Noradrenergic α2 Receptor Modulates Cav2.2-Mediated Nociception in Parkinson's Disease Through Spinal Neuro-glial Network.

Parkinson's disease (PD)-associated pain, linked to locus coeruleus noradrenergic (LC-NE) degeneration, involves spinal dorsal horn (SDH) nociceptive dysregulation. Using a unilateral 6-OHDA rat PD model combined with DSP-4-induced NE depletion, this study investigated the potential linkage between α2 adrenergic receptor dysfunction and Cav2.2 channel dysregulation in pain pathogenesis. 6-OHDA-induced rats exhibited mechanical/thermal hypersensitivity, exacerbated by DSP-4 co-administration, alongside SDH neuronal hyperactivity (c-FOS), gliosis (GFAP + astrocytes, IBA1 + microglia), inflammatory cytokine elevation, and Cav2.2 upregulation. Clonidine (α2 agonist) concomitantly restored spinal NE levels, reversed nociceptive thresholds, suppressed glial activation, normalized glutamate/GABA imbalance, and downregulated Cav2.2 expression. Notably, Ω-conotoxin GVIA (Cav2.2 antagonist) similarly produced alleviated hypersensitivity, attenuated neuroinflammation, and rebalanced excitatory-inhibitory synaptic transmission. LC-NE degeneration exacerbates PD pain through α2 receptor-associated Cav2.2 hyperactivity in the SDH, potentially driving neuro-glial crosstalk, excitatory-inhibitory dysregulation, and inflammatory signaling.