Active Signal Conduction through the Sensory Dendrite of a Spider Mechanoreceptor Neuron

Abstract

Rapid responses to sensory stimulation are crucial for survival. This must be especially true for mechanical stimuli containing temporal information, such as vibration. Sensory transduction occurs at the tips of relatively long sensory dendrites in many mechanoreceptors of both vertebrates and invertebrates, but little is known about the electrical properties of these crucial links between transduction and action potential generation. The VS-3 slit-sense organ of the spider Cupiennius salei contains bipolar mechanosensory neurons that allow voltage-clamp recording from the somata, whereas mechanotransduction occurs at the tips of 100- to 200-microm-long sensory dendrites. We studied the properties of VS-3 sensory dendrites using three approaches. Voltage-jump experiments measured the spread of voltage outward from the soma by observing total mechanically transduced charge recovered at the soma as a function of time after a voltage jump. Frequency-response measurements between pseudorandom mechanical stimulation and somatic membrane potential estimated the passive cable properties of the dendrite for voltage spread in the opposite direction. Both of these sets of data indicated that the dendritic cable would significantly attenuate and retard a passively propagated receptor potential. Finally, current-clamp observations of receptor potentials and action potentials indicated that action potentials normally start at the distal dendrites and propagate regeneratively to the soma, reducing the temporal delay of passive conduction.

Spider Peripheral Mechanosensory Neurons Are Directly Innervated and Modulated by Octopaminergic Efferents

“…tentials in spider VS-3 neurons are initiated in dendrites (Gingl and French, 2003;Gingl et al, 2004), but an additional initiation site is probably located in the axon hillock, because these neurons can also fire action potentials when the dendrites are severed (Sekizawa et al, 1999). Interestingly, GABAergic inhibition also occurs in the axons (Gingl et al, 2004), indicating that this is an important modulation site.…”

Random Stimulation of Spider Mechanosensory Neurons Reveals Long-Lasting Excitation by GABA and Muscimol

“…Previously, mechanically stimulated VS-3 neurons were shown to generate APs in the distal dendrite, close to the stimulation site (Gingl and French 2003;Gingl et al 2004). To learn whether muscimol-induced changes in firing rate occurred only for dendritic APs, we performed experiments where the VS-3 neuron somata were stimulated directly by the recording electrode.…”

“…This finding was also not shown by the simulated neurons. A possible explanation is that the voltage-clamp was limited to the neuron's cell body and nearby regions, whereas muscimol was still able to depolarize more remote regions, especially including the sensory dendrite, where action potentials are initiated (Gingl and French 2003;Gingl et al 2004). …”

“…Previous investigations showed that the distal dendrites of VS-3 neurons generate APs and that the inhibitory response to GABA A agonists occurs only in the axonal region (Gingl and French 2003;Gingl et al 2004). To learn whether the changes in the dynamic behaviors of dendritic and axosomatic regions are different when the GABA A receptor agonist muscimol is applied, we performed two series of experiments using either mechanical stimuli to generate dendritic APs or electrical stimuli to generate axosomatic APs.…”

The Complexity Based Analysis of the Correlation between Spider’s Brain Signal and Web

“…Between all studies done on animal behavior, spiders have aroused the attention of some scientists [1][2][3][4][5].An important behavior of spiders is building the web and several works have been done on studying this behavior [6][7].Between these works, few scientists have tried to analyze the behavior of spider on building its web by applying drugs on spider. The first study refers to the work done by Witt [8] in 1948.…”