Norepinephrine Is Necessary for Experience-Dependent Plasticity in the Developing Mouse Auditory Cortex

Abstract

Critical periods are developmental windows during which the stimuli an animal encounters can reshape response properties in the affected system to a profound degree. Despite this window's importance, the neural mechanisms that regulate it are not completely understood. Pioneering studies in visual cortex initially indicated that norepinephrine (NE) permits ocular dominance column plasticity during the critical period, but later research has suggested otherwise. More recent work implicating NE in experience-dependent plasticity in the adult auditory cortex led us to re-examine the role of NE in critical period plasticity. Here, we exposed dopamine ␤-hydroxylase knock-out (Dbh Ϫ/Ϫ ) mice, which lack NE completely from birth, to a biased acoustic environment during the auditory cortical critical period. This manipulation led to a redistribution of best frequencies (BFs) across auditory cortex in our control mice, consistent with prior work. By contrast, Dbh Ϫ/Ϫ mice failed to exhibit the expected redistribution of BFs, even though NE-deficient and NE-competent mice showed comparable auditory cortical organization when reared in a quiet colony environment. These data suggest that while intrinsic tonotopic patterning of auditory cortical circuitry occurs independently from NE, NE is required for critical period plasticity in auditory cortex.

ERK signaling pathway regulates sleep duration through activity-induced gene expression during wakefulness

“…activated by wakefulness and chemical stimulation. Surprisingly, NE alone could reproduce the effect of the whole cocktail on the expression of our candidate genes, confirming the essential role of NE in wakefulness and associated neuronal plasticity(29). To understand through which pathway NE stimulates gene expression its receptors were pharmacologically blocked by antagonists.…”

Contrast Enhancement without Transient Map Expansion for Species-Specific Vocalizations in Core Auditory Cortex during Learning

“…Without uniform and complete sampling across the entire AC of individual animals though, increases in single-unit responsiveness percentages do not necessarily imply increases in the cortical area engaged by the sound. While our negative results on spatial representational expansion in the thalamorecipient layer of cortex are based on a lower spatial sampling density than that used in other mouse studies (Guo et al, 2012; Kim et al, 2013), we note that the same methods were sufficient to reveal map expansion in a developmental sound exposure paradigm (Shepard et al, 2015a). Perhaps brief expansion occurs at some other maternal time point outside of those used here to bracket the peak in pup calling rates.…”

Preventing neurodegeneration by adrenergic astroglial excitation

“…Diffuse innervation by projections of LC neurons reaches practically all parts of the brain and the spinal cord [9]. The majority of axons arising from the LC terminate in the neocortex and hippocampus [10][11][12]. Excitation of LC neurons leads to an almost simultaneous activation of neural networks across many CNS regions.…”