The α2δ Auxiliary Subunit Reduces Affinity of ω-Conotoxins for Recombinant N-type (Cav2.2) Calcium Channels

The ω-conotoxins from fish-hunting cone snails are potent inhibitors of voltage-gated calcium channels. The ω-conotoxins MVIIA and CVID are selective N-type calcium channel inhibitors with potential in the treatment of chronic pain. The β and α2δ-1 auxiliary subunits influence the expression and characteristics of the α1B subunit of N-type channels and are differentially regulated in disease states, including pain. In this study, we examined the influence of these auxiliary subunits on the ability of the ω-conotoxins GVIA, MVIIA, CVID and analogues to inhibit peripheral and central forms of the rat N-type channels. Although the β3 subunit had little influence on the on- and off-rates of ω-conotoxins, coexpression of α2δ with α1B significantly reduced on-rates and equilibrium inhibition at both the central and peripheral isoforms of the N-type channels. The α2δ also enhanced the selectivity of MVIIA, but not CVID, for the central isoform. Similar but less pronounced trends were also observed for N-type channels expressed in human embryonic kidney cells. The influence of α2δ was not affected by oocyte deglycosylation. The extent of recovery from the ω-conotoxin block was least for GVIA, intermediate for MVIIA, and almost complete for CVID. Application of a hyperpolarizing holding potential (-120 mV) did not significantly enhance the extent of CVID recovery. Interestingly, [R10K]MVIIA and [O10K]GVIA had greater recovery from the block, whereas [K10R]CVID had reduced recovery from the block, indicating that position 10 had an important influence on the extent of ω-conotoxin reversibility. Recovery from CVID block was reduced in the presence of α2δ in human embryonic kidney cells and in oocytes expressing α1B-b. These results may have implications for the antinociceptive properties of ω-conotoxins, given that the α2δ subunit is up-regulated in certain pain states. The ω-conotoxins from fish-hunting cone snails are potent inhibitors of voltage-gated calcium channels. The ω-conotoxins MVIIA and CVID are selective N-type calcium channel inhibitors with potential in the treatment of chronic pain. The β and α2δ-1 auxiliary subunits influence the expression and characteristics of the α1B subunit of N-type channels and are differentially regulated in disease states, including pain. In this study, we examined the influence of these auxiliary subunits on the ability of the ω-conotoxins GVIA, MVIIA, CVID and analogues to inhibit peripheral and central forms of the rat N-type channels. Although the β3 subunit had little influence on the on- and off-rates of ω-conotoxins, coexpression of α2δ with α1B significantly reduced on-rates and equilibrium inhibition at both the central and peripheral isoforms of the N-type channels. The α2δ also enhanced the selectivity of MVIIA, but not CVID, for the central isoform. Similar but less pronounced trends were also observed for N-type channels expressed in human embryonic kidney cells. The influence of α2δ was not affected by oocyte deglycosylation. The extent of recovery from the ω-conotoxin block was least for GVIA, intermediate for MVIIA, and almost complete for CVID. Application of a hyperpolarizing holding potential (-120 mV) did not significantly enhance the extent of CVID recovery. Interestingly, [R10K]MVIIA and [O10K]GVIA had greater recovery from the block, whereas [K10R]CVID had reduced recovery from the block, indicating that position 10 had an important influence on the extent of ω-conotoxin reversibility. Recovery from CVID block was reduced in the presence of α2δ in human embryonic kidney cells and in oocytes expressing α1B-b. These results may have implications for the antinociceptive properties of ω-conotoxins, given that the α2δ subunit is up-regulated in certain pain states. The N-type (Cav2.2) voltage-gated calcium channels play an important role in the control of neurotransmitter release from nerve terminals (1Nowycky M.C. Fox A.P. Tsien R.W. Nature. 1985; 316: 440-443Crossref PubMed Scopus (1596) Google Scholar, 2Fox A.P. Nowycky M.C. Tsien R.W. J. Physiol. 