Antigen retrieval pre-treatment causes a different expression pattern of Cav3.2 in rat and mouse spinal dorsal horn

Ca(v)3 channels consist of three isoforms, Ca(v)3.1 (α1G), Ca(v)3.2 (α1H), and Ca(v)3.3 (α1I), which produce low-threshold spikes that trigger burst firings in nociceptive neurons of the spinal dorsal horn (SDH) and dorsal root ganglion (DRG). Although Ca(v)3.2 plays a crucial role in pathological pain, it is distribution in SDH still remains controversial. One study showed that Ca(v)3.2 is ubiquitously expressed in neurons, but another study implied that Ca(v)3.2 is expressed restricted to astrocytes. To unravel these discrepancies, we used methods of immunohistochemistry either with or without antigen retrieval (AR) pre-treatment to detect Ca(v)3 in SDH and DRG from both rats and mice. Moreover, Ca(v)3.2 mRNA was detected in mice SDH using in situ hybridization. We found that the expression pattern of Ca(v)3.2 but not Ca(v)3.1 and Ca(v)3.3 in SDH were largely different with or without AR pre-treatment, which showed a neuron- like and an astrocyte-like appearance, respectively. Double staining further demonstrated that Ca(v)3.2 was mainly costained with the neuronal marker NeuN in the presence of AR but was with glial fibrillary acidic protein (GFAP, marker for astrocytes) in the absence of AR pre-treatment. Importantly, Ca(v)3.2 mRNA was mainly colocalized with Ca(v)3.2 but not GFAP. Together, our findings indicate that AR pretreatment or not impacts the expression pattern of Ca(v)3.2, which may make a significant contribution to the future study of Ca(v)3.2 in SDH.