I am recently new in trying my hand at fiber photometry, but recently implanted fiber optics as well as viruses to monitor both dopamine and serotonin neurotransmission. I successfully implanted two fiber optics, injected the virus bilaterally, and added screws in the skull to reinforce their placement. The screws were placed deep enough to hold in the skull, but not so deep as to be flush against the surface of the skull. Three screws were put into place (one approximately 5 mm posterior from the injections), two screws ~1 mm anterior from the injections. After implanting the screws and optics, I briefly scoured the skull with a drill bit to provide a rough surface and applied the dental cement. These dental cement caps were secure 2 months following surgeries until I attempted to record from these animals.
My problem is, when I went to attach the optic cables to the implanted fibers, the caps popped off. It was also difficult to secure the plastic sleeves that are designed to cover half of the optic cable, and half of the fiber optic to prevent bleed-through of light onto the implanted optics. (I'm wondering if an excess build-up of dental cement surrounding the fiber optic made this difficult). However, the caps still should not have popped off as I attempted to attach these cables.
Does anyone have any advice for successfully ensuring that these "caps" remain attached to keep the fibers in place while attaching the optics?
Hi Kimberley,
This is a common problem with implanting optic fibres. I’ll try to give some possible ideas for troubleshooting, and it’s great how much info you‘ve provided.
1. On a general note, this does happen sometimes, regardless of how experienced you are, so you need to do more than 2 animals.
2. Why did you leave them 2 months? The longer you leave them, the more likely they will loosen. If you’re using AAV’s to insert you sensors, they usually have good expression after a couple of weeks (in my experience).
3. It’s good that you scoured the surface with a drill bit. I would do that before putting screws in so that you can be sure to clear the entire surface. And be thorough, this is an important step. FYI I only ever put in a single screw, and have minimal problems. Also, some of my colleagues would dab superglue round the edge of the cement to “seal” the edge. I didn’t do that, but it‘s worth a try if you’re still having issues.
4. What kind of cement did you use? I had real issues with the old powdered dental cement we had. Then we switched to a more modern light-cured cement and my problems all but disappeared.
5. What fibres did you use? I had real issues with ceramic fibres gripping the mating sleeve too tight and being ripped out. I would suggest using steel cannulae.
I hope some of these suggestions might be useful. Feel free to message me if you want to discuss further.
Best of luck!
Nic
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