Effect Of Low-level Laser Therapy On Fear Conditioning And The Mechanisms In Mice

In order to survive in a dynamic environment,animals must be able to distinguish between dangerous and safe environments.When an environment is associated with a noxious stimulus?such as a foot shock?,the brain forms a fearful memory of the environment?context?.Repeated exposure to the same context,but no foot shock,the fear memory of the context gradually recedes.The hippocampus is considerable for the contextual memory of rodents.When people have experienced a traumatic event,they will have reactions such as nervousness and fear.These reactions will disappear for most people in the course of time.However,for people with Posttraumatic Stress Disorder?PTSD?,there are still intense and disturbing thoughts and feelings associated with their experiences for a long time after the traumatic event.PTSD is a mixed form of disease,some of which are characterized by excessive excitement and others by emotional instability.They may relive the event through flashbacks or nightmares.These feelings continue or even increase,and these feelings become so strong that they make it impossible to lead a normal life.Low-level laser therapy?LLLT?uses red or near-infrared?NIR?light with wavelengths between 600 and 1000 nm and powers between 5 and 500 mw.When applied to the skin,light can penetrate deeply into tissues with photobiological stimulation effects due to the absorption of light by the skin.Therefore,LLLT treatment is economical,safe and non-invasive.Studies have found that red/NIR light can increase ATP synthesis by stimulating complex IV of the respiratory chain.In addition,light absorption by ion channels leads to the release of Ca²⁺,which activates the expression of transcription factors and genes.LLLT therapy enhances neuronal metabolism and stimulates neurogenesis and synapse development,and it is increasing in the application of neural and psychological therapeutic effect.This study explores the fear memory in mice after LLLT treatment and extinction impact.In a behavioral experiment in which the tone cued fear conditioning,behavioral results indicate that red light reduces the fear response of C57 mice to conditional fear and promotes the extinction of spatial fear memory.This suggests that LLLT can be used as a novel way to improve memory.The effect of LLLT on brain metabolism was determined by chemiluminescence determination of ATP concentrations in the hippocampus and prefrontal cortex.The results showed that LLLT increased the concentration of ATP in vivo.This indicates that red light enhances the metabolism of the cerebral cortex.The expression of protein in hippocampus and cortex was detected by immunohistochemistry and western blot.Correlation between PV and ErbB4 levels suggests that the protein may affect the activity of inhibitory neurons in mice by affecting the activity of GABA interneurons.A related change in c-fos levels suggests that the protein may affect the activity of excitatory neurons in mice by affecting glutamatergic neurons.Immunohistochemical results of red light treated mice showed an increase in the number of hippocampal PV neurons and an increase in the number of c-fos neurons.This indicates that red light has an increased activity on brain excitatory neurons and inhibitory neurons.After the mice were treated with red light and subjected to the behavior of tone cued fear conditioning,The results show that reducing the number of PV neurons,increasing the number of c-fos neurons in hippocampus.This indicates that the activity of red light on brain excitatory neurons is increased,and the activity of inhibitory neurons is decreased,which in turn affects the brain's excitation/inhibition balance activity and affects learning and memory.We therefore focus on the inhibitory activity of neurons role in learning and memory.We used western blot to explore changes in ErbB4 in learning and memory.The results of the experiment revealed that ErbB4 soon showed a change in the first rise and fall after the mice received the tone cued fear conditioning.This experimental result illustrates the correlation between ErbB4 and learning.After the mice received tone cued fear conditioning,ErbB4 also showed an elevated change after 4 hours.This experimental result illustrates the correlation of ErbB4 with memory.After the LLLT-treated mice received the tone cued fear conditioning,the ErbB4 levels in the mice still showed relevant changes.After the tone cued fear conditioning,the red-light treatment group had a lower trend of ErbB4.We hypothesize that LLLT reduces the inhibitory neuronal activity of the brain.Our results reveal the dependent function of PV neurons in fear memory and it may be highly correlated with the possible molecular stress-related psychiatric disorders,such as PTSD and anxiety.The focus of this article is on fear memory,which is the most relevant disease associated with anxiety and PTSD.Fear and anxiety disorders manifest themselves as associative memory networks in the brain.The model used to study association fear learning and memory is Pavlov conditional fear reflex.Based on the influence of LLLT on inhibitory neuronal activity and memory and its extinction,focusing on the neurobiological principles of emotional learning and memory,aiming at cracking the dynamic interaction between the plasticity and stability of emotional memory,so as to prevent and cure the disorders of human fear.