The anxiolytic effect of chronic inositol depends on the baseline level ofanxiety

Inositol, a precursor for membrane phosphoinositides involved in signal tra nsduction, has been found to be clinically effective in a number of psychia tric disorders and to reverse behavioural effects of lithium. To gain insig ht into the mechanism of action of inositol, it is critical to establish it s efficacy in animal models. Following the initial report by Cohen et al. ( 1997b) that inositol was anxiolytic in the elevated plus maze model of anxi ety, the effect of chronic intraperitoneal and chronic dietary inositol adm inistration in rats was tested in four experiments. There was a significant increase in closed arm and total arm entries following chronic injection o f inositol, but no effect of inositol when it was given chronically in rat chow. Because the first 2 experiments suggested that the mode of drug administrat ion affected the control levels of anxiety (open arm entries and time in op en arms) in control groups, the effect of chronic dietary inositol was test ed in rats that were exposed to a mild and a more severe form of stress. Ch ronic saline injections elevated anxiety in the plus maze, which was only m arginally affected by chronic dietary inositol. Following 3 weeks administr ation of 5% dietary inositol rats were pre-exposed to a cat. There was a cl ear increase in number of entries into open arms, suggesting an anxiolytic effect of inositol.