(options)
Animals
Primigestational, Sprague Dawley rats, (N=30) will be brought to our animal facility on pregnancy day 15. Rats will be housed in individual transparent polycarbonate cages (46×25×20 cm) from the time they arrive. Rat chow (distributed on cage floors) and water from spigots, will be accessible through a small hole in the back of each cage, and will be available ad libitum. Animals will be monitored daily until parturition.
Procedures
In phase 1, primiparous mothers will be randomly assigned to three groups. In Group 1, 5 rat mothers will be injected 0.4 ug of oxitocin in 10ul of normal saline (pH 5.0). Oxytocin has shown to increase maternal behaviors in rats. In One group will receiveGroup 2, 5 rat mothers will be injected an OT analogue antagonist, d(CH2)5–8-ornithine-vasotocin, which has been shown to reduce maternal affiliative behaviors towards their pups. In A second group will receive oxytocin, which has been shown to increase maternal behaviors in virgin rats. Group 3, (control) 5 rat mothers will be injected 10ul of saline solution as control . A third control group will receive a saline solutions.Injections will be administered f ollowing delivery, immediately after the expulsion of the first pup, from postpartum day 1 to 7.
Behavioral Observations
Litters will be culled to 6 pups with as even sex distribution as possible. Beginning at postpartum day two events in each dam’s homecage will be videorecorded. using 2 camcorders with mirrors placed so that the reflection of events will be captured from 2 angles. Using Noldus, The Observer Software, four daily 15 minute segments will be used to code mother and pup behaviors. Each 15 minute segment will be coded in 15 second intervals. Mother and pup behaviors will be coded using a pre-defined dictionary of behaviors. Definitions of mother behaviors will include will include pup licking, scratching, upright posture over pups, prone on pups, retrieving, regrouping, nest building. Trained observers will be blind to the experimental treatments, and 10% of the videotapes will be double coded to test for inter-observer reliability.
Mother-child interactions will be observed during this first phase as it is expected that there will be variations due to treatments. If this variation is systematic, it is expected that it will have an effect on infant developmentIn phase 2, after infants have been weaned and at xx day of developmentpostnatal day 25–30, they will be anesthetized with ketamine (70 mg/kg) and xylazine (7 mg/kg) and microelectrode arrays and/or be inserted the nanoprobes will be implanted in the nucleus accumbens, VTA and prefrontal cortex (as routinely done in the O’Donnell lab). Following a one-week recovery, multichannel recordings will be conducted during a task testing and invivo recording of the following neuronal groups will be
reward using a concurrent random interval procedure in which choices will be offered varying in reinforcer magnitude and delay.
