PYROGLUTAMYL PEPTIDASE-I LEVELS AND THEIR LEFT-RIGHT DISTRIBUTION IN THE RAT RETINA AND HYPOTHALAMUS ARE INFLUENCED BY LIGHT-DARK CONDITIONS

To evaluate the effects of light and darkness on pyroglutamyl peptidas e I activity (pGluPI) and its left-right distribution, pGluPI was meas ured bilaterally in the retina and hypothalamus under selected light-d ark schedules. Rats under a 12 h light-dark cycle were divided into fo ur experimental groups. After the end of the 12 h dark period, the ani mals were kept two additional hours in darkness (group 1), or light (g roup 2). After the end of the 12 h Light period, the animals were kept two additional hours in darkness (group 3), or light (group 4). Exper iments were done in light or darkness depending on the 2 h period. In the retina, a previous 12 h light period led to higher values of enzym e activity than dark periods. Left-right predominance, however, depend ed on the previous 2 h period: the light period led to left predominan ce, whereas right predominance was found after the 2 h dark period. In the hypothalamus, a left predominance was found only in group 3. Thes e results demonstrate that environmental Light conditions influence pG luPI activity in the rat retina and hypothalamus.