Effects Of LHA-NAc ShMCH Neural Pathway On Food Intake And Gastric Motility In Rats And Its Potential Mechanism

Objective:In this study,a series of experimental methods such as immunofluorescence histochemical staining,single cell extracellular discharge and in vivo gastric motility recording were used to observe the effects of activation/inhibition of MCH neurons in the LHA or microinjection of MCH into NAc Sh on food intake and gastric motility,and to explore its possible mechanism.It is hoped that this study can further improve the theory of central energy metabolic balance and provide a new strategy for the treatment of metabolic diseases.Methods:（1）The effects of MCH on the discharge activity of NAc Sh gastric distension sensitive（GD）neurons were observed by single extracellular discharge recording.（2）The LHA-NAc Sh MCH neural pathway was observed by retrograde tracing and fluorescence immunohistochemistry.（3）The MCH neurons in LHA were activated by chemical genetic method.The effects of intraperitoneal injection of virus activator clozapine N-oxide（CNO）to activate LHA MCH neurons on feeding,gastric motility and gastric emptying in rats were observed.（4）The effects of activation of MCH neurons in the LHA on the firing activity of NAc Sh GD neurons were observed by single extracellular discharge recording.Results:（1）the effect of microinjection of MCH into NAc Sh on food intake of rats:compared with NAc Sh microinjection of NS,NAc microinjection of MCH significantly increased the food intake of rats at 0-2 h,but there was no significant change in food intake at 2-4 h after administration.Compared with MCH group,microinjection of MCH+SNAP94847 mixture into NAc Sh significantly reduced the promoting effect of MCH on food intake in rats,but SNAP94847 alone had no significant effect on food intake in rats.（2）the effect of microinjection of MCH into NAc Sh on gastric motility in rats:the results of in vivo gastric motility study showed that microinjection of MCH into NAc Sh could significantly promote the amplitude and frequency of gastric motility in rats.When NAc Sh was microinjected with MCH+SNAP94847 mixture,the amplitude and frequency of gastric motility in rats were significantly lower than those in MCH group,but SNAP94847 alone by NAc Sh had no significant effect on the amplitude and frequency of gastric motility in rats.Further statistical analysis of the results using gastric motility index（MI%）showed that microinjection of MCH into NAc Sh significantly increased MI%in rats.Compared with MCH group,microinjection of MCH+SNAP94847 mixture into NAc Sh could completely block the promoting effect of MCH on MI%in rats,but NAc Sh injection alone had no significant effect on MI%in rats.（3）the effect of microinjection of MCH into NAc Sh on gastric emptying in rats:compared with NAc Sh microinjection of NS group,NAc Sh microinjection of MCH significantly promoted gastric emptying of rats.Compared with MCH group,microinjection of MCH+SNAP94847 mixed solution of NAc Sh significantly reduced the promoting effect of MCH on gastric emptying of rats,but there was no significant effect on gastric emptying of rats treated with SNAP94847 alone.（4）the effect of microinjection of MCH into NAc Sh on the discharge activity of GD neurons:the discharge frequency of 62 GD-E neurons decreased significantly after microinjection of MCH into NAc Sh,the discharge frequency of 21 GD-E neurons increased significantly,while the discharge frequency of the other 13 neurons did not change significantly.Among the 67 GD-I neurons,the discharge frequency of 51 GD-I neurons increased significantly,11GD-I neurons decreased significantly,and 5 GD-I neurons had no significant change.The excitatory/inhibitory effect of MCHR1 antagonist SNAP94847 and MCH,MCH on GD neurons could be completely blocked by NAc Sh,but SNAP94847 alone had no significant effect on the discharge activity of GD neurons.（5）the LHA-NAc Sh MCH neural pathway:FG-labeled neurons in LHA could be observed under fluorescence microscope.MCH immunofluorescence histochemical staining showed that MCH-immunoreactive neurons were found in LHA,and some MCH-immunoreactive neurons were also labeled by FG.（6）the effect of excited LHA MCH neurons on food intake in rats:compared with sham-excited LHA MCH neurons group,excited LHA MCH neurons significantly increased food intake in 0-2 h in rats,but had no significant effect on 2-4 h food intake in rats.Compared with the excited LHA_MCH+NAc Sh _NSgroup,the food intake of the excited LHA_MCH+NAc Sh _SNAP94847group decreased significantly.（7）the effect of stimulating LHA MCH neurons on gastric motility in rats:compared with sham-excited LHA MCH group,stimulating LHA MCH could significantly promote the amplitude and frequency of gastric motility in rats.Compared with the excited LHA_MCH+NAc Sh _NSgroup,the amplitude and frequency of gastric motility in the excited LHA_MCH+NAc Sh _SNAP94847group decreased significantly.The results were statistically analyzed by gastric motility index（MI%）.The results showed that MI%increased significantly in rats excited by LHA MCH,while microinjection of SNAP94847 into NAc Sh could completely inhibit the promoting effect of excited LHA MCH neurons on MI%.（8）the effect of excitatory LHA MCH neurons on gastric emptying in rats:compared with sham-excited LHA MCH group,stimulating LHA MCH could significantly promote gastric emptying in rats.Compared with microinjection of NS into NAc Sh and then stimulating LHA MCH neurons,microinjection of SNAP94847 into NAc Sh could completely block the promoting effect of excited LHA MCH neurons on gastric emptying.（9）the effect of stimulating LHA MCH neurons on the discharge activity of NAc Sh GD neurons:after stimulating LHA MCH neurons,the discharge frequency of 51 of 83 GD-E neurons decreased,23 increased,and 9 had no significant change.The discharge frequency of 41 of 56 GD-I neurons increased significantly after stimulation of MCH neurons in LHA,while the discharge frequency of 10 neurons decreased significantly,and 5 neurons had no significant change.If NAc Sh was preinjected with MCHR1 antagonist SNAP94847 to reactivate LHA MCH neurons,the excitatory/inhibitory effect of activated LHA MCH neurons on NAc Sh GD neurons could be completely blocked.Conclusion:NAcSh MCH can promote food intake,gastric motility and gastric emptying in rats,MCH can also regulate the neurons in NAc Sh that receive gastric sensory afferent information,the regulatory effect of MCH in NAc Sh may be related to MCHR1;there is a MCH neural pathway among rat LHA-NAc Sh,which can regulate food intake,gastric motility and gastric emptying,and regulate the neurons in NAc Sh that receive gastric sensory afferent information,and the regulatory effect of this pathway may be related to NAcSh MCHR1.