Fig. 7.

IA. The training apparatus was a two-compartment, rectangular acrylic chamber. A start compartment (10 × 14 × 23 cm) was painted white, illuminated with a lamp (25 W), and separated from a larger dark compartment (10 × 14 × 37 cm) by a sliding white door. The floor of the apparatus was composed of stainless steel plates that delivered a foot shock (0.7 mA, 1 sec) generated by a master shocker. For the training trial, each rat was placed in the start compartment, the sliding door opened, and the rat allowed to enter the dark compartment (all four paws inside). After a brief foot shock (0.7 mA, 1 sec) was delivered through the floor, the rat was removed immediately from the chamber. For the testing trial 24 hr later, the rat was returned to the start box, the sliding door opened, and the rat allowed to reenter the dark compartment. A higher value for the latency to enter the dark compartment during the testing trial reflected better retention. Aging resulted in a nonsignificant decrease in retention latencies, but NGF treatment caused a nonsignificant increase in retention latencies, which was intermediate between those of 23MO-CON and 4MO-CON groups. Vertical lines indicate interquartile ranges.