The Study Of PUFAs In The Specific Brain Of The SHR And Effects Of Methylphenidate On Attentional Set-Shifting And PUFAs

Background:Attention deficit/hyperactivity disorder (ADHD) is among the most common neuropsychiatric disorders in children characterized by developmentally inappropriate symptoms of inattention, impulsivity and hyperactivity. These symptoms manifest as distractibility, difficulty in sustaining attention, and a failure to appropriately control motor responses. Some have suggested that all of these symptoms can be attributed to a primary deficit of cognition in ADHD sufferers, particularly impairment of executive functions. Previous studies have reported deficits of attentional set-shifting-a type of executive functions, in individuals with ADHD. Assessing set shifting in an animal model can provide basis for elucidating relatively precise neural mechanisms of ADHD. The spontaneously hypertensive rat (SHR) has been evaluated extensively as an animal model of ADHD, including neurochemical, genetic, and behavioral characteristics. The WKY to be the control group, the use of WKY as a control for SHR has been questioned of instability in its behavioural profile,for example,the studies founded that WKY may be used as an animal model of depression, so we selected another unrelated outbred albino strain Sprague-Dawley (SD) rats as an additional genetic/control to find if there were strain differences in our behavior test.Attentional set-shifting is a form of executive function that represents behavioral flexibility. It requires attending to relevant stimuli while ignoring irrelevant stimuli and subsequently shifting the allocation of attention, either within "dimensions" or between "dimensions". Deficits of set-shifting in individuals with ADHD have been investigated with some different neuropsychological tests, Recently, the attentional set-shifting task (ASST), which is a similar procedure to commonly used testing of attentional set-shifting in humans with ADHD named the Wisconsin Card Sorting Task (WCST), was developed for rats and mice model studies. In ASST, This ability of shifting is tested as behavioral flexibility (extra-dimensional shift). Meanwhile, other prefrontal cortex depended cognition functions including working memory (reversal learning), procedural memory (intra-dimensional shift) can also be measured separately. Assessing attentional set-shifting in an animal model of ADHD can help address some of the limitations of human study and provide a basis for elucidating relatively precise neural mechanisms.Long chain fatty acids, particularly arachidonic acid and docosahexaenoic acid, are integral components of neural membrane phospholipids. A deficiency of docosahexaenoic acid markedly affects neurotransmission, membrane-bound enzyme and ion channel activities, gene expression, intensity of inflammation, and immunity and synaptic plasticity. From the first report describing signs of fatty acid deficiency in hyperactive children, a number of observational and epidemiological studies and intervention trials have investigated the relationship between n-3PUFA deficiency and ADHD symptoms. Numerous investigators have evaluated the effect of n-3PUFA on motor activity in rodents. Several have reported an increase in locomotion in n-3PUFA-deficient rodents.Methylphenidate (MPH) is one of the most commonly used psycho-stimulants for the treatment of ADHD, which has been found to improve spatial working memory, response inhibition, and other cognitive functions in children with ADHD and corresponding behavior in animal models of ADHD. Some studies show that MPH produced an inverted U dose response curve on cognitive performance. At lower dose (lower than5.0mg/kg for rats), MPH could reduce movement, impulsivity and increase cognitive function. In contrast, higher dose of MPH (no less than 5.0mg/kg for rats)may impair cognition, elicit increase in locomotor activity. Do the different dose of MPH can do difference actions on the attentioal set-shifting and PUFAin the brain? further examination of this issue may be needed.Part IThe study of behavioral in the SHR/WKY/SDObjectiveAdded another unrelated outbred albino strain Sprague-Dawley (SD) rats as an additional genetic/control to find if there were strain differences in behavior test.MethodsTo characterize behavioural alterations, we used attentional set-shifting test, open—field environment test and morris water maze to study motor activity,as well as attention set-shiting and cognitive behaviours in juvenile SHR,WKY and SD rats. All the behavior in the tests were monitored by aCCD video Camera and analyzed off-line.ResultsIn ASST,the mean latency of SHR was decreased than the other group (p<0.001). the SHR rats needed significantly more trials to reach criterion compared with control strains (p<0.001) at all stages, Both the WKY [paired t(7)=-2.676, p=0.032] and SD rats [paired t(7)=-4.255, p=0.004] had fewer times of trials to criterion at the ID compared to the ED. But we didn't find any difference at times of trials between the ED and the ID stages [paired t(7)=-0.456, p=0.662] for SHR rats. The SHR rats had significantly more perseverative and regressive errors compared with control strains (p<0.01). In open field environment, ambulatory and rearing leaning and grooming activities were significantly higher in SHR than in Wistar-Kyoto(WKY)controls, but there was no significant difference between the SHR and SD