To avoid confusion, the naming convention was continued with the letter D. There are 3 alpha-1 adrenergic receptor subtypes: alpha-1A, -1B and -1D, all of which signal through the Gq/11 family of G-proteins.

Different subtypes show different patterns of activation.

The majority of alpha-1 receptors are directed toward the function of epinephrine, a hormone that has to do with the fight-or-flight response.

Alternative splicing of this gene generates four transcript variants, which encode four different isoforms with distinct C-termini but having similar ligand binding properties.

[6] α1A-adrenergic receptor subtypes increase inhibition at dendrodendritic synapses, suggesting a synaptic mechanism for noradrenergic modulation of olfactory driven behaviors.