Diabetic rats show reduced cardiac-somatic reflex evoked by intrapericardial capsaicin.
Painless myocardial infarction is a serious complication of diabetes. The present study examined whether cardiac nociception was altered in the streptozotocin-induced diabetic rat model by assessing intrapericardial capsaicin-evoked electromyography (EMG) responses in the spinotrapezius muscle. Somatic sensitivities to mechanical and thermal stimulation of the skin were also determined. Intrapericardial administration of capsaicin evoked a concentration-dependent EMG response, which was reproducible with repeated administration. However, the capsaicin-induced EMG responses were different in streptozotocin-induced diabetic rats and controls. Intrapericardial capsaicin produced fewer EMG responses, which were delayed and reduced in streptozotocin-treated rats compared to controls. Pretreatment with capsazepine, a TRPV1 antagonist, significantly decreased capsaicin-evoked EMG activity in both streptozotocin-treated and control rats. In addition, streptozotocin-treated rats showed a decreased paw withdrawal threshold in response to mechanical stimulation but no change in response to radiant heat stimulation. These results suggest that streptozotocin-induced diabetic rats develop somatic mechanical hypersensitivity (allodynia), but reduced cardiac nociception. Decreased TRPV1 function may contribute to the reduction of cardiac nociception in the diabetic rat.
Department of Physiology and Pathophysiology, Xi'an Jiaotong University School of Medicine, Shaanxi 710061, People's Republic of China.
Xiao-Hua
XH
Liu
Chao
C
Qin
Jian-Qing
JQ
Du
Yan
Y
Xu
Na
N
Sun
Jing-Shi
JS
Tang
Qiang
Q
Li
Robert D
RD
Foreman
D000818:Animals; D001696:Biomechanical Phenomena; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D002211:Capsaicin / Q000008:administration & dosage* / Q000031:analogs & derivatives / Q000494:pharmacology*; D003920:Diabetes Mellitus / Q000378:metabolism / Q000503:physiopathology*; D004558:Electric Stimulation; D004576:Electromyography; D006321:Heart / Q000187:drug effects / Q000294:innervation / Q000503:physiopathology*; D007267:Injections; D008297:Male; D010496:Pericardium; D051381:Rats; D017207:Rats, Sprague-Dawley; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000473:pathology*; D050916:TRPV Cation Channels / Q000378:metabolism; D013696:Temperature
D001786:Blood Glucose; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; C071423:capsazepine; D002211:Capsaicin