Dense transient receptor potential cation channel, vanilloid family, type 2 (TRPV2) immunoreactivity defines a subset of motoneurons in the dorsal lateral nucleus of the spinal cord, the nucleus ambiguus and the trigeminal motor nucleus in rat

Abstract

The transient receptor potential cation channel, vanilloid family, type 2 (TRPV2) is a member of the TRPV family of proteins and is a homologue of the capsaicin/vanilloid receptor (transient receptor potential cation channel, vanilloid family, type 1, TRPV1). Like TRPV1, TRPV2 is expressed in a subset of dorsal root ganglia (DRG) neurons that project to superficial laminae of the spinal cord dorsal horn. Because noxious heat (>52 °C) activates TRPV2 in transfected cells this channel has been implicated in the processing of high intensity thermal pain messages in vivo. In contrast to TRPV1, however, which is restricted to small diameter DRG neurons, there is significant TRPV2 immunoreactivity in a variety of CNS regions. The present report focuses on a subset of neurons in the brainstem and spinal cord of the rat including the dorsal lateral nucleus (DLN) of the spinal cord, the nucleus ambiguus, and the motor trigeminal nucleus. Double label immunocytochemistry with markers of motoneurons, combined with retrograde labeling, established that these cells are, in fact, motoneurons. With the exception of their smaller diameter, these cells did not differ from other motoneurons, which are only lightly TRPV2-immunoreactive. As for the majority of DLN neurons, the densely-labeled populations co-express androgen receptor and follow normal DLN ontogeny. The functional significance of the very intense TRPV2 expression in these three distinct spinal cord and brainstem motoneurons groups remains to be determined.