| Oxytocin is a kind of neuroendocrine hormone,which is mainly synthesized and secreted by hypothalamic paraventricular nucleus(PVN)cells,and then released into the peripheral blood by the posterior pituitary gland.It has important functions of promoting childbirth and stimulating breastfeeding.And with the deepening of oxytocin research,researchers are paying more attention to their impact on social behavior and mental diseases.Ferumoxytol is a longterm research magnetic nanomaterial in our laboratory,it is a kind of superparamagnetic iron oxide(SPIO)nanoparticles coated with polysaccharide envelope,which has excellent stability and biocompatibility.We injected ferumoxytol as a magnetic enhancer into the PVN of the mouse,and exerted a rotating magnetic field.The nanoparticles responded to the magnetic field to form a locally enhanced magnetic stimulation at the PVN,thereby promoting the secretion of oxytocin from the PVN.Then,the secretion of oxytocin was regulated by adjusting the injection conditions of magnetic nanoparticles and the parameters of magnetic field.In addition,the effects of this method on the social ability of mice were explored through behavioral experiments.The specific work is as follows:Firstly,the brain stereotactic technique was used to inject magnetic nanoparticles into the PVN of the mouse,and magnetic resonance imaging(MRI)was performed on the brain of the mouse to detect MRI images of 1 week,2 weeks,3 weeks,and 4 weeks,respectively.The blackness value of the position of the PVN corresponded to the amount of magnetic nanoparticles.It was found that until the fourth week,magnetic nanoparticles remained stable in the PVN of the mouse,and the amount of the magnetic nanoparticles continued to decrease over time.In addition,by contrast with normal mouse MRI images,the injected mice did not have significant injury symptoms including inflammation,bleeding,etc.These indicated that this method was safe.Then,the injected mice were treated by the rotating magnetic field,and it was found that the mice which were injected magnetic nanoparticles and exerted magnetic field had significant differences in oxytocin level compared with the control group,while the mice injected physiological saline and the mice injected ferumoxytol but not exerted magnetic field did not have significant differences.It indicated that nanomaterial-enhanced magnetic stimulation promoted the expression of oxytocin in the PVN of mice.Based on this,by adjusting the injection conditions of magnetic nanoparticles,it was found that the oxytocin level increased with the increase of the injection concentration,and the oxytocin level decreased with the increase of the injection volume.Then,by adjusting the parameters of the rotating magnetic field,it was found that the oxytocin level increased with the increase of the magnetic field intensity,the oxytocin level increased with the increase of the magnetic field stimulation time,and the oxytocin level did not change significantly with the increase of frequency.Finally,after using magnetic fields in the injected mice,3-chambered social test was carried out.It was found that our magnetic nanoparticle-enhanced neuromagnetic stimulation method can promote the social ability of mice.Further,we found that there is a certain correlation between blood oxytocin levels and the social ability. |
