Pharmacological studies of a novel prolyl endopeptidase inhibitor, JTP-4819, in rats with middle cerebral artery occlusion.

We studied behavioral and pharmacological effects of a novel prolyl endopeptidase inhibitor, (S)-2-[[(S)-2-(hydroxyacetyl)- 1-pyrrolidinyl]carbonyl]-N-(phenylmethyl)-1-pyrrolidine-car boxamide (JTP-4819), in rats with middle cerebral artery occlusion. Administration of JTP-4819 (0.1 and 1 mg/kg p.o for 7 days) significantly prolonged passive avoidance latency, while the latency of rats with middle cerebral artery occlusion receiving the vehicle was significantly shorter than that of sham-operated rats. The prolonged escape latency in the Morris water maze task in rats with middle cerebral artery occlusion was also significantly reduced by administration of JTP-4819 (0.3 and 1 mg/kg p.o.). Interestingly, administration of JTP-4819 (0.3-3 mg/kg p.o. for 15 days) restored the decreased cortical thyrotropin-releasing hormone (TRH)-like immunoreactivity content of rats with middle cerebral artery occlusion but did not affect the cortical and hippocampal substance P- or arginine vasopressin-like immunoreactivity content. These results suggest that JTP-4819 ameliorates memory impairment due to middle cerebral artery occlusion by restoring the cortical TRH content.