1987; 394: 149-172Crossref PubMed Scopus (970) Google Scholar) and are important drug targets for the treatment of pain (3Malmberg A.B. Yaksh T.L. Pain. 1995; 60: 83-90Abstract Full Text PDF PubMed Scopus (213) Google Scholar, 4Saegusa H. Kurihara T. Zong S. Kazuno A. Matsuda Y. Nonaka T. Han W. Toriyama H. Tanabe T. EMBO J. 2001; 20: 2349-2356Crossref PubMed Scopus (280) Google Scholar) and ischemic brain injury (5Yamada K. Teraoka T. Morita S. Hasegawa T. Nabeshima T. Neuropharmacology. 1994; 33: 251-254Crossref PubMed Scopus (36) Google Scholar). Native N-type Ca2+ channels are hetero-oligomers that comprise a pore-forming α1 subunit (α1B) and at least two auxiliary subunits, β and α2δ, which modulate the α1 subunit function (6McEnery M.W. Snowman A.M. Sharp A.H. Adams M.E. Snyder S.H. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 11095-11099Crossref PubMed Scopus (89) Google Scholar, 7Witcher D.R. De Waard M. Sakamoto J. Franzini-Armstrong C. Pragnell M. Kahl S.D. Campbell K.P. Science. 1993; 261: 486-489Crossref PubMed Scopus (178) Google Scholar). Two splice variants of the α1B subunit have been identified that occur predominantly in the central (α1B-d) and peripheral (α1B-b) nervous systems (8Lin Z. Haus S. Edgerton J. Lipscombe D. Neuron. 1997; 18: 153-166Abstract Full Text Full Text PDF PubMed Scopus (149) Google Scholar, 9Lin Z. Lin Y. Schorge S. Pan J.Q. Beierlein M. Lipscombe D. J. Neurosci. 1999; 19: 5322-5331Crossref PubMed Google Scholar). Additional splice variants that lack large parts of the domain II-III linker region, including the synaptic protein interaction site, have also been isolated from human brain cDNA libraries (10Kaneko S. Cooper C.B. Nishioka N. Yamasaki H. Suzuki A. Jarvis S.E. Akaike A. Satoh M. Zamponi G.W. J. Neurosci. 2002; 22: 82-92Crossref PubMed Google Scholar). Multiple isoforms of the β and α2δ subunits also exist that can interact with the α1 subunit to produce N-type Ca2+ channels with different gating properties, allowing the fine tuning of synaptic transmissions (11Wu L.G. Westenbroek R.E. Borst J.G. Catterall W.A. Sakmann B. J. Neurosci. 1999; 19: 726-736Crossref PubMed Google Scholar). A distinguishing feature of N-type channels is their high sensitivity to block by ω-conotoxins, which are relatively small (∼25 residue) polypeptides isolated from the venom of the marine snail of the genus Conus (12Olivera B.M. Miljanich G.P. Ramachandran J. Adams M.E. Annu. Rev. 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MVIIA from Conus magus is being tested in clinical trials as a treatment for neuropathic pain, but dose-limiting side effects are a concern (18Atanassoff P.G. Hartmannsgruber M.W. Thrasher J. Wermeling D. Longton W. Gaeta R. Singh T. Mayo M. McGuire D. Luther R.R. Reg. Anesth. Pain Med. 2000; 25: 274-278PubMed Google Scholar, 19Jain K.K. Expert Opin. Investig. Drugs. 2000; 9: 2403-2410Crossref PubMed Scopus (84) Google Scholar, 20Levin T. Petrides G. Weiner J. Saravay S. Multz A.S. Bailine S. Psychosomatics. 2002; 43: 63-66Crossref PubMed Scopus (26) Google Scholar). ω-Conotoxin CVID from Conus catus (21Lewis R.J. Nielsen K.J. Craik D.J. Adams T. Adams D.J. T. A. R. J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google which to have a therapeutic Lewis R.J. Pain. 2002; Full Text Full Text PDF PubMed Scopus Google is also in clinical trials M. R. C. and D. in of the on in Pain and J. D. and M. for the of Scholar). The effects of auxiliary subunits on the properties of Ca2+ channel α1 subunits have been expressed α1 subunits produce channels with properties that from of the channel A.M. Nature. 1991; PubMed Scopus Google Scholar, A. Pragnell M. Campbell K.P. Neuropharmacology. 1993; 32: PubMed Scopus Google Scholar). The observed of the β and α2δ subunits are with the α1 subunit in a expression as oocytes used human embryonic used human embryonic cells is to the of Ca2+ channel by and influence the of channel and Waard M. Campbell K.P. J. Physiol. 1995; PubMed Scopus Google Scholar, N. R. D. J. J. PubMed Scopus Google Scholar, J. Physiol. PubMed Scopus Google Scholar, M. G. Y. J. Physiol. 