Serotonin Receptor Expression on Astrocytes Near Spinal Phrenic Motor Circuitry

Abstract

Spinal 5‐HT2 and 5‐HT7 receptor activation both trigger respiratory motor plasticity expressed as long‐lasting phrenic motor facilitation, although via distinct cellular mechanisms. Although most studies of serotonin‐dependent spinal respiratory plasticity have focused on motoneurons, 5‐HT receptors are also expressed in glia. Although little is known concerning the function of glia in spinal respiratory plasticity, glia play important roles in in other models of neuroplasticity. Here we present preliminary results concerning 5‐HT receptor expression on GFAP‐positive astrocytes near spinal phrenic motor circuitry. Using immunofluorescence and pseudorabies virus as a retrograde transynaptic tracer from the diaphragm of adult rats, we identified phrenic motoneurons, pre‐phrenic cervical interneurons and nearby GFAP‐positive astrocytes. Initial results indicate 5‐HT2A and 5‐HT7 receptor co‐localization in GFAP positive cells in the vicinity of phrenic‐associated neurons in the cervical gray matter, raising the possibility that spinal astrocytes play an important role in 5‐HT‐dependent phrenic motor plasticity.