BRAIN OXIDATIVE-METABOLISM AND LEARNING IN THE MORRIS WATER MAZE

By using a recently developed quantitave histochemical technique for m easuring cytochrome oxidase activity (CO) in the CNS, a mitochondrial enzyme whose levels are closely related to 2-deoxyglucose incorporatio n and with brain functional activity, the levels of oxidative metaboli sm were obtained in the mammillary bodies from the hypothalamus of the rat. The study included an spatial learning procedure with the Morris circular pool, in which the animals must find a hidden platform below cloudy water, with the starting point being changed in each trial in oder to avoid intra-maze cues. The results show a progressive statisti cally significant decrease (p<0.0000001, N=10) of the escape latencies across the 4 learning days, reaching an steady state from the third d ay on; the transfer test in the 5th day, where the platform is removed , show significant (p less than or equal to 0.05) longer time spent in the quadrant that had the platform during learning. By comparing the CO levels 28 days after learning in the chosen nuclei from the mammill ary bodies, with a control group (N=8) that was untrained, there were statistically significant differences across nuclei from this region i n both groups (p<0.00001); however, there were no differences between the trained and control groups in the CO activity from each one of the nuclei studied.