title: Characterization of upper thoracic spinal neurons receiving noxious cardiac and/or somatic inputs in diabetic rats.
abstract: The aim of the present study was to examine spinal processing of cardiac and somatic nociceptive input in rats with STZ-induced diabetes. Type 1 diabetes was induced with streptozotocin (50mg/kg) in 14 male Sprague-Dawley rats and citrate buffer was injected in 14 control rats. After 4-11 weeks, the rats were anesthetized with pentobarbital, ventilated and paralyzed. A laminectomy enabled extracellular recording of T(3) spinal cord neuronal activity. Intrapericardial administration of a mixture of algogenic chemicals (bradykinin, serotonin, prostaglandin E(2) (all at 10(-5)M), and adenosine (10(-3)M)) was applied to activate nociceptors of cardiac afferent nerve endings. Furthermore, somatic receptive properties were examined by applying innocuous (brush and light pressure) and noxious (pinch) cutaneous mechanical stimuli. Diabetes-induced increases in spontaneous activity were observed in subsets of neurons exhibiting long-lasting excitatory responses to administration of the algogenic mixture. Algogenic chemicals altered activity of a larger proportion of neurons from diabetic animals (73/111) than control animals (55/115, P<0.05). Some subtypes of neurons exhibiting long-lasting excitatory responses, elicited prolonged duration and others, had a shortened latency. Some neurons exhibiting short-lasting excitatory responses in diabetic animals elicited a shorter latency and some a decreased excitatory change. The size of the somatic receptive field was increased for cardiosomatic neurons from diabetic animals. Cutaneous somatic mechanical stimulation caused spinal neurons to respond with a mixture of hyper- and hypoexcitability. In conclusion, diabetes induced changes in the spinal processing of cardiac input and these might contribute to cardiovascular autonomic neuropathy in patients with diabetes.
authors.affiliation: Dept. Pharmacology and Pharmacotherapy, Faculty of Pharmaceutical Sciences, Copenhagen University, DK-2100 Copenhagen, Denmark. mlmuus@yahoo.dk
authors.forename: Marie Louise M
authors.initials: ML
authors.lastname: Ghorbani
authors.forename: Chao
authors.initials: C
authors.lastname: Qin
authors.forename: Mingyuan
authors.initials: M
authors.lastname: Wu
authors.forename: Jay P
authors.initials: JP
authors.lastname: Farber
authors.forename: Majid
authors.initials: M
authors.lastname: Sheykhzade
authors.forename: Bjarne
authors.initials: B
authors.lastname: Fjalland
authors.forename: Niels C B
authors.initials: NC
authors.lastname: Nyborg
authors.forename: Robert D
authors.initials: RD
authors.lastname: Foreman
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000503:physiopathology*; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D006321:Heart / Q000294:innervation*; D008297:Male; D009475:Neurons, Afferent / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000503:physiopathology*; D013904:Thoracic Vertebrae