Tail-pinch stress increases extracellular DOPAC levels (as measured by in vivo voltammetry) in the rat nucleus accumbens but not frontal cortex: antagonism by diazepam and zolpidem

The effect of a tail-pinch stress on dopamine metabolism in the nucleus accumbens and frontal cortex was investigated in the awake unrestrained rat by measuring extracellular 3,4-dihydroxyphenylacetic acid (DOPAC) levels through the use of in vivo differential pulse voltammetry. Mild tail pressure for 8 min caused a large (maximal effect + 70%) and sustained (more than 2 h) increase in the amplitude of the DOPAC oxidation peak in the nucleus accumbens but not in the prefrontal cortex. A similar increase in DOPAC levels was observed in the nucleus accumbens postmortem 1 h after tail-pinch stress. The tail-pinch induced increase in extracellular DOPAC levels in the nucleus accumbens was antagonized by pretreatment with diazepam (5 mg/kg i.p.) or zolpidem (5 mg/kg i.p.), a novel non-benzodiazepine hypnotic possesing anxiolytic properties. These results suggest that in contrast to other stressors, tail-pinch selectively activates dopaminergic systems projecting to the nucleus accumbens.