Galanin is a 29-amino acid neuropeptide that coexists with acetylcholi
ne in the medial septum/diagonal band in the rat and impairs choice ac
curacy on an operant delayed-nonmatching-to-position (DNMTP) working-m
emory task. M40, a peptidergic galanin antagonist, has previously been
shown to block several physiological actions of galanin. The present
experiments tested the ability of M40 to block the effects of galanin
an DNMTP performance. M40 completely blocked choice-accuracy deficits
induced by galanin administration in both the lateral ventricle and ve
ntral hippocampus, at doses of M40 approximately 5-fold the molar dose
of galanin. M40 appears to be an effective galanin antagonist in a ro
dent memory paradigm, indicating that this compound may prove useful i
n investigating the role of endogenous galanin in learning and memory.