Passive avoidance training enhances cell proliferation in 1-day-old chicks.
One-day-old domestic chicks were injected i.p. with bromodeoxyuridine (BrdU) before training on a one-trial passive avoidance task where the aversive experience was a bead coated with a bitter tasting substance, methyl anthranilate (MeA). Animals were tested 24 h later; those avoiding (if MeA-trained) or pecking if water (W)-trained (which they peck appetitively), along with a group of untrained naïve chicks, were used to determine cell proliferation either 24 h or 9 days post BrdU injection. In all three groups, BrdU positive cells were identified sparsely throughout the forebrain but labelling was pronounced around ventricular zone (VZ) surfaces at both 24 h and 9 days post-BrdU-injection. Double immunolabelling with neuronal specific antibodies, to either NeuN, or beta-tubulin III, confirmed that most BrdU labelled cells appeared to be neurons. Unbiased stereological analysis of labelled cells in selected forebrain areas 24 h post BrdU injection showed a significant MeA-training induced increase in labelled cells in both the dorsal VZ surface bordering the intermediate and medial hyperstriatum ventrale (IMHV) and the tuberculum olfactorium (TO). By 9 days post-BrdU-injection, there was a significantly greater number of BrdU labelled cells in MeA-trained birds within the IMHV, lobus parolfactorius (LPO) and TO. These results demonstrate that avoidance training in 1-day-old chicks has a marked effect on cell proliferation, in the LPO and IMHV, regions of the chick previously identified as a key loci of memory formation, and in a second region (TO), which has olfactory functions, but has not been previously investigated in relation to avoidance learning.
Dermon
C R
CR
Department of Biology, University of Crete, 71409, Greece.
Zikopoulos
B
B
Panagis
L
L
Harrison
E
E
Lancashire
C L
CL
Mileusnic
R
R
Stewart
M G
MG
D000818:Animals; D000831:Animals, Newborn; D001362:Avoidance Learning / Q000502:physiology*; D001973:Bromodeoxyuridine; D002455:Cell Division / Q000502:physiology; D002645:Chickens; D007150:Immunohistochemistry; D009473:Neuronal Plasticity; D009474:Neurons / Q000166:cytology*; D016548:Prosencephalon / Q000166:cytology* / Q000502:physiology*; D013997:Time Factors
D001973:Bromodeoxyuridine