ABSTRACT
Objective:This study aimed to explore the Ventromedial Hypothalamic Orexin-1 and Orexin-1 Receptors in Regulation of Gastric Acid Secretion in Conscious Rats.Methods:Rats were anaesthetized and fitted with a stainless steel carmula placed just above the VMH or paracele,after random allocation orexin-A,[Pro34]-peptide YY and [CPP1-7,NPY19-23,Ala31,Aib32,Gln34] -pancreatic polypeptide were injected in the VMH;SB-334867 was intraperitoneal injection;atropine was subcutaneous injection;GR-231118 and CGP-71683 were injected in the paracele.Using pyloric ligation model,tests the effect of different drugs on rat gastric acid secretion and gastric juice volume.Results:OXA induced dose-dependent increase of gastric acid secretion;SB-334867 induced dose-dependent inhibition of gastric acid secretion.The stimulatory effect of OXA on acid secretion was inhibited by SB-334867;atropine induced dose-dependent increase of gastric acid secretion and block the effect of orexin-A on gastric acid secretion;the gastric acid secretion was inhibited by GR-231118 or CGP-71683,and GR-231118 or CGP-71683 were blocked the effect of orexin-A on gastric acid secretion;Intraventromedial hypothalamic injections of [CPP1-7,NPY19-23,Ala31,Aib32,Gln34]-pancreatic polypeptide increased gastric acid secretion.Conclusion:It is suggested that endogenous orexin-A acts on the ventromedial hypothalamus to stimulates acid secretion.This stimulatory effect is probably mediated through orexin receptor,Y1 and Y5 receptor,and the vagus nerve system.
ABSTRACT
Various brain areas like the ventromedial hypothalamus (VMH) are known to influence food intake and body weight. Though obesity is more common in females, the reports on gender difference in the neural regulation of energy homeostasis are not adequate. Therefore, the present study was conducted to assess the gender difference in the effect of VMH lesion on food intake (FI), body weight (BW), serum lipid profile, thyroid profile, glucose and insulin levels and glucose-insulin ratio (GIR) in Wistar albino rats. Twenty-four Wistar albino rats were divided equally into control and experimental groups with 6 male and 6 female rats in each. In the experimental group, bilateral electrolytic lesion of VMH was performed by stereotaxy and post-lesion parameters were recorded. In the control group, VMH sham lesion was made. Male-female difference in each parameter was determined. Following VMH lesion, FI was increased (females, P<0.01) and BW (males, P<0.05) and GIR decreased in males (P<0.001), which was significantly correlated with BW. T3 was more significantly correlated with FI and BW in females (P<0.000 and P<0.001). Following VMH lesion, male rats exhibited significant weight gain in the absence of proportionate hyperphagia indicating that weight-gain was mainly metabolic in nature. Also, the male rats developed more susceptibility to insulin resistance. The female rats developed resistance to weight-gain inspite of hyperphagia, which could be due to the higher T3 level.
ABSTRACT
The amygdala, dorsal periaqueductal gray (dPAG), and medial hypothalamus have long been recognized to comprise a neural system responsible for the generation and elaboration of unconditioned fear in the brain. This neural substrate is well known to be under tonic inhibitory control exerted by ã-aminobutyric acid (GABA) mechanisms. Some evidence also suggests that these structures integrate conditioned fear. A recent study using the fear-potentiated startle paradigm showed that GABAergic mechanisms in the anterior hypothalamic nucleus (AHN) and dorsomedial part of the ventromedial hypothalamic nucleus (VMHDM) regulate conditioned fear. The present study examined the extent to which GABAergic mechanisms in these brain regions are involved in conditioned fear by measuring freezing in response to a light used as a conditioned stimulus (CS). The GABA A receptor agonist muscimol and the GABA-synthesizing enzyme glutamic acid decarboxylase inhibitor semicarbazide were used as an enhancer and inhibitor of GABA mechanisms, respectively. Muscimol and semicarbazide were injected into the AHN or VMHDM of rats before fear conditioning. Muscimol injections into the AHN and VMHDM significantly reduced conditioned freezing, whereas inhibition of GABA transmission increased this conditioned response in the AHN. The present study further supports the hypothesis that GABAergic mechanisms in the AHN and VMHDM exert inhibitory control on the neural substrates of conditioned fear in the hypothalamus.
