Adrenocorticotrophic hormone and melanocyte stimulating hormone do not affect performance in hippocampus-lesioned or...

Pigeons, given bilateral lesions of the hippocampus, as well as unoperated control subjects, were trained on an operant task in which they had to peck a left hand key if both members of a successively presented stimulus pair were the same, and a right hand key if they were different. During extensive training, the 'same' pairs (green-green or red-red) were presented at twice the frequency of the 'different' pairs (green-red or red-green), thus biasing responding to the left hand key. The effects of intramuscular (i.m.) injections (0, 10 and 100 micrograms/kg) of an active fragment of adrenocorticotrophic hormone (ACTH4-10) and alpha-melanocyte stimulating hormone (MSH) were then studied. On any given test (peptide or saline) day, all stimulus pairs were presented with equal frequency. Although the control birds' performance was consistently better than the lesioned birds, neither ACTH4-10 nor MSH affected performance under any conditions. It is concluded that peripheral injection of these peptides has little, if any, effect on cognitive behaviour in birds.