Olfactory bulb α2-adrenoceptor activation promotes rat pup odor-preference learning via a cAMP-independent mechanism.

In this study, three lines of evidence suggest a role for α(2)-adrenoreceptors in rat pup odor-preference learning: olfactory bulb infusions of the α(2)-antagonist, yohimbine, prevents learning; the α(2)-agonist, clonidine, paired with odor, induces learning; and subthreshold clonidine paired with subthreshold β-adrenoceptor activation also recruits learning. Increased mitral cell layer pCREB occurs with clonidine-infusion, but cAMP is not increased. Similar results using a GABAa-antagonist suggest that disinhibition may support clonidine-induced learning. We suggest that norepinephrine can act through multiple bulbar adrenoceptor subtypes to induce odor learning and that cAMP-dependent, as well as cAMP-independent, signals may act as unconditioned stimuli.