Paroxetine Increases δ Opioid Responsiveness in Sensory Neurons

Area of Science:

• Pharmacology and Pain Management
• Neuroscience and Receptor Signaling

Background:

• Current mu opioid receptor (MOR) therapeutics have high abuse potential, driving the need for safer analgesics.
• Delta opioid receptor (DOR) agonists show promise for fewer side effects but are ineffective in non-inflammatory pain.
• G protein-coupled receptor kinase 2 (GRK2) inhibits DOR activity in non-inflamed tissues.

Purpose of the Study:

• To investigate if paroxetine, a GRK2 inhibitor, can enhance peripheral DOR analgesic efficacy in the absence of inflammation.
• To explore paroxetine's potential as an adjuvant therapy for non-inflammatory pain conditions.

Main Methods:

• Administered paroxetine to male rats to assess its effects on GRK2 association with DOR in peripheral tissues.
• Utilized GRK2 overexpression to antagonize paroxetine's effects on DOR competence.
• Evaluated paroxetine's ability to induce peripheral DOR-mediated analgesia without inflammation.

Main Results:

• Paroxetine reduced GRK2 binding to DOR in peripheral tissues, enhancing DOR-mediated analgesia.
• These effects were specific to peripheral tissues in male rats and were blocked by GRK2 overexpression.
• Paroxetine successfully induced peripheral DOR analgesic competence in the absence of inflammation.

Conclusions:

• Paroxetine induces peripheral DOR analgesic competence via a GRK2-dependent mechanism, offering a novel approach to pain management.
• This study provides the first evidence for using an FDA-approved GRK2 inhibitor to improve DOR efficacy in non-inflammatory pain.
• Paroxetine may be a suitable co-therapy with peripherally-restricted opioids to enhance analgesia and reduce side effects.