Abstract
Hemorrhages occurring within the thalamus lead to a pain syndrome. Clinical treatment of thalamic pain is ineffective, at least in part, due to the elusive mechanisms that underlie the induction and maintenance of thalamic pain. The present study investigated the possible contribution of a protein-protein interaction between postsynaptic density protein 95 (PSD-95) and neuronal nitric oxide synthase (nNOS) to thalamic pain in mice. Thalamic hemorrhage was induced by microinjection of type IV collagenase into unilateral ventral posterior medial/lateral nuclei of the thalamus. Pain hypersensitivities, including mechanical allodynia, heat hyperalgesia, and cold allodynia, appeared at day 1 post-microinjection, reached a peak 5-7 days post-microinjection, and persisted for at least 28 days post-microinjection on the contralateral side. Systemic pre-treatment (but not post-treatment) of ZL006, a small molecule that disrupts PSD-95-nNOS interaction, alleviated these pain hypersensitivities. This effect is dose-dependent. Mechanistically, ZL006 blocked the hemorrhage-induced increase of binding of PSD-95 with nNOS and membrane translocation of nNOS in thalamic neurons. Our findings suggest that the protein-protein interaction between PSD-95 and nNOS in the thalamus plays a significant role in the induction of thalamic pain. This interaction may be a promising therapeutic target in the clinical management of hemorrhage-induced thalamic pain.