Earlier this year I started taking the inactive form of B6 pyridoxine hydrochloride and found really amazing cognitive benefits. Over time (the course of several months) the effects began to fade. I figured the problem could be either 1) a down-regulation of dopamine receptors or 2) deficiency of a co-factor required for the conversion in the liver into the active form P5P. Ceasing the B6 to upregulate dopamine receptors again didn't seem to work even after 2 whole months without it, and all the suspected co-factors related to B6 that I know of (riboflavin, zinc, etc.) didn't do anything.
Eventually I decided to bite the bullet (or pill, in this instance) and try the already activated form P5P, even though I wasn't convinced that bypassing the conversion in the liver was going to do anything. What followed was an immediate restoration of ALL the positive cognitive benefits I had initially received, followed by a MASSIVE DROP in cognitive ability. Absurd headache, impaired memory (forgetting things seconds after hearing them), generally making a lot of unusually dumb mistakes at work, etc. This had NEVER been a side effect of taking the inactive B6. And now P5P only has negative effects with no benefits at all, although I've never experienced the peripheral neuropathy that some people seem to.
My question is, does anyone know of any co-factors that are necessary for proper functioning of the already activated B6? Would the liver slow down B6 conversion as a preventative measure to avoid the neurological effects of having too much circulating active B6 without adequate levels of this mystery co-factor?