Overview of Relevant Neuroanatomy and Neurophysiology

Neurons offer some of the most important targets in drug design (see figure 4.1). 

Synaptic transmission is the process whereby neurons communicate with each other and with the target organs whose physiology they are influencing synaptic transmission permits the action potential to jump from one neuron to the next. It is imperative 

A neurotransmitter is a chemical messenger that mediates the passage of electrical information from one neuron to an adjacent neuron. To be defined as a classical neurotransmitter, a molecule must be synthesized and stored in a neuron, released from that neuron in a Ca dependent process, diffuse to an adjacent neuron, specifically dock with a receptor on that adjacent neuron, and have its binding to this receptor blocked by a competitive antagonist. A neuromodulator, on the other hand, is a molecule which is present in the synaptic cleft and which modifies either the frequency or the efficiency of the neurotransmitter molecule, thereby either amplifying or attenuating the neurotransmitter action. 

The traditional neurotransmitters have been recognized for a number of decades and include acetylcholine, norepinephrine, and glutamate. The number of neurotransmitters has increased rapidly in the past 10-20 years as the methodology for their detection has 

It should be kept in mind that a single synapse may operate with as many as four transmitters simultaneously, in any combination of amine and peptide, or even peptide and peptide, within the groupings shown. The peptide neurotransmitters are stored separately, always in large synaptic vesicles are synthesized in the cell body of the neuron and are transported to the synapse after post-translational processing by fast (ATP-driven) transport systems. Amine neurotransmitters are synthesized in the synapse and are stored in small or large vesicles. Different populations of the same type of neurons may differ in their content of cotransmitters. 

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