rat, the same difference was observed in WKY and SD rat. In the morris water maze test, the SHR was the most quickly rat to find the platform among the three group rats. In contrast, on the morris water maze there was siginificant difference in the time spend in objective quadrant than the other2groups. There is no difference between WKY and SD.ConclusionOur findings reveal that1. The SHR may be impaired in impulse, attentional set-setupping and attentional set-shifting. That all maybe led from perseverative and impaired of attention sustaining in SHR.2.This ASST may be the suitable method to study the attentional set-shifting of juvenile rats.3. The SHR and SD rats all manifest most hyperactivity in the open field test, so it should be questioned that WKY was suitable for only one control of SHR?4.the SHR have a good ability in apace learn but a poor retention of memory than the other groups.5. The SHR rat was the suitable model used for the study of the behavioral in the ADHD including attentional set-shifting, impulse and apace retention of memory.SignificanceThis research reveal that juvenile SHR manifest behaviours resembling a developmental disorder of ADHD, such as hyperactivity, attention deficit, and disorder of cognition.It is important to supply the evidence to further study. Part ⅡThe study of PUFAs in the specific brain of the SHR rat and the correlation of the behavioral and PUFAs in SHRObjectiveTo study the PUFAs, especially AA and DHA in the specific brain of the SHR rat and identify the correlation between the PUFAs and behavioral in the SHR.MethodsSHR/WKY/SD rats were killed by decapitation and the brains rapidly removed, Frontal cortex, striatum, hippocampus, temporal lobe, parietal lobe, corpus callosum and cerebellum were isolated from each brain by free-hand dissection on ice.then analysis the fatty acids by GC.ResultsSHR has the highest DHA content and AA content in the three groups, especially in frontal cortex, cerebellum,corpus callosum and hippocampus than WKY and SD rat, t SD rat is the lowest one. But the rate of DHA/AA in the SHR was the lowest than the other two rats, the rate of DHA/AA in the SD was the lowest in frontal cortex, other brain was higher than the other rats. So, the rate of DHA/AA is most important for the funchtion of the brain. correlation analysis show us that hyperactivity in SHR was correlated with frontal cortex, cerebellum and temporal lobe, space learning and retention of memory ability was correlated with cerebellum, temporal lobe, striatum and hippocampus, attentional set-shifting was correlated with frontal cortex and striatum.Conclusion1. SHR has the highest DHA content and AA content in the three groups, but the rate of DHA/AA in the specific brain of SHR were lowest in the three rats.2. the rate of DHA/AA in SHR special brain was lower than others maybe induced hyperactivity, poor retention of memory and impaired in attentional set-shifting.3.The correlation analysis between behavioral and PUFA in specific brain identifyed the specific brain execute the different function.SignificanceDisclosed the important role of PUFAs in the behavioral characteristic of hyperactivity, poor retention of memory and impaired in attentional set-shifting of SHR.. Part ⅢEffects of Methylphenidate on Attentional Set-Shifting and PUFAs in specific brain of SHRObjectiveDifferent dose effects of MPH on attentional set shifting and PUFAs in specific brain of the SHRs were investigated in order to delineate the effects of MPH on attentional set-shifting deficits and fat station in ADHD,enhance the understanding of the effects of drug treatment on ADHD.Methods24SHRs were randomly assigned to3groups of8each:MPH-L (lower dose of MPH), MPH-H (higher dose of MPH) and SHR-vehicle (saline) groups. Rats in the MPH-L group were treated daily with MPH by dose of2.5mg/kg, in the MPH-H treated with5mg/kg MPH, while animals in the SHR-vehicle were treated daily with vehicle (saline). Peritoneal injection was conducted for14consecutive days. Rats were tested in the ASST at the age of5weeks,after test,the rats were killed by decapitation and the brains rapidly removed, Frontal cortex, striatum, hippocampus, temporal lobe, parietal lobe, corpus callosum and cerebellum were isolated from each brain by free-hand dissection on ice.then analysis the fatty acids by GC.ResultsThe revealed significantly longer latency of the MPH-H and MPH-L group compared with the SHR-vehicle group(p<0.01). Significant differences between the SHR-vehicle and MPH-L groups in their abilities to perform overall stages (p<0.01), more trials were needed in ED than in ID for rats in the MPH-L [t(7)=3.667, p=0.035] and the MPH-H [t(7)=3.434, p=0.041] groups. Similarly, more trials were needed in CD than in ID for rats in the MPH-L [t(7)=4.515, p=0.006] and the MPH-H [t(7)=5.716, p=0.002] groups. Post-hoc tests revealed significant difference in perseverative and regressive errors between the MPH-L and SHR-vehicle groups (p<0.01). There is no different between MPH-treatment and MPH-evhicle of PUFAs in specific brain.ConclusionMPH treatment of ADHD in the SHRs may ameliorate deficits in attentional set-shifting differently, and lower doses were more effective than higher doses. MPH treatment for2weeks can not changed the PUFAs in the SHR specific brain.SignificanceWe provided the first evidence of the dose-dependent effect of MPH on attentional set-shifting performance and PUFAs of brain in SHRs.