The possibility of alleviating chronic neuropathic pain and related behaviors by the direct suppression of the parabrachial nucleus.

OBJECTIVE

This study aims to observe the effects of direct suppression of the parabrachial nucleus (PBN) on chronic neuropathic pain (CNP) and CNP-related behaviors in mice.

METHODS

A CNP model was established using partial sciatic nerve ligation (PSNL) in mice. Two groups were established: the experimental (PSNL) group and the control (sham) group. An assessment of PBN-region c-Fos expression was conducted following von Frey hair stimulation in the PSNL group and the sham group, and the effects of pain induction were detected using behavioral experiments. The PBN activity of the mice with CNP was manipulated using the designer receptors exclusively activated by designer drugs method. Effective and empty virus groups were used to study the effects of PBN activity inhibition on the pain threshold and pain-related behavior in mice with CNP.

RESULTS

The mechanical pain threshold (MPT) of the mice in the PSNL group was significantly lower than in the sham group. After von Frey stimulation, the c-Fos-positive, PBN-region neurons in the PSNL group were increased compared with the sham group. The central distance in the open field test and the time spent in the central area were lower in the PSNL group than in the sham group. The mice in the PSNL group had a lower duration and fewer entries in the open arm of the elevated plus-maze than the mice in the sham group. There was no difference in immobility time between the PSNL group and the sham group. PBN activity inhibition in mice with CNP did not affect their MPT or anxiety-like behavior.

CONCLUSION

CNP can induce anxiety-like behavior and increase PBN-induced pain in mice. However, direct inhibition of the PBN neuron activity alone cannot improve CNP or CNP-related behavior.