| Objective: Feeding and obesity are closely related to oxytocin(OT).Central injection of OT in normal-weight rats,OT injection in diet-induced or genetically engineered obese rats,causes a decrease in food intake and body weight,and also increases energy expenditure.The physiological functions of the paraventricular nucleus(PVN)include regulating food intake and maintaining environmental stability in the body.It is an important nuclear group involved in regulating energy balance and body weight.However,in the current research on PVN,the OT-induced anorexia effect is less involved.Therefore,the main purpose of this study was to investigate the effect of PVN injection on the feeding of fasted rats and the effects of maltose solution and dextrin solution intake in normal rats to clarify the OT-induced anorexia effect.Methods: 1.Fluorescence immunohistochemical staining and RT-PCR were used to observe the expression of OT receptor immunoreactive cells and OT receptor m RNA in PVN;2.The DAB staining method was used to observe the effect of intra-PVN injection of OT on the expression of c-Fos in the hypothalamic feeding-related brain region,so as to indirectly observe the activation of PVN neurons.3.Using ventricle nuclear tube placement,intake measurement and other experimental methods to observe the microinjection of OT,OT receptor antagonist L-368899 in PVN,the effect of hunger stimulation and sweetener-induced feeding.4.The effects of microinjection of OT or OT receptor antagonist L-368899 on gastric acid secretion in rats were observed by measuring gastric acid secretion in rats.Results: 1.Immunohistochemical studies showed that PT receptor immunopositive neurons were expressed in PVN;RT-PCR results also showed that OT receptor m RNA was expressed in PVN.PVN injection of 2.0 ?g OT showed a significant increase in c-fos expression in the nucleus accumbens(NAc),paraventricular nucleus(PVN),supraoptic nucleus(SON),and midbrain ventral tegmental area(VTA)(P< 0.05 or P < 0.01).2.Compared with the NS group,injection of 2.0 ?g and 4.0 ?g of OT in PVN significantlydecreased the food intake of 0-2h and 0-4h in fasted rats in a dose-dependent manner(P<0.01 or P < 0.01).The results showed that there was no significant difference in water intake between 0-2 h and 0-4 h in rats after injection of 0.2 ?g OT,0.4 ?g OT,2.0 ?g OT,and 4.0 ?g OT in PVN(P < 0.05).Compared with the NS group,injection of 2.0 ?g and 4.0 ?g of OT in PVN significantly reduced the intake of 10% sucrose solution from 0-2 h in rats,and the decrease rate was 50%.Injection of 0.2 ?g,0.4 ?g,2.0 ?g,and 4.0 ?g of OT in PVN significantly reduced the intake of 0.1% saccharin solution in rats compared with NS rats(P<0.01 or P < 0.01).Injection of 2.0 ?g and 4.0 ?g of OT into PVN significantly decreased gastric acid secretion in rats in a dose-dependent manner(P<0.05).3.Compared with NS+2.0 ?g OT group,pre-injection of 4.0 ?g L-368899 in fasted rat PVN significantly attenuated the inhibitory effect of OT on 0-2h and 0-4h feeding(P < 0.05).Compared with the NS+2.0 ?g OT group,1.0 ?g L-368899 was pre-injected into the PVN,and the intake of 10% sucrose solution in the fasted rats was significantly increased within 0-2 h(P < 0.05).Compared with the NS+2.0 ?g OT group,1.0 ?g L-368899 was pre-injected into the PVN,and the intake of 0.1% saccharin solution in the fasted rats increased significantly within 0-2 h(P<0.05).Pre-injection of 1.0 ?g L-368899 into rat PVN significantly attenuated the inhibitory effect of OT on gastric acid secretion in rats(P<0.05).Conclusion: Microinjection of OT into PVN can activate microinjection of OT in PVN in feedingrelated brain regions such as NAc,PVN,SON,VTA,etc.,which can significantly attenuate the feeding behavior induced by hunger stimulation and reward,and play a role through OTR. |
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