The Role Of Extracellular Signal-regulated Kinase And Protein Kinase C Signal Transduction Pathway And Immediate Early Genes Expression In Alteration Of Memory Function Of Mice Exposed To Lead Acetate

1. The relationship between protein kinase C and remember behavior alteration of mice exposed to lead.IntroductionLead has high affinity to nerve and it can be accumulated in nerve tissues, which can cause long - period damage to nervous system, especially to memory and learning function. As is known that lead can interfere the formation and ma-intainance of LTP by abnormally enhancing or inhibiting the activity of PKC in hippocampus and the distribution of isoenzyme PKC-y. We just want to study and analyze the effects of different concentration of lead on the activity of PKC and the function of learning and memory.Methods(1) Chronic exposure to lead:The mice were divided into several groups on the 7th day after mated and fed with water containing different concentration of lead, 2. 4 mmol/L, 4. 8mmol/L, 7.2 mmol/L, and 9.6mmol/L respectively. The control was fed with tap water. After breast feeding, their descendents were fed with the same water, then killed them on the 1st, 8th, 15th, 22nd, 30th day after birth respectively and took out of the brains, stored at - 70℃.(2) Measurement of the activity of PKC in brains:① in cytoplasma;Took out the samples, cut the hippocampi into pieces and added buffer (glucose 0.32mol/l, HEPES PH 7.5) , then shattered with ultrasound, centri-fuged at 27000g for Ih at 4TI, moved the supernant into a new tube. Measured the protein content by Lowery method and the activity of PKC by advanced Takai method. Mixed 20ul fluid with 20ul substrate at 30℃ for 8 minutes, then added 10ul termination agent and took 25ul product to carry on flashing test.②　On cytomembrane;Resolved the precipitation in buffer D( contained Triton X - 100) shattered by ultrasound ,4℃ vibrated for 60min, centrifuged at 45000g for 1 hour,took the supernatent to mesure protein concentration and then mesure the PKC activity.(3) Examination of the ability of learning and memory:Trained the descendents on the 3rd or 4th week after birth and took PAR test. When a mouse went into the dark hole, feared it with electric shock and strong light. Repeated this training every day or every other day. After training, mice of different group became feard to go into the dark hole in different degree. Recorded the difference of the time of memory formation and maintainance between the experimental group and the control and analyzed the effects of lead on memory and learning function.Results(1) Effect of different concentration of lead on the activity of PKC For the control, the activity of PKC increased gradually at the early devel-opping stage and rose sharply on the 15th day, reached the peak, then decreased on the 22nd day and increased shortly until the 30th day with the activityalmost turned back to the level at birth or even lower.Compared with the control, groups treated with different concentration of lead showed a graph of different cytoplasmic activity of PKC. Most of the groups reached the peak at P15, but the 0. 5 mmol/L and 2.4 mmol/L group reached the peak at P30. After P15 , the activity of PKC increased when treated with low concentration of lead but decreased with high concentration of lead.The activity of PKC on cytomembrane in mice brain showed; 1) the value of PKC activity was lower than that of cytoplasma, 2) the activity of each group reached the peak at P22, 3) the value of PKC activity varied with lead concentration, especially for the 9.6mmol/L group.(2) Effects on the ability of learning and memoryTrained the mice from the 3rd ~4th week after birth for totally 7 times each group and the interval was 1. 28 ~ 1.43 days in average. Compared the average value of experimental group with that of the control, when fed with water containing low concentration of lead, we got longer memory maintaining time in experimental groups than the control during the first few trainings and shorter time when fed with water containing high concentration of lead. During the middle and late period, we got shorter time in all experimental groups.