Glycoprotein Synthesis Is Necessary for Memory of Sickness‐Induced Learning in Chicks

Abstract

Can current biochemical models of memory account for sickness-induced learning? We show that chicks can form an association between pecking a coloured but tasteless lure and becoming ill (LiCl, i.p.) 30 min later. We go on to demonstrate amnesia for this association, induced by intracranial administration of 2-deoxygalactose (10 micromole per hemisphere, in a 10 microl vol), an inhibitor of the synthesis of glycoproteins of the synaptic membrane, 10 min before pecking. Further, we show that this 2-deoxygalactose-induced amnesia is not state dependent. Thus the brain representation of the lure must be held, and require macromolecular syntheses, similar to those found in other forms of learning, for a considerable time before it can be associated with new significant experience. This is incompatible with contiguous synaptic firing views of memory.

Two critical periods of protein and glycoprotein synthesis in memory consolidation for visual categorization learning in chicks.

“…Increased incorporation of fucose has been also shown in the chick brain after passive avoidance training (Rose and Harding 1984;McCabe andRose 1985, 1987). Intracerebral administration of 2-deoxygalactose (2-D-gal), a competitive inhibitor of glycoprotein fucosylation, produced amnesia in chicks both in passive avoidance and in a sickness-induced learning paradigm (Rose andJork 1987;Barber et al 1989;Barber and Rose 1991). However, as with ANI, we have recently found a second time window during which 2-D-gal administration affects memory consolidation for the passive avoidance task.…”

Memory formation: its molecular and cell biology

“…49 The existence of this second time window of biochemical plasticity does not match any hitherto known phase of memory formation. A clue as to its implications however, is provided by the observations that (a) chicks trained to peck at even at dry bead retain a memory of it for a few hours and this memory is itself dependent on glycoprotein synthesis 50 and (b) if the chicks are trained on a weakly aversive stimulus, such as quinine, rather than the strongly aversive MeA, their avoidance response on test declines over a period of 6-9 hrs and, under these circumstances, there is no enhancement of glycoprotein synthesis over that in the W-trained chicks. 51 My interpretation of these data is that weak and rapidly decaying memories evoke only the first wave of glycoprotein synthesis; to produce a longer lasting memory requires the second wave, during which synapses are stabilized in some new configuration by means of newly synthesized NCAM.…”

Selective associations in day-old chicks: When do CS traces become available for sickness-conditioned learning?

“…Learning of this task was impaired by an inhibitor of glycoprotein synthesis injected near the time of presentation of the bead, whereas injection of the inhibitor near the time of LiCl injection did not affect learning (A. J. Barber et al, 1989). This indicates that a memory for the visual characteristics of the bead, dependent on glycoprotein synthesis, is made at the time of pecking, even though there are no immediate aversive consequences to pecking.…”

“…On the other hand, researchers interested in the biology of learning and memory have used these phenomena to tease apart the processes involved in creating and using memories (e.g., A. J. Barber, Gilbert, & Rose, 1989). Both groups of researchers depend on an animal's ability to form a memory for events in which the signal value is not evident at the time the memory is created (cf.…”

“…J. Barber et al (1989) modified the sicknessconditioned learning task to clearly separate training from the illness-inducing LiCl injection. In their version of the task, chicks were offered a dry bead, allowed to peck, and then injected 30 min later with LiCl.…”