The role of leptin in striped hamsters subjected to food restriction and refeeding

Food restriction （FR） and refeeding （Re） have been suggested to impair body mass regulation and thereby making it easier to regain the lost weight and develop over-weight when FR ends. However, it is unclear if this is the case in small mammals showing seasonal forging behaviors. In the present study, energy budget, body fat and serum leptin level were measured in striped hamsters that were exposed to FR-Re. The effects of leptin on food intake, body fat and genes expressions of several hypothalamus neuropeptides were determined. Body mass, fat content and serum leptin level decreased during FR and then increased during Re. Leptin supplement significantly attenuated the increase in food intake during Re, decreased genes expressions of neuropepetide Y （NPY） and agouti-related protein （AgRP） of hypothalamus and leptin of white adipose tissue （WAT）. Hormone-sensitive lipase （HSL） gene expression of WAT increased in leptin-treated hamsters that were fed ad libitum, but decreased in FR-Re hamsters. This indicates that the adaptive regulation of WAT HSL gene expression may be involved in the mobilization of fat storage during Re, which partly contributes to the resistance to FR-Re-induced overweight. Leptin may be involved in the down regulations of hypothalamus orexigenic peptides gene expression and consequently plays a crucial role in controlling food intake when FR ends.

Analysis on Interrelation between Electroacupuncture-lnduced Cumulative Analgesic Effect and Hypothalamic Cholinergic Activities in Chronic Neuropathic Pain Rats

Objective： To observe the effects of repeated electroacupuncture （EA） of Zusanli （ST36）Yanglingquan （GB34） on hypothalamic acetylcholinesterase （AchE） and vesicular acetylcholine （ACh） transporter （VAChT） activities and choline acetyltransferase （CHAT） mRNA and muscarinic M1 receptor （MIR） mRNA expression in chronic constrictive injury （CCI） and/or ovariectomy （OVX） rats so as to reveal its underlying mechanism in cumulative analgesia. Methods： A total of 103 female Wistar rats were randomly divided into normal control （n=15）, CCI （n=15）, CCI＋EA2d （n=15）, CCI＋EA2W （n=15）, OVX＋CCI （n=13）, OVX＋CCI＋EA2d （n=15）, and OVX＋CCI＋EA2W groups （n=15）. CCI model was established by ligature of the unilateral sciatic nerve with surgical suture. Memory impairment model was established by removal of the bilateral ovaries. Morris water test was conducted to evaluate the OVX rats＇ memorylearning ability, and the thermal pain threshold （PT） of the bilateral paws was detected the next morning after EA. EA （2/15 Hz, 1 mA） was applied to bilateral ST36-GB34 for 30 min, once daily for 2 days or 2 weeks, respectively. Hypothalamic AChE activity was detected by histochemistry, VAChT immunoactivity was determined by immunohistochemistry, and ChAT mRNA and MIR mRNA expressions were assayed by reverse transcription-polymerase chain reaction （RT-PCR）. Results： In comparison with the normal control group, the AChE activity in hypothalamic arcuate nucleus （ARC） and supraoptic nucleus （SON） regions of CCI group, AChE activity in paraventricular nucleus （PVN）, ARC, and SON regions of OVX＋CCI group, and hypothalamic muscarinic M1R mRNA expression levels in both CCI and OVX＋CCI groups were down-regulated significantly （P〈0.05）. Compared with the CCI group, the AChE activities in hypothalamic ARC and SON regions of CCI＋EA2d and CCI＋EA2W groups and PVN region of CCI＋EA2W group and hypothalamic ChAT mRNA and M1R mRNA expression levels in CCi＋EA2W group were up-regulated considerably （P〈0.05）. In comparison with the OVX＋CCI group, the AChE activities in PVN, ARC, and SON regions and the expressions of hypothalamic ChAT mRNA and VAChT in ARC region of OVX＋CCI＋EA2W group were up-regulated remarkably （P〈0.05）. The effects in rats of CCI＋EA2W group were evidently superior to those of OVX＋CCI＋EA2d group in up-regulating AChE activities in PVN, ARC, and SON regions, VAChT immunoactivity in ARC region, and expression levels of hypothalamic ChAT mRNA and MIR mRNA （P〈0.05）. Similar situations were found in OVX＋CCI rats after EA2W. It suggested a cumulative effect after repeated EA of ST36-GB34. Comparison between CCI＋EA2W and OVX＋CCI＋EA2W groups showed that the effects in rats of the former group were evidently better than those of the latter group in up-regulating AChE activity in ARC and SON regions and the expressions of hypothalamic ChAT mRNA and M1 mRNA （P〈0.05）, suggesting a reduction of EA2W effects after OVX. Conclusion： Repeated EA can significantlyup-regulate AChE and VAChT activities and ChAT mRNA and MIR mRNA expressions in the hypothalamus of CCI and OVX＋CCI rats, which may contribute to the cumulative analgesic effects of repeated EA and be closely related to the animals＇ neuromemory ability.