Effects of LHA-NAc orexinergic pathway on gastric motility and reward feeding in rats / 中华行为医学与脑科学杂志

ABSTRACT

Objective:To investigate the regulation of orexinergic pathway from the lateral hypothalamic area (LHA) to the nucleus accumbens (NAc) on gastric function and reward feeding.Methods:(1)Forty-eight rats were randomly selected and divided into six groups normal saline (NS) group, 1 μg orexin-A group, 5 μg orexin-A group, 10 μg orexin-A group, 20 μg orexin receptor antagonist (SB334867) group, 20 μg SB334867 + 5 μg orexin-A group with eight in each group according to the random number table. The gastric motility of rats was observed by injecting orexin-A and SB334867 into NAc. (2)Thirty-two rats were randomly selected and divided into four groups according to the random number table, with eight in each group. They were divided into NS + sham stimulation (SS) group, NS + electrical stimulation (ES) group, SB334867(20 μg) + SS group, and SB334867(20 μg) + ES group. The gastric motility of rats were observed by electro-stimulation of rat LHA and rat NAc injection of SB334867. (3)In order to observe the feeding-behavior related conditioned place preference (CPP) and gastric function (such as gastric emptying and gastric secretion), thirty-two rats were randomly divided into four groups with eight in each group by using the method of NAc injection of orexin-A and SB334867 according to the random number table NS group, orexin-A(5 μg), SB334867(20 μg), SB334867(20 μg) + orexin-A(5 μg). (4)Thirty-two rats were randomly selected in accordance with the random number table and divided into four groups with eight in each group NS + SS group, NS + ES group, SB334867(20 μg) + SS group, SB334867(20 μg) + ES group, using electro-stimulation of rat LHA and rat NAc injection of SB334867, observing the feeding-behavior related CPP and gastric function (such as gastric emptying and gastric secretion).Results:(1)In the gastric motility experiment, both the NAc microinjection of orexin-A and electrical stimulation of the LHA significantly increased the amplitudes and frequencies of gastric contraction in rats, and these effects could be blocked by the pre-administration of SB334867 (10 min after administration of orexin-A 10 μg orexin-A group (60.78±5.67)% vs NS group (7.35±1.08)%; t=26.18, P<0.05). (2)The results of gastric emptying showed that the rates of gastric emptying were significantly increased by the NAc microinjection of orexin-A and electrical stimulation of LHA, which were blocked by the SB334867 pretreatment (after electrical stimulation of LHA NS + SS group (71.18±17.78)% vs NS+ ES group (132.23±31.18)%; t=4.81, P<0.05). (3)Orexin-A microinjection in the NAc and electrical stimulation of the LHA significantly increased gastric acid secretion, and these effects could be blocked by pre-injection of SB334867 in NAc (90 minutes after administration of orexin-A orexin-A group(100.18±23.23) vs NS group (39.23±7.69); t=7.05, P< 0.05) in the gastric secretion experiment.(4)The results of CPP showed that the rats were kept in the chocolate compartment for a longer time after the NAc microinjection of orexin-A and electrical stimulation of the LHA, which could be blocked by the SB334867 pretreatment in NAc (after LHA was electrically stimulated NS+ SS group (36.23±6.23)% vs NS+ ES group (53.36±6.66)%; t=5.31, P<0.05). Conclusion:There is an orexinergic pathway from LHA to NAc that may regulate gastric function and food reward.