Care and Maintenance of Degus

Degu care and techniques (PDF, 1.2M): an in-depth article explaining the care of degus, husbandy, maintenance of a colony, and other techniques.

Circadian Rhythms

Tutorial on circaidan analysis using actograms (PDF, 1020K): a comprehensive article that explores the benefits of using wheel-running behavior as a measure of circiadian rhythms and explains how the actograms genrated by recorded wheel-running activty can be analyzed and interpreted.

The Clocks that Time Us (PDF, 4.9M): an excellent article that explains some of the history of the discovery of circadian rhythms, how these rhythms are observed and quantified, and the biological processes involved.

Measuring Sleep

Sleep is measured by implanting screw electrodes and a thermistor to collect brain temperature. After surgery, the animals are allotted 14 days of recovery before 7 days of habituation to the recording chamber. In the recording chamber, EEG and brain temperature are recorded. We also collect videotape recordings. The animals were individually housed on a 12:12 LD cycle at a temperature of 18± 1° C.

To make the recordings, animals are tethered to a swivel, which is attached to an amplifier. The amplifier is connected to the computer, which allows data to be amplified, digitized, and stored for the sleep scoring program ICELUS (Mark Opp, Ann Arbor, MI). Locomotor activity data is also collected by infrared devices. Data is scored manually in 12s epochs using the computer-assisted sleep scoring program ICELUS.

To analyze the data, sleep is examined across all time points then divided into time blocks for further analysis. Examining data across blocks enabled more in depth analysis of sleep-wake patterns.

Screen shot of sleep analysis:

Surgical Techniques

• Vasectomy
• Peripheral blood sampling by jugular venipuncture: used for sampling peripheral blood at infrequent intervals (daily or twice a week) or repeatedly over short periods of time (no greater than 40 samples per 24 hours).
• Peripheral blood collection via an indwelling jugular cannula: used to obtain more frequent blood samples from the jugular vein of freely moving animals kept in a pen or small room, typically at intervals of 6 minutes over a period of 6-12 hours.
• Subcutaneous Silastic estradiol implant: Introducing exogenous estradiol into sheep during our studies is required to (1) treat pregnant females with excess estradiol during critical periods of fetal development, and (2) maintain a controlled level of circulating estradiol in gonadectomized animals. We need to sustain constant blood levels of estradiol for prolonged periods (1-100 weeks) and wish to avoid repeated injections or constant infusion.
• Subcutaneous Silastic testosterone implant: Delivery of exogenous testosterone by subcutaneous implant is being investigated as an alternative to twice weekly injections for prenatal androgen treatment.
• Progesterone delivery: We have two procedures for administering progesterone (1)intravaginal devices that release progesterone, (2)subcutaneous implants. Whenever possible we use the intravaginal route of delivery because it is less invasive. We use the vaginal route to synchronize estrous cycles or in experiments where precise control of circulating progesterone is not essential. However, some experiments require a precisely controlled progesterone concentration within a very limited range and, in these instances, subcutaneous progesterone implants are the method of choice
• Intravenous, intramuscular and subcutaneous injection

