Acute Inositol Induces Anxiety in Rats Hagit Cohen, Noa Bar-haim, and Moshe Kotler Key Words: Inositol, anxiety, cholecystokinin, panic, animal models BIOL PSYCHIATRY 1996;40:426-427 Introduction Inositol is a key intermediate in the phosphatidylinositol (PI) cycle. The PI cycle serves as a second messenger system for numerous brain neurotransmitters. Some cholecystokinin (CCK) receptors are linked to PI (Bianchi et al 1994). Agam et al (1994) showed that inositol, given at high doses peripherally, enters the brain and raises brain inositol levels significantly as measured both chemically and behaviorally. Benjamin et al (1995) showed that treatment with inositol at doses of 12 g daily for 4 weeks decreased the frequency and severity of panic attacks versus placebo. This study explored whether inositol might block the anxiogenic effect of acute administration of CCK in rats (Craw- ley 1995; de Montigny 1989; Harro et al 1990). Methods Thirty-nine male Wistar rats, weighing 200-250 g, were habit- uated to the housing conditions for at least 10 days. The animals were housed 4 per cage in an animal room with stable temper- ature and reversed 12-hour light/dark cycle with food and water. All testing was performed during the dark phase using a dim light, during the period from April to May, 1994. Behavioral testing was conducted in an elevated plus maze made of Perspex. This apparatus consists of two open arms and two enclosed arms, with an open roof. The apparatus is configured such that the two open arms are opposite to each other. The maze is elevated to 0.5 m. When placed individually in the central platform, rats were faced toward different arms on different days in random- ized order, for 6-rain sessions. Ratings were made by reviewing the video recordings by observers blind to the original treatment From the Mental Health Center, Anxiety and Stress Research Unit, Ben Gurion University of the Negev, Beer-Sheva, Israel. Address reprint requests to Dr. Hagit Cohen, Department of Psychiatry, Ben-Gurion University of Negev, Anxiety and Stress Res. Unit, P.O. Box 4600, Beer-Sheva Mental Health Center, Beer-Sheva, Israel. Received November 20, 1995; revised January 5, 1996. conditions. In general, time in closed arms indicates anxiety and time in open arms indicates anxiolytic effects. Inositol 2.5 g/kg 10% solution in saline was injected IP in the morning hours. As placebo, injections of glucose plus mannitol in a ratio of 1:3 were used to control for both osmotic and food value of inositol. Preliminary experiments showed that mannitol or glucose was no different from saline in effects on the anxiety model. CCK-tetrapeptide (CCK-4) (50 Ixg/kg SC) (Calbiochem) or saline was injected 6 hours after the inositol and after 3 min the rats were placed in the elevated plus maze. Results Results are summarized in Table 1. CCK-4 significantly en- hances anxiety. Inositol surprisingly also significantly enhances anxiety. Additional measurements such as number of entries into closed arms, time spent on the platform, and number of entries into open arms, showed identical trends that did not reach significance. Total enters to the arms was unchanged by inositol, suggesting an absence of sedative or neurotoxic effects. Discussion A controlled double-blind study suggests that inositol may have antipanic properties in humans after chronic use (Benjamin et al 1995). An acute dose of inositol was not found to have clear psychoactive properties in humans (Levine et al 1994). The present study of acute inositol unexpectedly demonstrated anxi- ety-inducing effects that appeared comparable in magnitude to 50 p,g/kg SC CCK-4 and that neither blocked nor potentiated the CCK-4 induced anxiety. Clomipramine, a clear antipanic agent when given chronically, has been reported to exacerbate anxiety when given acutely (Ramos et al 1993). Thus, chronic inositol administration must be studied for effects on anxiety. The dose of inositol used in these experiments (2.5 g/kg) is much lower than the minimum dose necessary for behavioral © 1996 Society of Biological Psychiatry 0006-3223/96/$15.00 PII 0006-3223(96)00011-2