Ca2+ -free medium enhances the magnitude of slow peak in compound action potential of frog sciatic nerve in vitro.
Indian J Exp Biol
;
2004 Jan; 42(1): 43-7
Artigo
em Inglês
| IMSEAR
| ID: sea-62838
ABSTRACT
The present investigation was carried out to know the effect of Ca2+ on different peaks of compound action potential (CAP) representing the fibers having different conduction velocity. CAP was recorded from a thin bundle of nerve fibers obtained from desheathed frog sciatic nerve. Suction electrodes were used for stimulating and recording purposes. In Ca2+ -free amphibian Ringer, two distinct peaks (Peak-I and Peak-II) were observed. The threshold, conduction velocity (CV), amplitude and duration of Peak-I were 0.32 +/- 0.02 V, 56 +/- 3.0 m/sec, 2.1 +/- 0.2 mV and 0.75 +/- 0.1 ms, respectively. The Peak-II exhibited ten times greater threshold, eight times slower CV, three times lower amplitude and four times greater duration as compared to Peak-I. Addition of 2 mM Ca2+ in the bathing medium did not alter CAP parameters of Peak-I excepting 25% reduction in CV. But, in Peak-II there was 70-75% reduction in area and amplitude. The concentration-attenuation relation of Peak-II to various concentrations of Ca2+ was nonlinear and 50% depression occurred at 0.35 mM of Ca2+. Washing with Ca2+ -free solution with or without Mg2+ (2 mM)/verapamil (10 microM) could not reverse the Ca2+ -induced changes in Peak-II. Washing with Ca2+ -free solution containing EDTA restored 70% of the response. The results indicate that Ca2+ differentially influence fast and slow conducting fibers as the activity of slow conducting fibers is greatly suppressed by external calcium.
Texto completo:
DisponíveL
Índice:
IMSEAR (Sudeste Asiático)
Assunto principal:
Ranidae
/
Nervo Isquiático
/
Fatores de Tempo
/
Potenciais de Ação
/
Cálcio
/
Ácido Edético
/
Meios de Cultura
/
Relação Dose-Resposta a Droga
/
Eletrodos
/
Eletrofisiologia
Idioma:
Inglês
Revista:
Indian J Exp Biol
Ano de publicação:
2004
Tipo de documento:
Artigo
Similares
MEDLINE
...
LILACS
LIS