Left-right asymmetry in firing rate of extra-retinal photosensitive neurons in the crayfish

Abstract

The purpose of this paper is to explore the firing rate of the caudal photoreceptors (CPRs) from the sixth abdominal ganglion of the crayfish Cherax quadricarinatus. We use simultaneous extracellular recordings on left and right CPR in the isolated ganglion (n = 10). The CPRs showed an asymmetry in the spontaneous activity and light-induced response. In darkness, we observed one subgroup (70%) in which the left CPR (CPR-L) and right CPR (CPR-R) had spontaneous firing rates with a median of 18 impulses/s and 6 impulses/s, respectively. In another subgroup (20%), the CPR-R had a median of 15 impulses/s and the CPR-L had 8 impulses/s. In both groups, the differences were significant. Furthermore, the CPRs showed an asymmetrical photoresponse induced by a pulse of white light (700 Lux, 4 s). In one subgroup (30%), the CPR-L showed light-induced activity with a median of 73%, (interquartile range, IQR = 51), while the CPR-R had a median of 41%, (IQR = 47). In another subgroup (70%), the CPR-R showed a median of 56%, (IQR = 51) and the CPR-L had a median of 42%, (IQR = 46). In both groups, the differences were significant. Moreover, we observed a differential effect of temperature on CPR activity. These results suggest a functional asymmetry in both activities from left and right CPRs. These CPR activity fluctuations may modulate the processing of information by the nervous system.

Asymmetric Firing Rate from Crayfish Left and Right Caudal Photoreceptors Due to Blue and Green Monochromatic Light Pulses

“…Our results support the presence of the SWS, and the LWS opsins in the CPRs, which showed sensitivities to blue and green light, respectively [20,21]. In addition, the current results provide support for the functional asymmetries described recently as a novel property for both CPR-L and -R when comparing their responses induced by white light pulses in the same species of crayfish C. quadricarinatus [34]. At room temperature of 24 (±1) • C, we found a significant difference in the amplitude, time to peak, and duration in action potentials extracellularly recorded from CPR-L and -R in most of the comparisons (Tables 1-6).…”

“…At room temperature of 24 (±1) • C, we found a significant difference in the amplitude, time to peak, and duration in action potentials extracellularly recorded from CPR-L and -R in most of the comparisons (Tables 1-6). Some factors could contribute to these differences: the position within the connective tract connective of the CPR-L-axon is in Wiersma area 82, which is more superficial with respect at to the position of the CPR-R-axon that is in area 79 of the cord map of the crayfish [33,34]. The waveform of the extracellular action potential varies with electrode position relative to the recorded cell [36], the amplitude of the action potential is function on the diameter of the axon [37] and neurons with many dendrites will produce large amplitude spikes [38].…”

“…In both conditions, the difference was significant. Moreover, a differential effect of temperature on CPRs activity from the crayfish Cherax quadricarinatus was also noted [34].…”

“…Electrophysiological experiments were performed following a previously described procedure [34]. Briefly, we isolated the abdominal ganglia chain from the crayfish under ice-cold conditions, with a modified physiological saline Van Harreveld (VH) solution [35], (205 mM NaCl, 5.4 mM KCl, 2.6 mM MgCl 2 , 13.5 mM CaCl 2 , and 10 mM HEPES), and pH to 7.4.…”

“…Here both photosensitive neurons were arbitrarily simplified; based on [11]. Extracellular recordings were performed using a suction electrode; adapted from [34]. From recordings observed in the averaged potentials (Figure 1c,e), Tables 1 and 2 shown data analysis for these electrophysiological parameters.…”