Figure 4From: Single dose of morphine produced a prolonged effect on dopamine neuron activitiesVTA DA neurons fail to response to subsequent challenge following a single morphine exposure. Rats received morphine (20 mg/kg, s.c.) or saline, and then challenged with morphine (5 mg/kg, i.v.) at 24 hours. A: firing rate. B: firing rate distribution in same neuron. C: representative segments of firing spike train before (upper panel) and after (low panel) the challenge. D: spectral charts before (upper panel) and after (low panel) the challenge.Back to article page