Ontogenetic and Imprinting‐Induced Changes in Chick Brain Protein Metabolism and Muscarinic Receptor Binding Activity

Abstract

Over the 20-min period following exposure of young chicks to a flashing light as an imprinting stimulus there is an increased incorporation of [14C]leucine into an acidic (tubulin-enriched) protein fraction of the anterior dorsal forebrain in birds which have learnt the characteristics of the stimulus as compared with, either birds which have been exposed to an imprinting stimulus but learn poorly, or chicks kept in the dark. This brain region has been implicated in several studies as the locus for a number of biochemical modulations that accompany learning. The amount of [14C]leucine incorporated does not seem to be determined by precursor pool availability; it does, however, correlate with a well-validated measure of the extent to which birds have learnt to recognise the characteristics of the stimulus, as shown by a two-choice discrimination test. There is no change in the total content of tubulin dimer as assayed by colchicine binding under these conditions. Additionally, in birds which show evidence of learning, the binding of quinuclidinyl benzilate, an irreversible muscarinic ligand, is altered in both the posterior dorsal forebrain and midbrain regions. None of these effects could be simply the result of visual stimulation. The meaning of these changes is discussed.

Effects of nefiracetam, DM-9384 on amnesia and decrease in cholineacetyltransferase activity induced by cycloheximide

“…The dysfunction of GABAergic and cholinergic neuronal systems plays an important role in the CXM-induced memory impairment of the passive avoidance task, since GABA agonists and acetylcholine (ACh) esterase inhibitors attenuate CXM-induced amnesia . Furthermore, there is much evidence that 3,-aminobutyric acid (GABA) play a role in the regulation of brain protein synthesis (Tapia et al, 1967;Sandoval et al, 1976), and that the cholinergic neuronal system is involved in the formation of memory (Rose etal., 1980;Longstaff and Rose, 1981;Sershen etal., 1982).…”

Altered Colchicine‐Binding Capacity in Chick Brain Regions: Relationship to Intensity or Information Content of Visual Input

“…In addition to describing a relationship between tubulin content and light conditions, Rose et al studied cerebral tubulin in relation to various behavioral paradigms in the chick. Colchicine binding activity was elevated in the anterior dorsal forebrain after passive avoidance learning (Mileusnic et al, 1980) but not after imprinting toward a flashing light or training in a two-way discrimination task (Longstaff and Rose, 1981).…”

Molecular approaches to learning and memory.

“…Other investigators [ 12,29,42] have also suggested the involvement of cholinergic synapses in the forebrain roof of chicks in the development of imprinting behavior, based on their findings that the activities of ChAT, AChE, and QNBbinding sites are elevated after the establishment of imprinting behavior.…”