Hippocampal dynorphin B injections impair spatial learning in rats: a κ-opioid receptor-mediated effect

• Published in: Neuroscience 1998, Vol.85 (2), p.375-382
• Main Authors: Sandin, J, Nylander, I, Georgieva, J, Schött, P.A, Ögren, S.O, Terenius, L
• Format: Article
• Language: English
• Subjects: Animals; Behavior, Animal - drug effects; Dose-Response Relationship, Drug; dynorphin; Dynorphins - administration & dosage; Endorphins - administration & dosage; FARMACI; hippocampus; Hippocampus - drug effects; kappa-receptors; Male; Maze Learning - drug effects; MEDICIN; Medicin och hälsovetenskap; MEDICINE; Microinjections; Naltrexone - administration & dosage; Naltrexone - analogs & derivatives; nor-binaltorphimine; PHARMACY; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa - antagonists & inhibitors; Receptors, Opioid, kappa - physiology; Spatial Behavior - drug effects; spatial learning
• ISSN: 0306-4522; 1873-7544; 1873-7544
• DOI: 10.1016/S0306-4522(97)00605-2

The hippocampus plays a central role in the acquisition and storage of information. Long-term potentiation in the mossy fibre pathway to the CA3 region in the hippocampus, an animal model of memory acquisition, is modulated by dynorphin peptides. This study investigated the possible role of hippocampal dynorphin in spatial learning. Male rats were trained in the Morris Water Task after microinjection with different doses of dynorphin B (1, 3.3 or 10 nmol/rat) or artificial cerebrospinal fluid (as control) into the CA3 region of the dorsal hippocampus. Dynorphin B was found to impair spatial learning at all tested doses. The synthetic κ 1-selective opiate receptor antagonist nor-binaltorphimine (2 nmol) also given into the hippocampus fully blocked the acquisition impairment caused by dynorphin B (10 nmol), while nor-binaltorphimine alone did not affect learning performance. These findings suggest that dynorphin peptides could play a modulatory role in hippocampal plasticity by acting on hippocampal κ-receptors and thereby impair spatial learning.