RESUMEN
The influence of cocaine, amphetamine, cathinone, pargyline and nomifensine on inward calcium current was studied using internally perfused neurons of the snail Lymnaea stagnalis. While nomifensine and pargyline inhibited inward calcium current in the concentrations 10(-7)-10(-4) M and did not affect them in the concentrations 10(-9)-10(-8) M, cocaine, amphetamine and cathinone had a biphasic action on inward calcium current, causing activation (10-30 percent) at 10(-9)-10(-7) M, and inhibition at higher concentrations. Only cathinone caused a shift of the I-V characteristics of the membrane along the potential axis. It is suggested that drugs of abuse affect membrane excitability and inward calcium current in neurons directly.
Asunto(s)
Calcio/metabolismo , Neuronas/efectos de los fármacos , Psicotrópicos/farmacología , Alcaloides/farmacología , Anfetamina/farmacología , Animales , Cocaína/farmacología , Relación Dosis-Respuesta a Droga , Electrofisiología , Técnicas In Vitro , Transporte Iónico/efectos de los fármacos , Lymnaea , Potenciales de la Membrana/efectos de los fármacos , Neuronas/metabolismo , Nomifensina/farmacología , Pargilina/farmacología , PerfusiónRESUMEN
The influence of taurine (in concentrations of 10(-8) to 10(-2) mole/liter) on the fast sodium, calcium, and potassium, the slow potassium, and the leakage currents of the somatic membrane of the neurons of the pond snail was investigated. A monotonic decrease was demonstrated in the calcium and the slow potassium currents with an increase in the concentration of taurine. The sodium currents increased at taurine concentrations of 10(-8)-10(-4) mole/liter, while at concentrations of 10(-3)-10(-2) mole/liter they decreased. The fast potassium currents remained essentially unchanged at all concentrations of taurine. The leakage currents of the membrane at small concentrations of taurine decreased somewhat, and increased insignificantly at higher concentrations of it. All of the effects of taurine were reversible. It is hypothesized that the mechanism of the neuromodulatory, anticonvulsant, antihypoxic effects of taurine is at its base associated with changes in the electrically regulated ionic channels of the cell membrane.
Asunto(s)
Canales Iónicos/efectos de los fármacos , Lymnaea/metabolismo , Neuronas/metabolismo , Taurina/farmacología , Animales , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismo , Electrofisiología , Neuronas/efectos de los fármacos , Canales de Potasio/efectos de los fármacos , Canales de Sodio/efectos de los fármacosRESUMEN
Isolated and internally dialysed neurons from the molluscs Lymnaea stagnalis were investigated under voltage-clamp conditions. The increasing of taurin concentration (from 1.10(-8) to 1.10(-2) mol/l) reduced the calcium inward--and delayed potassium outward currents, and exerted no effect on the fast potassium outward current. Sodium inward current was increased by taurin concentrations 1.10(-8)-1.10(-4) mol/l, and reduced by 1.10(-3)-1.10(-2) mol/l. Membrane leakage currents were reduced by small taurin concentrations and increased by large concentrations.
Asunto(s)
Canales Iónicos/efectos de los fármacos , Lymnaea/efectos de los fármacos , Neuronas/efectos de los fármacos , Taurina/farmacología , Animales , Membrana Celular/efectos de los fármacos , Membrana Celular/fisiología , Relación Dosis-Respuesta a Droga , Técnicas In Vitro , Canales Iónicos/fisiología , Lymnaea/fisiología , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Neuronas/fisiologíaRESUMEN
Phenamine (10(-12)-10(-5) M/l) increased by 20-60 per cent the input (sodium and calcium) currents (Iin), the output slow potassium (Ikm) and fast potassium (Ikb) ones, and decreased the currents in higher concentrations. The volt-ampere characteristics of the membrane (VAC) and the curves of stationary inactivation (CSI) shifted along the potentials axis. The phenamine analogue IEM 1365 only decreased the currents leaving the VAC and CSI unaltered. Another analogue IEM 1370 only decreased the Iin whereas VAC and CSI also shifted along the potentials axis. The ion channels seem to be blocked in a decrease of the currents and the membrane surface potential induced with fixed charges seems to change.