Rodent Biology

Question 1

What is the mouse reproduction cycle?

Answer 1

Sexual maturity: 6-8 weeks
Estrus cycle: 4-5 days
Gestation: 19-21 days
Weaning: 3 weeks

Question 2

What is the rat reproduction cycle?

Answer 2

Sexual maturity: 6-8 weeks
Estrus cycle: 4-5 days
Gestation: 19-23 days
Weaning: 3 weeks

Question 3

What is the process of mouse pups developing?

Answer 3

Day 1: very red, hairless, eyes and ears shut, milk seen in stomach
Day 3: ear flaps open, pigment develops
Day 10: fur and muscular activity increased
Day 12: Eyes mostly open and nibble food
3 weeks: Weaning and popcorn stage

Question 4

Mouse vital statistics

Answer 4

HR: 306-700bpm
RR: 85-200 b/m
Temp: 36.5*C

Question 5

Rat vital statistics

Answer 5

HR: 250-450 b/m
RR: 70-115 b/m
Temp: 36.5*C

Question 6

What are inbred and outbred strains?

Answer 6

Inbred - brother-sister mating for 20 generations (99% genetic homology)
Outbred - genetically heterozygous E.g. wistar, SD, Long evans, C57/Bl6, CD1

Question 7

What are the effects of albinism?

Answer 7

c-locus = melanocytes but no tyrosinase = light sensitive, retinal degeneration at low light (60 lux for 30 weeks = blind)

Question 8

What is coprophagy?

Answer 8

Eating own faeces = vitamins, prevention = decrease growth by 10-20%, stress

Question 9

What are the barriers to IP injections?

Answer 9

Caecum - large in rodents, if injected will have to abandon animals, can be on right/left (usually left)

Question 10

How do rodents thermoregulate?

Answer 10

No sweat glands, lick fur, change circulation to hairless areas E.g. tail

Question 11

Effects of rodent metabolic size?

Answer 11

High surface area :body volume ratios
=> dissipate body heat, compensate w/ increase metabolic rate
Scaling drug doses between species E.g. dog dose in mice = inefficacy, mouse dose in rate in dogs = toxicity

Question 12

How to house rodents right?

Answer 12

• Hygiene
• Digging, nesting, gnawing
• Enrichment

Question 13

What are the standard housing environments for rodents?

Answer 13

Light: 60/100 lux
Noise: <65DBb
Space: 100cm2/30g mouse, 330cm2 min
Head: 20-24*C
Ventilation: ~20ACH
RH: 45-65%
Disease control: SPF/Conventional

Question 14

How do pheromones affect rodent reproduction?

Answer 14

Lee-Boot effect: F no M = estrus cycles suppressed
Whitten effect: M to F group = estrus cycle synchronized
Bruce effect: New M in F group after mating = no implantation

Question 15

How to feed rodents correctly?

Answer 15

• mice and rats = same chow
• transgenic = more protein and energy
• ad libitum (obese, tumours)
• group housing = X restricted feeding

Question 16

What is the harderian gland?

Answer 16

Produce porphyrin in tears = lubrication normally but accumulate in stress

Question 17

What are the similarities and differences between rat and mouse GIT?

Answer 17

Similarities: Stomach (glandular/aglandular regions), large caecum, diffuse pancreas
Differences: Rat = no gall bladder

Question 18

What are rodent urinary systems like?

Answer 18

• More concentrated than man (mouse = 4x, rat = 2x)
• Excrete urine 1-2 drops/time
• Rich in proteins => allergenic

Question 19

How do you detect estrus cycle in mice?

Answer 19

Swollen, moist, open vaginal opening, pink

Question 20

What are copulatory plugs in mice?

Answer 20

• Made of sperm, ejaculate, and mucus that harden in cervix
• Forms after copulation, doesn’t guarantee conception
• Best done in morning

Question 21

How do you sex rodents?

Answer 21

• M = longer anogenital distance
• Nipple line in F = Day 8
• Hair between testicles and anus = Day 9
• Line between vagina and anus