects of rolipram in CAR and that the PDE4B-regulated cyclic adenosine monophosphate signaling pathway may play a role in the pathophysiology and pharmacotherapy of psychosis.