Passive Avoidance Learning Results in Region‐Specific Changes in Concentration of and Incorporation into Colchicine‐Binding Proteins in the Chick Forebrain

Abstract

Incorporation of [14T]leucine into trichloracetic acid‐precipitable material and tubulin‐enriched fractions, and total tubulin levels as determined by colchicine‐binding activity and retention on DE81 filter discs, were measured in various regions of the chick brain following training on a one‐trial passive avoidance task, suppression of pecking at a chromed bead as a consequence of the aversive taste of methylanthranilate. Radioactive pulse time was 0.5 h. The only brain region in which changes were found was the anterior forebrain roof, the same area in which biochemical changes in response to exposure of the birds to an imprinting stimulus have been observed previously. In the anterior forebrain roof the changes observed as a consequence of training were detectable at 0.5 and 24 h after the 10‐s training experience but not 48 h subsequently. One‐half hour after training, there were increases of the order of 20 or 30% in [14T]leucine incorporation into particulate and postmitochondrial TCA‐precipitable material and a tubulin‐enriched fraction purified as above. There were comparable increases in the total amount of colchicine‐binding activity. By 48 h, none of these increases were detectable. Subcellular fractionation of the particulate fraction showed that most of the increase of incorporation into the tubulin‐enriched fraction and in colchicine‐binding activity was present in the soluble content of the synaptosomes; there were no increases in either measure in the synaptic membrane fraction. The possible role of changed levels and turnover of tubulin in the plastic responses of the brain to learning experiences is discussed.

Increased Incorporation of [3H]Fucose into Chick Brain Glycoproteins Following Training on a Passive Avoidance Task

“…However, the problems of interpretation of data based on incorporation of precursors administered systemically, and the appropriate measure for the precursor pool size, are not inconsiderable (for discussion, see e.g., Dunn, 1977;Rose and Haywood, 1976). The time courses of these changes are comparable to those we have also found for elevated incorporation of [*4C]leucine into, and total amount of colchicine-binding protein (presumably tubulin) in, the same brain region (Mileusnic et al, 1980). Glycoproteins are known to be present in high concentrations in synaptic junctions (Zatz and Barondes, 1970;Kelly and Cotman, 1977;Margolis and Margolis, 1977), and the increased incorporation of labelled fucose observed may be an index of enhanced production of glycoproteins or increased fucosylation of proteins already present in the synaptic membrane.…”

“…The present series of experiments shows that, following learning, there is an elevation of [3H]fucose incorporation into a TCA-insoluble particulate fraction of the anterior forebrain roof that persists for up to 24 h after the training episode. A subsequent paper reports a persistent increase in [14C]leucine incorporation into, and quantity of, a tubulin-enriched fraction (as defined by colchicine binding) in the same region (Mileusnic et al, 1980).…”

Memory formation and the regulation of gene expression

“…Interference with protein synthesis during that wave blocks LTM formation as described above. Proteins whose expression have been found increased at this time include the immediate early genes c-fos and c-jun (30 min post-training [17,18]), and tubulin (1 h later [155]). A second wave of protein synthesis essential for LTM formation appears 5 -8 h post-training.…”

Fetus Sound Stimulation: Cilia Memristor Effect of Signal Transduction

“…We believe that cilia and microtubules as acoustical and electrical organelles are responsible for signal transduction with memory and learning properties [26]. …”