....could you please explain how if IMI and all its metabolites are completely degraded
to CO2 in a matter of hours, how its binding could be "irreversible"? Thank you in advance!"

1.  Degradation does not occur in the synapse.  It has to diffuse out of there first.

2.  Kinetics of equilibrium will cause the IMI to dislodge from the synapse eventually, as Mark pointed out.  But it has to leave the synapse to be degraded, meaning that it first has to diffuse out.  There is a reason animals have acetylcholinesterase in their synapses....relying on diffusion to shut off the signal is not a functional solution.  Nanomolar concentrations are big when we are talking about synaptic activation.  It only takes a few molecules of IMI to mess up a synapse, and that's in the radioactive noise. (the synapse is about 20 nm across between neuronal membranes, 300-400 nm wide, and diffusion in and out of that space is somewhat further limited by membranes)

Consider curare.  It too will leave a synapse due to equilibrium kinetics.  But the physiological effects in the meantime are profound.

3.  Suchail points out that the metabolites are MORE toxic than the original IMI and are responsible for extended chronic (but not acute) toxicity.  This means the metabolites are also effective synaptic agonists.  They persist longer than the parent compound, and she doesn't discuss the implications beyond saying that they increase the chronic toxicity of IMI.  Examine figures 2 and 3.

She says:

"...in 10-day chronic toxicity studies, all imidacloprid metabolites revealed equal toxicity to bees, but the total dose ingested by the bees was about 3000-100 000 times lower than the doses needed to produce the same effect after acute intoxication." (2001) She also says "These results strongly suggest that 5-hydroxyimidacloprid and/or olefin contribute to extending the action of imidacloprid in honeybees." (2003)


May I take this opportunity to say that I am tired of being characterized as an anti-neonic activist.   I am merely pointing out that I believe we still don't fully understand what the role of neonics is within the cocktail of problems that bees are exposed to.  There are many (hundreds of) papers both good and mediocre that list pros and cons of neonics as the best available solution to pest management and beekeeping.  To say that the evidence is "overwhelming" for responsible neonic use in every circumstance is a bit overstated, in my view.  I believe neonic use should be more closely tailored to the specific environment, and I dislike prophylactic applications as wasteful and costly.  I have said this over and over, and I would appreciate it if those who attack my remarks keep in mind that this is a DISCUSSION.


Christina


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