Conditioned place preference but not rewarding self-stimulation after electrical activation of the external lateral parabrachial nucleus

The objective of this experiment was to examine the rewarding effect of electrical stimulation of the external lateral parabrachial nucleus (LPBe) and of the lateral hypothalamus (LH) in concurrent Conditioned Place Preference (cCPP) and Brain Self-Stimulation Rewarding tasks. As expected, LH-stimulated animals readily learned cCPP tasks and developed self-stimulation behaviours following the rate–frequency procedure. As previously demonstrated, stimulation of the parabrachial complex generated rewarding or aversive behaviours in cCPP procedures. However, stimulation of this subnucleus induced consistent cCPP behaviours but not brain self-stimulation in rewarding LPBe animals. These results are analysed in the context of the different natural and artificial rewarding effects found in the LPBe nucleus.