Which of the following is NOT a receptor blocked by Tricyclic Antidepressants?

Tricyclic antidepressants (TCAs) are known for their broad pharmacological profile, which includes blocking several types of receptors beyond their primary action of inhibiting the reuptake of neurotransmitters such as norepinephrine and serotonin. Among the receptors that TCAs block are Histamine-1, muscarinic cholinergic receptors, and α1-adrenergic receptors.

Histamine-1 receptor blockade can lead to sedative effects, while the muscarinic receptor antagonism is responsible for a range of anticholinergic side effects, such as dry mouth, constipation, urinary retention, and blurred vision. The α1-adrenergic receptor blockade can contribute to orthostatic hypotension as a side effect.

In contrast, blocking β-adrenergic receptors is not a primary feature of TCAs. While some TCAs might have a weak effect on β-adrenergic receptors, the significant and clinically relevant actions of TCAs do not involve the blockade of these receptors. This distinction is crucial as it reflects the unique side effect profile and therapeutic implications of the drug class, making the correct answer appropriate for the question posed.