ABSTRACT
Objective@#To investigate whether γ-aminobutyric acid (GABA) receptor signaling pathway is involved in the regulation of thalamic undefined (ZI)-nucleus accumbens (NAc) neural pathways on gastric distraction (GD)-sensitive neuronal firing activity and the impact on food intake, the number of times and the frequency in rats.@*Methods@#Six rats were randomly selected and the neural pathway between ZI and NAc in rat thalamus was observed by fluorescent gold (FG) retrograde tracing method.Eighty-two rats were randomly selected, and the gastric balloon was placed in gastric cavity, the microelectrode was placed in the NAc, and the stimulating electrode was placed in the ZI. The single-cell discharge recording method was used to observe the effect of electrical stimulation ZI on the excitability of GD-sensitive neurons in rat NAc.Eighteen rats were randomly selected and were divided into three groups according to the random number table. They were NS group, GABA group, GABA + GABA receptor antagonist bicuculline (BIC) group with 6 in each group, and the rat NAc was used to embed the cannula. The method of GABA and BIC was injected to observe the changes of cumulative food intake in rats for 4 h. Eighteen rats were randomly selected and randomly divided into three groups: sham stimulation (SS) group, 50 μA electrical stimulation group, 50 μA electrical stimulation + BIC group with 6 in each group. The 4 h cumulative food intake of rats was observed by electro-stimulation of rat ZI and rat NAc injection of BIC.@*Results@#Fluorescent gold retrograde tracking combined with fluorescent immunohistochemical staining showed that there were visible GABA and fluorescent gold double labeled neurons in ZI. Electrical stimulation of ZI, the frequency of GABA-sensitive GD neurons in rat NAc increased significantly (GD-E increase: (78.8±8.4)%, GD-I increase: (89.3±9.2)%, P<0.01), but the inhibitory effect was antagonized by BIC (GD-E increase: (113.8±13.6)%, GD-I increase: (121.8±14.2)%, P<0.01). Microinjection of GABA in rat NAc significantly increased the cumulative food intake for 4 h ((155.72±18.84) kcal, t=3.41, P<0.05), which was antagonized by partial BIC (123.43±15.11) kcal, t=3.28, P<0.05). Electrical stimulation of ZI significantly increased the food intake in rats ((39.07±11.27) kcal, t=2.96, P<0.05), and this effect can be partially antagonized by BIC ((34.17±10.85)kcal, t=2.33, P<0.05).@*Conclusion@#The ZI-NAc neural pathway regulates the discharge activity of rat gastric distension (GD)-sensitive neurons and the feeding status of rats, and the GABA receptor signaling pathway may be involved in mediating the process.
ABSTRACT
Objective To investigate whether γ-aminobutyric acid (GABA) receptor signaling pathway is involved in the regulation of thalamic undefined (ZI)-nucleus accumbens (NAc) neural pathways on gastric distraction (GD)-sensitive neuronal firing activity and the impact on food intake,the number of times and the frequency in rats.Methods Six rats were randomly selected and the neural pathway between Zl and NAc in rat thalamus was observed by fluorescent gold (FG) retrograde tracing method.Eighty-two rats were randomly selected,and the gastric balloon was placed in gastric cavity,the microelectrode was placed in the NAc,and the stimulating electrode was placed in the ZI.The single-cell discharge recording method was used to observe the effect of electrical stimulation ZI on the excitability of GD-sensitive neurons in rat NAc.Eighteen rats were randomly selected and were divided into three groups according to the random number table.They were NS group,GABA group,GABA + GABA receptor antagonist bicuculline (BIC) group with 6 in each group,and the rat NAc was used to embed the cannula.The method of GABA and BIC was injected to observe the changes of cumulative food intake in rats for 4 h.Eighteen rats were randomly selected and randomly divided into three groups:sham stimulation (SS) group,50 μA electrical stimulation group,50 μA electrical stimulation + BIC group with 6 in each group.The 4 h cumulative food intake of rats was observed by electro-stimulation of rat ZI and rat NAc injection of BIC.Results Fluorescent gold retrograde tracking combined with fluorescent immunohistochemical staining showed that there were visible GABA and fluorescent gold double labeled neurons in ZI.Electrical stimulation of ZI,the frequency of GABA-sensitive GD neurons in rat NAc increased significantly (GD-E increase:(78.8±8.4) ％,GD-I increase:(89.3±9.2) ％,P＜0.01),but the inhibitory effect was antagonized by BIC (GD-E increase:(113.8 ± 13.6)％,GD-I increase:(121.8± 14.2)％,P＜0.01).Microinjection of GABA in rat NAc significantly increased the cumulative food intake for 4 h ((155.72± 18.84) kcal,t=3.41,P＜0.05),which was antagonized by partial BIC (123.43± 15.11) kcal,t =3.28,P＜ 0.05).Electrical stimulation of ZI significantly increased the food intake in rats ((39.07± 11.27) kcal,t =2.96,P＜0.05),and this effect can be partially antagonized by BIC ((34.17 ± 10.85) kcal,t =2.33,P＜ 0.05).Conclusion The ZI-NAc neural pathway regulates the discharge activity of rat gastric distension (GD)-sensitive neurons and the feeding status of rats,and the GABA receptor signaling pathway may be involved in mediating the process.
