This week’s theme was a deeper dive into neurotransmitter systems. The chapter first started by telling about the ways those systems can be studied experimentally, starting from the three criteria needed for a substance to be classified as a neurotransmitter, related to its fabrication, release, and effect. All these three layers have to be studied, so that a substance can be deemed to be a neurotransmitter with reasonable confidence, and I was surprised by how intricate the whole field seems to be.
In the next part, Different types of neurons were classified using their primary type of neurotransmitter. Cholinergic, Catecholaminergic, Serotonergic, and Amino Acidergic neuron types were presented. ATP which is sometimes present as a co-transmitter was also presented. The end-note on retrograde messengers such as endocannabinoids was very puzzling and exciting, and it will be fun to see in the future whether they really play an essential role in neurotransmission regulation or if their effect is marginal. The rest of the chapter laid light on different types of neurotransmitter-gated channels, as well as on the mechanisms of g-protein coupled receptors and the subsequent signaling pathways. It was interesting to note the heterogeneity of responses possible for one neurotransmitter.
All in all, the chapter left an impression to me that a lot is yet to be known with regards to neurotransmitters. All of the knowledge still feels quite new and hard to grasp, but I hope that as we study different subsystems of the brain, I will acquire a more intuitive understanding of the different neurotransmitters and how they link to higher-level systems in the nervous system. This chapter feels like one where I will come back to a lot in the following months.