Tolerance to repeated rewarding electrical stimulation of the parabrachial complex

• Stimulation of the parabrachial area induces naloxone-related behavioral preferences.
• The external lateral subnucleus (LPBe) was repeatedly stimulated in this study.
• Animals received daily or alternate sessions of rewarding electrical stimulation.
• As in the insula, only the daily-stimulated group showed decay in place preferences.
• These results suggest that LPBe-induced reward might also be subject to tolerance.

The parabrachial complex has been related to various rewarding behavioral processes. As previously shown, electrical stimulation of the lateral parabrachial external (LPBe) subnucleus induces opiate-dependent concurrent place preference. In this study, two groups of animals (and their respective controls) were subjected to sessions of rewarding brain stimulation daily or on alternate days. The rats stimulated every other day maintained a consistent preference for the place associated with the brain stimulation. However, as also found in the Insular Cortex, there was a progressive decay in the initial place preference of animals receiving daily stimulation. These data suggest that the rewarding effects induced by electrical stimulation of LPBe subnucleus may be subject to tolerance. These findings are discussed with respect to other anatomical areas showing reward decay and to the reinforcing effects induced by various electrical and chemical rewarding agents.