ABSTRACT
Objective To investigate the effects of orexin-A on firing activity of gastric distensionsensitive (GD) neurons in the basomedial amygdala (BMA) and food intake in diet-indaced obese rats.Methods Healthy male Wistar rats were selected,and the diet-induced obesity (DIO) rat model and dietinduced resistant (DR) rat model were established by high-fat diet.The effects of orexin-A and an opioid receptor antagonist naloxone on BMA GD neurons were observed by recording the extracellular potentials of single neurons.The effects of orexin-A and naloxone on the food intake of different rats were observed by using BMA catheterization.The mRNA expression and protein expression of orexin-1 receptor (OX-1R) and μ opioid receptor were detected by real-time PCR and Elisa,respectively.Results After microinjection of orexinA into the BMA,the firing frequency of GD-sensitive neurons in the normal rats was significantly increased (GD-E:(78.3±6.9)％,GD-Ⅰ:(55.5±4.7) ％,P＜0.01),and this effect was completely blocked by OX-1R receptor antagonist SB334867,and naloxone partially blocked the discharge-promoting effect of orexin-A;Compared with the normal rats,the firing frequency of GD-sensitive neurons in the DIO (GD-E:(91.6±7.1) ％,GD-Ⅰ:(67.9±8.1) ％) and DR(GD-E:(87.9±6.8) ％,GD-Ⅰ:(69.2±5.8) ％) rats was significantly increased after BMA injection of orexin-A (P＜0.05).After administration of orexin-A into the BMA,food intake of the normal rats,DIO rats and DR rats ((2.38±0.34) g,(3.75 ±0.32) g,(4.01 ±0.38) g,respectively) was significantly increased (P＜0.01),and the food intake of DR and DIO rats were significantly higher than that of normal rats (P＜0.05).After BMA was injected with naloxone,the food intake of rats was inhibited,and the food intake of the DIO rats was significantly lower than that of the DR rats (P＜0.05),food intake of the DR rats was significantly lower than that of the normal rats (P＜0.05).The results of real-time PCR showed that the mRNA levels of OX-1R in DIO and DR rats were(5.85±0.45)and (6.03±0.42)were higher than that of normal rats,and the difference was significant (P＜0.05);and mRNA levels of μ-opioid receptors in DIO and DR rats((4.51±0.42) and (8.31±0.41) times) were higher than those in normal rats (P＜0.05).The results of Elisa showed that the protein levels of OX-1R in DIO ((2.98±0.28) ng/μl)and DR rats ((3.05±0.31) ng/μl) were higher than those in normal rats ((1.53±0.31) ng/μl,P＜0.05).The content of μ-opioid receptor protein in DR rats ((4.21±0.35) ng/μl) was higher than that of DIO rats ((2.77±0.27) ng/μl),and higher than that of normal rats((1.48±0.32) ng/μ),the difference was significant (P＜0.05).Conclusion BMA orexin-A promotes the spontaneous discharge of GD-sensitive neurons and food intake in normal rats,DIO rats and DR rats,μ-opioid receptors may be involved in the regulation of this process.