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Titolo:
CHANGES IN SODIUM AND CALCIUM-CHANNEL ACTIVITY FOLLOWING AXOTOMY OF B-CELLS IN BULLFROG SYMPATHETIC-GANGLION
Autore:
JASSAR BS; PENNEFATHER PS; SMITH PA;
Indirizzi:
UNIV ALBERTA,DEPT PHARMACOL EDMONTON T6G 2H7 ALBERTA CANADA UNIV TORONTO,FAC PHARM,MRC,NERVE CELL & SYNAPSE GRP TORONTO M5S 2S2 ON CANADA
Titolo Testata:
Journal of physiology
, volume: 472, anno: 1993,
pagine: 203 - 231
SICI:
0022-3751(1993)472:<203:CISACA>2.0.ZU;2-3
Fonte:
ISI
Lingua:
ENG
Soggetto:
MEMBRANE-PROPERTIES; SENSORY NEURONS; ELECTROPHYSIOLOGICAL CHARACTERISTICS; ACTIVATION KINETICS; POTASSIUM CURRENTS; PERIPHERAL AXOTOMY; INACTIVATION; CAT; MODULATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
41
Recensione:
Indirizzi per estratti:
Citazione:
B.S. Jassar et al., "CHANGES IN SODIUM AND CALCIUM-CHANNEL ACTIVITY FOLLOWING AXOTOMY OF B-CELLS IN BULLFROG SYMPATHETIC-GANGLION", Journal of physiology, 472, 1993, pp. 203-231

Abstract

1. Currents mediated by Ca2+ channels using Ba2+ as a charge carrier (I(Ba)), Na+ currents (I(Na)) and voltage- and Ca2+-dependent K+ currents (I(C)) were recorded from bullfrog paravertebral sympathetic ganglion B-cells using whole-cell patch-clamp recording techniques. Currents recorded from control cells were compared with those from axotomizedcells 13-15 days after transection of the postganglionic nerve. 2. Axotomy reduced peak I(Ba) at - 10 mV (holding potential = - 80 mV) from3.3 +/ 0.3 nA (n = 42) to 1.7 +/- 0.1 nA (n = 39, P < 0.001). Tail I(Ba) at - 40 mV following a step to + 70 mV from a holding potential of- 80 mV was also reduced in axotomized neurones (9.7 +/- 0.6 nA for forty-two control neurones and 5.2 +/- 0.3 nA for thirty-nine axotomized neurones; P < 0.001). Minimal changes were observed in the kinetics of activation and deactivation. 3. Pharmacological experiments using 2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-p yridine-5-carboxylicacid methyl ester (Bay K 8644), nifedipine and omega-conotoxin showedthat axotomy predominantly affected the N-type Ca2+ channels which carry the majority of I(Ca) in these neurones. L-type Ca2+ current was little affected and T-type Ca2+ currents were not observed in control or axotomized cells. 4. Development of inactivation at 0 mV and recovery from inactivation of I(Ba) at - 80 mV exhibited three distinct components in both control and axotomized neurones: 'fast', 'intermediate' and 'slow'. The relative proportions of both the 'fast' and 'intermediate' components of inactivation at 0 mV were almost doubled after axotomy (fast component was 15% in control and 29% in axotomized neurones;intermediate component was 17% in control and 26% in axotomized neurones). 'Fast' and 'intermediate' inactivation tended to develop more rapidly and recover more slowly after axotomy. The rate of onset of 'slow', inactivation was unaffected by axotomy but the steady-state level at -40 mV was increased. Most of the change in I(Ba) properties may besecondary to enhanced inactivation associated with axotomy. 5. Axotomy reduced I(C) (measured at the end of a 3 ms step from -40 to +20 mV)from 34.5 +/- 4.9 (n = 26) to 19.2 +/- 1.5 nA (n = 49, P < 0.005). This reduction may be secondary to the reduction in calcium channels available for activation from -40 mV following axotomy. 6. The TTX-sensitive and TTX-insensitive components of peak Na+ conductance (G(Na)) were both increased after axotomy. Total G(Na) was increased from 184.9 +/- 8.4 to 315.2 +/- 16.4 nS. (n = 37 for both P < 0.001). Most of the kinetic and steady-state properties of I(Na) were unchanged after axotomy. 7. These results suggest that the increase in spike width produced by axotomy of bullfrog sympathetic neurones involves a decrease in I(Ca) and consequent reduction in I(Ca). The complement of ion channelsexpressed after axotomy is quite unlike that which might be expected in 'immature' or 'dedifferentiated' neurones.

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Documento generato il 07/07/20 alle ore 12:18:13