Slow transmission

The Metabotropic receptors combine to the second messenger systems. Therefore, they affect only ion channels indirectly through a cascade of events that take time to switch on and off. Accordingly their effects are slower in onset (tens of milliseconds to seconds) and longer lasting (seconds to minutes) than the ionotropic receptor action.

The Metabotropic receptors generate slow epsps and ipsps but can also have more diverse effects on nerve cell behavior than the ionotropic receptors. This can be credited to the widespread actions of the second messenger systems. Being freely diffusible they can spread through dendrites into the cell body or even the axon. This brings them into contact with channels throughout the nerve cell. The second messenger systems target a great range of ion channels (opening or closing them) involving: voltage-dependent K⁺ channels responsible for setting the overall excitability of the cell and voltage-dependent channels which create action potentials, Ca²⁺ channels needed for transmitter release (increasing or decreasing release), and ligand-gated ion channels (modifying the efficacy of fast transmitters).

The Metabotropic receptors also exert long-lasting effects on the nerve cells, dissimilar to their transient influence on the cell permeability and electrical excitability, as second messenger systems act in the nucleus to modify the gene transcription. This can modify the structure of neurons and how they connect to their neighbors. These mechanisms underlie a long-term memory.