Nitric oxide regulates synaptic transmission between spiny projection neurons

Recurrent axon collaterals are a major means of communication between spiny projection neurons (SPNs) in the striatum and profoundly affect the function of the basal ganglia. However, little is known about the molecular and cellular mechanisms that underlie this communication. We show that intrastriatal nitric oxide (NO) signaling elevates the expression of the vesicular GABA transporter (VGAT) within recurrent collaterals of SPNs. Down-regulation of striatal NO signaling resulted in an attenuation of GABAergic signaling in SPN local collaterals, down-regulation of VGAT expression in local processes of SPNs, and impaired motor behavior. PKG1 and cAMP response element-binding protein are involved in the signal transduction that transcriptionally regulates VGAT by NO. These data suggest that transcriptional control of the vesicular GABA transporter by NO regulates GABA transmission and action selection.United States Army Medical Research Acquisition Activity (Grant W81XWH-09-1-0108

Individual Pause-and-Go Motion Is Instrumental to the Formation and Maintenance of Swarms of Marching Locust Nymphs

<div><p>The principal interactions leading to the emergence of order in swarms of marching locust nymphs was studied both experimentally, using small groups of marching locusts in the lab, and using computer simulations. We utilized a custom tracking algorithm to reveal fundamental animal-animal interactions leading to collective motion. Uncovering this behavior introduced a new agent-based modeling approach in which pause-and-go motion is pivotal. The behavioral and modeling findings are largely based on motion-related visual sensory inputs obtained by the individual locust. Results suggest a generic principle, in which intermittent animal motion can be considered as a sequence of individual decisions as animals repeatedly reassess their situation and decide whether or not to swarm. This interpretation implies, among other things, some generic characteristics regarding the build-up and emergence of collective order in swarms: in particular, that order and disorder are generic meta-stable states of the system, suggesting that the emergence of order is kinetic and does not necessarily require external environmental changes. This work calls for further experimental as well as theoretical investigation of the neural mechanisms underlying locust coordinative behavior.</p></div

Locust density and duration of the experimental trials.

<p>Locust density and duration of the experimental trials.</p

Parameters in the detailed model.

<p>Parameters in the detailed model.</p

The motion of a single animal is characterized by an intermittent pause-and-go motion.

<p>Upon every walking initiation an animal makes a decision of whether or not to swarm based on tactile and visual stimuli. (A) A snapshot from an experiment showing the path of individual animals over 3 seconds. Filled circles show the location of pauses. (B) A typical sequence of pause-and-go transitions in a single animal. (C) The distribution of pause times shows a power-law decay. (D) The distribution of walk times is well approximated by an exponential distribution.</p

Typical response of the DCMD to approaching (A) and receding (B) stimuli.

<p>DCMD spike occurrence times (blue) were extracted from the extracellular recordings (black). Individual raster trials were then smoothed with a 20 ms Gaussian window and an evaluation of the instantaneous firing rate (red) was calculated by normalizing the resulting waveform so that its integral equals the number of spikes in the trial. (C) Firing patterns of DCMD in a solitarious and a gregarious animal, in response to the four types of visual stimuli. Each raster plot includes the response of DCMD to 30 sequential stimulations of the same kind, with the first at the bottom of the stack. Mean instantaneous firing rate across trials is shown in the histogram below each raster plot. While the response of DCMD to a single approach and recession bear similarity between the two phases, gregarious nymphs show higher numbers of spikes in response to multiple approach and recession than solitarious animals.</p

Experimental results.

<p>(A) The average number of animals walking within 5cm of to an individual that is starting to walk. The vertical line shows the time of walking initiation. Green line: random frames and animals. Purple line: all walking initiation events. Blue line: tactile stimuli-related events. Red line: non-tactile events. (B–D) Zoom-in showing the interaction between conspecifics. (B) Tactile interaction (C) Visual stimulus from the front and (D) Visual stimulus from the rear. (E) The average number of walking animals before and after walking initiation (time = 0). Colors indicate front (red), back (blue) and both (green). (F) The probability of changing orientation (U-turn) when resuming movement is a function of the order parameter. As increases, the probability of turning in the direction the crowd moves (blue) becomes larger than the probability of turning against it (red). As expected, fluctuation at small are large since the system spends a relatively short amount of time in this state. The line shows a linear least squares fit as a guide to the eye.</p

Experimental setup and visual stimuli used for DCMD recording.

<p>Locust was mounted in between two computer monitors (1366×768 pixels; A, side view; B, top view showing only front monitor). Details of the relative position of the animal in relation to the screens’ surface are shown, as well as an example of one stimulus type (two objects approaching in the back visual field) as seen on the back monitor (C, looking at the animal from the front).</p

Detailed model results.

<p>(A) The dynamics of the system can be approximated by a coarse-grained continuous-time Markov chains with four states: A relatively static state in which most of the animals are standing, and three active states in which most of the animals are walking. The three active states can be classified according to the order parameter and correspond to one disordered and two ordered movement patterns. Numbers show the relative time the system spends in each state and the transition rates as obtained in simulations of the detailed model. (B) A snapshot from simulation showing standing (black) and moving (CW-blue, CCW-red) agents. (C) The time evolution of the fraction of walkers (red) and order parameter (blue) in a typical simulation.</p

Parameters in the simplified model.

<p>Parameters in the simplified model.</p