Subject(s)
Animals , Rats , Conditioning, Psychological , GABA Agents , Hypothalamus, AnteriorABSTRACT
Objective: To investigate activities of lipo-related enzymes in ventromedial hypothalamic obese rats at acute phase in fed state. Methods: Female SD rats were divided into two groups, one group received bilateral electrolytic lesions of ventromedial hypothalamus(VMH), and another one was used as sham control. Samples of blood, livers, and subcutaneous, parametric and mesenteric adipose tissues ,and gastrocnemius were collected one week after VMH lesions and sham operations in fed state. Results: Serum insulin in VMH group was higher than that in sham group, meanwhile serum free fatty acids in VMH group were lower (P
ABSTRACT
Objective: To investigate how fatty liver was developed in ventromedial hypothalamus(VMH)-lesioned obese rats. Methods: Two groups of rats were prepared: (1)VMH-lesioned obese rats, and (2)sham VMH-lesioned rats. One week after VMH lesions, livers of all rats were isolated for morphological observation and for determination of microsomal triglyceride transfer protein(MTP), phosphatidate phyosphohydrolase (PAP), malic enzyme (ME), and glucose-6-phosphate dehydrogenase(G6PDH). Results: Triglyceride contents in livers of VMH-lesoned obese rats increased significantly, and were about 1.8-fold of control group. Activities of ME, G6PDH and PAP in the livers were also enhanced markedly compared to their controls. Many lipid droplets in cytoplasm of hepatocytes from VMH-lesioned obese rats were observed, while there was no similar finding in hepatocytes of control rats. MTP activity in livers of VMH-lesioned obese rats was higher than that in livers of sham-operated non-obese rats [0.201?0.013 vs. 0.175?0.014 ?g/(mg protein?h),[WTBX]P0.05). Conclusion: Hepatic triglyceride production and activity of MTP were increased in VMH-lesioned obese rats, but magnitude of the latter did not exceed the former. This resulted in hepatic triglyceride accumulation in spite of increase in transport of triglyceride out of liver by MTP. This may contribute to the development of fatty liver in VMH-lesioned obese rats.
ABSTRACT
Objective: To investigte the lipogenic and lipolytic metabolism at dynamic phase of obesity in ventromedial hypothalamus-lesioned obese rats. Methods: Female SD rats were divided into two groups, one group received bilateral electrolytic lesions of ventromedial hypothalamus(VMH),and the other one was used as sham control. Samples of blood, livers and subcutaneous, parametric and mesenteric adipose tissues were collected one week after VMH lesions and sham operations. Results: Activities of microsomal triglyceride transfer protein(MTP) in hepatocytes, and phosphatidate phosphohydrolase (PAP), malic enzyme(ME), glucose-6-phosphate dehydrogenase(G6PDH)in liver, parametric and mesenteric adipose tissue in VMH-lesioned rats were increased as compared to their sham counterparts. Activity of hormone sensitive enzyme(HSL) in parametric and mesenteric adipose tissue in VMH-lesioned rats was not changed when compared to sham group. Activity of HSL in subcutaneons adipose tissue was increased, while activity of HSL in gastrocnemius was decreased. Activity of lipoprotein lipase(LPL) in parametric and mesenteric adipose tissue and gastrocnemius were enhanced significantly compared to sham group. Conclusion: In dynamic phase of obesity of VMH-lesioned rats, hepatic production and transportation of triglyceride in these rats were increased significantly ,and lipogenic metabolism and storage of triglyceride in adipose tissues such as parametric and mesenteric adipose tissues were also enhanced.Meanwhile, lipolytic metabolism in subcutaneous adipose tissue and gastrocnemius was also increased.