| Objective:In recent years,the number of obese people in China has increased rapidly.Obesity can cause a variety of diseases and accelerate aging and death.The mechanism of obesity is complex,which is still unclear.In recent years,the central mechanism is the focus of research.Phoenixin(PNX)is an endocrine peptide found in the hypothalamus in 2013,which is involved in reproductive regulation.It mainly promotes gonadotropin-releasing hormone,which in turn increases the secretion of luteinizing hormone.Recent studies have shown that PNX is also involved in the regulation of physiological activities such as food intake,emotion,learning and memory.In the center,PNX neurons are mainly distributed in the hypothalamus,which is an important center for regulating food intake and energy metabolism.Some studies have shown that intracerebroventricular microinjection of PNX can significantly promote food intake in rats,and the level of PNX in hypothalamus of fasting animals increases significantly,and the level of PNX decreases after resumption of feeding.It has been reported that PNX receptor(Gpr 173)immunoreactive neurons are distributed in the hypothalamic paraventricular nucleus(PVN).PVN is located in the anterior hypothalamic area adjacent to the third ventricle.It can directly sense the changes of substances in cerebrospinal fluid and regulate energy metabolism.It has not been reported whether PVN is involved in the regulation of PNX on food intake or gastrointestinal function in rats.In this study,fluorescence immunohistochemical staining,single cell discharge recording and nuclear microinjection of drugs were used to observe the effects of microinjection of PNX into PVN on the discharge activity of gastric afferent information neurons,food intake,in vivo gastric motility and gastric emptying in rats,and to analyze and compare the differences of these effects between normal and obese rats,in order to improve the central mechanism of obesity.To provide new research ideas for the prevention and treatment of energy metabolism-related diseases such as obesity.Methods:Healthy male Wistar rats with a physique of 135 ±5 g were selected.A high-fat diet containing 14.19 g double distilled water,20.00 g casein,0.30 g cystine,7.28 g corn meal,10.00 g maltodextrin,17.28 g sucrose,5.00 g cellulose,2.5 g soybean oil,17.75 g lard,1.00 g inorganic salt,1.30 g calcium phosphate,0.55 g calcium carbonate,1.65 g potassium citrate,1.00 g vitamins,1.00 g inorganic salt,1.30 g calcium phosphate,0.55 g calcium carbonate,10.00 g maltodextrin,17.28 g sucrose,5.00 g cellulose,2.5 g soybean oil,17.75 g lard,1.00 g calcium carbonate.Choline bitartrate 0.20 g.The nutritional obesity model rats were established,and the rats fed with high-fat diet were obese rats whose body weight was more than 20% of the body weight of the rats fed with normal diet.The expression of PNX receptor(Gpr 173)immunoreactive cells in PVN was observed by fluorescence immunohistochemical staining,and the difference of expression between normal and obese rats was compared and analyzed,and the effects of PNX on the discharge activity of gastric stretch sensitive(GD)neurons and the regulation of gonadotropin releasing hormone receptor(GnRH-R)signal pathway in PVN of normal and obese rats were observed and compared.The effects of PNX on food intake,gastric motility and gastric emptying in normal and obese rats were compared by means of PVN nuclear catheterization and nuclear microinjection of drugs.Results:(1)Fluorescence immunohistochemical study showed that PNX receptor Gpr 173 immunoreactive cells were expressed in hypothalamic PVN of both normal and obese rats,and the number of Gpr 173 immunoreactive cells in PVN of obese rats was significantly higher than that of normal rats.(2)The effect of microinjection of PNX into PVN on the firing activity of PVN GD neurons.The results showed that there were GD neurons in PVN,that is,neurons in PVN that received the afferent information of gastric mechanical stretch.After microinjection of PNX,76.12% into PVN,the discharge frequency of gastric stretch excitability(GD-E)neurons decreased significantly,and the excitability of most(62.79%)gastric stretch inhibition(GD-I)neurons increased significantly(P< 0.05).If PVN was preinjected with PNX antibody,the inhibitory / excitatory effect of PNX on GD-E/GD-I neurons could be completely blocked.If Cetrorelix was injected in advance and then PNX,was injected in advance,the inhibitory /excitatory effect of PNX on GD-E/GD-I neurons could be completely blocked.The excitatory / inhibitory effect of PNX on GD neurons was attenuated,but there was no significant change in the firing activity of),GD neurons after PVN injection of PNXantibody or Cetrorelix(P>0.05).Compared with normal rats,the inhibitory or excitatory effect of PNX on PVN GD(GD-E or GD-I)neurons in obese rats was significantly enhanced.(3)The effect of microinjection of PNX into PVN on food intake in rats was studied.The results showed that the food intake of rats was significantly increased at 0-2 h after microinjection of PVN,but there was no significant change at 2-4 h after administration(P>0.05).When PVN was injected with PNX+Cetrorelix mixture,the food-promoting effect of PNX was weakened(P<0.05),while Cetrorelix alone had no significant effect on food intake in rats(P>0.05).Compared with normal rats,the food intake of obese rats was significantly increased(P<0.05).Microinjection of PNX,in normal rats or obese rats increased significantly in 0-2 h,and the promoting effect of PNX on food intake in 0-2 h of obese rats was more significant than that of normal rats(P<0.05).The effect of PNX on food intake in 0-2 h of obese rats was more significant than that of normal rats(P<0.05).The effect of PNX on food intake of obese rats was more significant than that of normal rats.(4)The effect of microinjection of PNX into PVN on gastric motility in rats.The results showed that the amplitude and frequency of gastric motility were significantly increased in rats after microinjection of PVN into PNX,and the promoting effect of PNX on amplitude and frequency of gastric motility could be weakened when PVN was microinjected with PNX+Cetrorelix mixture.There was no significant change in the amplitude and frequency of gastric motility in Cetrorelix,rats injected with PVN alone.Further statistical analysis showed that there was no significant difference in gastric motility index(MI%)between obese rats and normal rats(P>0.05).Microinjection of PNX into normal rats or obese rats showed a significant increase in MI%,and the increase of MI% in obese rats was more significant than that in normal rats.(5)The effect of microinjection of PNX into PVN on gastric emptying in rats.The results showed that microinjection of PNX into PVN could significantly promote gastric emptying in normal or obese rats,and the promoting effect of PNX on gastric emptying in obese rats was more significant than that in normal rats.The promoting effect of PNX on gastric emptying was partially blocked by PVN injection of Cetrorelix.There was no significant change in gastric emptying in rats treated with PVN alone(P>0.05).Conclusion:PNX in hypothalamic PVN is involved in the regulation of GD neuronal excitability,feeding,gastric motility and gastric emptying in normal and obese rats,especially in obese rats,which may be related to the increased expression of PVN Gpr 173 in obese rats,and the activity of GnRH-R signal pathway is also involved in the regulation of this process. |
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