The Parabrachial Complex of the brainstem, which processes visceral and sensory information, has beenassociated with several “motivated behaviors”. The external lateral subnucleus (LPBe), located at the mostlateral end of this area, seems to be part of different brain circuits involved in processes of both reinforcingand aversive nature. This structure has indeed been associated with the emotional, autonomic andvisceral processing of negative events, and is considered as a relay for the nociceptive spino-trigeminalparabrachial-hypothalamic system. Previous studies using electrophysiological techniques such asintracerebral electrical stimulation, carried out by our team, have shown that activation of this area caninduce consistent preferences or aversions towards gustatory and spatial stimuli with which it isassociated, with a preference for the latter. Since the identification of μ and κ opioid receptors in thisregion, some authors have suggested that μ receptors might be involved in positive reinforcementprocesses, whereas κ receptors might be related to the processing of aversive information. Preliminaryresults from our current research, in which animals received an injection of CTOP (a μ-receptor-specificantagonist), have shown that this drug can block aversion to spatial cues associated with electricalstimulation of the LPBe in the negative subgroup of male and female rats. These results will be discussedin relation to the role of the parabrachial area in the processing of stimuli with positive and negativevalence.
García et al. (Mon,) studied this question.