Involvement of Dorsal Hippocampal Muscarinic Cholinergic Receptors of CA1 Area on Anxiety Induced by Iron Oxide Nanoparticles in Adult Male Rats

Introduction: Recent findings revealed the biological effects of iron oxide nanoparticles on the central nervous system. Moreover, the brain cholinergic system plays a role in the modulation of anxiety behaviors. Therefore, this study aimed to evaluate the role of dorsal hippocampal muscarinic cholinergic receptors of the CA1 area on anxiety induced by iron oxide nanoparticles in adult male rats.   Materials & Methods: This experimental study was conducted on adult male Wistar rats with a weight range of 200-250 g. All animals were cannulated in the CA1 area using stereotactic surgery. One week after the recovery the intracerebroventricular injection followed by intraperitoneal (IP) injection after 5 min were administered. Anxiety-like behavior and locomotor activity were performed by elevated plus maze apparatus one week after the injections. The groups were divided into control (saline), iron oxide nanoparticle (5, 7.5 mg/kg,IP), pilocarpine (1,2 µg/rat, intra-hippocampal injection), pilocarpine (1µg/rat, intra-hippocampal injection)+iron oxide nanoparticle (7.5mg/kg, IP) ,and pilocarpine (2µg/rat, intra-hippocampal injection)+iron oxide nanoparticle (7.5mg/kg, IP). Ethics code: EE/96.24.3.88369/SCU.AC.IR   Findings: Iron oxide nanoparticles (7.5 mg/kg) increased the anxiety level, compared to the control group (P<0.05). However, pilocarpine injection (1μg/rat) before iron oxide nanoparticles (7.5 mg/kg) improved the anxiety induced by iron oxide nanoparticle (P<0.05).   Discussion &Conclusions: It seems that probably the anxiogenic effect of iron oxide nanoparticles is mediated through the reduction of dorsal hippocampal muscarinic cholinergic receptor functions in CA1area.