Spontaneous miniature outward currents in mechanically dissociated rat Meynert neurons

Abstract

Spontaneous miniature outward currents (SMOCs) were observed in mechanically dissociated rat Meynert neurons using nystatin perforated patch recordings under voltage‐clamp conditions. SMOCs were blocked by apamin, a selective blocker of small conductance Ca2+‐activated K+ (SK) channels, but not by blockers for other types of Ca2+‐activated K+ channel. Ryanodine (10‐100 μm) reduced both the amplitude and frequency of SMOCs. Caffeine (1 mm) increased the SMOC frequency. Blockers of the sarco/endoplasmic reticulum Ca2+‐ATPase completely abolished SMOCs, indicating a requirement for functioning sarco/endoplasmic reticulum (SR/ER) Ca2+ stores. Both Cd2+‐containing and Ca2+‐free solutions partially inhibited SMOC frequency, a result which suggests that Ca2+ influx contributes to, but is not essential for, SMOC generation. Thus, SMOCs are SK currents linked to ryanodine‐ and caffeine‐sensitive SR/ER Ca2+ stores, and are only indirectly influenced by extracellular Ca2+ influx. The development of this new, minimally invasive mechanical dissociation method has revealed that SMOCs are common in native CNS neurons.

Electrophysiological and morphological properties of neurons in the prepositus hypoglossi nucleus that express both ChAT and VGAT in a double‐transgenic rat model

“…Our previous studies demonstrated that a majority of PHN neurons fire spontaneously, whereas some PHN neurons exhibit SMOCs (Saito & Yanagawa, ; Zhang et al ., ); these outward currents display slower kinetics compared with the postsynaptic currents and are induced by Ca 2+ ‐activated K + channels, which are activated by Ca 2+ ‐induced Ca 2+ release from the endoplasmic reticulum via ryanodine receptors (Arima et al ., ; Cui et al ., ; Klement et al ., ; Saito & Yanagawa, ). In the present study, most D+ neurons (67/70) exhibited spontaneous firing (Fig.…”

Functional interactions between the SK2 channel and the nicotinic acetylcholine receptor in enteric neurons of the guinea pig ileum

“…It has been reported that the association of calcium channel subtypes and ryanodine-sensitive Ca 2+ stores with Ca 2+activated K + channels differs among cell types (Marrion and Tavalin 1998;Arima et al 2001;Stocker 2004). We studied the effects of nicardipine and ryanodine on nicotine-induced ACh release.…”

Spontaneous Opening of T-Type Ca2+Channels Contributes to the Irregular Firing of Dopamine Neurons in Neonatal Rats

“…Indeed, this mechanism has been used to explain the generation of SMOCs in mudpuppy parasympathetic cardiac neurons (Merriam et al, 1999) and rat Meynert neurons (Arima et al, 2001). One unique property of SMOCs in DA neurons lies in the voltage dependence.…”

“…SMOCs or SMHs are observed in various types of neurons (Brown et al, 1983;Mathers and Barker, 1984;Satin and Adams, 1987;Berridge, 1998;Seutin et al, 1998;Arima et al, 2001), as well as in smooth muscle cells, in which they are usually called spontaneous transient outward currents (STOCs) (Bolton and Imaizumi, 1996). SMOCs-STOCs are mediated by the activation of Ca 2ϩ -sensitive K ϩ channels.…”