1999; PubMed Scopus Google Scholar). a of the β3 subunit on N-type Ca2+ channel been in oocytes T. Lewis R.J. Adams D.J. J. Physiol. PubMed Scopus Google Scholar). N-type Ca2+ channels are in brain and peripheral with a of auxiliary subunits H. H. Mol. 1995; PubMed Scopus Google Scholar, A. J. Neurosci. 1997; PubMed Google Scholar, H. M.W. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Mol. 2001; PubMed Scopus Google Scholar). in subunit to to Although the role of auxiliary subunits is of α2δ subunits been in with neuropathic pain R.A. S. Mol. 2001; PubMed Scopus Google Scholar, M. Kurihara T. Han W. K. Tanabe T. 2002; PubMed Scopus Google Scholar, C.I. Myers R.R. J. Pharmacol. 2002; PubMed Scopus Google Scholar, C. G. S.H. Z. Han Proc. Natl. Acad. Sci. U. S. A. 2002; PubMed Scopus Google Scholar). In a study, we that CVID was a selective N-type Ca2+ channel (21Lewis R.J. Nielsen K.J. Craik D.J. Adams T. Adams D.J. T. A. R. J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar) that release at nerve terminals D.J. Smith A.B. Schroeder C.I. Yasuda T. Lewis R.J. J. Biol. Chem. 2003; 278: 4057-4062Abstract Full Text Full Text PDF PubMed Scopus (84) Google Scholar). CVID and MVIIA by the central and peripheral isoforms of the α1B subunit expressed in oocytes in the of the α2δ auxiliary subunit (21Lewis R.J. Nielsen K.J. Craik D.J. Adams T. Adams D.J. T. A. R. J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). In the study, we that the of the ω-conotoxins CVID and MVIIA to block N-type Ca2+ channel is reduced in the presence of α2δ, and we position 10 in ω-conotoxins as an important influence on the extent of recovery from channel and were from by in The was by oocytes in and for at were and at in an that and was in from cDNA an cDNA the rat central and peripheral isoforms of the N-type Ca2+ as as the rat β3 were by D. Lipscombe The α2δ subunit was a from N. and of were with of subunit a as for the and α2δ subunits were at a cells were in at for to were in a and to with were a with and were with and had that from in the were from a holding potential of by and a were at and at 10 and were a were with at a of at in a were used in these to with In an to the of by oocytes were with of at least to were in a small of oocytes was for at by at in oocyte with the of 10 of ω-Conotoxins were in and at a of were for at least in the presence of the of the ω-conotoxins the of of block and the of the recovery from block were from to the The for was and and cells were at in with and were to with and with α1B A. Pragnell M. Campbell K.P. Neuropharmacology. 1993; 32: PubMed Scopus Google β3 and protein with α2δ a calcium were to and for to were 10 10 and and at of were with a and were and at with an and was to were by from to were with control a allowing complete in were and with and in ω-conotoxins CVID, MVIIA, GVIA, and [O10K]GVIA were in M. A. D. J. PubMed Scopus Google and as K.J. Adams D. T. Craik D.J. Lewis R.J. J. Mol. Biol. 1999; PubMed Scopus Google Scholar). The reduced were in and for at in the presence of reduced and were by high K.J. Adams D. T. Craik D.J. Lewis R.J. J. Mol. Biol. 1999; PubMed Scopus Google Scholar). were on a with an of from rat brain was as K.J. Adams Lewis R.J. Schroeder T. Craik D.J. Biochemistry. 1999; PubMed Scopus Google Scholar). are from at least in were on a with a on a with a were were from of CVID, MVIIA, GVIA, and [O10K]GVIA in and at K. used for the of and [O10K]GVIA were from at and K. were the in as K.J. Adams Lewis R.J. Schroeder T. Craik D.J. Biochemistry. 1999; PubMed Scopus Google Scholar). of β3 and α2δ on the of N-type in were in oocytes the of of for the of the N-type Ca2+ channel by to from a holding potential of from in of the β3 subunit at a with the of with expressed the of In with a (8Lin Z. Haus S. Edgerton J. Lipscombe D. Neuron. 1997; 18: 153-166Abstract Full Text Full Text PDF PubMed Scopus (149) Google β3 had effects on the and of Ca2+ channel of the β3 subunit a hyperpolarizing in the from for to in the presence of β3 and of the and β3 subunits with the α2δ subunit in an of the A and the from the in the presence of the α2δ subunit was that with the β3 subunit Ca2+ channel from oocytes expressing α2δ also and the of α2δ β3 a small but of for to with β3 mV) and A of been for and Ca2+ channels M. G. Y. J. Physiol. 