All experimental procedures were carried out during the light portion of the day. The experiments were designed to fully comply with the rules and regulations
set forth by the PHS Policy on Humane Care and Use of Laboratory Animals and the National Institutes of Health guide for the care and use of laboratory animals, and were approved by the Rutgers University Animal Care and Facilities Committee (P. I. Tracey J. Shors, protocol no. 98-018). Surgery was performed prior to all other experimental treatment. Rats were anesthetised with intraperitoneal sodium GKT137831 mouse pentobarbital (60 mg/kg; Nembutal, 50 mg/mL; Lundbeck, Deerfield, IL, USA). Atropine (0.54 mg/mL; Vedco, St Joseph, MO, USA) was also injected intraperitoneally to keep the rat’s airways clear during surgery. The rat was secured to a stereotaxic device (David Kopf Instruments) with blunt ear bars. A local analgesic [bupivicaine (Marcaine), 2.5 mg/mL; Hospira, Lake Forest, IL, USA] was injected subcutaneously into the site of the incision. Four screws were implanted in the skull, one in each of the four quadrants delineated by skull sutures. The skull screws were connected in pairs to serve as reference and ground for the neural recordings. Two electrodes made of Formvar-insulated nichrome wire (bare diameter 50 μm; A-M Systems, Carlsboro, WA, USA) were lowered into the right hippocampus, aiming at the dentate
gyrus (3.5–4.2 mm Crizotinib price posterior to bregma, 1.5–2.0 mm lateral to bregma, and 3.4–3.8 mm below bregma). Two bipolar electrodes made of stainless steel wire insulated with Teflon (bare diameter 127 μm; A-M Systems) were implanted through the upper right eyelid. The whole construction was cemented in place with dental acrylic mass anchored to the skull via the skull screws. Upon awakening, the rats were given a 1-mL oral dose of acetaminophen (Children’s Acetaminophen, 32 mg/mL; Rite Aid), returned to their home cages, and monitored daily for 5 days
or until they had fully recovered. In humans, TMZ (75–200 mg/m2, MRIP i.e. approximately 2–5 mg/kg) has been effectively used to treat brain tumors for over 10 years (Lashkari et al., 2011). In the experiments reported here, TMZ (Sigma) was injected once a day for 3 days, and this was followed by 4 days of recovery, for up to 6 weeks (Fig. 1). Cyclic treatment was chosen because it is the most commonly used protocol in humans (200 mg/m2 per day for 5 consecutive days every 4 weeks; Lashkari et al., 2011). Also, this treatment protocol effectively reduced neurogenesis in mice (Garthe et al., 2009). TMZ was made into a 2.5 mg/mL solution with sterile water, and injected intraperitoneally at a dose of 25 mg/kg. The dose is similar to the most commonly used dose of approximately 200 mg/m2 in humans (see Oncology Tools – Dose Calculator at http://www.accessdata.fda.gov/scripts/cder/onctools/animalquery.cfm; human weight, 65 kg; human height, 170 cm; rat weight, 0.3 kg).