Rat Biology / Environment

Rats Macro Environment

Tem: 70-76

humidity: 30-70%

Ventilation: 10-15

Light cycle: 12- 14 hr

Dark cycle: 10-12 hr

Light intensity: 130 - 325 lux (prevent retinopathy)

Rat primary enclosure material

polycarbonate / polypropylene (autoclavable / can see through)

Norway rat description

Rattus Norvegius, tail 85% body, smaller tail and ears compared to black rat (Rattus rattus)

Chromodacryorrhea

porphryn stainning of eyes from harderian glan

Orbital plexus species

FROG:

Ferret

Rat

Oppossum

Guinea pig

Rat Vision type

dichromatic

Rat ocular range sensitivity

505 -509 nm

Rat hearing range

250 - 80 HZ

Rat most sensitive hearing range

8 - 32 HZ

Rat ultrasonic range of hearing for communication

22- to 80-kHz range is used for a variety of positive and negative communications, such as those emitted by pups left alone by their dam, or by adults during sexual and aggressive behavior

Rat Salivary Glands

Paired:

Parotid

Submandibular (mixed glands)

sublingual (mucous producing)

hybernating glands (fused brown fat with all glands)

Margo plicatus

separation glandular pyloric region and nonglandual cardiac region in stomach

Why can’t rats vomit?

1. lack anatomical or neuro components for vomiting reflex (most important)

2. Margo plicatus

Rat liver

4 lobes and no gall bladder

They Cant Get Water From Heaven (what rats do not have)

Tonsils

Costal Cartilage

Gallbladder

water taste receptors

Foramen of magendie

Haversian Canals

Species without gall bladder

Rat

horse

elephant

dolphin

pigeon

white tailed deer

European hamster

Chinese hamster

White tailed rat

Rat lungs

single left, four right

Geniturinary system

Male: bulbourithrogland (cowpers gland), seminal vesicles, and prostate

Female: bicornate uterus

CHOWRR (animals with bicornate uterus)

chinchilla, hamster, opossum, wood chuck, rat, rabbit

Kidney anatomy and research

Unipapillate (good for kidney cannulization and nephron transport)

Why is rat not good candidate for heart studies?

Atria blood supply is extracoronary from sublclavian and internal mammary vessels. Thus bad

Rat diet classification

natural ingredient (most common)

purified (single nutrient class diet)

chemically defined (costly and often unpalatable)

What diet is used for toxicological studies for good laboratory practice studies?

Certified natural ingredient

Most commonly used purified diet?

AIN-76

Body temp range rat

99.5 F

rat puberty, gestation, eyes open, weaning ages

Puberty (50 +- 10)

gestation (21 - 23 days)

eyes open (10-12 days)

weaning (21 days)

food and water consumption

5 g / 100 g body weight (food)

8 - 11 mls / 100 g body weight

Blood volume

6 ml / 100 g

Vaginal plate facts

1. born with it

2. cornify and degenerate at 20 -35 days

3. completely gone 40 - 80 days

Estrus / puberty facts

Estrus starts before puberty and can occur as early as 35 days, puberty can take 2 to 3 months

estrus cycle is 4 to 5 days, nonseasonal, for 4 days as an example, each stage of estrus lasts one day (estrus, metestrus, diestrus, proestrus)

Proestrus, uterus balloons (can be mistaken for hydrometra)

Ovulation: 8 - 11 hrs, during estrus, between midnight and 2 am usually. Ova remain viable for 10 - 12 hours

rat testical timeline facts (15,45,65,75)

1. Testes descend 15 days

2. Sperm produced at 45 days

3. fertility of spern at 65 days

4. Maximal sperm production 75 days

Confirmation of coitus

1. vaginal smear with sperm

2. observation of vaginal plug

3. observation of sexual behaviour

Parturition

21 to 23 days after coitus

Detection of estrus in rats

1. quivering ears when back and head stroked

2. lordosis (sway back) when pelvic area stimulated (Blandau test)

3. Vulva swollen and vagina is dry in appearance

4. vaginal cytology: 25 - 100% cornified epithelium cells

Why shouldnt you use a probe to assess for pregnancy in rats?

DONT USE VAGINAL PROBE AS IT CAN CAUSE PSEUDOPREGNANCY

Pregnancy rates are higher outbred or inbred strains?

Outbred (85% success rate)

Pregnancy detection in rats

1. after 10 days, can palpate fetuses

2. detect fetal heartbeat with dopler at 12 days

3. 14 days, mammary glands and nipples develop

How does chronic exposure to light effect pregnancy?

1. persistent estrus

2. ovarian cysts

3. conversion to corpus luteum

4. ovarian atrophy

5. early vaginal opening

What can persistent high temperature do to male rats?

can result in infertility due to irreversible degneration of seminiferous tubules.

Detection of Parturition

increased nest building 5 days prior to parturition

New born rat pup characteristics

1. atricial (require maternal care)

2. Closed ear canals

3. blind

4. hairless

5. can vocalize immediately at birth

6. poorly developed limbs and small tails

New born pup development

1. ears open 2.5-3.5 days, hearing starts at 9 days

2. eyelids open 14 - 17 days

3. fully haired at 7 - 10 days

maternal antibody transfer in rats

low rats at birth, maximize at 14 days and occur until 21 days (when gut closure occurs)

Micturition reflex in rats

not fully matured until 14 days, require maternal stimulation.

sperm collection, articifical insemination and embryo transfer facts

1. electro ejaculation possible (but sperm coagulate quick). Seminal vesicle dissection most common for collection

2. Artificial insemination: must induce psuedopregnancy first, embryo transfer used to eliminate pathogens in breeding lines

3. Use pregnant mare serum gonadotropin then human serum gonadotropin for superovulation

4. embryos collected 1 to 5 days after breeding, suspended in bovine serum albumin then transferred to a pseudopregnant mare

5. Nonsurgical transfer using a otoscope in the cervix has been reported.

6. Embryos used for testing human IVF drugs.