Subjects. Subjects were 24 female C57BL/6J mice (Harlan, UK), weighing 15-21 g at arrival (8-9 weeks). The mice were housed one per cage after the operation. The environment conditions were controlled and constant (21°C±1°C, humidity at 50%±10%, light period 0700¯1900 h). Food and water were available ad libitum.

Surgery. Hippocampal lesions were performed on 12 of the mice when they were 12 weeks old. Lesions were made by injection of NMDA. Sham-lesioned mice received skull incision and craniotomy but no intracebral. Mice were anaesthetised with Avertin (tribromoethanol) intraperitoneally (approx. 20ml.kg). Four holes were drilled on each side of the sagittal suture at the appropriate coordinates. For sites 1, 2 and 3 (1: AP(+) 1.8, L(+/-) 1.5, V(-) 1.8, and 2: AP(+) 1.3, L(+/-) 1.8, V(-) 2.0, and 3: AP(+) 0.7, L(+/-) 2.4, V(-) 2.0 relative to the inter-aural zero) an injection of 0.10ml were given. For site 4 (AP(+) 0.7, L(+/-) 3.1, V(-) 3.5 relative to the inter-aural zero) the volume of the injection was increased to 0.20ml. Each injection lasted for 60 sec, after which the needle was left in place for another 60 sec. It was then raised 0.2 mm (o.5 for site 4) and left for a further 3 min before full retraction. Injections were made with a 5ml Hamilton syringe, adapted with a 34 gauge stainless steel needle. Finally the scalp was sutures and the animal placed in a temperature (30°C) controlled recovery chamber until it regained locomotor ability. The mice were rehoused in groups of six after recovery from the amaesthetic, and given 10% glucose in the drinking water for 2-4 days afterwards. The mice were allowed to recover from the surgery for 2 weeks before starting the first experiments.

Results. ns were made by injection of NMDA. Sham-lesioned mice received skull incision and craniotomy but no intracebral. Mice were anaesthetised with Avertin (tribromoethanol) intraperitoneally (approx. 20ml.kg). Four holes were drilled on each side of the sagittal suture at the appropriate coordinates. For sites 1, 2 and 3 (1: AP(+) 1.8, L(+/-) 1.5, V(-) 1.8, and 2: AP(+) 1.3, L(+/-) 1.8, V(-) 2.0, and 3: AP(+) 0.7, L(+/-) 2.4, V(-) 2.0 relative to the inter-aural zero) an injection of 0.10ml were given. For site 4 (AP(+) 0.7, L(+/-) 3.1, V(-) 3.5 relative to the inter-aural zero) the volume of the injection was increased to 0.20ml. Each injection lasted for 60 sec, after which the needle was left in place for another 60 sec. It was then raised 0.2 mm (o.5 for site 4) and left for a further 3 min before full retraction. Injections were made with a 5ml Hamilton syringe, adapted with a 34 gauge stainless steel needle. Finally the scalp was sutures and the animal placed in a temperature (30°C) controlled recovery chamber until it regained locomotor ability. The mice were rehoused in groups of six after recovery from the amaesthetic, and given 10% glucose in the drinking water for 2-4 days afterwards. The mice were allowed to recover from the surgery for 2 weeks before starting the first experiments.

Discussion. ns were made by injection of NMDA. Sham-lesioned mice received skull incision and craniotomy but no intracebral. Mice were anaesthetised with Avertin (tribromoethanol) intraperitoneally (approx. 20ml.kg). Four holes were drilled on each side of the sagittal suture at the appropriate coordinates. For sites 1, 2 and 3 (1: AP(+) 1.8, L(+/-) 1.5, V(-) 1.8, and 2: AP(+) 1.3, L(+/-) 1.8, V(-) 2.0, and 3: AP(+) 0.7, L(+/-) 2.4, V(-) 2.0 relative to the inter-aural zero) an injection of 0.10ml were given. For site 4 (AP(+) 0.7, L(+/-) 3.1, V(-) 3.5 relative to the inter-aural zero) the volume of the injection was increased to 0.20ml. Each injection lasted for 60 sec, after which the needle was left in place for another 60 sec. It was then raised 0.2 mm (o.5 for site 4) and left for a further 3 min before full retraction. Injections were made with a 5ml Hamilton syringe, adapted with a 34 gauge stainless steel needle. Finally the scalp was sutures and the animal placed in a temperature (30°C) controlled recovery chamber until it regained locomotor ability. The mice were rehoused in groups of six after recovery from the amaesthetic, and given 10% glucose in the drinking water for 2-4 days afterwards. The mice were allowed to recover from the surgery for 2 weeks before starting the first experiments.