1999; PubMed Scopus Google Scholar, N. R. J. Physiol. PubMed Google Scholar). The channel and channel properties were also by β3 and α2δ subunits in a to their influence on of β3 and α2δ on the by ω-Conotoxins of N-type in the influence of different auxiliary subunits on the of ω-conotoxins at N-type Ca2+ we the ability of the ω-conotoxins CVID and MVIIA and the [K10R]CVID and [R10K]MVIIA to inhibit N-type by α1B α1B α1B β3 and off-rates of channel block and of for the different Ca2+ channel subunit were and of A and In the to block a and was by a A function also recovery from block The and recovery from block were for from for the peripheral (α1B-b) and central (α1B-d) isoforms of the N-type Ca2+ channel are in and and extent of block by the ω-conotoxins CVID, MVIIA, and analogues on the peripheral (α1B-b) N-type expressed in oocytes in with β3 and α2δ subunits ω-Conotoxins were at at β3 The extent of recovery from block was as in S.E. as β3 β3 β3 β3 in a and extent of block by the ω-conotoxins CVID, MVIIA, and their analogues on the central (α1B-d) N-type expressed in oocytes in with β3 and α2δ subunits ω-Conotoxins were at and at β3 The extent of recovery from block was as in S.E. as β3 β3 β3 β3 in a the α1B subunit expressed in with the β3 the of CVID MVIIA a of the by the peripheral the central of the N-type Ca2+ channel and CVID was less potent MVIIA, at the subunit and The analogues [K10R]CVID and MVIIA had of inhibition of α1B to CVID and MVIIA, of the α2δ subunit with α1B β3 subunit reduced the of the N-type Ca2+ channel for the ω-conotoxins and from at to at and both splice the of α2δ was for [K10R]CVID and CVID with MVIIA and The in by α2δ from a reduced for these ω-conotoxins on and The influence of α2δ on the and of ω-conotoxin block at α1B were also observed in the of the β3 Similar of were equilibrium for ω-conotoxins CVID and MVIIA inhibition of β3 in the presence of α2δ, and extent of block by ω-conotoxin CVID at β3 at different holding and 10 treatment De Waard M. Campbell K.P. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar) The extent of recovery from block was as in S.E. as α2δ in a Two of oocytes expressing β3 were to to MVIIA block this sensitivity was pronounced the oocytes were and was to results for CVID at (21Lewis R.J. Nielsen K.J. Craik D.J. Adams T. Adams D.J. T. A. R. J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google indicating that the inhibition observed is an oocyte Interestingly, a of as a function of ω-conotoxin a with a was pronounced for in the of α2δ but significantly different from in the presence of α2δ this in the to different on the of ω-conotoxin In the of α2δ, at CVID, the was whereas at 10 CVID the was greater of channel of ω-Conotoxin of N-type in observed for MVIIA R.J. A.M. Zamponi G.W. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar, R.W. Tsien R.W. J. Neurosci. 1997; PubMed Google recovery from block for MVIIA and CVID was to and expressed recovery from block was less for with at position 10 with with a at position 10 channels expressed CVID and [K10R]CVID had of recovery whereas [R10K]MVIIA had enhanced recovery with MVIIA β3 recovery from block was also greater for at position and for β3 channels was greater for of α2δ with β3 reduced recovery from block for CVID and [K10R]CVID but not for MVIIA and [R10K]MVIIA and In for β3 α2δ channels the recovery from block was significantly reduced for MVIIA and [R10K]MVIIA but not for CVID and recovery was least for MVIIA at and for [R10K]MVIIA at have that the extent of recovery from ω-conotoxin block is enhanced at hyperpolarizing holding A. R. Science. 1993; PubMed Scopus Google Scholar). In the study, a hyperpolarizing holding potential was to have influence on the extent of recovery from block, at least for CVID a that is from of ω-conotoxins and to the N-type Ca2+ channel A. R. Science. 