Effect of temperature on FAD and NADH-derived signals and neurometabolic coupling in the mouse auditory and motor cortex

Abstract

Tight coupling of neuronal metabolism to synaptic activity is critical to ensure that the supply of metabolic substrates meets the demands of neuronal signaling. Given the impact of temperature on metabolism, and the wide fluctuations of brain temperature observed during clinical hypothermia, we examined the effect of temperature on neurometabolic coupling. Intrinsic fluorescence signals of the oxidized form of flavin adenine dinucleotide (FAD) and the reduced form of nicotinamide adenine dinucleotide (NADH), and their ratios, were measured to assess neural metabolic state and local field potentials were recorded to measure synaptic activity in the mouse brain. Brain slice preparations were used to remove the potential impacts of blood flow. Tight coupling between metabolic signals and local field potential amplitudes was observed at a range of temperatures below 29°C. However, above 29 °C, the metabolic and synaptic signatures diverged such that FAD signals were diminished, but local field potentials retained their amplitude. It was also observed that the declines in the FAD signals seen at high temperatures (and hence the decoupling between synaptic and metabolic events), is driven by low FAD availability at high temperatures. These data suggest that neurometabolic coupling, thought to be critical for ensuring the metabolic health of the brain, may show temperature dependence, and is related to temperature-dependent changes in FAD supplies.

Corticothalamic gating of population auditory thalamocortical transmission in mouse

“…To examine the circuit mechanisms underlying the stochasticity of the responses, brain slices that retained connectivity between the IC, MGB, TRN and AC were used. The aCTC mouse brain slice ( 31–33 ), had an advantage that it retains the synaptic connections between these structures: hence, electrical stimulation of the IC was able to evoke a neuronal activity in all of these brain structures indicated by stimulus-evoked FA and Ca-signals as shown in Figure 2A and B. Both images showed only the average of the stimulus-evoked activity of the connected brain structures in the aCTC slice after several trials of IC stimulation.…”

“…For all in-vitro experiments, 15-18 days old mice were initially anesthetized with ketamine (100 mg/ kg) and xylazine (3 mg/kg) intraperitoneally and transcardially perfused with chilled (4 °C) sucrose-based slicing solution containing the following (in mM): 234 sucrose, 11 glucose, 26 NaHCO 3 , 2.5 KCl, 1.25 NaH 2 PO 4 , 10 MgCl 2 , 0.5 CaCl 2 . After the brain was taken out, it was cut to obtain auditory colliculo-thalamocortical brain slice (aCTC) as shown (Figure S1) and as described before ( 31–33 ). 600 μm thick horizontal brain slices were obtained to retain the connectivity between inferior colliculus (IC), medial geniculate body (MGB), thalamic reticular nucleus (TRN) and AC.…”

“…Following the electrical stimulation of IC, the first step was always to get a neuronal activation in all brain structures involved in the auditory circuit to make sure that aCTC slice retains the synaptic connection between IC, MGB, TRN, and AC. For imaging the cortical activation, one second electrical train pulses of (250uA, 40Hz, 1ms pulse width) to IC was the main stimulating protocol as described before ( 31 ). However, one second long of electrical stimulation was not suitable for electrophysiology experiments to record any post-stimulus signals that could be buried by the stimulus artifact.…”

A novel dynamic network imaging analysis method reveals aging-related fragmentation of cortical networks in mouse

“…We routinely observe these spontaneous activations in all brain slices that contain the cerebral cortex and are bathed in concentrations of SR95531 above 0.5 μM and generally such activations occur roughly every 30-60 seconds with no obvious periodicity. These electrical events strongly resemble the intra- and extracellular manifestations of paroxysmal depolarizing shifts, respectively [89–92], and we have previously found that they correlate with paroxysmal depolarizing shifts [93]. Therefore, we refer to them as paroxysmal depolarizations.…”

V-NeuroStack: 3D Time Stacks for Identifying Patterns in Calcium Imaging Data

“…To obtain these data, a two month-old male mouse expressing GCaMP6s on a Thy1 promoter (Jackson labs, Stock No: 024275) was used. 400 µm thick coronal brain slices through the motor cortex, as previously described (Ibrahim, 2017). Brain slices were exposed to a low concentration of a bath-applied GABAA blocker (GABAzine, 100 nM) to induce spiking activity.…”