PMID- 9776513
OWN - NLM
STAT- MEDLINE
DCOM- 19981229
LR  - 20190721
IS  - 0014-4819 (Print)
IS  - 0014-4819 (Linking)
VI  - 122
IP  - 2
DP  - 1998 Sep
TI  - Botzinger-complex expiratory neurons monosynaptically inhibit phrenic motoneurons 
      in the decerebrate rat.
PG  - 149-56
AB  - We examined respiratory neurons in the Botzinger complex of the medulla oblongata 
      in 18 vagotomized, paralyzed, ventilated, and decerebrated rats and tested the 
      hypothesis that bulbospinal expiratory neurons in this region monosynaptically 
      inhibit phrenic motoneurons. First, we surveyed the types of respiratory neurons 
      found in the Botzinger complex; only 11 of the 98 (approximately 11%) examined 
      were bulbospinal, and all discharged only during late expiration (E2), usually 
      with an augmenting discharge frequency (AUG). Then, we examined the spinal 
      projections of 34 E2-AUG neurons using antidromic activation and found that all 
      projected as far as the C4 or C5 segments of the spinal cord but no further 
      caudally. Most (30, approximately 88%) had only unilateral projections, the 
      majority (25, approximately 83%) ipsilateral, but 4 neurons (approximately 12%) 
      had bilateral projections. Their axons could be antidromically activated at low 
      currents (less than 10 microA) in the dorsal-lateral part of the spinal cord at 
      the C2-3 border; 0.5-1.2 mm (mean+/-SD 0.84+/-0.23 mm) below the dorsal surface 
      and 0.7-1.5 mm (1.19+/-0.25 mm) lateral from the midline. We sought evidence for 
      connections from bulbospinal E2-AUG neurons to 118 phrenic motoneurons by 
      computing spike-triggered averages (STAs) of their intracellular potentials 
      triggered by the action potentials of 38 unilaterally-projecting E2-AUG neurons. 
      Resting phrenic motoneuron membrane potentials ranged from -40 to -75 mV (-56+/-8 
      mV) and fluctuations with the respiratory cycle from 7 to 20 mV (14+/-4 mV). Of 
      the 118 STAs computed, hyperpolarizations were evident in 18 (approximately 15%) 
      STAs, evoked by 11 of 38 (approximately 29%) E2-AUG neurons. Their amplitudes 
      varied from 35 to 550 microV (105+/-113 microV), 10-90% fall times from 0.4 to 
      0.9 ms (0.63+/-0.17 ms), and half-amplitude widths from 1.3 to 3.2 ms (2.0+/-0.52 
      ms). Most (16/95, approximately 17%) of the STAs that displayed 
      hyperpolarizations were associated with ipsilateral trigger neurons but some 
      (2/23, approximately 9%) resulted from contralateral trigger neurons. We conclude 
      that Botzinger-complex, expiratory neurons project to the C4 and/or C5 segments 
      of the cervical spinal cord but no further caudal. Their axons are located 
      dorsolaterally in the upper cervical segments of the spinal cord, and they 
      monosynaptically inhibit phrenic motoneurons during the late part of expiration.
FAU - Tian, G F
AU  - Tian GF
AD  - Department of Physiology, University of Toronto, Ontario, Canada.
FAU - Peever, J H
AU  - Peever JH
FAU - Duffin, J
AU  - Duffin J
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - Germany
TA  - Exp Brain Res
JT  - Experimental brain research
JID - 0043312
SB  - IM
MH  - Animals
MH  - Decerebrate State/*physiopathology
MH  - Electric Stimulation
MH  - Male
MH  - Medulla Oblongata/*cytology/*physiology
MH  - Microelectrodes
MH  - Motor Neurons/*physiology
MH  - Neurons/*physiology
MH  - Phrenic Nerve/cytology/*physiology
MH  - Rats
MH  - Rats, Sprague-Dawley
MH  - Reflex, Monosynaptic/physiology
MH  - Respiratory Mechanics/physiology
MH  - Spinal Cord/cytology/physiology
MH  - Stereotaxic Techniques
MH  - Synapses/physiology
EDAT- 1998/10/17 00:00
MHDA- 1998/10/17 00:01
CRDT- 1998/10/17 00:00
PHST- 1998/10/17 00:00 [pubmed]
PHST- 1998/10/17 00:01 [medline]
PHST- 1998/10/17 00:00 [entrez]
AID - 10.1007/s002210050502 [doi]
PST - ppublish
SO  - Exp Brain Res. 1998 Sep;122(2):149-56. doi: 10.1007/s002210050502.