In summary, it can be seen that demonstration of PPN’s over-stimulation leads to a striking downfall in cholinergic neuron population. Using IHC in this experiment for detection this phenomenon is relatively successful, despite several drawbacks. In addition, neuronal excitotoxicity is probably a consequence of chronic CNO administration. Finally, pharmacological therapies that decrease astrocyte and neuron activity are suggested for patients who suffer from diminished neuronal loss so as to protect the neuron population.