Three diffusion parameters of nervous tissue, extracellular space (ECS) volume fraction (λ), tortuosity (α) and non-specific uptake (k’) of tetramethylammonium (TMA + ), were studied in the spinal cord of rats during experimental autoimmune encephalomyelitis (EAE). The three parameters were determined in vivo from concentration-time profiles of TMA+ using ion-selective microelectrodes. EAE was induced by injection of guinea-pig myelin basic protein (MBP), which resulted in typical morphological changes in the CNS tissue, namely inflammatory reaction, astrogliosis, blood-brain barrier (BBB) damage and paralysis. EAE was accompanied by a statistically significant increase of a (mean±S.E.M.) in the dorsal horn from 0.21±0.01 to 0.28±0.02, in the intermediate region from 0.22±0.01 to 0.33±0.02, in the ventral horn from 0.23±0.01 to 0.47±0.02 and in white matter from 0.18±0.03 to 0.30±0.03. There were significant decreases in tortuosity in the dorsal horn and in the intermediate region and decreases in non-specific uptake in the intermediate region and in the ventral horn. Although the inflammatory reaction and the astrogliosis preceded and greatly outlasted the neurological symptoms, the BBB damage had a similar time course. Moreover, there was a close correlation between the changes in extracellular space diffusion parameters and the manifestation of neurological signs. We suggest that the expansion of the extracellular space alters the diffusion properties in the spinal cord. This may affect synaptic as well as non-synaptic transmission, intercellular communication and recovery from acute EAE, and may contribute to the manifestation of neurological signs in EAE rats.
Although male rats generally outperform females in many spatial tasks, sometimes gender differences are not present. This preliminary study examined gender effects in the Enemy avoidance task, in which a rat on a stable circular arena avoids approaching a small mobile robot while collecting randomly dispersed small pellets. Whenever distance between robot and the rat dropped below 25 cm, animal was punished by a mild footshock. Female rats showed thigmotaxis, hypolocomotion and avoidance of robot in the habituation phase, when approaches were not punished. No statistically significant differences in avoidance learning under reinforcement training sessions were observed; but females still spent significantly more time at periphery of the arena and foraged less than males. We conclude that females were able to perform at the same level as males under reinforcement despite different behavioral strategy. The thigmotaxic behavior appears to function as innate escape strategy in female rats triggered by the stressing effect of the moving robot rather then the presence of shocks., J. Svoboda, ... [et al.]., and Obsahuje seznam literatury