Ontogenetic aspects of central cholinergic involvement in spontaneous alternation behavior

Four studies are reported examining the development of spontaneous alternation behavior in rats. Spontaneous alternation was found to increase from a rate of around 20% in 15‐16 day old rats to around 90% in 100‐day olds. Increasing the length of confinement in the 1st chosen goal arm did not affect alternation rats. Spontaneous alternation could be disrupted or facilitated in mature animals by the administration of either scopolamine hydrobromide or physostigmine sulphate, drugs which had no effect on the typical alternation pattern of 16‐day olds, but appeared to begin to have an effect at around 24 days. Dose response curves revealed certain age‐dose level interactions which were consistent with the hypothesis that cholinergic inhibitory mechanisms in the brain develop gradually in the rat.