Galanin is a selective marker of the retrotrapezoid nucleus in rats.

The rat retrotrapezoid nucleus (RTN) contains CO(2)-activated neurons that contribute to the central chemoreflex and to breathing automaticity. These neurons have two known markers, the transcription factor Phox2b and vesicular glutamate transporter 2 (VGLUT2). Noncatecholaminergic galanin-immunoreactive (ir) neurons within a region of the lower brainstem that seems identical to what is currently defined as the RTN have been previously described.

Selective lesion of retrotrapezoid Phox2b-expressing neurons raises the apnoeic threshold in rats.

Injection of the neurotoxin saporin-substance P (SSP-SAP) into the retrotrapezoid nucleus (RTN) attenuates the central chemoreflex in rats. Here we ask whether these deficits are caused by the destruction of a specific type of interneuron that expresses the transcription factor Phox2b and is non-catecholaminergic (Phox2b(+)TH(-)). We show that RTN contains around 2100 Phox2b(+)TH(-) cells.

GABAergic pump cells of solitary tract nucleus innervate retrotrapezoid nucleus chemoreceptors.

The retrotrapezoid nucleus (RTN) contains central respiratory chemoreceptors that are inhibited by activation of slowly adapting pulmonary stretch receptors (SARs). Here we examine whether RTN inhibition by lung inflation could be mediated by a direct projection from SAR second-order neurons (pump cells). Pump cells (n = 56 neurons, 13 rats) were recorded in the nucleus of solitary tract (NTS) of halothane-anesthetized rats with intact vagus nerves.