Regulation of vocal precision by noradrenergic modulation of a motor nucleus.

Recent theories of norepinephrine (NE) function suggest that NE modulates the transition between stereotyped, goal-directed behavior and more variable, exploratory behaviors that facilitate learning and adaptation. We provide evidence for context-dependent switching by NE that is analogous to this explore/exploit strategy in the vocal system of the zebra finch (). Stimulation of the locus coeruleus, the major source of NE in the brain, decreases song trial-to-trial variability, transforming the variable, exploratory "undirected" song into song that resembles the more stereotyped, exploitative "directed" song that males sing to females.

Stress and glucocorticoids impair memory retrieval via β2-adrenergic, Gi/o-coupled suppression of cAMP signaling.

Acute stress impairs the retrieval of hippocampus-dependent memory, and this effect is mimicked by exogenous administration of stress-responsive glucocorticoid hormones. It has been proposed that glucocorticoids affect memory by promoting the release and/or blocking the reuptake of norepinephrine (NE), a stress-responsive neurotransmitter. It has also been proposed that this enhanced NE signaling impairs memory retrieval by stimulating β(1)-adrenergic receptors and elevating levels of cAMP.

What birdsong can teach us about the central noradrenergic system.

Increasing evidence indicates that the noradrenergic system plays a key role in biasing the nervous system towards producing behaviors that help animals adapt to constantly changing environments. Most of the studies investigating noradrenergic function are performed in animals that have a limited repertoire of tractable natural behaviors. Songbirds, in contrast, with their rich set of precisely quantifiable vocal behaviors, provide a unique model system to study the noradrenergic system.

Dopamine binds to alpha(2)-adrenergic receptors in the song control system of zebra finches (Taeniopygia guttata).

A commonly held view is that dopamine exerts its effects via binding to D1- and D2-dopaminergic receptors. However, recent data have emerged supporting the existence of a direct interaction of dopamine with adrenergic but this interaction has been poorly investigated. In this study, the pharmacological basis of possible in vivo interactions between dopamine and alpha(2)-adrenergic receptors was investigated in zebra finches.

Noradrenergic projections to the song control nucleus area X of the medial striatum in male zebra finches (Taeniopygia guttata).

There is considerable functional evidence implicating norepinephrine in modulating activity in the vocal control circuit of songbirds. However, our knowledge of noradrenergic inputs to the song system is incomplete. In this study, cholera toxin subunit B (CTB) injections into area X revealed projections from the noradrenergic nuclei locus coeruleus and subcoeruleus, and injections of biotinylated dextran amines into these noradrenergic nuclei labeled fibers in area X.

A role for norepinephrine in the regulation of context-dependent ZENK expression in male zebra finches (Taeniopygia guttata).

Singing drives expression of the immediate-early gene ZENK in a context-dependent manner in certain nuclei within the avian song circuit of male zebra finches (Taeniopygia guttata). ZENK mRNA expression is low when males are engaged in female- or male-directed song, but high during solo song. Neurotransmitter systems like catecholamines with diffuse projections to forebrain regions are good candidates for regulation of such context-dependent brain activity.

The activation of birdsong by testosterone: multiple sites of action and role of ascending catecholamine projections.

Birdsong is a species-typical stereotypic vocalization produced in the context of reproduction and aggression. Among temperate-zone songbirds, it is produced primarily by males, and its frequency and quality are enhanced by the presence of the gonadal steroid hormone testosterone in the plasma. In the brain, the effects of testosterone on song behavior involve both estrogenic and androgenic metabolites of testosterone that are locally produced and act via their cognate receptors.