NADPH DIAPHORASE (NITRIC-OXIDE SYNTHASE) IN A PART OF THE CHICK BRAININVOLVED IN IMPRINTING

The intermediate and medial part of the hyperstriatum ventrale (IMHV) is a memory system in the chick forebrain in which certain learning-re lated changes occur after imprinting. We have enquired whether NADPH-d iaphorase, a presumed marker for nitric oxide synthase, is present in sections through the IMHV of chicks, either trained with an imprinting stimulus or dark-reared. Very few NADPH-d-positive cells were found i n the IMHV (0.37 +/- 0.07 S.E.M. cells per 0.3 mm X 0.9 mm sampling fr ame), in contrast to the palaeostriatum augmentatum (PA) (19.47 +/- 0. 77). Some stained cells in the PA were closely associated with blood v essels. The results do not support the hypothesis that learning-relate d changes in the IMHV depend on nitric oxide acting as a retrograde ne uronal messenger.