Insulin induces cobalt uptake in a subpopulation of rat cultured primary sensory neurons.
Previous findings show that both the vanilloid receptor 1 and the insulin receptor are expressed on small primary sensory neurons. As insulin evokes activity in second messengers which could induce opening of the vanilloid receptor 1, we examined, by using the cobalt-uptake technique, whether or not insulin can activate cultured rat primary sensory neurons through activating the vanilloid receptor 1. Capsaicin (50, 100 and 500 nm) induced concentration-dependent labelling in primary sensory neurons. Preincubation of cells in insulin (10 micromoles) for 10 min followed by a 2-min wash did not produce significant change in the capsaicin-induced labelling. Coapplication of insulin (10 micromoles) with capsaicin, however, potentiated the 50 and 100 nm capsaicin-evoked staining. Insulin itself also produced cobalt labelling in a concentration-dependent manner. The size-frequency distributions of neurons showing capsaicin- or insulin-induced cobalt accumulation were similar. The insulin-induced cobalt labelling was significantly reduced by the tyrosine kinase inhibitor, tyrphostin AG1024, the vanilloid receptor 1 antagonists, ruthenium red and capsazepine, the protein kinase inhibitor, staurosporine and the phospholipase C inhibitor neomycin. Double immunostaining of cultured primary sensory neurons and sections from dorsal root ganglia revealed that about one-third of the cells coexpress the insulin receptor and vanilloid receptor 1. These findings suggest that insulin activates a subpopulation of primary sensory neurons, probably through phosphorylation- and/or phosphatidylinositol(4,5)biphosphate hydrolysis-evoked activation of the vanilloid receptor 1. Although the insulin-induced activation of vanilloid receptor 1 seems to be a short-lived effect in vitro, in vivo it might play a role in the development of burning pain sensation in hyperinsulinism.
Sathianathan
Vivian
V
Department of Anaesthetics and Intensive Care, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London SW10 9NH, UK.
Avelino
António
A
Charrua
Ana
A
Santha
Peter
P
Matesz
Klara
K
Cruz
Francisco
F
Nagy
Istvan
I
D000818:Animals; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D002452:Cell Count; D018929:Cell Culture Techniques; D003035:Cobalt / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D007150:Immunohistochemistry; D007328:Insulin / Q000008:administration & dosage / Q000378:metabolism*; D009355:Neomycin / Q000494:pharmacology; D009475:Neurons, Afferent / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D047428:Protein Kinase Inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D011972:Receptor, Insulin / Q000032:analysis / Q000378:metabolism; D011955:Receptors, Drug / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012430:Ruthenium Red / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D050916:TRPV Cation Channels; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D020032:Tyrphostins / Q000494:pharmacology
D004791:Enzyme Inhibitors; D007328:Insulin; D047428:Protein Kinase Inhibitors; D011955:Receptors, Drug; D050916:TRPV Cation Channels; C494484:TRPV1 receptor; D020032:Tyrphostins; C447031:tyrphostin AG 1024; D012430:Ruthenium Red; D003035:Cobalt; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D010738:Type C Phospholipases; D019311:Staurosporine; D009355:Neomycin; C071423:capsazepine; D002211:Capsaicin