The Journal of Neurophysiology Vol. 86 No. 1 July 2001, pp. 438-446
Copyright ©2001 by the American Physiological Society
Pre-Bötzinger Neurons With Preinspiratory Discharges "In
Vivo" Express NK1 Receptors in the Rat
Patrice G.
Guyenet and
Hong
Wang
Department of Pharmacology, University of Virginia,
Charlottesville, Virginia 22908
Guyenet, Patrice G. and
Hong Wang.
Pre-Bötzinger Neurons With Preinspiratory Discharges "In
Vivo" Express NK1 Receptors in the Rat. J. Neurophysiol. 86: 438-446, 2001. Substance P
stimulates respiration, in part by a direct action on the
pre-Bötzinger complex (preBötC). This region of the medulla
oblongata contains neurons that are strongly immunoreactive for the
neurokinin-1 receptor (NK1R-ir), and a recent theory has postulated
that these cells might be the adult form of excitatory interneurons
that are essential for respiratory rhythmogenesis in neonates.
Here we sought to determine whether preBötC respiratory neurons
are indeed NK1R-ir in the adult rat. Preinspiratory (pre-I) neurons
were recorded in the preBötC region of halothane-anesthetized rats. Most pre-I cells could be antidromically activated from the
contralateral side of the medulla (7 of 10; latency 1.3 ± 0.2 ms), suggesting that most of them were propriomedullary neurons rather
than respiratory motoneurons or bulbospinal cells. Thirty-two pre-I
neurons including seven cells with contralateral projection were
labeled with biotinamide using the juxtacellular method. Eleven cells
(34.4%) were NK1R-ir, including three of the seven pre-I cells that
were antidromically activated from the contralateral side. In 3 control
rats we labeled 20 preBötC neurons with patterns of discharge
other than pre-I and found that none were detectably NK1R-ir. In
conclusion, some of the intensely NK1R-ir neurons of the adult
preBötC region are indeed respiratory interneurons as suggested
by Gray et al. The subtype of NK1R identified by the antibody is
detectable only in a small minority of preBötC respiratory cells,
most notably in pre-I interneurons. Given prior anatomical evidence,
these NK1R-ir pre-I interneurons are most likely glutamatergic. The
data are consistent with the possibility that the NK1R-ir pre-I
interneurons of the adult preBötC could be the adult form of a
class of inspiratory neurons that are rhythmogenic in the neonate
(either the pacemakers and/or an excitatory subtype of follower neurons).
