Effect of stress-related hormones on short term memory.

Adrenocorticotropic hormone (ACTH)1-24, ACTH4-10, corticosterone (CS) or arginine vasopressin (AVP) was administered subcutaneously to one day-old chicks immediately after learning a single trial passive avoidance task. Chicks were pretreated with 2 mM KC1 or 4 mM monosodium glutamate 5 min before learning. With KC1 or monosodium glutamate alone, no evidence of memory was observed on retention tests carried out as early as 5 min and as late as 24 h postlearning. However, the addition of ACTH1-24, ACTH4-10 or AVP to KC1-pretreated animals yielded normal retention levels up till 10 min, 10 min and 20 min after learning, respectively. Similar results were obtained with ACTH1-24 and AVP given to glutamate-pretreated birds. CS had no effect on KC1- or glutamate-induced amnesia. The calcium channel blocker, lanthanum chloride, also inhibited the formation of short-term memory, with amnesia still present as late as 24 h following learning. ACTH1-24, but not CS or AVP, yielded normal retention levels until 10 min postlearning in the presence of lanthanum chloride. Thus ACTH1-24 and AVP can overcome KC1 or glutamate inhibition of STM formation but will not prevent subsequent amnesia. The mechanisms underlying this action of ACTH1-24 and AVP are different. The possibility that the effect of ACTH1-24 is related to the role of calcium in STM formation is explored.