Lateral characteristics of oxytocin distribution in the mouse brain following intranasal peptide administration

BACKGROUND: Intranasal administration of oxytocin is an effective method for delivering the hormone to the central nervous system, bypassing the blood-brain barrier. This approach holds significant promise for psychiatric clinical applications. Previous studies have demonstrated that simultaneous oxytocin administration in both nostrils induces lateralized changes in monoamine metabolism in the mouse brain. AIM: To investigate the lateral characteristics of oxytocin penetration in the brain following intranasal administration. MATERIALS AND METHODS: Experiments were conducted on 12 male outbred white mice. The experimental group received intranasal oxytocin (5 IU/1 mL, 10 μL per nostril), while the control group received an equivalent volume of saline. Oxytocin levels were measured 15 minutes post-instillation in the hypothalamus, olfactory bulbs, striatum, and hippocampus on both sides of the brain using an enzyme-linked immunosorbent assay (ELISA). RESULTS: In the control group, oxytocin distribution was symmetric in the olfactory bulb and striatum. However, in the hippocampus, control mice exhibited asymmetry with a higher oxytocin concentration on the right side (p = 0.0192). In the experimental group, oxytocin levels significantly increased in the left hippocampus (p = 0.0223) and hypothalamus (p = 0.0036), with a trend observed in the left olfactory bulb (p = 0.0572). CONCLUSION: Intranasal oxytocin administration enhances oxytocin penetration into the left side of the brain, primarily through the left olfactory bulb and hippocampus, ultimately reaching the hypothalamus.