Modification of membrane-bound proteins of the hippocampus and entorhinal cortex by change in behavior in rats

Rats were trained in an instrumental task for 2 X 25 min during 1 day and 4 days and compared with active controls with respect to membrane-bound proteins solubilized by chloral hydrate and fractionated on polyacrylamide gels. Then 30-micrograms samples of the hippocampus and entorhinal cortex were labeled by 14C- and 3H-valine. The distribution of the stained electrophoretogram was recorded by microdensitometry. The results show that the 1-day training induced an increased synthesis of a membrane protein fraction of 50,000 mol wt already present in the brain membrane proteins of active controls. Training for 4 days resulted in an overall stimulation of the hippocampal membrane protein fractions, especially in the higher-molecular-weight range. The entorhinal cortex showed two stimulated membrane protein fractions, 50,000 and 120,000 mol wt. Together with previous studies, this study makes it probable that training to establish a new behavior induces a modulation of both soluble and membrane-bound protein patterns in the hippocampus and the entorhinal cortex with a time phase retardation for the latter.