Dual Roles of Voltage-gated Calcium Channels and γ-Aminobutyric Acid-mediated Signaling in Modulating Neurotensin Receptor Type 2-induced Antinociception.

BACKGROUND

The potential to mitigate pain by targeting a single receptor while simultaneously modulating peripheral and spinal circuits, offers an exciting nonopioid therapeutic strategy. Neurotensin receptor type 2 (NTSR2) is a promising yet underexplored pathway for nonopioid analgesia. The authors investigated the antinociceptive effects of NTSR2 activation and its mechanisms in rodent models of perioperative and chronic pain.

METHODS

Using NT79, a selective NTSR2 agonist, the authors assessed pain behaviors in male and female rats and mice. Animals were randomly assigned to receive saline (control) or NT79 at multiple doses. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated NTSR2 knockdown and pharmacologic inhibition of γ-aminobutyric acid (GABA) receptors were used to dissect NTSR2-dependent mechanisms. Dorsal root ganglion (DRG) calcium imaging, whole cell patch clamp electrophysiology, and spinal neurotransmitter assays evaluated the modulation of voltage-gated calcium channels and γ-aminobutyric acid-mediated (GABAergic) signaling.

RESULTS

Intrathecal NT79 produced robust, dose-dependent antinociception across pain models, species, and sexes, an effect abolished by NTSR2 knockdown. NT79 reduced high-voltage-activated calcium currents in DRG neurons, indicating a presynaptic inhibitory mechanism. In the spinal cord, NT79 enhanced GABA release and suppressed calcitonin gene-related peptide (CGRP) release. Pharmacologic blockade of GABA receptors partially reversed NT79's antinociceptive effects, as did NTSR2 knockdown in GABAergic neurons, supporting a central GABAergic mechanism in addition to the effect on central DRG terminals.

CONCLUSIONS

Taken together, these results demonstrate that NTSR2 activation produces sustained antinociception via dual-site modulation: inhibition of peripheral voltage-gated calcium channels and enhancement of spinal GABAergic signaling. These findings identify a novel, nonopioid mechanism of analgesia and support NTSR2 as a therapeutic target for chronic pain.