Another very interesting course that I attended during my first year of Neurobiology Master‘s was the one called “Neurochemistry and Neuropharmacology”. During this course, we finally started studying the different chemicals, called neurotransmitters, produced by neurons in the nervous system.
As I have already written in an old post, neurons communicate through electricity and chemical signals: it all starts with an electric signal, called action potential, that travels along the neuron up to its terminal end where it is then “converted” into a chemical signal so that it can “jump” from one neuron to another and transmit its information to the right centre of the brain. Eventually, in the Neurochemistry part of the course we started studying these neurotransmitters used by the brain, among whom the most important are the glutamate, that is able to bind to close neurons and “propagate” the electric signal produced by the neuron that first wanted to propagate the action potential, and the GABA, an inhibitory molecule that binds to neurons and prevent this electric signal from passing to the next neuron/neurons. Basically, every behaviour, action, thought, memory and so on we produce is determined by the delicate balance of this two molecules in our brain, along with the fine tuning of some other neurotransmitters like noradrenaline (very important during so called “fight or flight” situations), serotonin (the molecule of “happiness”), oxytocin (the “love” molecule) and so on.
I will definitely write posts about each and every one of these molecules, since these are the basis of the animal and, consequently, human behaviour, but for today I would like to talk about other kinds of molecules that we studied in the second part of this course, the Neuropharmacology one. We began by the definition of neurotoxins (substances that alters the structure or function of the nervous system, such as snake venom, pesticides or cocaine) and we continued on a more pharmacological path by analysing how to direct drugs into the brain (a pretty complicated matter that I will definitely talk about later on, since it is one of these days challenges to deliver drugs in the brain, in order to help treating patients with dementia, epilepsy, stroke and so on).
However, today for the SFR I would like to reconnect with the unfortunate theme of depression and anxiety by talking about benzodiazepines (BDZ). This is a class of psychoactive drugs that acts on the GABA neurotransmitter producing an anxiolytic, hypnotic and sedative effect. These drugs are used in a variety of indications such as alcohol dependence, seizures, insomnia, but also anxiety disorders, panic and agitation. But let’s see how BDZs work, their beneficial effects and their contraindications and potential threats.
“Science Related Fact” (SRF):
The BDZ are a class of drugs that enhance the effect of the inhibitory neurotransmitter GABA via modulating its receptor (a protein on the membrane of the neuron that will change the electric currents in the neuron). To do this, the BDZs bind to a site on this receptor and they decrease the currents in the neuron, preventing the formation of the action potential. However, the BDZ action can happen only if the neurotransmitter GABA is already bound to the receptor. On a behavioural level, this effect produces sedation and hypnosis, that will in turn increase the total time of sleep and the sense of deep sleep and rest, while decreasing the REM phase (that is the phase when actually dream during sleep). It also decreases anxiety and promotes muscles relaxation.
Generally, benzodiazepines are well-tolerated and are safe and effective drugs in the short term, but there are some adverse reactions that should be taken into account when using this class of drugs. There could be a psychomotor impairment, such as sense of tiredness, increased reaction time or confusion, thus leading to impaired drive or impossibility to handle complex machines.
All of these reactions to BDZ could be seriously amplified by other sedatives, such as alcohol, something that BDZs users usually underestimate, leading to serious risks as respiratory depression. On top of this, there is a chance of developing addiction, with the common withdrawal symptoms of anxiety, insomnia, dysphoria and tremor (see schematic below for some numbers on DBZs addiction in the UK).