Technical Support: Tethers

How do Instech's tethers compare to standard jacket tethers, such as those made by Lomir Biomedical and Alice King Chatham Medical Arts?

The constraining nature of standard jacket tethers has been shown to induce stress and alter normal behavior in rats. Jacket tethers also require a bit more maintenance as they need to be adjusted for changes in body size and replaced when the rats damage them by clawing and biting. In comparison, all of Instech's tethers have been carefully designed with the animal's comfort in mind. This leads to lower equipment costs, less time spent replacing tethers, and better research results.

What is the best tether for rats?

Instech offers 3 primary types of tethers for rats: button tethers, head block tethers, and harness tethers. Head block tethers are mostly used for microdialysis while button and harness tethers are used for standard infusion or sampling. Within button tethers, Instech offers 2 standard types: a reusable plastic button and a single-use Dacron mesh button. Dacron mesh works well for longer-term studies (more than 1 week), as the tissue will grow into it and form a strong connection. Our plastic button is typically used in short- to medium-term studies. The big difference between button and the harness tethers is that buttons usually need to be surgically implanted, whereas harnesses do not.

My rats don't seem to like the infusion harness. Why is this?

It's important to install the harness correctly, otherwise it can bother the animal. First, make sure the harness is oriented correctly: the piece of tubing that joins the belly bands under the animal should be running parallel with the animal's spine. Second, make sure it's not too tight. You should leave enough slack so that you can easily fit your index finger between the belly bands and the animal.

What is the best tether for mice?

Most researchers conducting standard infusion work now use our CIH62 infusion harness with a swivel that is mounted in a counter-balanced lever arm to take the weight of the tether off the mouse. The polysulfone button tether with a piece of Dacron mesh (LW62) is an alternative. For microdialysis, most researchers use the MINF head block tether.

Why are there couplers on your polysulfone and Dacron mesh button tethers?

They make removing and reattaching the tether easier. You can leave the coupler off and attach the spring directly to the button if you want to.
How can I store the tether after the button has been attached to the animal but before the tether has been attached to the swivel? [USER TIP]
Detach the spring at the coupler. Drill a .120" hole (for PS95) in a ping pong ball, stuff the catheter inside it, and place it over the 1 inch piece of coupler spring that remains attached to the button and the animal.

Can I use a "shoebox" type cage with a swivel and tether system?

We do not recommend using a swivel in a fixed mount on a shoebox-type cage because the tether can become tangled or caught on a water bottle. Instead, use our single-axis counter-weighted arm to remove slack from the tether as the animal moves around, without restricting the animal's movement.

Can you provide me with a complete system - cage and all?

Yes, we can work with cage manufacturers to deliver you a complete, ready-to-use system. Call for more details.

Do your spring tethers come in lengths other than 1 foot?

Yes, we can cut custom lengths of most spring up to 4 feet long.

Why do I need to put a spring around the cannula anyway?

The spring protects the cannula and transmits torque to the swivel. We offer spring stock in a range of sizes and stiffnesses.

What type of catheters do you recommend using with your system?

Most customers make catheters from polyethylene or silicone tubing. Call us for information on reliable sources of preformed catheters for specific protocols.

Are your tethers reusable?

All of our tethers except for our Dacron-mesh buttons are reusable. If part of your tether is lost or damaged, you can purchase replacement parts.

Are your tethers autoclavable?

Yes, all of our tethers are autoclavable.

On your polysulfone and Dacron tethers, how do I separate the spring from the button?

Twist the spring clockwise for both attachment and removal. This compresses the spring so that you can pull it out or push it in easily.

Is there a way to take an NMR image of a tethered animal?

Use our beryllium-copper spring stock (PS95BC) with a polysulfone or Dacron-mesh button.