Jammin’ on that royal jelly


[Image by Thomas Shahan via Creative Commons]

If you watched the Sapolsky video below, you know that he touched on something that we forget about: pheromones. I think people like to think that pheromones are limited to those baser animals, or insects, and that our behavior is more controlled. The idea that smells are influencing our choices all the time is not something most people realize. So here’s some neuroscience research on one of my favorite things – social insects.

We’re going to be talking about bees today, and about how bees use a pheromone known as queen mandibular pheromone (QMP) that controls their social behavior. This pheromone is a complex blend of chemicals designed to entice workers to feed and groom the queen. As the attendant bees exchange food with nest mates, they spread it throughout the colony. However, not all bees attend the queen – it is mainly young bees, with the older ones being the colony’s foragers. It’s interesting then, that reactions to QMP are age-dependent: very young bees find it attractive, while the older foragers try to stay away from it. What’s going on here?

Well, one component of QMP is homovanyllil alcohol (HVA). This chemical interferes with dopamine signaling, a neurotransmitter responsible for learning (in particular, learning aversive memories). But each bee is a little different; some like QMP more, some less. Why? Well, when you examine transcription levels of various neurotransmitter receptors, there’s no correlation between behavior and transcription levels in the brain – but there is in the antennae. In particular, Amoa1 and Amdop3 were significantly higher in bees attracted to QMP, which are an octopamine receptor and D2-like dopamine receptor activated by HVA, respectively. Futhermore, activation of AmDOP3 inhibits accumulation of a molecule known as cAMP; one effect of this lack of accumulation is that signaling of D1-type receptors are inhibited (Amdop1/2).

Here’s what you do next: stuff a bunch of QMP in the face of bees from emergence and see what changes. One effect is that Amdop1 transcription levels in the antennae fall significantly (though not Amdop2). Another effect is that bees exposed to the QMP are much more attracted to it, in every age group tested. What’s happening here? The theory is that octopamine enhances sensitivity to pheromone cues and to positive appetitive stimuli, while dopamine reinforces aversive stimuli. QMP activates AmDOP3 receptors, which in turn downregulates AmDOP1 receptors; this interference with dopamine inhibits the unattractive parts of QMP. Since Amdop3 levels correlate highly with QMP attractiveness, and since Amdop3 decreases with age, it is likely that this is a primary reason for the switch from caring to foraging behavior. After proffering that explanation, however, Amoa1 is forgotten because no developmental effect is seen.

So there you have it. Queen pheromone affects dopamine signaling behavior not just in the brain, but also at the level of primary sensory neurons. Apparently, this shift between avoidance and approach behavior among mammalian mothers and offspring is also due to dopamine signaling… Oh, and for the record, I know the picture above is a yellow jacket and not a bee, but it looks pretty sweet, doesn’t it?

Vergoz V, McQuillan HJ, Geddes LH, Pullar K, Nicholson BJ, Paulin MG, and Mercer AR. Peripheral modulation of worker bee responses to queen mandibular pheromone. PNAS 2009 106:20930-20935; doi:10.1073/pnas.0907563106

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Plants: they work!

bee_on_flower

Here’s a good blog called Howplantswork that focuses on, well, how plants work. It’s only updated once a month or so, but going through old posts is fascinating. Some highlights:

  • Plant versus plant: some plants kill other plants using natural herbicides
  • Nervous plants? (part 2) [ie, do plants have a nervous system?
  • Flowers: what you see versus what the bees see ]
  • Plant “RAM”? – some plants could record environmental experiences for future reference by altering their DNA
  • The World-Wide-Web: Are plants inter-connected by a subterranean fungal network?
  • Bee raves

    Meandering through an issue of Science I found a small report on bee raves! Unfortunately, the report wasn’t as exciting as the title made it out to be. Some scientists wanted to find out if maybe cocaine acted as an insecticide, so they went out and gave small amounts of cocaine to bees. The result? Bees, which do a little dance to signal where and how important new sources of pollen are, danced even more when dosed with cocaine. Both the amount of dancing and the vigor of dancing increased from cocaine. Also, bees apparently suffer cocaine withdrawal. Silly bees.

    And can you imagine being those scientists? Hello, I am a scientist, I give cocaine to bees and watch them dance, good thing I got a PhD.

    Here is a great video of bees from the BBC, but they won’t let me embed it into my blog so you’re going to have to visit the youtubes.