| Ghrelin,the endogenous ligand for the growth hormone secretagogue receptor(GHSR),which is an important feeding peptide in the development of depressive symptoms.Ghrelin is a hormone synthesized predominantly by specialized gastrointestinal endocrine cells and is released during periods of negative energy balance.In response to energy insufficiency,ghrelin induces a potent feeding response via activation of the growth hormone secretagogue receptor(GHSR,ghrelin receptor).Accumulating evidence has suggested that ghrelin may play a role in signaling and reversing states of energy insufficiency.For example,ghrelin levels rise following food deprivation,and ghrelin administration stimulates feeding and increases body weight and adiposity.GHSR-/-mice showed significantly greater social avoidance than wild-type littermates,thus indicating an exacerbation of the depressive-like symptoms normally induced by CSDS.Moreover,although there was no difference in body weight following CSDS between the two genotypes,food intake was significantly elevated in wild-type,but not GHSR-/-mice.These findings suggest that activation of ghrelin signaling pathways in response to chronic stress may be a homeostatic adaptation that helps an individual cope with stress,but at the expense of increased caloric intake.genetic blockade of ghrelin signaling in GHSR-/-mice negated these calorie restriction-associated anxiolytic-and antidepressant-like effects.Further analyses demonstrated that the observed differences between the two genotypes cannot be attributed to differences in sensorimotor coordination,general locomotor activity or body weight.Although there is a very strong evidence about the antidepressant effect of ghrelin and that the GHSR-/-mice are more susceptible to CSDS than GHSR+/+ mice,the underlying mechanism are still unknown.We still don't know whether there is morphological change in the neuron structure of GHSR-/-mice compared with GHSR+/+ mice.The aim of this study was to investigate the morphologyof ghrelin receptor(GHSR)deficiency in GHSR deficient(GHSR-/-)mice.We fous on the stuty of branch numbers and spine densities on pyramidal neurons in the cortex of GHSR-/-mice and GHSR+/+ mice.GHSR-/-and control(GHSR+/+)mice were genotyped by PCR.Using the heterozygous mice(GHSR+/-mice)to mate with heterozygous mice(GHSR+/-mice),we can get three genotypes of mice:GHSR-/-mice,GHSR+/+ mice and GHSR+/-mice.GHSR+/-mice is used as the control group and GHSR-/-mice is used as the experiment group.All the mice we used in the experiment is three months old.Because the morphology change in GHSR-/-mice may have some difference by sex,we divided the GHSR-/-mice and control mice(GHSR+/+ mice)into two groups:the male mice and female mice.The some sex littlemates GHSR-/-mice and GHSR+/+mice were matched together.During the experiment,all the message about the mice,like the genotype,the sex,the bring up cage were identified seriously.If there are two bands in the 175bp and 354bp,the mice genotypes are heterozygous mice(GHSR+/+mice).If there is only one band in 354bp,the mice genotypes are control mice(GHSR+/+ mice).If there is only one band in 175bp,the mice genotypes are experiment mice(GHSR-/-mice).After the mice brain tissue was dyed by the classic golgi staining method,the optical microscope was used to analysis the structure of the pyramidal neurons in the cortex and hippocamous of GHSR-/-mice and GHSR+/+mice.The result of our experiment demonstrated that the morphological change in pyramidal neurons in GHSR-/-mice and GHSR+/+ mice have a significant difference in the sex.We found that the number of branches in cortex significantly decreased in male mice when GHSR knockout mice(GHSR-/-mice)compared with control mice(GHSR+/+ mice).The total number of branches in male GHSR-/-mice are 14.75±0.957427 and the total number of branches in male GHSR+/+ mice are 22.42857±1.812654.There was a significant decrease in the total number of branches in the male GHSR-/-mice and male GHSR+/+ mice(P<0.001).The number of the first dendrites in male control mice(GHSR+/+ mice)were 5.625±0.517549,The number of the first dendrites in male GHSR-/-mice were 3.75±0.957427.There was a significantly decrease in the number of the first dendrites(P<0.05).The number of the secondary dendrites in male control mice(GHSR+/+ mice)were 7.625±0.744024,The number of the secondary dendrites in male GHSR-/-mice were 5.5±1.There was a significantly decrease in the number of the secondary dendrites(P<0.05).The number of the third dendrites in male control mice(GHSR+/+ mice)were 9.285714±1.253566,The number of the third dendrites in male GHSR-/-mice were5.5±0.57735.There was a significantly decrease in the number of the third dendrites(P<0.05).However,there was no significant difference in the number of branches in female cortex between the GHSR knockout mice(GHSR-/-mice)and the control mice(GHSR+/+mice).The total number of branches in female GHSR+/+ mice were 28.83333±3.169045,and the total number of branches in female GHSR-/-mice were 27.6±3.19089.The number of the first dendrites in female GHSR+/+ mice were 5.5=0.547723,and the number of the first dendrites in female GHSR-/-mice were 5.4±0.894427.The number of the secondary dendrites in female GHSR+/+ mice were 10.66667±1.032796,and the number of the first dendrites in female GHSR-/-mice were 9.2±1.095445.The number of the third dendrites in female GHSR+/+mice were 12.66667±0.816497,and the number of the first dendrites in female GHSR-/-mice were 12±1.414214.The spine density in GHSR konckout mice was also significant decrease compared with control in male mice,the spine density in GHSR konckout mice was no significant difference compared with control in female mice.Both the branch numbers and spine density change in male mice in the cortex.Neither the branch numbers nor the spine density change in female mice in the cortex.We then make a comparison of spine density between the GHSR knockout mice and control mice in the cortex.The spine density was analysis by calculating the number of spines in the secondary dendrites in the pyramidal neurons.The number of spines per 20um in the secondary dendrites in the male GHSR+/+ mice were 15.5±1.290994 and that in the male GHSR-/-mice were 9.6±0.547723.The spine density was significantly decreased in GHSR-/-mice compared with the spine density in GHSR+/+ mice(p<0.001).The number of spines per 20um in the secondary dendrites in the female GHSR+/+ mice were 17.6±1.81659 and that in the male GHSR-/-mice were 18.2±1.30384.The spine density was no significantly difference in GHSR-/-mice compared with the spine density in GHSR+/+mice(p>0.05).There were no significant difference in the spine density in the CA1 and CA3 region of hippocampus for both male and female GHSR-/-mice(P>0.05).The spine number in the length of 20 um secondary dendrites was 23.16667±1.169045 and 20.83333±1.47196 respectively in CA1 region of GHSR-/-male mice and GHSR+/+ mice respectively.The spine number in the length of 20 um secondary dendrites was 21.42857±1.718249 and 21.1666712.136976 respectively in CA3 region of GHSR-/-male mice and GHSR+/+ mice respectively.The spine number in the length of 20 um secondary dendrites was 24.4±1.140175 and 23.85714±1.345185 respectively in CA1 region of GHSR-/-female mice and GHSR+/+ mice respectively.The spine number in the length of 20 um secondary dendrites was 23±0.894427 and 21.33333±2.42212 respectively in CA3 region of GHSR-/-female mice and GHSR6+/+ mice respectively. |
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