Mark,

Good points.   In animals, "irreversible receptor binding" is usually taken to mean the receptor will not recover, because either there is no metabolic breakdown in the synapse (thus releasing the ligand from the receptor), and/or binding to the receptor is chemically irreversible (binding affinity is very high--makes covalent bonds or the like) and will not go away until the neuron is dead.  If there is no mechanism for clearance, the ligand won't leave the synapse once it is there.  That means "cumulative" to us, because continued exposure will bring in more molecules, and the ones there don't leave because they are bound to the nACh receptors and don't degrade.

Except for the Colorado potato beetle, I don't know of any literature telling how other insects (including bees) detoxify/metabolize neonics.  I also haven't looked to see if anyone has measured the half-life of the compound within the bee.  It is interesting, however, that these compounds often last for years in the SOIL, where the world's greatest decomposers...the fungi...reside.  If the fungi can't do it....I wonder how the bees could clear or break down the compound?  Well, the beetles can.  Damn them.  (I hate hive beetles.)  So it seems more than likely to me that the coumaphos and neonics, once in the bee, can stay there til "death them do part" from the bee.

The intended pest targets of these chemicals clearly can't break them down, or they wouldn't work anymore.

Also, there are nACh receptors in lots of places besides the brain.  This study, in my opinion, is more valuable for demonstrating that neonics and organophosphates do, in fact, behave as we predicted at the nACh receptor of the honeybee, than it is valuable for saying that this happens in the mushroom bodies of the bee brain.  All the nACh receptors in the honeybee will show this behavior no matter what subtype they belong to or where they are...this is true of virtually every other animal studied, but we didn't have proof for the bee...and we do now.

Christina

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