The effects of anti-Parkinson drugs on cortical neurones.

1. The effects of a potential anti-Parkinson drug, benapryzine, have been compared with those of benzhexol, atropine and procaine on the excitatory responses induced by acetylcholine and L-glutamate on feline cortical neurones using the microiontophoretic technique.2. All the drugs tested reduced the excitatory responses evoked by acetylcholine and L-glutamate. However, benapryzine, benzhexol and procaine more effectively reduced the excitatory responses to L-glutamate than those to acetylcholine whereas atropine was more effective against acetylcholine-induced excitation.3. In the presence of procaine the amplitude of the extracellular spikes was decreased. This effect was also observed during applications of benapryzine and benzhexol.4. Tests on the isolated frog sciatic nerve indicated that benapryzine and benzhexol had local anaesthetic actions respectively greater than and equivalent to those of procaine.5. It was concluded that the effects of benapryzine and benzhexol on cortical neurones were probably related to their local anaesthetic properties. The possibility that a local anaesthetic action may account for the effects of these drugs and of many other commonly used anti-Parkinson drugs in Parkinson's disease is discussed.