Abstract
Objective
To investigate the influence of dopamine (DA) and DA receptor's antagonist on the transmission of noxious information in the central nervous system of normal rats or morphinistic rats.Methods
The influence of DA on the electric activity of the pain-excited neuron (PEN) in the caudate nucleus (Cd) of normal rats or morphinistic rats was recorded after the sciatic nerve was noxiously stimulated.Results
DA shortened the average latency of the evoked discharge of PEN in the Cd of normal rats, indicating that DA could increase the activity of PEN and pain sensitivity in normal rats. This effect could be inhibited by Droperidol. DA increased the average latency of the evoked discharge of PEN in the Cd of morphinistic rats, indicating that DA could inhibit the activity of PEN and pain sensitivity in morphinistic rats.Conclusion
The responses to painful stimulation were completely opposite between normal rats and morphinistic rats after the intracerebroventricular injection of DA.