Hi all,
I recently begin to learn single-unit recording in the primary visual cortex of mouse brain using tungsten electrodes. Sometimes (but not very often), there is significant bleeding during when I try to remove the skull and the meninges, but in all the cases the vessels eventually stopped to bleed. I wish to know how will bleeding affect neurons nearby? Will neurons die because they have less O2 and glucose supplied?
Blood on the electrode will increase the impedance and decrease the signal to noise ratio. Blood in neural tissue will cause irritation and aberrant acitvity, due to compounds such as glutamate. Bleeding is therefore better avoided. For acute experiments you can put a ligature around the lateral sinus and the blood will drain to the opposite jugular vein. Puncture of the sinus is the main cause of bleeding when recording from the visual cortex.
Dear Zhou,
That will depend on the level of tissue and bleeding. If there is significant level of blood supply to the area that you are recording from, the reduction in local oxygen supply can cell death. Another factor is the swelling associated with damage to the Pia mater and damage other tissue ( interstitial) damage. Usually as you go down with your electrode you should be able to see/hear (from amplifier) discharges of damaged neurons. If your electrode tip is not blocked and you hear/see no discharges at all. That is bad news, meaning substantial damage. That is what I used to do in my studies, for an example see below.
Best wishes,
Refik
Article A comparative study of pre-sympathetic and B??tzinger neuron...