Effects of extracellular Ca2+ on membrane and seal resistance in patch-clamped rat thalamic and sensory ganglion neurons.
We studied the effects of [Ca2+]ext changes on seal resistance in patch-clamp experiments. Recordings were made on rat peripheral and thalamic neurons. Increasing [Ca2+]ext from 0.5 to 4.5 mM, reduced the ionic currents evoked at potentials from -100 to +50 mV, in cell-attached recordings, in all the neurons tested. The effect was greater at negative potentials. The change in seal conductance (deltaG) decreased with higher resistance seals and became very low over 1 Gohm (<0.5 nS). However, the ratio deltaG/G(0.5 Ca2+) rose from close to 0 up to 0.6, indicating that Ca2+ has a stronger effect when the microelectrode and the membrane are sealed more tightly. These findings suggest that changes in seal resistance may be misleading in experiments in which extracellular Ca2+ changes are used.
Formenti
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Institute of Human Physiology II, University of Milan, Milano, Italy. alessandro.formenti@unimi.it
De Simoni
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D000818:Animals; D002118:Calcium / Q000494:pharmacology* / Q000502:physiology; D018929:Cell Culture Techniques; D002462:Cell Membrane / Q000187:drug effects* / Q000502:physiology; D017097:Electric Impedance; D017950:Ganglia, Sensory / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D013788:Thalamus / Q000166:cytology / Q000187:drug effects* / Q000502:physiology
D002118:Calcium