Membrane Receptors for Corticosterone: A Mechanism for Rapid Behavioral Responses in an Amphibian

This paper reviews evidence that, in some cases, steroid hormones rapidly modulate behaviors by binding to specific cell-surface receptors on neurons. The evidence comes from research with an amphibian model, Taricha granulosa. In Taricha, stress and corticosterone inhibit reproductive behaviors with a rapidity that is inconsistent with traditional models for steroid action (models in which intracellular steroid receptors function as transcription factors). A series of radioligand binding assay studies identified a corticosteroid receptor in neuronal membranes that appears to mediate the rapid behavioral responses in Taricha. Studies with various steroids showed a strong correlation between their potencies to inhibit the behavior and their potencies to inhibit corticosterone binding. Neurophysiological studies of caudal brainstem neurons found that corticosterone administration rapidly modulates neuronal activity and selectively suppresses sensory processing. Another series of studies provided evidence that this corticosterone receptor interacts with G proteins in neuronal membranes. The studies suggest that there are G protein-coupled receptors for corticosteroids that provide all alternative mechanism by which this hormone regulates brain functions and behaviors.