Factors that determine synaptic strength

Factors that determine synaptic strength

A. Presynaptic factors

1. Availability of neurotransmitter
• Availability of precursor molecules
• Amount (or activity) of the rate-limiting enzyme in the pathway for neurotransmitter synthesis
2. Axon terminal membrane potential
3. Axon terminal Ca2+
4. Activation of membrane receptors in presynaptic terminal
• Axo-axonic synapses
• Autoreceptors
• Other receptors
5. Certain drugs and diseases, which act via the above mechanisms

B. Postsynaptic factors

1. Immediate past history of electrical state of postsynaptic membrane (e.g. excitation or inhibition from temporal or spatial summation)
2. Effects of other neurotransmitters or neuromodulators acting on postsynaptic neuron
3. Up- or down-regulation and desensitization of receptors
4. Certain drugs and diseases

C. General factors

• Area of synaptic contact
• Enzymatic destruction of neurotransmitter
• Geometry of diffusion path
• Neurotransmitter re-uptake

Drugs that bind to a receptor and produce a response similar to the normal activation of that receptor are called agonists. Drugs that bind to the receptor but are unable to activate it and block it are called antagonists.

Reference: Widmaier EP, Raff H, Strang KT. Vander's Human Physiology: the mechanisms of body function. 12 ed.New York: McGraw-Hill International Edition; 2011.