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Neurotransmitters

Neurotransmitters are the biochemicals  that carry information from one neuron  to another.  When an action potential  arrives at the terminal axonal membrane , a neurotransmitter may be released into the synapse, where it can then diffuse through the synaptic fluids and interact with the receptors on either the presynaptic neuron  or the postsynaptic neuron .  Neurotransmitters interact with protein structures  referred to as receptors .

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Receptors are often located in the neuronal membrane and interact in a lock- and-key fit with neurotransmitters.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A given neurotransmitter may have many different types of receptors that interact with only that neurotransmitter, each functioning in a way unique from the other receptors.  Most psychotropic drugs appear to initiate their responses by interacting in some way with receptors, making psychopharmacology, in many ways, the study of receptor physiology .

 

The binding of neurotransmitters to receptors, in some cases, results in the opening of ion channels  in the neuronal membrane , which results in a fast cellular response to the neurotransmitter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In other cases, the binding of a neurotransmitter to its receptor results in a complex chain of biochemical reactions involving numerous other chemical entities called second messengers .

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ultimately, these second messengers are thought to lead to physiological or behavioral responses.

 

Table: Receptor Agonist, Antagonist, and Partial Agonist

 

 

 

 

 

 

 

 

 

 

 

Many psychotropic drugs  at least initiate their actions on the brain by binding to receptors normally utilized by naturally occurring neuortransmitters.  When a drug is added to an already delicately balanced neurotransmitter-receptor system, the effect of the drug may take several forms:

 

     1.  The drug may cause the receptor to work like it would if it were bound by a naturally

          occurring neurotransmitter.  In this situation, the drug is said to be a receptor agonist .

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

     2.  The drug may prohibit the receptor from doing what it would do in the presence of its

          neurotransmitter, such that the receptor function is essentially blocked or antagonized.  In

          this situation, the drug is said to be a receptor antagonist .

 

 

 

 

 

 

 

 

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