NK1 receptor and the ventral medulla of the rat: bulbospinal and catecholaminergic neurons

Abstract

Bulbospinal C1 neurons are sympathoexcitatory and excited by substance P. However the substance P receptor (NK1 receptor), has been reported to be absent from the somata of C1 neurons. In this study, using double and triple labelling immunofluorescence and retrograde tracing, we provide evidence that the NK1 receptor is present on 5.3% of C1 neurons, and that 4.7% of C1 neurons receive close oppositions from NK1 receptor immunoreactive terminals, indicating a pre-synaptic and post-synaptic site for the action of substance P. These results provide support for the sympathoexcitatory actions of substance P on C1 neurons. We also demonstrate the NK1 receptor on bulbospinal neurons of the ventral respiratory group, in a region overlapping the pre-Bötzinger Complex.

Differential regulation of the central neural cardiorespiratory system by metabotropic neurotransmitters

“…(e) Other peptides As noted earlier, many other peptides play an important role in the tonic and reflex regulation of the cardiorespiratory systems, including substance P (Gilbey et al 1983;Makeham et al 2001Makeham et al , 2005, pituitary adenylate cyclase-activating polypeptide (PACAP; Farnham et al 2008), somatostatin (Burke et al 2008), galanin (Stornetta et al 2009;figure 2b), which is present in many chemosensitive neurons in the retrotrapezoid nucleus, and thyrotropin-releasing hormone (Murphy et al 1995;Sun et al 1995Sun et al , 1996. The effects of these neuromodulators are site specific and in most cases their physiology is still very poorly understood.…”

The chemical neuroanatomy of breathing

“…It should be acknowledged, however, that while NK1 receptive neurons are prominent in the preBötC, they are also prevalent in numerous other structures in ventrolateral medulla (Fig. 4) including the BötC (see above), and on a subset (~ 5%) of the sympathoexcitatory C1 bulbospinal neurons in the ventrolateral medulla (Makeham et al, 2001). NK1 receptors are also colocalized on chemosensitive glutamatergic neurons in the RTN (see below) and a loss of these NK1 receptor positive RTN neurons appears to result from induced mutations in the Phox2B transcription factors that mimic those occurring in patients with congenital central hypoventilation syndrome (CCHS).…”

Identification of neurotransmitters and co-localization of transmitters in brainstem respiratory neurons

“…Directly adjacent in the rostral most part of the rVRG and sometimes overlapping the preBötC are large I-AUG neurons with direct projections to the phrenic motor nucleus. A fraction of these neurons are also NK1-R immunoreactive (Makeham et al, 2001; Guyenet et al, 2002) and glutamatergic (Guyenet et al, 2002) and some co-express pre-pro-enkephalin (Stornetta et al, 2003b). This data reinforces the report by Gray et al (1999) that the population of NK1-R neurons in the preBötC /rVRG area is heterogeneous.…”