The Expression Of NPY In Hippocampus Of Intrauterine Growth Retardation Rats And Its Relationship With Learning, Memory Emotion And Behavior

Intrauterine growth retardation (IUGR) is that, with various internal andexternal elements, the intrauterine growth of fetus is retarded which leads tonot achieve of reaching their full growth potential. The clinical diagnosisstandard of IUGR is that neonates whose birth weight is below the10thpercentile or lower than the2SD for gestational age of the average birthweight of the normal infants. The nature of IUGR is fetus’ response ofintrauterine environment. Intrauterine growth of fetus is a complicate processcontaining three indispensable factors, maternal, placental and fetal factors.IUGR will appear if anyone of these factors is abnormal. It is not a disease,but can cause infants many perinatal diseases, and even lead a perinatal infantto die. IUGR can also restrict the development of nervous system, and lead tothe abnormal neurodevelopment of infancy, childhood even adult period.Because of various adverse reasons, the normal intrauterine growth offetus was restricted and their original growth rhythm was deviated. Once thedisadvantageous factors are removed, infants’ growth could accelerate tocatch up and even transcend the average growth rate of the same age andgender of children. It is catch-up growth. The rapid growth after birth of themajority of children with IUGR can reduce morbidity and infection rate.Previous studies have examined that catch-up growth occurred after birth,especially the first3years which is the key of development of nervous system.Thus, catch-up growth is likely to ameliorate the brain retardation caused byIUGR.Neuropeptide Y (NPY) is a36amino acid peptides belonging to the NPYfamily. NPY is widely distributed in the central and peripheral nervous system,and there is a high level in hippocampus. As a neurotransmitter or quenched, NPY mediates its physiological effects through combining with its receptorswhich belong to G-protein-coupled receptor superfamily and currently containeight members, Y1, Y2, Y3, Y4, Y5, Y6, Y7and Y8. Hippocampus is animportant part of the limbic system of brain. It is associated with theregulation of learning, memory, emotion and behavior, in particular inshort-term and spatial memory. There are many kinds of neurotransmitters inhippocampus, especially NPY and its receptors. Thus, NPY, in hippocampus,may be found up with mood. The expression of NPY decreased in patientswith learning and memory impairments. A large number of studies weredemonstrated that there are changes of NPY expression in depression patients.And intracerebroventricular (ICV) administration of NPY, rat models ofanxiety found anti-anxiety behavior.In this study, we set up to the rat model of IUGR by starvation method inpregnant rats. Three experimental groups of young rats were tested, IUGRgroup, catch-up growth group and control group. Then we examined thechanges of learning, memory, emotion and behavior in all groups with Morriswater-maze test, elevated plus maze test and open field test. Furthermore, theexpression of NPY in hippocampus was detected with western blotting. Ourfinal purpose was exploring the relationship between NPY expression, inhippocampus, and the regulation of learning, memory, emotion and behavior.Objective: To observe the alteration of the learning, memory, emotionand behavior in all young rats, and evaluate the function of catch-up growth.And to investigate the relationship between NPY expression in hippocampusand the regulation of learning, memory, emotion and behavior of IUGR/catch-up growth young rats, and explore the possible mechanics.Methods: The IUGR rat model was established with food restrictionduring pregnancy. We chose healthy adult Sprague Dawley rats and put themrandomly into cages in portion of2:1with gender. After female rats hadconceived naturally, pregnant rats were randomly divided into two groups,food restriction group and no food restriction group during pregnancy period.At delivery, pups were born from restricted or normally fed mothers. According to the IUGR standard, pups were respectively put into experimentalgroup and control group. Pups of experimental group were randomly dividedinto RR group (IUGR group, mothers continued food restriction duringlactation period) and RC group (Catch-up growth group, mothers were fednormally during lactation period). Weekly, body weight and height of pupswere measured. Form day24to28, Morris water-maze test was executed todistinguish the differences of learning and memory among all groups. Andthen, elevated plus maze test and open field test were carried out in order toobserve the changes of emotion and behavior. While accomplishing these tests,the expression of NPY in hippocampus was detected with western blotting.Results:1. Morris water-maze test, compared with both RC group andCC group, escape latency of pups in RR group lengthened significantly(P<0.05), and the number of times of crossing platform in RR group lessenedvisibly. However, compared with CC group, the escape latency and thenumber of times of crossing platform of RC group were similar (P>0.05).2.Elevated plus maze test, compared with both RC group and CC group, OE%and OT%of pups in RR group decreased obviously (P<0.05), while, there wasno significant difference between pups in RC group and in CC group (P>0.05).3. Open field test, compared with both RC group and CC group, CL%of pupsin RR group reduced overtly (P<0.05), the number of standing on hind legsand dung were more (P<0.05). Nevertheless, compared with CC group, theCL%and the number of standing on hind legs and dung of RC group had nosignificant difference (P>0.05).4. Expression of NPY, the results of westernblotting showed that the expression of NPY in hippocampus increasedgradually from0d to28d after birth in all groups. At0d, NPY of RR, RC andCC groups had no significant difference (P>0.05). However, at28d, NPY waslower than RC and CC group (P<0.05), and compared with CC group, NPY inRC group had no significant difference all along (P>0.05).Conclusion:1. IUGR may be harmful for the learning, memory, emotionand behavior of young rats. Catch-up growth may improve the loss.2. IUGRmay influence the abilities above of rats through regulating the expression of NPY in hippocampus.3. Catch-up growth may enhance the expression ofNPY to ameliorate the abnormal coursed by IUGR.