NA-ATPASE ACTIVITY IN YOUNG CHICKS AFTER TASTE STIMULATION(, K+)

The activity of specific ouabain-sensitive Na+,K+-ATPase was studied i n crude membrane fraction of the brain of 1- to 3-day-old chicks after the administration of a chemical aversant methylanthranilate (MeA), s hown in previous behavioral studies to induce avoidance of pecking of an otherwise attractive stimulus. Enzyme activity was dramatically dec reased (by 40-50%) in the time interval between 10 min-2 h after MeA a dministration onto the tongue of awake chicks. It was possible to loca lize these changes in Na+,K+-ATPase activity into forebrain structures contained within the dorsal ventricular ridge comprising the hyperstr iatum accessorium (HA), hyperstriatum ventrale (HV), hyperstriatum dor sale (HD), and parts of neostriatum (N). In contrast, Na+,K+-ATPase ac tivity in the ectostriatum (E), the medial neostriatum (NM), and the p aleostriatal complex were unaffected. Results from experiments involvi ng preincubation of membrane fractions and with partial purification u sing detergents, suggest that some substances with inhibitory effects were produced under the effect of MeA and bound to membrane fractions in their respective areas. A similar decrease of Na+,K+-ATPase activit y as after MeA administration in vivo was observed when inhibitory med iators (GABA, glycine) were added to membrane fractions in vitro. Thes e findings may have implications for memory processing in chicks follo wing aversive learning using MeA as the aversant.