TY - JOUR
T1 - Physiological concentrations of choline activate native α7-containing nicotinic acetylcholine receptors in the presence of PNU-120596 [1-(5-chloro-2,4-dimethoxyphenyl)-3-(5-methylisoxazol-3-yl)-urea]
AU - Gusev, Alexander G.
AU - Uteshev, Victor V.
PY - 2010/2
Y1 - 2010/2
N2 - The use of PNU-120596 [1-(5-chloro-2,4-dimethoxyphenyl)-3-(5- methylisoxazol-3-yl)-urea], a positive allosteric modulator of α7 nicotinic acetylcholine receptor (nAChR), may be beneficial for enhancing cholinergic therapies. However, the effects of PNU-120596 on activation of native α7-containing nAChRs by physiological concentrations of choline are not known and were investigated in this study using patch-clamp electrophysiology and histaminergic tuberomammillary neurons in hypothalamic slices. In the presence of PNU-120596, subthreshold (i.e., inactive) physiological concentrations of choline (-10 μM) elicited repetitive step-like whole-cell responses reminiscent of single ion channel openings that were reversibly blocked by 20 nM methyllycaconitine, a selective α7 nAChR antagonist. The effects of choline and PNU-120596 were synergistic as administration of 10 to 40 μM choline or 1 to 4 μM PNU-120596 alone did not elicit responses. In voltage clamp at -60 mV, the persistent activation of α7-containing nAChRs by 10 μM choline plus 1 μM PNU-120596 was estimated to produce a sustained influx of Ca2+ ions at a rate of 8.4 pC/min (-0.14 pA). In the presence of PNU-120596 in current clamp, transient step-like depolarizations (-5 mV) enhanced neuronal excitability and triggered voltage-gated conductances; a single opening of an α7-containing nAChR channel appeared to transiently depolarize the entire neuron and facilitate spontaneous firing. Therefore, this study tested and confirmed the hypothesis that PNU-120596 enhances the effects of subthreshold concentrations of choline on native α7-containing nAChRs, allowing physiological levels of choline to activate these receptors and produce whole-cell responses in the absence of exogenous nicotinic agents. In certain neurological disorders, this activation may be therapeutically beneficial, more efficacious, and safer than treatments with nAChR agonists.
AB - The use of PNU-120596 [1-(5-chloro-2,4-dimethoxyphenyl)-3-(5- methylisoxazol-3-yl)-urea], a positive allosteric modulator of α7 nicotinic acetylcholine receptor (nAChR), may be beneficial for enhancing cholinergic therapies. However, the effects of PNU-120596 on activation of native α7-containing nAChRs by physiological concentrations of choline are not known and were investigated in this study using patch-clamp electrophysiology and histaminergic tuberomammillary neurons in hypothalamic slices. In the presence of PNU-120596, subthreshold (i.e., inactive) physiological concentrations of choline (-10 μM) elicited repetitive step-like whole-cell responses reminiscent of single ion channel openings that were reversibly blocked by 20 nM methyllycaconitine, a selective α7 nAChR antagonist. The effects of choline and PNU-120596 were synergistic as administration of 10 to 40 μM choline or 1 to 4 μM PNU-120596 alone did not elicit responses. In voltage clamp at -60 mV, the persistent activation of α7-containing nAChRs by 10 μM choline plus 1 μM PNU-120596 was estimated to produce a sustained influx of Ca2+ ions at a rate of 8.4 pC/min (-0.14 pA). In the presence of PNU-120596 in current clamp, transient step-like depolarizations (-5 mV) enhanced neuronal excitability and triggered voltage-gated conductances; a single opening of an α7-containing nAChR channel appeared to transiently depolarize the entire neuron and facilitate spontaneous firing. Therefore, this study tested and confirmed the hypothesis that PNU-120596 enhances the effects of subthreshold concentrations of choline on native α7-containing nAChRs, allowing physiological levels of choline to activate these receptors and produce whole-cell responses in the absence of exogenous nicotinic agents. In certain neurological disorders, this activation may be therapeutically beneficial, more efficacious, and safer than treatments with nAChR agonists.
UR - http://www.scopus.com/inward/record.url?scp=76749165730&partnerID=8YFLogxK
U2 - 10.1124/jpet.109.162099
DO - 10.1124/jpet.109.162099
M3 - Article
C2 - 19923442
AN - SCOPUS:76749165730
SN - 0022-3565
VL - 332
SP - 588
EP - 598
JO - Journal of Pharmacology and Experimental Therapeutics
JF - Journal of Pharmacology and Experimental Therapeutics
IS - 2
ER -