Effect of adrenocorticotropic hormone on appetitive discrimination learning in the rat

Influence of MSH and corticosterone on stimulus control over an operant response

Several previous papers have indicated that MSH/ACTH-like neuropeptides facilitate the reversal of brightness discrimination in a runway task. The present experiment was undertaken to explore the development during both acquisition and reversal of stimulus control over an operant response. Male albino adult rats were treated daily with either 10 micrograms of MSH, 500 micrograms of corticosterone or a placebo in a double blind procedure during the establishment of an on-light control over availability of reinforcement. Having completed this regime the conditions were reversed so that reinforcement was present only when the chamber-light was off. The results indicated that treatment with MSH during acquisition produced a significant decrease in % correct responses compared to animals treated with either the placebo or corticosterone with neither of these latter groups differing from the other. During the reversal phase of training there was a trend for both MSH and corticosterone to lower % correct responses. The discussion focuses on other literature which has shown opposite effects of corticosterone on aversive and appetitively motivated tasks.

Infantile spasms: some new theoretical aspects

Infantile spasms begin in a very active phase of brain development. The new neuropathological techniques have shed light on changes in the fine structure of brain in children with infantile spasms. An understanding of the action of adrenocorticotropic hormone on the biochemistry and development of the brain provides, in an indirect way, a partial explanation of the biochemical events in this syndrome; most of these actions are well documented in animal experiments. Some anticonvulsants are also effective in treating infantile spasms, and modern research has explained many actions of these agents as well. The principal mechanism causing retardation in most children is unknown. Some future aspects of the research are reviewed.