Surgery free rat closed head repetitive mild injury model of traumatic brain injury
vedad.delic
Abstract
This is a surgery-free closed head weight drop injury protocol for repetitive mild TBI of adult rats. The model consists, of a guide tube and weight cylinders that deliver an injury to the calvarium of an anesthetized rat in prone position on a sponge causing rotational acceleration.
Rats typically recover without incident with the most common adverse occurrence being a nose bleed. 4 injuries 2 weeks apart with 1.5 kg weight did not result in detectable pathology, but 8 injuries resulted in regional astrogliosis, microgliosis, encephalomalacia, without overt motor deficits.
Steps
Apparatus Setup
Ensure that the TBI platform is stable with pin in the 5th hole from the bottom
25 cm height.
Load weights. If loading multiple weights into the guide tube, load smaller weights first to ensure proper balance.
Turn on Isoflurane system with following settings:
- Open O2 gas tank connected to apparatus
- Turn knob to 4-5% v/v for isoflurane
- Gas delivery rate to 1.5 L/min for O2
- Turn on valve for gas delivery to gas chamber and wait at least 10 seconds for chamber to fill before placing animal in
Delivery of hit
Anesthetize the animal for 2 minutes in the gas chamber. Must be full anesthetized as to not respond to toe pinch.
- Good time to weigh the rat
Place anesthetized animal carefully into a decap cone and then under the weight-drop apparatus so that the top of the skull completely underneath the guide tube covering the entire calvarium. Arrange body in prone position on sponge. The guide tube should be lightly touching the head while the animal is on the sponge underneath.
- Ensure that the rat forelimbs are folded back and that the tongue is not between incisors.
Pull the pin to release weights
quickly retract weights up the guide tube using the attached string
Place animal in recovery cage on its back, and time for the righting reflex
Recovery observation
Full recovery
- Quickening of breath
- rat has righted itself completely with paws underneath he body
- if minor bleeding present, it has rapidly resolved
- Once fully recovered place rat in home cage
- observe rats for 3 days, twice a day for continued signs of recovery
Not recovering
- no breathing for more than 30s (rapid color change in tail, snout, paws)
- very labored breathing that is not improving
- seizures
- profuse bleeding
- rat not woken up and not righted within 10 minutes
- Euthanize rat
