Biochemicals - Excitation and Inhibition

Doctor Josh Dubnau explains that the genes active in different neurons can make them excitatory (e.g. glutamate) or inhibitory (e.g. GABA). These neurotransmitters are critical to learning.

What’s interesting about the circuits in our brain is that individual circuits contain neurons of different types. Their type is determined by which genes are active within those neurons. This really is important for determining what the function of those neurons might be. For example, one type of neurons are excitatory, which means that when the signal to another neuron, they turn that neuron on. Another type of neuron is inhibitory – when they signal to the downstream neuron, they repress its activity. So there are excitatory neurotransmitters that are released by the excitatory neurons – glutamate is the most common excitatory neurotransmitter in humans, in fruit flies it is acetylcholine. GABA is the main inhibitory neurotransmitter of neurons. Which genes are active in which neurons determines whether they are, for example GABAergic (which means they release an inhibitory neurotransmitter) or glutamatergic (they release an excitatory neurotransmitter). The next neuron down contains different machinery to receive neurotransmitter signals. Glutamate is activating glutamate receptors – AMPA is a glutamate receptor. Whether or not a neuron expresses a particular receptor for a neurotransmitter on its surface determines how well that neuron responds to a particular neurotransmitter.