**7.4 Sites of action of antidepressant drugs**

Diagram is showing noradrenergic (top) and serotonergic (bottom) nerve terminals. Sevsral types of drugs such as SSRIs, SNRIs and TCAs increase the availability

**Figure 1.** *Modulation of GPCR signaling and activation of protein kinase & ion channel.*

of noradrenergic or serotonergic neurotransmitters at synaptic cleft by blocking the transporter of norepinephrine and serotonin neurotransmitter at presynaptic terminals. MAOIs used for the inhibition of catabolism of norepinephrine and serotonin. Some antidepressant drugs like trazodone has direct effects on serotonergic receptors. Antidepressant drugs are used for the treatment of chronic depression, desensitizes presynaptic autoreceptors and heteroreceptors. These are responsible for producing long lasting changes in monoaminergic neurotransmission. Effect of antidepressant drug on postsynaptic receptors, including modulation of GPCR signaling and activation of protein kinase & ion channel (See **Figure 1**) [75].
