The ethanol sensitivity of calcium taken up by a depolarization-dependent process in mouse strains DBA and C57BL

Isradipine and other calcium channel antagonists attenuate ethanol consumption in ethanol-preferring rats

The present work is concerned with studying of the ability of different calcium channel antagonists to modify voluntary ethanol ingestion by rats selectively bred for high ethanol preference. The compounds were given s.c. thrice daily for 5 days at doses that did not produce locomotor impairment. While nifedipine, darodipine, and verapamil (each at the dose of 20 mg/kg thrice daily) produced a modest reduction in ethanol intake, isradipine (at the dose of 1 mg/kg three times a day) reduced ethanol intake by over 70%. For all compounds, the reduction in ethanol intake was compensated by a proportional increase in water consumption and the inhibitory effect persisted throughout the 5 days of treatment. The data indicate that calcium channel antagonists exhibit quite different potency in reducing ethanol preference, however this action is a general property of this class of compounds.

The role of neuronal calcium channels in dependence on ethanol and other sedatives/hypnotics

This review discusses the importance of neuronal calcium currents in dependence on ethanol, barbiturates, benzodiazepines and opiates. The main sections describe the actions of ethanol on control of intracellular calcium and on calcium and calcium-dependent conductance mechanisms. In particular, the effects of both acute and chronic ethanol treatment on dihydropyridine-sensitive, voltage-dependent, calcium channels are described. The later sections cover the effects of barbiturates, benzodiazepines and opiates on these systems. The conclusions suggest that dihydropyridine calcium channel antagonists may offer a new therapeutic approach to the treatment of ethanol and opiate dependence.

Fura-2 measurement of cytosolic free calcium in rat brain cortical synaptosomes and the influence of ethanol

The effects of ethanol on resting and KCl-depolarized cytosolic calcium concentrations ([Ca2+]i) were measured in purified rat cortical synaptosomes using the calcium indicator fura-2. Ethanol (500-700 mM) significantly elevated the resting [Ca2+]i by 13-25% in the presence of 100 microM external calcium. In the absence of external Ca2+, ethanol (50-200 mM) significantly increased [Ca2+]i by 17-23%. Ethanol (200-700 mM) also significantly decreased KCl-induced rise in [Ca2+]i (delta K) by 40-82% in fura-2 loaded preparations incubated in the absence or presence of external calcium. Ethanol did not produce a significant change in delta K at 50 and 100 mM concentrations. These results suggest that ethanol may cause an elevation in [Ca2+]i via mobilization of intracellular calcium stores which may be linked to a calcium-dependent inactivation of voltage-sensitive calcium channels.

Ethanol increases synaptosomal free calcium concentration

The effect of ethanol on synaptosomal free calcium concentration [( Ca2+]i) and 45Ca2+ uptake was studied in vitro. Synaptosomes were prepared from forebrains of adult rats and incubated in the presence of ethanol 50-500 mM. [Ca2+]i determined by means of the Ca2+-sensitive dye, fura-2, was increased by ethanol in polarized and depolarized synaptosomes, whereas 45Ca2+ uptake was decreased. The results suggest that ethanol may influence neuronal calcium homeostasis by increasing rather than decreasing [Ca2+]i.

Effect of ethanol on GABA uptake and release from hypothalamic fragments

A study was performed on the effect of ethanol on the basal and K+-evoked efflux of endogenous GABA from rat hypothalamic fragments. The amount of GABA present in the medium and in the tissue was measured by radioreceptor assay. In vitro addition of ethanol (50 and 100 mM) enhanced the K+-evoked efflux of GABA in a Ca++-dependent manner, and increased tissue GABA content. Since K+-evoked outflow induced by ethanol was not affected by the presence of nipecotic acid, ethanol appears to alter the uptake of endogenous GABA. An inhibitory effect of ethanol on 3H-GABA uptake was observed under K+ depolarization. On the other hand, acute ethanol administration produced a decrease in basal and K+-evoked efflux from hypothalamic fragments and in tissue GABA concentration. Changes in GABA efflux may lie behind some of the neuropharmacological effects of ethanol.