CCK activates excitatory ventral tegmental pathways to the posterior nucleus accumbens

In urethane-anaesthetized male rats, electrical stimulation of the ventral tegmental area (VTA) produced either excitation (n = 26) or inhibition (n = 5) in the activity of neurones in the posterior nucleus accumbens (PNAc). Local administration of sulfatedcholecystokinin octapeptide (CCK8, 0.03 microgram) into the stimulation site enhanced the neuronal excitability in 10 out of 21 PNAc neurones that demonstrated the excitation to VTA stimulation, but did not affect the remaining 11 neurones. Similar administration, on the other hand, was without effect in any of PNAc neurones (n = 5) that displayed the inhibition to VTA stimulation. These results suggest that CCK8 may act at the VTA to elicit an activation of the excitatory pathways from the VTA to the PNAc.