Intracellular recordings from interneurons and motoneurons in intact flying locusts

Abstract

SUMMARYIntracellular recordings were made from the neuropile processes of thoracic neurones of Locusta migratoria during bilateral kicks of the hindlegs. Electromyographic (EMG) recordings showed that the pattern of flexor and extensor tibiae muscle activity during kicks in this extensively dissected preparation was similar to that seen during a jump. Intracellular recordings from hindleg flexor and extensor motoneurones and from 13 identified interneurones revealed additional features of the motor programme for jumping and kicking and of the mechanism which triggers these events.There was a discrete burst of activity in the fast extensor tibiae (FETi) motoneurone at the end of the co-contraction phase, generated by a system that appeared to be separate from that triggering the kick. The excitatory connection from FETi to flexors was not responsible for initiating flexor activity and was of little functional importance in maintaining this activity during the co-contraction phase. The initial flexor excitation came from another, unidentified, central source.A pair of identified interneurones, the M-neurones, discharged with a high frequency burst just prior to the kick. Since these neurones inhibit hindleg flexor tibiae motoneurones, this observation provides further support for their proposed role as the neurones responsible for triggering kicks and jumps. Our data do not support the proposal that the activation of the M-neurones depends on them receiving progressively increasing proprioceptive input during the co-contraction phase. Throughout co-contraction, the M-neurones were hyperpolarized. Their activation was rapid and strong enough to cause them to discharge at rates as high as 400 spikes s" 1 . We suggest that the pulse-like activation of the M-neurones is produced centrally by a higher order system of interneurones.Another pair of previously identified interneurones, the C-neurones, were not necessary for the generation of the co-contraction phase of the motor programme. Their pattern of activity and their known connections indicated that they provide additional excitation to the flexors and extensors towards the end of co-contraction.Many other interneurones discharged either during co-contraction or when a kick was triggered. We conclude that the system generating the motor programme for a kick (jump) is more complex than proposed in previous studies.

Prothoracic DUM neurons of the cricket Gryllus bimaculatus ? responses to natural stimuli and activity in walking behavior

“…The body cavity was flushed with saline (pH 6.6; in g/l: 8.2 NaC1, 0.75 KCI, 0.4 NaHCO3, 0.45 NaH2PO4"2 H20, 0.4 MgC12-6 H20, 0.3 CAC12-2 H20, 5 glucose and, optionally, 1.5 trehalose, 0.11 N-Tris-(hydroxymethyl)methyl-2-aminoethanesulfonic acid). The prothoracic ganglion was ventrally supported by a silver platform, which also served as an indifferent electrode for recording, and stabilized by a silver ring, which was gently pressed to the dorsal surface of the ganglion (Wolf and Pearson 1987). Electrodes pulled from thin-walled glass capillaries and tipfilled with 5% Lucifer Yellow CH (Sigma) in 0.1 M LiC1 had initial resistances of 30-70 Mr2 and were inserted dorsally into the ganglion.…”

Frequency Control of Motor Patterning by Negative Sensory Feedback

“…All experiments were performed at room temperature (ϳ22°C) on adult locusts, Locusta migratoria (L.), obtained from a laboratory culture at the University of Ulm. Animals were mounted ventral side up to a fork-shaped holder by their thoracic sternites, and the thoracic ganglia were exposed (details by Wolf and Pearson, 1987). Standard recording techniques were used .…”

Flight motor patterns of locusts responding to thermal stimuli

“…Additionally, the activity of flight intemeurons can be recorded during intact tethered flight (Wolf and Pearson 1987). These preparations will dlow us to determine how the pattern of interneuron activity is modified during thermal presentations in almost intact flight.…”