Figure 3.
Effect of naltrexone (NTX, 2.25 mg kg−1) alone or in combination with intrastriatal morphine (100 μM) on the extracellular concentration of dopamine (DA) in the rat striatum. Morphine (MO) was administered intrastriatally via microdialysis probe instead of Ringer solution as shown by the shaded horizontal bar. Naltrexone or saline was given at the time indicated by the arrow. All values are presented as percentages of the basal level±s.e.mean (n=5–6). Contrast analysis after analysis of variance for repeated measurements; 0–220 min: Saline+morphine vs naltrexone+morphine P<0.01.