Assaying activity-dependent arteriole and capillary responses in brain slices.

Significance: Neurovascular coupling (NVC) is the process that increases cerebral blood flow in response to neuronal activity. NVC is orchestrated by signaling between neurons, glia, and vascular cells. Elucidating the mechanisms underlying NVC at different vascular segments and in different brain regions is imperative for understanding of brain function and mechanisms of dysfunction. Aim: Our goal is to describe a protocol for concurrently monitoring stimulation-evoked neuronal activity and resultant vascular responses in acute brain slices. Approach: We describe a step-by-step protocol that allows the study of endogenous NVC mechanisms engaged by neuronal activity in a controlled, reduced preparation. Results: This ex vivo NVC assay allows researchers to disentangle the mechanisms regulating the contractile responses of different vascular segments in response to neuronal firing independent of flow and pressure mediated effects from connected vessels. It also enables easy pharmacological manipulations in a simplified, reduced system and can be combined with Ca 2 + imaging or broader electrophysiology techniques to obtain multimodal data during NVC. Conclusions: The ex vivo NVC assay will facilitate investigations of cellular and molecular mechanisms that give rise to NVC and should serve as a valuable complement to in vivo imaging methods.

Homocysteine sensitizes the mouse neuromuscular junction to oxidative stress by nitric oxide.

Homocysteine (HCY), a redox-active metabolite of the methionine cycle, is of particular clinical interest because of its association with various neurodegenerative diseases including amyotrophic lateral sclerosis. It has been previously established that HCY exacerbates damage to motor neurons from reactive oxygen species (ROS) such as hydrogen peroxide. To assess the role of HCY at the mammalian neuromuscular junction, neurotransmission was monitored by electrophysiology at the mouse epitrochleoanconeus muscle. Preparations were preincubated in HCY before inducing ROS and recordings were taken before and after ROS treatment. In this study, HCY was observed to sensitize the neuromuscular junction to ROS-induced depression of spontaneous transmission frequency, an effect we found to be mediated by a N-methyl-D-aspartate receptor (NMDAR) and nitric oxide (NO). The NMDAR antagonist D, L-2-amino-5-phosphonopentanoic acid prevented the HCY-induced sensitization to oxidative stress. Disrupting NO activity with either the nitric oxide synthase I antagonist Nω-nitro-L-arginine methyl ester hydrochloride or the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide potassium salt also prevented sensitization. Moreover, replacing HCY with the exogenous NO donor Diethylamine NONOate diethylammonium was sufficient to reconstitute the effects of HCY-induced sensitization to ROS. Interestingly, a novel secondary effect was observed where HCY itself depresses quantal content, an effect found to be mediated by NMDARs independently of nitric oxide and ROS. Collectively, these data present a novel model of two distinct pathways through which HCY alters neurotransmission at the neuromuscular junction. Characterizing HCY's mechanism of action is of particular clinical relevance as many treatments for amyotrophic lateral sclerosis are centered on mitigating HCY-induced pathologies.

Multifractal foundations of visually-guided aiming and adaptation to prismatic perturbation.

Visually-guided action of tossing to a target allows examining coordination between mechanical information for maintaining posture while throwing and visual information for aiming. Previous research indicates that relationships between visual and mechanical information persist in tossing behavior long enough for mechanical cues to prompt recall of past visual impressions. Multifractal analysis might model the long-term coordinations among movement components as visual information changes. We asked 32 adult participants (6 female, 25 male, one not conforming to gender binary; aged M=19.77, SD=0.88) to complete an aimed-tossing task in three blocks of ten trials each. Block 1 oriented participants to the task. Participants wore right-shifting goggles in Block 2 and removed them for Block 3. Motion-capture suits collected movement data of the head, hips, and hands. According to regression modeling of tossing performance, multifractality at hand and at hips together supported use of visual information, and adaptation to wearing/removing of goggles depended on multifractality across the hips, head, and hands. Vector-autoregression modeling shows that hip multifractality promoted head multifractality but that hand fluctuations drew on head and hip multifractality. We propose that multifractality could be an information substrate whose spread across the movements systems supports the perceptual coordination for the development of dexterity.