1993; PubMed Scopus Google Scholar). the that position 10 was to influence the of MVIIA and CVID inhibition of N-type calcium we the [O10K]GVIA to the of position 10 for reversibility. Interestingly, this also enhanced with and that an interaction the at position 10 and the N-type calcium channel is a in the ω-Conotoxin CVID of N-type in to the results α1B β3 was expressed in oocytes inhibition was of CVID were to inhibit α1B expressed in cells reduced may in to the effects of the and β3 subunits on to the used as the in these which can influence the of ω-conotoxins R.J. A.M. Zamponi G.W. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google and S. S. M.E. G. Neuropharmacology. 1993; 32: PubMed Scopus Google Scholar). Similar in the two expression systems were also observed for MVIIA not with the results in coexpression of the α2δ subunit reduced CVID but to a extent A and of CVID was in the presence of the α2δ subunit to from rat brain were to position 10 the affected for N-type channels These results that the ω-conotoxins had a to that of their at brain N-type calcium to from rat brain in a and the role of 10 in to was used to that may with this with for a of is a for in the 10 in MVIIA and with the from CVID in the in [R10K]MVIIA whereas the in the in [O10K]GVIA were in and in CVID with an did not in of the D.J. Smith A.B. Schroeder C.I. Yasuda T. Lewis R.J. J. Biol. Chem. 2003; 278: 4057-4062Abstract Full Text Full Text PDF PubMed Scopus (84) Google Scholar). were for [R10K]MVIIA and which from their of these that in MVIIA with the did not the of the which is with the relatively small in the observed which the to in of as with The of the [O10K]GVIA was not by the to and a to The effects of auxiliary β and α2δ subunits on the pore-forming α1 subunit of calcium channels have been Waard M. Campbell K.P. J. Physiol. 1995; PubMed Scopus Google Scholar, J. Physiol. PubMed Scopus Google Scholar, M. G. Y. J. Physiol. 1999; PubMed Scopus Google Scholar, N. R. J. Physiol. PubMed Google Scholar). The of the was to these auxiliary subunits influence the of ω-conotoxins to inhibit by N-type (Cav2.2) calcium channels. of the peripheral (α1B-b) and central (α1B-d) isoforms in oocytes Ca2+ channel that were enhanced with the β3 the β3 subunit had on the ability of the ω-conotoxins CVID, MVIIA, and their analogues to inhibit by the α1B In the central was to block the peripheral for ω-conotoxins the observed was In to the of both the central and peripheral isoforms of the N-type Ca2+ channel and the for as observed M. G. Y. J. Physiol. 1999; PubMed Scopus Google the α2δ subunit reduced ω-conotoxin for N-type channels expressed in of the α2δ subunit with α1B β3 subunits a in the sensitivity of the channel to block by CVID, MVIIA, and for the inhibition of N-type by ω-conotoxin MVIIA in the presence of the α2δ subunit were to R.W. Tsien R.W. J. Neurosci. 1997; PubMed Google Scholar, N. Y. Acad. Sci. 1999; PubMed Scopus Google Scholar, J. C. Zamponi G.W. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). The α2δ subunit a in sensitivity at both the peripheral and central isoforms of the N-type Ca2+ In the presence of α2δ, selectivity for the central the peripheral was MVIIA [K10R]CVID [R10K]MVIIA CVID and indicating that at position 10 to central with the results in the α2δ subunit also the ω-conotoxin CVID sensitivity of α1B channels expressed in the was not as with an in cells in which α2δ the to S. S. M.E. G. Neuropharmacology. 1993; 32: PubMed Scopus Google Scholar). results that the in by α2δ was a of the ω-conotoxin is that this may from the of the and domain to the ω-conotoxin site, which in the of the channel J. C. Zamponi G.W. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). oocytes may for the observed the two expression systems used the of the α2δ on ω-conotoxin was not by oocyte the effects were in to an α2δ of in to α2δ effects to the of we were to this from α1B expressed in cells in the of α2δ were small to by as the A of to on the N-type Ca2+ channel protein as this to both the and In R. De Waard M. Campbell K.P. J. Neurosci. 