Article

Respiratory pattern in midline-lesioned brainstems and hemibrainstems from adult turtles.

Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, 2015 Linden Drive, Madison, Wisconsin 53706, United States.
Respiratory Physiology & Neurobiology (impact factor: 2.24). 08/2008; 164(3):338-49. DOI:10.1016/j.resp.2008.08.004 pp.338-49
Source: PubMed

ABSTRACT Discrete midline lesions uncouple left and right respiratory motor output in mammals, but not in frogs and lampreys. To address this question in reptiles, isolated adult turtle brainstems were cut along the midline while recording respiratory motor output (bursts of action potentials) on left and right hypoglossal (XII) nerves. XII motor bursts were synchronized as long as a small portion of the midline was still intact. When turtle brainstems were completely cut along the midline and separated into hemibrainstems, XII motor bursts were produced that could be abolished by mu-opioid receptor (MOR) activation or exposure to high pH (7.80) solution. Also, 13/57 hemibrainstems expressed episodic discharge (>1.75bursts/episode). To test whether crossed connections were necessary to express a long-lasting increase in burst frequency (i.e., frequency plasticity), phenylbiguanide (PBG, 5-HT(3) receptor agonist, 20microM) was bath-applied to hemibrainstems. Although PBG significantly increased burst frequency by 0.43+/-0.10bursts/min after 60min, no frequency plasticity was observed because burst frequency returned to near baseline levels after a 2-h washout. Thus, crossed connections in turtle brainstems synchronize respiratory motor output and are not required for normal respiratory pattern formation, but are required for PBG-dependent frequency plasticity.

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    P A Martin, G S Mitchell
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    The Journal of Physiology 11/1993; 470:601-17. · 4.72 Impact Factor
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Keywords

2-h washout
 
20microM
 
action potentials
 
baseline levels
 
burst frequency
 
bursts
 
Discrete midline lesions uncouple
 
episodic discharge
 
hemibrainstems
 
long-lasting increase
 
mammals
 
midline
 
MOR
 
normal respiratory pattern formation
 
recording respiratory motor output
 
reptiles
 
respiratory motor output
 
small portion
 
turtle brainstems synchronize respiratory motor output
 
XII motor bursts