omega-Conotoxin GVIA disrupts memory formation in the day-old chick.

Calcium channel antagonists have previously been shown to alleviate age-associated reductions in memory acquisition and enhance retention for a number of different tasks. We have investigated the effects of pretraining injections of nifedipine, nimodipine, and amlodipine (L-type calcium channel antagonists) and omega-conotoxin GVIA (an N-type calcium channel antagonist) on passive avoidance and visual discrimination learning in day-old Ross 1 chunky chicks. None of the L-type calcium channel antagonists at any time or dose tested caused amnesia for the passive avoidance task or enhanced weak learning, and nifedipine did not affect acquisition or retention of the visual discrimination task. However, pretraining bilateral intracerebral injections of 1.25 pmole/hemisphere omega-conotoxin GVIA produced amnesia for the passive avoidance task in chicks tested 30 min or 3 h after training. The same dose of omega-conotoxin GVIA significantly reduced the rate of acquisition of the visual discrimination task, but did not affect retention of the task when tested 30 min or 3 h after training. These data indicate that calcium uptake via presynaptic N-type omega-conotoxin-sensitive but not L-type dihydropyridine-sensitive calcium channels is necessary for memory formation in young chicks.