CCK ACTIVATES EXCITATORY VENTRAL TEGMENTAL PATHWAYS TO THE POSTERIOR NUCLEUS-ACCUMBENS

IN urethane-anaesthetized male rats, electrical stimulation of the ven tral tegmental area (VTA) produced either excitation (n = 26) or inhib ition (n = 5) in the activity of neurones in the posterior nucleus acc umbens (PNAc). Local administration of sulfatedcholecystokinin octapep tide (CCK8, 0.03 mu g) into the stimulation site enhanced the neuronal excitability in 10 out of 21 PNAc neurones that demonstrated the exci tation to VTA stimulation, but did not affect the remaining 11 neurone s. Similar administration, on the other hand, was without effect in an y of PNAc neurones (n = 5) that displayed the inhibition to VTA stimul ation. These results suggest that CCK8 may act at the VTA to elicit an activation of the excitatory pathways from the VTA to the PNAc.