Combined pCPA and muscarinic antagonist treatment produces a deficit in rat water maze acquisition.

A 3-day treatment with p-chlorophenylalanine (pCPA, 100 mg/kg/day) produced a significant decrease (63-89%) in 5-HT levels in both the hippocampus and the cortex of rats, while noradrenaline, adrenaline, and dopamine levels were unaffected. Treatment with pCPA alone did not affect the acquisition of a spatial learning task in the water maze. Treatment with low doses of either scopolamine (0.25 mg/kg) or atropine (10 mg/kg) was also insufficient to cause a significant impairment of water maze acquisition. However, a combined treatment of a 3-day pCPA regimen with the low dose of atropine or scopolamine produced a significant deficit in the acquisition of a water maze task.