Ethanol-induced increases in [Ca2+]i and inositol (1,4,5) triphosphate in rat hepatocytes

Rat hepatocytes were studied for [Ca2+]i with Fura-2 at the single cell level using a microfluorometer-imaging system which showed that both the number of cells elevating [Ca2+]i and the magnitude of [Ca2+]i increase were directly dependent upon ethanol concentration between 50 mM and 1 M. Peak [Ca2+]i increases ranged from 27 nM with 50 mM ethanol to 57 nM after 1 M ethanol. Ethanol appeared to initiate calcium release from intracellular stores and caused a dose dependent production of inositol(1,4,5) triphosphate (Ins(1,4,5)P3) in hepatocytes. Low concentrations of ethanol (50-100 mM) did not significantly raise Ins(1,4,5)P3 although 300 mM-1 M increased Ins(1,4,5)P3 comparable to that found with vasopressin (5 nM). In summary, physiologic amounts of ethanol raise [Ca2+]i in rat hepatocytes, although at lower levels (50-100 mM) the changes may or may not be related to an Ins(1,4,5)P3 pathway.     

In-Vitro and In-Vivo Action of Cannabinoids

The discovery of endocannabinoids such as anandamide and the wide spread localization of cannabinoid receptors in the brain and peripheral tissues, suggests that the cannabinoid system represents a previously unrecognized ubiquitous net work in the nervous system, whose physiology and function is unfolding. In this study, we tested the hypothesis that some of the actions of anandamide are independent of a cannabinoid receptor mechanism. This was accomplished by the use of cannabinoid agonist and antagonist interaction in an in-vitro and in-vivo test systems. In-vitro, we used Xenopus laevis oocytes expression system and two-voltage clamp technique in combination with differential display polymerase chain reaction to determine whether the differential display of genes following treatment with anandamide may be linked to AMPA glutamate receptor. The differential expression of genes in vivo after the sub-acute administration of anandamide could not be directly linked with the AMPA glutamate receptor. In the voltage clamp studies we investigated the effects of anandamide on recombinant AMPA GluR3 sub-unit currents generated by kainic acid in oocytes expressing the AMPA glutamate receptor. In the in-vitro studies, we present evidence that anandamide inhibited the kainate activated currents in oocytes expressing AMPA glutamate receptor involves cAMP transduction via a cannabinoid receptor independent mechanism. In the in-vivo studies, SR141716A, the CB1 antagonist, induced anxiolysis, that was dependent on the mouse strain used in the anxiety model and blocked the anxiogenic effects of anandamide or methanandamide whereas SR141716A had no effect on the anandamide inhibition of kainate activated currents in-vitro.