The opioid peptide dynorphin(1 - 13) impairs memory formation in chick
s (5). We examined whether this occurs for both aversively and appetit
ively motivated learning. Four-day-old chicks were injected with dynor
phin(1-13) into the intermediate medial hyperstriatum ventrale and tra
ined on either a peck avoidance (PA) or an appetitive discrimination (
AD) task; 2-day-old chicks were trained on PA. In 2-day-old chicks, dy
norphin was amnestic for PA at 0.0 1, 0.03, or 0.1 mM. In 4-day-old ch
icks, dynorphin impaired memory formation for PA at 0.1 mM, and for AD
training at 0.03 mM. Thus, similar doses of dynorphin impair memory f
ormation for both appetitive and aversive conditioning.