Cerebral Glycogen Distribution and Aging

In the brain, glycogen metabolism has been implied in synaptic plasticity and learning, yet the distribution of this molecule has not been fully described. We investigated cerebral glycogen of the mouse by immunohistochemistry (IHC) using two monoclonal antibodies that have different affinities depending on the glycogen size. The use of focused microwave irradiation yielded well‐defined glycogen immunoreactive signals compared with the conventional periodic acid‐Schiff method. The IHC signals displayed a punctate distribution localized predominantly in astrocytic processes. Glycogen immunoreactivity (IR) was high in the hippocampus, striatum, cortex, and cerebellar molecular layer, whereas it was low in the white matter and most of the subcortical structures. Additionally, glycogen distribution in the hippocampal CA3‐CA1 and striatum had a ‘patchy’ appearance with glycogen‐rich and glycogen‐poor astrocytes appearing in alternation. The glycogen patches were more evident with large‐molecule glycogen in young adult mice but they were hardly observable in aged mice (1–2 years old). Our results reveal brain region‐dependent glycogen accumulation and possibly metabolic heterogeneity of astrocytes

Distinct temporal integration of noradrenaline signaling by astrocytic second messengers during vigilance

Astrocytes may function as mediators of the impact of noradrenaline on neuronal function. Activation of glial α1-adrenergic receptors triggers rapid astrocytic Ca2+ elevation and facilitates synaptic plasticity, while activation of β-adrenergic receptors elevates cAMP levels and modulates memory consolidation. However, the dynamics of these processes in behaving mice remain unexplored, as do the interactions between the distinct second messenger pathways. Here we simultaneously monitored astrocytic Ca2+ and cAMP and demonstrate that astrocytic second messengers are regulated in a temporally distinct manner. In behaving mice, we found that while an abrupt facial air puff triggered transient increases in noradrenaline release and large cytosolic astrocytic Ca2+ elevations, cAMP changes were not detectable. By contrast, repeated aversive stimuli that lead to prolonged periods of vigilance were accompanied by robust noradrenergic axonal activity and gradual sustained cAMP increases. Our findings suggest distinct astrocytic signaling pathways can integrate noradrenergic activity during vigilance states to mediate distinct functions supporting memory

Distinct temporal integration of noradrenaline signaling by astrocytic second messengers during vigilance

Astrocytes may function as mediators of the impact of noradrenaline on neuronal function. Activation of glial α1-adrenergic receptors triggers rapid astrocytic Ca2+ elevation and facilitates synaptic plasticity, while activation of β-adrenergic receptors elevates cAMP levels and modulates memory consolidation. However, the dynamics of these processes in behaving mice remain unexplored, as do the interactions between the distinct second messenger pathways. Here we simultaneously monitored astrocytic Ca2+ and cAMP and demonstrate that astrocytic second messengers are regulated in a temporally distinct manner. In behaving mice, we found that while an abrupt facial air puff triggered transient increases in noradrenaline release and large cytosolic astrocytic Ca2+ elevations, cAMP changes were not detectable. By contrast, repeated aversive stimuli that lead to prolonged periods of vigilance were accompanied by robust noradrenergic axonal activity and gradual sustained cAMP increases. Our findings suggest distinct astrocytic signaling pathways can integrate noradrenergic activity during vigilance states to mediate distinct functions supporting memory

Uncoupling root hair formation and defence activation from growth inhibition in response to damage‐associated Pep peptides in Arabidopsis thaliana

・In Arabidopsis thaliana, PROPEPs and their derived elicitor‐active Pep epitopes provide damage‐associated molecular patterns (DAMPs), which trigger defence responses through cell‐surface receptors PEPR1 and PEPR2. In addition, Pep peptides induce root growth inhibition and root hair formation, however their relationships and coordinating mechanisms are poorly understood. ・Here, we reveal that Pep1‐mediated root hair formation requires PEPR‐associated kinases BAK1/BKK1 and BIK1/PBL1, ethylene, auxin and root hair differentiation regulators, in addition to PEPR2. ・Our analysis on 69 accessions unravels intraspecies variations in Pep1‐induced root hair formation and growth inhibition. The absence of a positive correlation between the two traits suggests their separate regulation and diversification in natural populations of A. thaliana. ・Restricted PEPR2 expression to certain root tissues is sufficient to induce root hair formation and growth inhibition in response to Pep1, indicating the capacity of non‐cell‐autonomous receptor signalling in different root tissues. Of particular note, root hair cell‐specific PEPR2 expression uncouples defence activation from root growth inhibition and root hair formation, suggesting a unique property of root hairs in root defence activation following Pep1 recognition

Whisker-evoked CBF changes measured by laser Doppler flowmetry from the barrel cortex.

<p>(<b>A</b>) Single example trace of 10 Hz air puff stimulation experiment. The recording was made from a WT mouse. (<b>B</b>) Proportion of barrel cortex astrocytes that elicited Ca²⁺ elevations after whisker stimulation (10 Hz, 20 s) for WT (n = 3) and IP₃R2 KO (n = 3). (<b>C</b>) Mean CBF of WT (black) and IP₃R2 mice (white) during 20 s whisker stimulation was compared. The number of tested animal for each stimulation paradigm is shown in parenthesis. Whisker stimulation with 5 or 10 Hz significantly increased cerebral blood flow in WT and KO when compared with prestimulus period. No significant differences in CBF response were observed between WT and KO in any of the stimulation paradigms.</p

Overview of the stNBM experiment.

<p>(<b>A</b>) Sketch for experimental set up. A laser Doppler probe is placed above the thinned skull at the primary somatosensory cortex. A bipolar stimulation electrode is inserted to target the nucleus basalis of Meynert (NBM) in the ipsilateral side. (<b>B</b>) An example trace of laser Doppler flowmetry from a wild type mouse in response to a single train NBM stimulation (stNBM, arrow). (<b>C</b>) <i>In vivo</i> two-photon imaging of Fluo-4 AM loaded astrocytes in the somatosensory cortex of C57BL/6J (WT, upper panels) and IP₃R2-KO (lower panels). (<b>D</b>) Proportion of barrel cortex astrocytes that elicited Ca²⁺ elevations upon stNBM.</p

Averaged traces of laser Doppler flowmetry in C57BL/6J and IP₃R2-KO mice.

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066525#s2" target="_blank">Results</a> for C57BL/6J and IP₃R2-KO mice are represented in blue and red traces, respectively. Each experimental condition has N>5 animals. Upon 200 µA stNBM, the cerebral blood flow (CBF) showed an immediate increase, followed by a transient decrease that overshot the baseline both in WT (<b>A</b>) and KO (<b>E</b>). CBF change by the stNBM is attenuated by the muscarinic receptor antagonist atropine (ATR) (<b>B</b>). Weak stNBM stimulation (50 µA) resulted in negative laser Doppler flowmetry signal (<b>C</b>) and similar changes were observed in KO (<b>F</b>). Stimulation outside the NBM failed to induce CBF increase (<b>D</b>). Shaded areas represent s.e.m.</p