Targeted ablation of mesenteric projecting sympathetic neurons reduces the hemodynamic response to pain in conscious, spinal cord-transected rats.
Individuals with spinal cord injuries above thoracic level 6 (T(6)) experience episodic bouts of life-threatening hypertension as part of a condition termed autonomic dysreflexia. The paroxysmal hypertension can be caused by a painful stimulus below the level of the injury. Targeted ablation of mesenteric projecting sympathetic neurons may reduce the severity of autonomic dysreflexia by reducing sympathetic activity. Therefore, cholera toxin B subunit (CTB) conjugated to saporin (SAP; a ribosomal inactivating protein that binds to and inactivates ribosomes) was injected into the celiac ganglion to test the hypothesis that targeted ablation of mesenteric projecting sympathetic neurons reduces the pressor response to pain in conscious, spinal cord-transected rats. Nine Sprague-Dawley male rats underwent a spinal cord transection between thoracic vertebrae 4 and 5. Following recovery (5 wk), all rats were instrumented with a radio telemetry device for recording arterial pressure and bilateral catheters in the gluteus maximus muscles for the infusion of hypertonic saline (hNa(+)Cl(-)). Subsequently, the hemodynamic responses to intramuscular injection of hNa(+)Cl(-) (100 microl and 250 microl, in random order) were determined. Following the experiments in the no celiac ganglia injected condition (NGI), rats received injections of CTB-SAP (n = 5) or CTB (n = 3) into the celiac ganglia. CTB-SAP rats, compared with NGI and CTB rats, had reduced pressor responses to hNa(+)Cl(-). Furthermore, the number of stained neurons in the celiac ganglia and spinal cord (segments T(6)-T(12)), was reduced in CTB-SAP rats. Thus, CTB-SAP retrogradely transported from the celiac ganglia is effective at ablating mesenteric projecting sympathetic neurons and reducing the pressor response to pain in spinal cord-transected rats.
Lujan
Heidi L
HL
Department of Physiology, Wayne State University School of Medicine, 540 E. Canfield Ave., Detroit, MI 48201, USA.
Palani
Gurunanthan
G
Peduzzi
Jean D
JD
DiCarlo
Stephen E
SE
D000818:Animals; D020211:Autonomic Dysreflexia / Q000209:etiology / Q000503:physiopathology / Q000628:therapy; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002772:Cholera Toxin / Q000494:pharmacology*; D003243:Consciousness; D004195:Disease Models, Animal; D005727:Ganglia, Spinal / Q000187:drug effects / Q000502:physiology; D005728:Ganglia, Sympathetic / Q000187:drug effects* / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007273:Injections, Intramuscular; D008297:Male; D010146:Pain / Q000150:complications* / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D054789:Ribosome Inactivating Proteins, Type 1 / Q000494:pharmacology*; D012462:Saline Solution, Hypertonic / Q000494:pharmacology; D000076985:Saporins; D013119:Spinal Cord Injuries / Q000150:complications* / Q000503:physiopathology; D013563:Sympathectomy, Chemical; D013904:Thoracic Vertebrae; D017833:Visceral Afferents / Q000187:drug effects / Q000502:physiology
D054789:Ribosome Inactivating Proteins, Type 1; D012462:Saline Solution, Hypertonic; C420112:cholera toxin B-saporin conjugate; D002772:Cholera Toxin; D000076985:Saporins