Effect of streptozotocin-induced diabetes on the activity of calcium channels in rat dorsal horn neurons.
We have previously found that spinal dorsal horn neurons from streptozotocin-diabetic rats, an animal model for diabetes mellitus, show the prominent changes in the mechanisms responsible for [Ca2+]i regulation. The present study aimed to further characterize the effects of streptozotocin-induced diabetes on neuronal calcium homeostasis. The cytoplasmic Ca2+ concentration ([Ca2+]i) was measured in Fura-2AM-loaded dorsal horn neurons from acutely isolated spinal cord slices using fluorescence technique. We studied Ca2+ entry through plasmalemmal Ca2+ channels during potassium (50 mM KCl)-induced depolarization. The K+-induced [Ca2+]i elevation was inhibited to a different extent by nickel ions, nifedipine and omega-conotoxin suggesting the co-expression of different subtypes of plasmalemmal voltage-gated Ca2+ channels. The suppression of [Ca2+]i transients by Ni2+ (50 microM) was the same in control and diabetic neurons. On the other hand, inhibition of [Ca2+]i transients by nifedipine (50 microM) and omega-conotoxin (1 microM) was much greater in diabetic neurons compared with normal animals. These data suggest that under diabetic conditions the activity of N- and L- but not T-type voltage-gated Ca2+ channels substantially increased in dorsal horn neurons.
Voitenko
N V
NV
Department of General Physiology of Nervous System, Bogomoletz Institute of Physiology, Kiev, Ukraine.
Kruglikov
I A
IA
Kostyuk
E P
EP
Kostyuk
P G
PG
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000502:physiology*; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D003929:Diabetic Neuropathies / Q000503:physiopathology*; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009532:Nickel / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D020671:Posterior Horn Cells / Q000737:chemistry* / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013268:Stimulation, Chemical; D020960:omega-Conotoxins / Q000494:pharmacology
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D005456:Fluorescent Dyes; D020960:omega-Conotoxins; C049925:fura-2-am; D011189:Potassium Chloride; C022838:nickel chloride; D009532:Nickel; D009543:Nifedipine; D002118:Calcium; D016257:Fura-2