PROSTAGLANDIN EP3 RECEPTOR SIGNALLING AS A CONTRIBUTOR TO SEX DIFFERENCES IN STRESS-RELATED DISORDERS MEDIATED BY THE LOCUS COERULEUS

Stress and pain are interconnected and show sex differences in vulnerability and behavioural outcomes. The locus coeruleus (LC) integrates stress, nociception, and affective processing, exhibiting sex-dependent anatomical and functional features. Prostaglandin E₂ signalling via EP3 receptor in LC neurons modulates these responses. This study examined whether sex-specific LC-EP3 signalling shapes behavioural and molecular outcomes in acute stress and chronic neuropathic pain.
Male and female mice underwent acute restraint stress or chronic constriction injury (CCI). Pharmacological (EP3 agonist sulprostone) and viral vector-based approaches selectively manipulated EP3 signalling in LC noradrenergic neurons. Anxiety-like and nociceptive behaviours were assessed, alongside molecular analyses including Western blotting, proximity ligation assays, cAMP measurements, and pCREB expression in LC projection areas (DRt-dorsal reticular nucleus and BLA-basolateral amygdala).
The results showed that basal EP3 receptor expression was higher in females, possibly explaining why, during acute stress, intra-LC sulprostone selectively reduced anxiety-like behaviour and produced analgesia in females. Anxiety-like and analgesic behaviour induced by LC chemogenetic activation was abolished by sulprostone. In CCI, intra-LC sulprostone produced anxiolytic and analgesic effects only in males, reflecting sex-specific differences in EP3 expression, prostaglandin-synthesising enzymes, receptor dimerisation, and cAMP signalling. EP3 overexpression in the LC induced analgesia in both sexes but reduced anxiety-like behaviour only in males CCI, indicating downstream signalling alterations in females. Intra-LC sulprostone and EP3 overexpression induced sex-dependent changes in pCREB levels in the DRt and BLA.
Overall, these findings demonstrate that sex-specific LC-EP3 signalling differentially regulates behavioural and molecular responses across acute stress and chronic neuropathic pain.