Pak. J. Pharm. Sci., 2007, Vol.20(4), 295-299 295 ORIGINAL ARTICLE DOSE RELATED EFFECTS OF BUSPIRONE ON SERUM ELECTROLYTE BALANCE, PLASMA OSMOLALITY AND SYSTOLIC BLOOD PRESSURE (SBP) IN RATS RESHMA FAROOQ, DARAKHSHAN J. HALEEM AND M. A. HALEEM Department of Biochemistry, University of Karachi, Karachi-75270, Pakistan ABSTRACT Buspirone is a potent anxiolytic that decreases serotonin transmission. Changes in electrolyte balance, plasma osmolality and systolic blood pressure are often associated with stress-induced anxiety in rats as well as in human but effects of buspirone on changes in serum electrolytes balance, plasma osmolality and SBP of rats has not been reported. Present study concerns the effects of different doses of buspirone (0.25, 0.5, and 1mg/kg) on serum electrolyte, plasma osmolality and systolic blood pressure (SBP) of rats. Anxiolysis related variable are also monitored. Results show that the administration of buspirone (0.25mg/kg and 0.5mg/kg) significantly increased the serum concentration of electrolytes and plasma osmolality but decreased the serum level of magnesium. These doses also reduced the systolic blood pressure (SBP). A dose of 1mg/kg buspirone produced no effect on the concentration of serum electrolytes, and plasma osmolality. Anxiolytic effects of the drug were dose dependent but 1mg/kg dose decreased the effect. The results are discussed in the context of serotonin receptors (5-HT 1A ) to be involved in buspirone-induced changes of electrolytes, SBP and plasma osmolality. Keywords: Stress-induced anxiety, buspirone, electrolytes changes, systolic blood pressure and plasma osmolality. INTRODUCTION Buspirone a partial agonist of (5-hydroxy tryptamine) 5- HT 1A reduced anxiety in human and as well as in rats (Viadya et al., 2005; Griebel et al., 1998; Pokk and Zharkosky, 1998). Previous research reported that buspirone binds with somatodentric receptors to modulate 5-HT release from the presynaptic neuron in various regions of brain including the hippocampus (Haleem, 1999; Sakaue et al., 2000; Haleem and Parveen, 1994). A decrease in serotonin transmission reduces the anxiety (Johnson, 2004; Malt et al., 2003). Buspirone also acts via other hormones such as the noradrenaline and adrenaline and adrenal corticoid hormones (Liu et al., 2004; Pshennikove et al., 1990) to decrease sympathetic activity (Owusu and Serogin, 2004). Decreased activity of these hormones by buspirone in stressed rats may alter serum electrolyte balance, plasma osmolality and SBP of rats. If changes of electrolytes are involved in stress-induced hypertension it would be expected buspirone and other 5- HT 1A agonists elicit this effect by changing the electrolyte balance. The present study concerns with dose related effects of buspirone on serum electrolytes, plasma osmolality and systolic blood pressure (SBP) in rats. Anxiolytic effects of drug are also monitored in light and dark activity box. MATERIAL AND METHODS Animals Male albino Wistar rats (n=24) weighing 175-250g purchased locally were caged individually in a quiet temperature controlled room (25±4C°) for 3 days. Rats had free access to water and standard rodent diet. Drug Buspirone purchased from Research Biochemical U.S.A was dissolved in deionized water and injected at doses of 0.25mg/kg, 0.5mg/kg and 1mg/kg intraperitonealy. Control animals were injected with deionized water (1ml/kg). Experimental protocol Male albino Wistar rats (n=24) were injected buspirone i.p at doses of 0.25mg/kg, 0.5mg/kg and 1mg/kg. Control animals were injected with deionized water (1ml/kg). The animals injected with water or buspirone were kept back in their home cages. Light- dark box activity was monitored for 5 minutes starting 45 minutes post injections. SBP of rats were also noted 45minutes post injection. Animals were decapitated 1hr post injection to collect serum and plasma respectively in non-heparinized and heparinized tubes for the analysis of serum Corresponding author: Reshma Farooq, Department of Biochemistry, University of Karachi, Karachi-75270, Pakistan