How much does chocolate stimulate adrenergic receptors?

June 11, 2010 10:28 PM

NeuroscienceFilter: How much does chocolate stimulate adrenergic receptors?

I am extremely sensitive to any medication that has an effect on adrenergic receptors, including adrenergic agonists (pseudoephedrine, clonidine, oxymetazoline), SNRIs (duloxetine), TCAs (amitriptyline), and methylphenidate. Even taking Afrin nasally gave me various central side effects, some of which were bothersome and long-lasting. I'm working with my doctor to figure out why.

I've cut chocolate out of my diet because it contains the stimulants caffeine and theobromine. I know the adrenergic effect of these chemicals is probably small, but I'm having a hard time quantifying it. If it's Does anyone know how to estimate how a milk chocolate bar would compare to a pill of Elavil or Ritalin in terms of adrenergic stimulation?

posted by wireless to science & nature (3 answers total)

I don't think anyone knows. Moreover, it isn't just caffeine and theobromine in chocolate which are clinically significant.
posted by Chocolate Pickle at 10:53 PM on June 11, 2010

It's impossible to quantify. First of all, it isn't quite as simple as "stimulating your adrenergic receptors". You might already know this, but the effect of neurotransmitters in the brain can be modulated in a variety of ways. Some chemicals bind directly to the receptors and mimic their effects, some promote release of the natural chemical, some prevent reuptake of the those chemicals already being released. Raw chocolate can contain many chemical stimulants, the most active of which appears to be theobromine, as you mention. It appears to be somewhat weaker than caffeine, but again it depends on what kind of chocolate you are talking about, and whether you are comparing it to a cup of instant coffee or a triple shot espresso. I doubt the effects of even a pure dark chocolate bar would come close to the lowest dose (10 mg?) of Ritalin or Adderall, which are more or less straight amphetamines and much stronger than caffeine per gram. As you well know, these types of things affect each person somewhat differently, and so there is no easy way to translate the chemical potency into the effects it will have on a particular person in a quantifiable way.
posted by sophist at 12:29 AM on June 12, 2010

I found a very interesting page (that I cannot vouch for the accuracy of, though I think it's well-argued and has references to the literature) which claims that caffeine owes the vast majority of its neurotransmitter-related effects to an ability to block adenosine receptors on the surfaces of neurons.

Adenosine typically accumulates in the extracellular space during conditions of fatigue — ie, when the rate of ATP utilization exceeds the rate of ATP synthesis...

and so by blocking these adenosine receptors, caffeine would tend to interrupt the negative feedback loop which would cause many neurons to reduce their activity when they are fatigued.

Experiments on mice may give an indication of the effects of chronic caffeine administration. The density of cortical A1 adenosine receptors increased 20% whereas the density of A2A receptors in the basal ganglia did not change. Densities of cortical serotonin receptors increased by 26-30%, cortical cholinergic receptor densities increased 40-50% and cortical GABAA receptor densities increased 65%. Cortical & cerebellar adrenergic receptor densities decreased by 25% [CELLULAR AND MOLECULAR NEUROBIOLOGY 13(2):247-261 (1993)]. [my emphasis]

The fact that chronic administration of caffeine caused a decrease of 25% in adrenergic receptors implies a surprisingly strong enhancement of adrenergic activity by caffeine which the mouse brains are attempting to compensate for (in order to maintain homeostasis) by reducing the number of receptors.

If you really wanted to have a rough idea of how adrenergic caffeine is compared to the other things you mention, I suppose you could experiment and see how much of each was needed to effect an equivalent 25% reduction of adrenergic receptors in this mouse model.

The page also claims that caffeine is seven times more potent than theobromine.
posted by jamjam at 2:11 AM on June 12, 2010