Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of the stomach in rabbits under conditions of hunger and satiation

Ghrelin projection from the lateral hypothalamus area to the dorsal vagal complex and its regulation of gastric motility in cisplatin-treated rats

OBJECTIVE

To investigate ghrelin projection from the lateral hypothalamus area (LHA) to the dorsal vagal complex (DVC) and its regulation of gastric motility in cisplatin-treated rats.

MATERIALS AND METHODS

In the present study, the protein and mRNA expression of ghrelin and its receptor GHSR-1a were measured by Western blot and PCR, respectively. The ghrelin fiber projections arising from the LHA and projecting to the DVC were investigated by retrograde tracing combined with fluoro-immunohistochemical staining. The effects of ghrelin in the DVC, electrical stimulation of the LHA, and electrical lesion of the DVC on gastric motility were measured in cisplatin-treated rats.

RESULTS

Ghrelin fibers originating in the LHA projected to the DVC. The protein and mRNA expression of GHSR-1a was greater in cisplatin-treated rats than in saline-treated rats. Conversely, the expression of ghrelin in the LHA and DVC was reduced in cisplatin-treated rats. Cisplatin treatment also reduced gastric contractions. Ghrelin administrated into the DVC significantly promoted gastric motility, an effect completely blocked by treatment with the ghrelin receptor antagonist [D-Lys-3]-GHRP-6. In addition, electrical stimulation of the LHA promoted gastric motility, though this effect was much weaker in cisplatin-treated rats than in control rats. The excitatory effect of electrical stimulation of the LHA on gastric motility was partially blocked by pretreatment of the DVC with [D-Lys-3]-GHRP-6. Electrical lesion of the DVC diminished the excitatory effect that was induced by electrical stimulation of the LHA.

CONCLUSIONS

DVC, especially AP, may have a role for gastric contraction induced by the stimulation of the LHA. This regulation on gastric motility was weaker in cisplatin-treated rats than in saline-treated rats, possibly due to reduced ghrelin expression in the LHA and ghrelin projection from the LHA to the DVC.

Expression of gastrointestinal nesfatin-1 and gastric emptying in ventromedial hypothalamic nucleus- and ventrolateral hypothalamic nucleus-lesioned rats

AIM: To determine the expression levels of gastrointestinal nesfatin-1 in ventromedial hypothalamic nucleus (VMH)-lesioned (obese) and ventrolateral hypothalamic nucleus (VLH)-lesioned (lean) rats that exhibit an imbalance in their energy metabolism and gastric mobility.

METHODS: Male Wistar rats were randomly divided into a VMH-lesioned group, a VLH-lesioned group, and their respective sham-operated groups. The animals had free access to food and water, and their diets and weights were monitored after surgery. Reverse transcription-polymerase chain reaction and immunostaining were used to analyse the levels of NUCB2 mRNA and nesfatin-1 immunoreactive (IR) cells in the stomach, duodenum, small intestine, and colon, respectively. Gastric emptying was also assessed using a modified phenol red-methylcellulose recovery method.

RESULTS: The VMH-lesioned rats fed normal chow exhibited markedly greater food intake and body weight gain, whereas the VLH-lesioned rats exhibited markedly lower food intake and body weight gain. NUCB2/nesfatin-1 IR cells were localised in the lower third and middle portion of the gastric mucosal gland and in the submucous layer of the enteric tract. Compared with their respective controls, gastric emptying was enhanced in the VMH-lesioned rats (85.94% ± 2.27%), whereas the VLH lesions exhibited inhibitory effects on gastric emptying (29.12% ± 1.62%). In the VMH-lesioned rats, the levels of NUCB2 mRNA and nesfatin-1 protein were significantly increased in the stomach and duodenum and reduced in the small intestine. In addition, the levels of NUCB2 mRNA and nesfatin-1 protein in the VLH-lesioned rats were decreased in the stomach, duodenum, and small intestine.

CONCLUSION: Our study demonstrated that nesfatin-1 level in the stomach and duodenum is positively correlated with body mass. Additionally, there is a positive relationship between gastric emptying and body mass. The results of this study indicate that gastrointestinal nesfatin-1 may play a significant role in gastric mobility and energy homeostasis.