Chronic cervical spinal sensory denervation reveals ineffective spinal pathways to phrenic motoneurons in the rat.
We hypothesized that pretreatment with chronic cervical dorsal rhizotomy (CDR; C(3)-C(6)) would reveal ineffective crossed spinal pathways to phrenic motoneurons. Anesthetized CDR (1 week post-rhizotomy) and control rats were spinally hemisected at C(2), and phrenic potentials were evoked by stimulating the ventrolateral funiculus contralateral and rostral to hemisection. Phrenic potentials contralateral to the stimulating electrode were evoked at lower stimulus currents (CDR=640 +/- 46 microA; control=900 +/- 50 microA; P<0.05) and potential amplitude was significantly greater in CDR versus control rats (P<0.05). The serotonin receptor antagonist methysergide (4 mg/kg, i.v.) had no effect on the crossed phrenic potential amplitude (91+/-17% of control at 800 microA; P>0.05). Thus, CDR enhances crossed phrenic pathways but serotonin receptor activation is not necessary to maintain this effect.
Fuller
David D
DD
Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, 2015 Linden Drive West, Madison, WI 53706, USA. fullerd@svm.vetmed.wisc.edu
Johnson
Stephen M
SM
Johnson
Rebecca A
RA
Mitchell
Gordon S
GS
D000818:Animals; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D009046:Motor Neurons; D009434:Neural Pathways / Q000503:physiopathology; D010791:Phrenic Nerve / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019051:Rhizotomy; D012701:Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013116:Spinal Cord / Q000503:physiopathology*
D012702:Serotonin Antagonists; D012701:Serotonin; D008784:Methysergide