The blockade of μ‑opioid receptors in the lateral hypothalamus enhances panic attack‑like behaviour and diminishes defensive antinociception.

The lateral hypothalamus (LH) sends neural pathways to structures involved on predator‑related defensive behaviours, escape and antinociception. The aim of this study was to investigate the role played by μ-opioid receptors located on LH neurons in defensive behaviour and unconditioned fear‑induced antinociception elicited by electric stimulation of LH. To achieve the goals, the μ1-opioid receptor selective antagonist naloxonazine was administered at different concentrations in the LH, and the defensive behaviour and fear‑induced antinociception elicited by electrical stimulation of LH were evaluated.