Anatomy and physiology of neurons composing the commissural ring nerve of the cricket,Acheta domesticus

Abstract

The commissural ring nerve (RN) of the cricket Acheta domesticus links together the two cercal motor nerves of the terminal abdominal ganglion. It contains the axons of almost 100 neurons including two bilateral clusters of eight to 13 ventrolateral neurons and approximately 75 neurons with midline somata within the terminal abdominal ganglion. The ventrolateral neurons have an ipsilateral dendritic arborization within the dorsal neuropil of the ganglion and their axons use the RN as a commissure in order to enter the contralateral nerves of the tenth ganglionic neuromere. In contrast, most midline neurons have bifurcating axons projecting bilaterally into the neuropil of the ganglion as well as into the RN where they often branch extensively before entering the contralateral tenth nerves. Most RN neurons have small, non‐spiking somata with spike initiation zones distant from the soma. Many midline neurons also produce double‐peaked spikes in their somata, indicative of multiple spike initiation zones. Spontaneous neuronal activity recorded extracellularly from the RN reveals several units, some with variable firing patterns, but none responding to sensory stimuli. The RN is primarily composed of small (50 nm diameter) axon profiles with a few large (0.5–1 μm diameter) profiles. Occasionally, profiles of nerve terminals containing primarily small clear vesicles and a few large dense vesicles are observed. These vesicles can sometimes be clustered about an active zone. We conclude that the primary function of the RN is to serve as a peripheral nerve commissure and that its role as a neurohemal organ is negligible. J. Exp. Zool. 286:350–366, 2000.© 2000 Wiley‐Liss, Inc.

Hidden synaptic differences in a neural circuit underlie differential behavioral susceptibility to a neural injury

“…Since the early description of the crustacean cardiac ganglion (Bullock and Terzuolo, 1957), there have been numerous reports on multiple spike initiation zones in single neurons. Such neurons include crustacean stomatogastric ganglion neurons (Moulins et al, 1979; Meyrand et al, 1992; Combes et al, 1993; Smarandache and Stein, 2007; Thuma et al, 2009), molluscan giant neurons (Tauc and Hughes, 1963; Zecevic, 1996; Antic et al, 2000), and insects sensory neurons (Heitler and Goodman, 1978; Killian et al, 2000). In these neurons, individual spike-initiation zones can independently fire, which can also be the target for neuromodulation (Daur et al, 2009; Bucher and Goaillard, 2011).…”

Regulation of motor patterns by the central spike‐initiation zone of a sensory neuron

“…In small nervous systems it may be advantageous to combine multiple functions in a single cell for neural economy (Heitler & Goodman, 1978; Clark et al. , 2006), for example by adding spatially separated axonal spike‐initiation zones that innervate different targets (Killian et al. , 2000).…”

Spatial dynamics of action potentials estimated by dendritic Ca2+ signals in insect projection neurons

“…The recordings from the dendrites of GIs 10-2 and 9-3 often indicated action potentials with double peaks at different amplitudes (Fig. 3B), thereby suggesting the presence of multiple SIZs [31]. Furthermore, the action potentials evoked by stimulation ipsilateral to the recording site had a shorter delay than those evoked by contralateral side stimulation ( Fig.…”

“…It is also possible that the action potential itself is generated at the dendritic shaft close to the activated input sites, thereby causing greater depolarization. In some arthropod neurons, multiple SIZs have been identified, each of which generates action potentials independently [5][6][7]31]. The recordings from the dendrites of GIs 10-2 and 9-3 often indicated action potentials with double peaks at different amplitudes (Fig.…”