Concurrent stimulation-induced place preference in lateral hypothalamus and parabrachial complex: differential effects of naloxone.

Place preference induction by intracerebral electrical stimulation was initially shown by Olds and Milner. It has since proven possible to induce concurrent stimulation-induced place preference (cCPP) after electrical stimulation of the lateral hypothalamus (LH) and, more recently, of the external lateral parabrachial nucleus (LPBe). The objective of this experimental study was to examine whether the rewarding effects of electrical stimulation of the LH and LPBe involve the activation of similar opioid systems in an alternative cCPP task. Administration of the opioid antagonist naloxone (4mg/kg) blocked the conditioned place preference effect induced after LPBe but not after LH stimulation (at 4 or 10mg/kg). These results are interpreted in relation to the presence of multiple reward systems that might anatomically and neurochemically differ with respect to the involvement of the opioid system.