1997; PubMed Google Scholar) that the of to the channel was by the of α2δ, by the of the is that the at In to coexpression of the α2δ subunit reduced the of recovery from block this to specific to both the α1B expressed and to the of with the being for CVID analogues in cells expressing the peripheral and for MVIIA analogues in cells expressing the central isoform. The for this in the α2δ on recovery α1B is not The effects of α2δ on ω-conotoxin to to of to produce inhibition of α2δ β3 expressed in D. and R. J. was that the sensitivity of to CVID block was two of greater expressed in the of the β3 subunit (21Lewis R.J. Nielsen K.J. Craik D.J. Adams T. Adams D.J. T. A. R. J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). In the study, of oocytes expressing had high ω-conotoxin in this the was for is not to CVID and from in α1B in as a of auxiliary protein Similar were also at expressed were on-rates of block at different of CVID, which is of in α1B in In to the of auxiliary subunits on an in the extent of recovery from block by different ω-conotoxins was also Recovery from block by CVID was greater that for MVIIA, whereas block was Interestingly, CVID was reduced for the peripheral of the N-type channel in the presence of α2δ, whereas MVIIA was reduced at the central in the presence of In the this may CVID to inhibit the by peripheral and MVIIA to inhibit the and by central A for the central by MVIIA not is to central peripheral selectivity may have to pain given that a splice of the N-type calcium channel been identified in peripheral pain T.J. C. Lipscombe D. Neuron. Full Text Full Text PDF PubMed Scopus Google Scholar). is that the selectivity of MVIIA for central isoforms of the N-type calcium channel may a therapeutic CVID in rat of Lewis R.J. Pain. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar) and neuropathic pain J. Pharmacol. 2002; PubMed Scopus Google Scholar). In an to which on ω-conotoxins influence we a of position 10 that had been identified as calcium channel selectivity D.J. Smith A.B. Schroeder C.I. Yasuda T. Lewis R.J. J. Biol. Chem. 2003; 278: 4057-4062Abstract Full Text Full Text PDF PubMed Scopus (84) Google Scholar). [R10K]MVIIA had enhanced as with MVIIA for both the central and peripheral isoforms of the N-type Ca2+ to CVID, [K10R]CVID had at the peripheral of the N-type Ca2+ channel little influence at the central isoform. The influence of position 10 on was to GVIA, with [O10K]GVIA enhanced recovery. these results that position 10 is a of ω-conotoxin reversibility. to a specific interaction 10 of the and on the N-type Ca2+ channel the of the is little but in the of the subunit for the of in the of the channel have been identified P.T. Horne W.A. Tsien R.W. Nature. 1994; PubMed Scopus Google Scholar). In a by J. C. Zamponi G.W. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google was to a of and MVIIA as of this to a a block by these ω-conotoxins In to the α2δ which affected the ω-conotoxin position 10 had a on the extent of of ω-conotoxins, of the auxiliary subunit of in ω-conotoxins CVID with did not the with the In the small in did not influence the as with In the in with a the of that the an important interaction the The that the results of the that this in the of the that to the N-type calcium channel to CVID and was by that in for [O10K]GVIA to the N-type channels in rat brain as with the of in effects on but not on the of from rat brain in to a of in and the channel the of in observed in the recovery from block by MVIIA are to in the side properties by the to CVID and [R10K]MVIIA greater as with [K10R]CVID and is these different in their to from rat brain These results the that with the N-type channels a different as with MVIIA and CVID K.J. Schroeder T. Lewis R. J. Mol. Recognit. 2000; 13: 55-70Crossref PubMed Scopus (97) Google Scholar). In we that the α2δ subunit the sensitivity of N-type calcium channels to block by ω-conotoxins in with results observed for α1B expressed in cells. the recovery from block by the ω-conotoxins MVIIA and is on the of the at position a to that the α2δ subunit is up-regulated in of neuropathic pain C.I. Myers R.R. J. Pharmacol. 2002; PubMed Scopus Google in and recovery from block may influence ω-conotoxins different in

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