NTSR2 Agonist NT79 Produces Antinociception by Inhibiting Calcium Channels and Enhancing Spinal GABA Signaling

The urgent need for effective, non-opioid pain therapies drives research into novel analgesic pathways. Current pain management often relies on opioids, which carry significant risks of addiction and side effects. Neurotensin receptor type 2 (NTSR2) represents a promising, yet underexplored, target for analgesia due to its potential to modulate both peripheral and spinal pain circuits. Understanding the precise mechanisms by which NTSR2 activation alleviates pain is crucial for developing safer and more effective treatments, addressing a critical gap in non-opioid pain management strategies.

Researchers investigated the antinociceptive effects and mechanisms of NT79, a selective NTSR2 agonist, in male and female rats and mice. Animals were randomly assigned to receive saline or NT79 at multiple intrathecal doses. To dissect NTSR2-dependent mechanisms, CRISPR/Cas9-mediated NTSR2 knockdown and pharmacologic inhibition of GABA receptors were employed. Modulation of voltage-gated calcium channels and GABAergic signaling was evaluated using dorsal root ganglion (DRG) calcium imaging, whole cell patch clamp electrophysiology, and spinal neurotransmitter assays.

Intrathecal NT79 produced robust, dose-dependent antinociception across various pain models, species, and sexes. This analgesic effect was completely abolished by NTSR2 knockdown, confirming receptor specificity. Mechanistically, NT79 significantly reduced high-voltage-activated calcium currents in DRG neurons, suggesting a presynaptic inhibitory action. In the spinal cord, NT79 enhanced GABA release, a key inhibitory neurotransmitter, while simultaneously suppressing the release of calcitonin gene-related peptide (CGRP), a pronociceptive neuropeptide. Pharmacologic blockade of GABA receptors partially reversed NT79's antinociceptive effects, highlighting the involvement of central GABAergic signaling. > NTSR2 knockdown specifically in GABAergic neurons also reversed NT79's antinociceptive effects, further supporting a crucial role for central GABA in addition to its peripheral actions.