Orexin/Hypocretin Receptor 1 Signaling Mediates Pavlovian Cue-food Conditioning And Extinction

Objective: To investigate the effects of orexin Receptor-1 on Feeding conditioned reflex.Methods: A total of 6 healthy adult rats were selected to observe the distribution of orexin-1 receptor in hypothalamus by fluorescence immunohistochemical staining.Experiment 2: acquired training 1: 40 rats were randomly divided into two groups: saline(NS)group and SB-334867(SB)group,20 rats in each group.The rats received the acquisition training,30 minutes prior to session,rats received an injection of either SB or normal saline.Then the rats were trained for four times conditioned stimulation-unconditioned stimulation(CS-US),with intervals of 5min.Acquired training 2: the NS group divide into two groups: namely NS/NS group(n=10)and NS/SB group(n=10);The SB group also divided into two groups:,namely SB/NS group(n=10),SB/SB group(n=10).After the 48 hour feeding reflex acquired training 1,the rats received the acquisition training 2,and 30 minutes prior to session,rats received an injection of either SB or normal saline.Then the rats were trained for four times conditioned stimulation-unconditioned stimulation(CS-US),with intervals of 5min.The conditioned stimulus(CS)was a 10 s tone(2 kHz),and the unconditioned stimulus(US)was food pellets delivered into the food cupExperiment 3: extinction training 1: 40 rats were randomly divided into two groups: NS group and SB group,20 rats in each group.Two groups of rats were given intraperitoneal injection of NS or SB-334867 before extinction training 1 30 min,and the rats were trained for four times conditioned stimulation(the rats were given 10 s,2KHz sound stimulation),without giving rats corresponding foods,each training interval is 5min.Extinction training 2: the NS group were divided into two groups,namely NS/NS group(n=10),NS/SB group(n=10),SB group is also divided into two groups,namely SB/NS group(n=10),SB/SB group(n=10).).After the 48 hour extinction training 1,the rats received the a extinction training 2,and 30 minutes prior to each session,rats received an injection of either SB or normal saline and Rats were given four times conditioned stimulation(CS)(the rats were given 10 s,2KHz sound stimulation)without giving rats corresponding foods,each training interval is 5min.Results: The results of fluorescence immunohistochemistry showed that there were orexin-1 receptors in the multiple nuclei of hypothalamus,such as the paraventricular nucleus of the hypothalamus(PVN),the lateral hypothalamic area(LHA),arcuate nucleus of hypothalamus(ARC),ventromedial nucleus of hypothalamus(VMH).During the acquired training 1,with the increase of number of conditioned stimulus,in the SB-334867 group and NS control group,rats' food exploration time percentage(food exploration time refers to the percentage,standing in front of food directly in the face of food or put nose poke into the groove of the percentage of the time of the observation time)were significantly increased(P < 0.05 ~ 0.01),in the SB-334867 group and NS group,rats feeding interval(feeding time interval refers to the conditioned stimulus to near the time of food)were significantly reduced(P < 0.05)but there was no significant difference between them(P > 0.05).During the acquired training 2,as conditioned stimulus frequency increases,food exploration time percentage(%)of rats increased significantly(P < 0.05 0.01),the NS/NS group,SB/SB group,NS/SB,and SB/NS group rats' feeding time interval were significantly reduced(P < 0.05).However,the percentage of time(%)of rat food in rats was not significantly changed(P > 0.05),and no significant change in the time interval between the rats in rats(P > 0.05).Results analysis showed that in the conditioned stimulus(10s),compared with NS/NS group,the percentage of food inquiry behavior of NS/SB,SB/SB,and SB/SB was significantly reduced(P < 0.05).There was no significant difference in food inquiry behavior between the two groups(P BBB 0.05)in the two periods after the conditioned stimulus and the conditioned stimulus.Further statistical results showed that the average feeding interval between NS/SB group,SB/NS group,and SB/SB group was significantly extended(P < 0.05),compared with NS/NS group rats,after 2 subabdominal injection sb-334867.During the period of reflection 1 negative training,the results showed that as the number of conditions to stimulate more,two group(NS group and SB)food exploration time percentage of rats were significantly reduced(P < 0.05),the feeding interval significantly longer(P < 0.05),but there is no significant difference between groups(P > 0.05).During the period of regression training 2,the results of the study showed that,compared with NS/SB group and NS/NS group,the food exploration behavior of rats in SB/NS group increased significantly(P < 0.05).However,in the first stimulus,compared with NS/NS group,the food exploration behavior of rats in NS/SB group was significantly reduced(P < 0.05).The results of this study showed that the feeding interval between NS/SB group and SB/SB was significantly increased compared with the previous 2 stimuli(P < 0.05).However,in the first stimulus to four stimuli,in the process of SB/NS group and NS/NS group rats the feeding interval of no significant change(P > 0.05),In the second two stimuli,the feeding interval SB/NS group rats was lower than that in group NS/SB,and SB/SB group and NS/NS group(P < 0.05).This study also found that during the period after the conditioned stimulus,the percentage of food inquiry behavior of rats in SB/NS group was significantly higher than that in NS/NS group and NS/SB group(P < 0.05)Conclusion: The OX1 R signaling pathway is involved in the regulation of the production and extinction of feeding conditioned reflexes.