27
II
Drugs and Their
Human Receptors
The plant-derived drugs that we want to consider in more detail in this
chapter interfere with two important signalling pathways, G proteincoupled receptor signalling (GPCR signalling) and ion channel signalling.
These ways of signal transduction are used by our cells to communicate
with each other, and they also play important roles in synaptic signalling
in the nervous system. We explore the components and general function
of these signalling pathways and look how individual endogenous and
plant-derived compounds affect them. In most cases, the drugs in
question function as receptor agonists or antagonists; sometimes they
act on neurotransmitter transporters or as allosteric regulators of ion
channel function. Many neurotransmitters, e.g. acetylcholine, bind to
several receptors that can be of different nature, including GPCRs and
ion channels. We will see that there are very specific drugs able to
distinguish different kinds of receptors, while others act on multiple
receptors. Cannabis, muscarine and atropine, caffeine, cocaine, opiates
and some psychedelics, nicotine, curare, thujone, strychnine and some
other plant-derived drugs will be covered, and the endogenous ligands
for the respective receptors will be discussed.
Contents
Chapter 3
GPCRs – 29
Chapter 4
Ion Channels – 43
Chapter 5
GPCRs as Targets for Plant-Derived Drugs – 57
Chapter 6
Ion Channels as Targets for Plant-Derived
Drugs – 83