Systemic administration of rolipram increases medullary and spinal cAMP and activates a latent respiratory motor pathway after high cervical spinal cord injury.
OBJECTIVE
High cervical spinal cord hemisection interrupts descending respiratory drive from the rostral ventral respiratory group in the medulla to the ipsilateral phrenic motoneurons. Hemisection results in the paralysis of the ipsilateral hemidiaphragm. Chronic administration of rolipram, a specific phosphodiesterase-IV inhibitor, promotes synaptic plasticity and restores phrenic nerve function after a high cervical spinal cord lesion. Here, we test the hypothesis that an acute administration of rolipram will increase spinal and medullary levels of 3',5'-cyclic adenosine monophosphate (cAMP) and induce phrenic nerve recovery after cervical (C2) spinal cord hemisection.


METHODS
Male Sprague-Dawley rats were subjected to left C2 hemisection surgery 1 week before experimentation. Bilateral phrenic nerve activity was recorded in anesthetized, vagotomized, and pancuronium paralyzed rats, and rolipram was intravenously applied (2 mg/kg).


RESULTS
Intravenous administration of rolipram increased phrenic nerve output in uninjured control and left C2 spinal cord-hemisected rats. In addition, rolipram restored respiratory-related activity to the left phrenic nerve made quiescent by the hemisection. In both uninjured and hemisected rats, rolipram significantly enhanced phrenic inspiratory burst amplitude and burst area compared with predrug values. Also, rolipram concomitantly increased spinal and medullary cAMP.


CONCLUSIONS
These results suggest that a phosphodiesterase inhibitor capable of elevating cAMP levels can enhance phrenic nerve output and restore respiratory-related phrenic nerve function after high cervical spinal cord injury. Thus, targeting the cAMP signaling cascade can be a useful therapeutic approach in promoting synaptic efficacy and respiratory recovery after cervical spinal cord injury.
Kajana
Satkunendrarajah
S
Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Goshgarian
Harry G
HG
D000818:Animals; D002574:Cervical Vertebrae; D000242:Cyclic AMP / Q000378:metabolism*; D004195:Disease Models, Animal; D007839:Functional Laterality; D007275:Injections, Intravenous / Q000379:methods; D008297:Male; D010726:Phosphodiesterase Inhibitors / Q000008:administration & dosage*; D010791:Phrenic Nerve / Q000187:drug effects / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012119:Respiration / Q000187:drug effects; D012125:Respiratory Center / Q000187:drug effects*; D020889:Rolipram / Q000008:administration & dosage*; D013119:Spinal Cord Injuries / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology
D010726:Phosphodiesterase Inhibitors; D000242:Cyclic AMP; D020889:Rolipram