Behavioural Techniques

• First 48 Hours of Maternal/Lamb Interactions: (1) number of minutes of direct nuzzling and licking contact between ewe and each lamb, (2) time until lamb stands, (3) time until first suckling bout, (4) number of suckling bouts in 48 h. In addition, the distance between lamb(s) and ewe when they are resting will be determined. The duration and number of bouts with lambs in physical contact with the ewe or more than 1 meter away from the ewe will be recorded.
• Association Preferences: record the association preferences of lambs on two days each week for 2 hours each day. The distance between each lamb and nearest neighbor(s), including ewes and other lambs, will be recorded at 15 min intervals.
• Play Behavior: recorded twice weekly for 2 hours at sunrise or sunset (when animals are most active). All events of play and the participants will be recorded by observers with an ethogram checklist. Behaviors to be recorded include: head or body butts, running/gamboling, anogenital sniffing, nudging, mounting, pawing the ground, and taking turns standing atop objects, such as hay bales.
  Sheep ethnogram (PDF, 72K)
• Weaning Induced Stress responses: A natural form of stress during a lamb’s early life is the sudden removal of the ewe during weaning at 6-9 weeks of age. We will collect the behavioral responses of the lambs before and after ewe removal. Blood samples will be collected at 3 PM the day before ewe removal, and at 10AM and 3 PM for 3 days after ewe removal
• Curiosity & Startle Responses: The umbrella test will be used to test an animal’s startle and curiosity behaviors during the juvenile period before the first breeding season, and again during the anestrous season following their first breeding season. A blood sample is collected prior to the test.
• Dominance Behavior over Food: To facilitate this analysis, twice per week the lambs will not be given free access to the feed bins containing sheep pellets at dawn. The 2 h observation period will begin by placing the feed bins into an area of the pen only available to lambs. Hand-held video camera will be used to record the behaviors at each bin continuously. All interactions resulting in displacement of an animal from the feed bin (head- or body-butts, nudges, pawing the ground or animal) will be recorded. Failed attempts at displacement will also be recorded.
• Isolation Stress Test: Animals are held in an isolation pen while housed in an indoor animal room. Initially, another familiar animal is in the room with the test animal. They are left there without food for 1 h. The bleats of the test animal are recorded for the last 20 min of the partnered period, and then the partner is removed for 2 h. The number of bleats of the now isolated test animal is recorded at 10 min intervals for 2 h. In some studies, blood samples will be collected.
• Partner Preference & Mating Test: Partner preference will be tested by introducing each ewe individually into a neutral arena that contains two pens on opposite sides of the arena. In one pen will be 3 anestrous ewes and the other pen will contain 2 rams and one anestrous ewe. The amount of time that the test animal spends in an area near each pen or the neutral area during a 3-min test will be recorded. Following the check for partner interest, the test animal will be introduced into a pen with 2 estrus ewes for 10 min to record male-typical behaviors. Lastly, the test animal will be introduced into a pen with a reproductively active vasectomized ram. The proceptive and receptive behaviors will be recorded. Each of the behavioral tests will be recorded on videotape.
• Induction of Estrus for Mating Test: Ewes that will be the source animals for mating tests with males will be brought into estrus with CIDRs and estradiol implants.

Restraint Stress

Adult female rats are paired with males for timed mating. The time of expected birth is determined by daily vaginal lavage. During the final week of pregnancy the pregnant females undergo daily prenatal stress exposure. Pregnant females are placed into a restraint device for 45 min 3 X/day at 9 AM, noon and 4 PM from days 15-21 of pregnancy (with day of mating counted as day 0).

Behavioral Circadian Analysis

Animals are placed in 26.7 x 20.3cm cages with Nalgene running wheels (9.0cm wide and 35.4cm diameter) to monitor circadian locomotor activity rhythms for twenty-four days. The first fourteen days were on a 14:10 LD schedule to acclimate the animals to the wheels. The following ten days were in constant darkness (DD) to allow free-running circadian activity. Wheel-running activity is monitored using VitalView software and hardware. Data are viewed using ActiView software. Activity data are collected in ten-minute bins.

During the LD phase, data are collected and scored for phase angle of entrained activity-onset (psi-on; the difference between the time of lights off and the time of activity onset), phase angle of entrained activity-offset (psi-off; the difference between the time of lights off and the time of activity offset), duration of activity in hours (alpha; the difference between psi-off and psi-on), peak activity (the maximum number of wheel revolutions per bin), mean activity (the average number of wheel revolutions over all bins of recorded activity per day), activity amplitude (the difference between the peak activity and the mean activity), and peak cosine (the time of day when overall activity peaks).

Data from DD are scored for duration of activity in hours (alpha; defined in constant conditions as the difference between activity onset and activity offset), peak activity, mean activity, peak cosine, and period length (tau; beginning at activity onset and ending at the nextonset of activity).

Attention Task

Sustained attention or vigilance is generally defined as the state of readiness to detect and respond to certain specified changes in the stimulus situation, occurring unpredictably and rarely. Several variables contribute to vigilance performance, including memory load, event rate, sensory modality, and temporal and spatial (un)certainty. The task we use was developed and validated by our collaborator, Dr. Martin Sarter.

in general, rats are singly housed and activity is monitored with infra-red motion detectors (IR device). Food is available ad libitum, but water is restricted to the rewards during the daily training period plus one hour ad libitum post training. Animals have been trained daily on an operant sustained attention task beginning at ZT4 (4 hours after lights on). The task requires the animals to detect visual signals presented unpredictably for a variable duration and which were randomly intermixed with non-signal trials. Animals are mildly water deprived and rewarded with waterfor reporting detection of a signal (hit) or the absence of a signal (correct rejection). Errors (misses or false alarms) do not yield consequences. An individual training session lasts about 40 min each day.

Illustration of main attention task parameters: