Glutamate (neurotransmitter)
In neuroscience, glutamate refers to the anion of glutamic acid in its role as a neurotransmitter: a chemical that nerve cells use to send signals to other cells. It is by a wide margin the most abundant excitatory neurotransmitter in the vertebrate nervous system. It is used by every major excitatory function in the vertebrate brain, accounting in total for well over 90% of the synaptic connections in the human brain. It also serves as the primary neurotransmitter for some localized brain regions, such as cerebellum granule cells.
Protriptyline
Protriptyline acts by decreasing the reuptake of norepinephrine and to a lesser extent serotonin (5-HT) in the brain. Its affinity for the human norepinephrine transporter (NET) is 1.41 nM, 19.6 nM for the serotonin transporter and 2,100 nM for the dopamine transporter. TCAs act to change the balance of naturally occurring chemicals in the brain that regulate the transmission of nerve impulses between cells. Protriptyline increases the concentration of norepinephrine and serotonin (both chemicals that stimulate nerve cells) and, to a lesser extent, blocks the action of another brain chemical, acetylcholine. The therapeutic effects of protriptyline, like other antidepressants, appear slowly. Maximum benefit is often not evident for at least two weeks after starting the drug.