title: Nitric oxide signalling augments neuronal voltage-gated L-type (Ca(v)1) and P/q-type (Ca(v)2.1) channels in the mouse medial nucleus of the trapezoid body.
abstract: Nitric Oxide (NO) is a diffusible second messenger that modulates ion channels, intrinsic excitability and mediates synaptic plasticity. In light of its activity-dependent generation in the principal neurons of the medial nucleus of the trapezoid body (MNTB), we have investigated its potential modulatory effects on native voltage-gated calcium channels (Ca(V)) within this nucleus. Whole-cell patch recordings were made from brain slices from P13-15 CBA mice. Slices were incubated with the inhibitor of neuronal nitric oxide synthase (nNOS) 7-nitroindazole (10 µM) and pharmacological blockers used to isolate Ca(2+) current subtypes. Unpaired observations in the presence and absence of the NO-donors sodium nitroprusside (SNP, 100 µM) or Diethyl-ammonium-nonoate (DEA, 100 µM) were made to elucidate NO-dependent modulation of the expressed Ca(V) subtypes. A differential effect of NO on the calcium channel subtypes was observed: Ca(V)1 and Ca(V)2.1 (L+R- and P/Q+R-type) conductances were potentiated, whereas N+R-type (Ca(V)2.2) and R-type (Ca(V)2.3) current amplitudes were unaffected. L+R-type currents increased from 0.36 ± 0.04 nA to 0.64 ± 0.11 nA and P/Q+R-type from 0.55 ± 0.09 nA to 0.94 ± 0.05 nA, thereby changing the balance and relative contribution of each subtype to the whole cell calcium current. In addition, N+R-type half-activation voltage was left shifted following NO exposure. NO-dependent modulation of P/Q+R and N+R-type, but not L+R-type, channels was removed by inhibition of soluble guanylyl cyclase (sGC) activity. This data demonstrates a differential effect of NO signalling on voltage-gated calcium entry, by distinct NO-dependent pathways.
authors.affiliation: Neurotoxicity at the Synaptic Interface, MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom.
authors.forename: Adam J B
authors.initials: AJ
authors.lastname: Tozer
authors.forename: Ian D
authors.initials: ID
authors.lastname: Forsythe
authors.forename: Joern R
authors.initials: JR
authors.lastname: Steinert
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D006162:Guanylate Cyclase / Q000378:metabolism; D007191:Indazoles / Q000494:pharmacology; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D000071756:Soluble Guanylyl Cyclase
chemical_list: D015220:Calcium Channels; D007191:Indazoles; D020030:Nitric Oxide Donors; D018160:Receptors, Cytoplasmic and Nuclear; D009599:Nitroprusside; D009569:Nitric Oxide; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D002118:Calcium; C080122:7-nitroindazole