CHICKS INJECTED WITH ANTISERA TO EITHER S-100-ALPHA OR S-100-BETA PROTEIN DEVELOP AMNESIA FOR A PASSIVE-AVOIDANCE TASK

The cellular expression of S-100 beta protein is upregulated in Alzhei mer's disease and in Down's syndrome, and this protein has been implic ated in memory-related processes in laboratory animals. However, the p ossibility that the alpha subunit of S-100 is also involved in memory has not yet been examined. In the present study, day-old black Austral orp white Leghorn cockerel chicks (Gallus domesticus) received injecti ons of monoclonal antisera to S-100 alpha (1:50) or S-100 beta (1:500) into each hemisphere immediately after training on a one-trial passiv e avoidance task. The chicks displayed significantly lower retention l evels than control birds that had been injected with antisera to carbo nic anhydrase, or with saline (p < .01). S-100 alpha antisera had an a mnestic effect when injected between 0 and 20 min after training, with memory deficits occurring from 30 min post-learning, at the point of transition between the A and the B phases of the Gibbs-Ng intermediate memory stage. By contrast, the S-100 beta antisera needed to be injec ted either 5 min before or immediately after training and produced amn esia 10 min earlier, at the start of the A phase of the intermediate m emory stage. We conclude that the two subunits of the S-100 protein ar e required at different points in the sequence of events leading to th e consolidation of passive avoidance memory. (C) 1997 Academic Press.