In vitro pharmacological studies play a crucial role in elucidating the molecular and cellular mechanisms underlying the effects of antidepressants on the central nervous system (CNS). These studies employ cellular models, brain tissue samples, and isolated molecular systems to examine drug interactions with key neurotransmitter systems. Critical areas of research include receptor binding assays for serotonin, norepinephrine, and dopamine receptors, as well as inhibition of neurotransmitter reuptake, primarily through serotonin and norepinephrine transporters. Additionally, antidepressants influence enzyme activity, particularly through monoamine oxidase inhibition, and modulate ion channels, such as voltage-gated sodium and potassium channels, affecting neuronal excitability. Further investigations explore the role of antidepressants in promoting neuroplasticity through neurotrophic factors like brain-derived neurotrophic factor (BDNF), which is associated with synaptic remodelling and resilience against stress-induced neuronal damage. Antidepressants also impact intracellular signalling pathways, including the cAMP/PKA, MAPK/ERK, and mTOR pathways, contributing to their therapeutic efficacy. Moreover, in vitro studies facilitate the assessment of oxidative stress modulation and the regulation of stress-related pathways implicated in depression. These insights not only enhance our understanding of antidepressant pharmacology but also pave the way for identifying novel therapeutic targets, ultimately advancing the development of more effective treatments for depression and other mood disorders.