Figure 1.
Schemata showing the standard preparation.
A deafferented ganglia (T2 meso- T3 metathoracic) with intact nerves to a wing elevator and wing depressor muscle (WE-M113, WD-M127) and severed nerves to leg muscles: N3B, which carries seven trochanteral levator motoneurons (TL) that innervate muscle M131 and the slow extensor tibiae motoneuron (SETi) to muscle M135; N5A, through which the common inhibitor (CI) and slow and fast trochanteral depressor motoneurons project to innervate the trochanter depressor muscle (TD, M133A). B Electromyograms from WE-M113 and WD-M127 showing fictive flight induced by bath application of the muscarinic agonist pilocarpine. We evaluated the rhythm cycle length (WD-WD), the WD-WE latency and the phase of the elevator in the depressor cycle (WE/WD-WD - not indicated). C Nerve recordings from nerves N3B and N5A showing fictive walking evoked by pilocarpine. The TL units in N3B serve to monitor the swing phase and the TD units the stance phase. We measured step-cycle length (TL-TL), the length of the swing phase (TL burst length) and the TL-TD latency (#, end of TL burst to begin of TD activity). Further details in text.
Figure 2.
A general comparison of natural and pharmacologically induced walking and flight motor activity in intact and deafferented locusts.
A Walking. Bars giving the start and end of the swing (grey) and stance (black) phases within the step cycle. Top (natural): data for naturally occurring, free walking from [34] (means of the activity of two antagonistic coxal muscles). Bottom (PC): Pilocarpine (1 mM) induced fictive walking (this paper, medians of 19 animals, 15 cycles each). B Flight. Bars giving the range of the phase of wing elevator (WE) units in the depressor cycle (WD-WD). Top (natural): Standard deviation (s.d.) of phase for intact tethered flying locusts from [35]. Middle (deaf.): Interquartile range (i.q.r.) of phase for wind-induce fictive flight of deafferented locusts (this paper, 35 animals, 100 cycles each). Bottom (PC): Interquartile range (i.q.r.) of phase for pilocarpine (1 mM) induced fictive flight of deafferented locusts (this paper, 19 animals, 100 cycles each). C, D Sequential plots comparing pilocarpine (PC, 1 mM) induced fictive walking and fictive flight respectively. C Step cycle length (black circles) and duration of the TL burst (grey circles) for 40 step cycles over a 3 min period. D Wing depressor cycle length (WD-WD, black circles), wing depressor-elevator latency (WD-WE, grey squares) and wing depressor-trochanteral depressor latency (WD-TD, black triangles) for 40 fictive flight cycles over a 3 s interval. Note that the flight sequence analyzed here comprises an entire stance phase of simultaneously occurring fictive walking. Abbreviations as in Fig. 1.
Figure 3.
Exemplary simultaneous recordings showing motor activity in leg (upper two traces) and wing motor units (lower two traces) evoked by drug application in deafferented locust preparations: A pilocarpine (1 mM), B octopamine (100 mM), C tyramine (100 mM); i, ii each show a longer sequence and detail respectively.
Abbreviations as in Fig. 1. Note that at the given concentrations pilocarpine and tyramine usually both evoke fictive walking together with flight, while octopamine evokes fictive flight in wing and leg motor units. The swing and stance phases of fictive walking are indicated by bars in Ai and Ci. Note coupling of leg unit TD to the WD (arrows in Aii, Bii).
Figure 4.
Bar charts giving the concentration dependent occurrence (%) of different types of motor activity evoked by: A pilocarpine, B octopamine, C tyramine in leg nerves (i upper charts) and wing muscles (ii lower charts).
Key (leg nerves): white bars: no activity; grey bars: pattern unclear; purple bars: fictive flight; light green bars: swing phase only; dark green bars: fictive walking. Key (wing muscles): white bars: no activity; blue bars: elevator only; red bars: depressor only, purple bars: fictive flight activity. Numbers in parenthesis give the number of preparations for each test group.
Figure 5.
Charts comparing key features of fictive walking patterns released by tyramine (TA, circles: 100 mM) and by a low and higher concentration of pilocarpine (PC, squares: 0.1 mM, triangles: 1 mM).
A Step cycle length, B TL burst length, C relative TL burst length (as % of step cycle length), D TL-TD latency. Symbols give the median, ticks the interquartile range and asterisks significant differences between indicated groups (Mann Whitney U test for unpaired data sets *p<0.05, **p<0.01, ***p<0.001). Numbers in parenthesis (chart A) give the number of preparations for each test group.
Figure 6.
Charts comparing key features of fictive flight patterns released by pilocarpine (PC, triangles: 1 mM), octopamine (OA, squares: 100 mM) and tyramine (TA, circles: 100 mM).
A Flight rhythm cycle length (WD-WD), B WD-WE latency, C phase of wing elevator in wing depressor cycle (WE/WD-WD), D WD-TD latency (coupling of leg unit TD to the wing unit WD), E phase of leg unit in wing depressor cycle (TD/WD-WD). Symbols give the median, ticks the interquartile range and asterisks significant differences between indicated groups (Mann Whitney U test for unpaired data sets *p<0.05, **p<0.01, ***p<0.001); n in the key gives numbers of preparations for each group evaluated.
Figure 7.
Charts comparing the degree of temporal coupling between different motor units for activity evoked by pilocarpine (PC, triangles: 1 mM), octopamine (OA, squares: 100 mM) and tyramine (TA, circles: 100 mM).
Temporal coupling was evaluated from the statistical dispersal for non-parametric data sets as given by the interquartile ranges, IQR, of the latencies and phases between units recorded for each animal in a group [33]: A WD-WE latency, B phase of wing elevator in wing depressor cycle (WE/WD-WD), C WD-TD latency (coupling of leg unit TD to the wing unit WD), D phase of leg unit in wing depressor cycle (TD/WD-WD). Abbreviations as in Fig. 1. Symbols give the median (of the IQRs), ticks the IQR (of this median) and asterisks significant differences between indicated groups (Mann Whitney U test for unpaired data sets *p<0.05, **p<0.01, ***p<0.001).
Figure 8.
Phase histograms giving the timing of different motor units (TL, TD, WE) within the cycle length for a representative recording of the flight rhythm (WD-WD cycle, normalized) as evoked by A pilocarpine (1 mM), B octopamine (100 mM), C tyramine (100 mM) and D wind: TL (upper trace in each panel), TD (second trace) and WE (third trace) in a normalized WD-WD cycle.
Each bin gives the number of spikes occurring in 1/50th of the cycle length.
Figure 9.
Evaluation of wind-evoked fictive flight.
A Simultaneous extracellular recordings of leg and wing motor units in a deafferented locust preparations with an intact head (abbreviations as in Fig. 1). B Bar giving the effectiveness of the wind stimulus as assessed from the percentage (%) of evoked flight sequences recorded for 35 animals, each in response to a series of 10 successive wind stimuli. C WD-WD cycle length. D WD-WE latency in ms. E phase of wing elevator in wing depressor cycle (WE/WD-WD). F WD-TD latency. G phase of leg unit in wing depressor cycle (TD/WD-WD). Columns in B–G give the median, and ticks the IQR.
Figure 10.
Relative changes (%) in A the effectiveness of wind stimulation to initiate flight, and B cycle length (WD-WD) of wind evoked fictive flight after treatment with (from left to right): octopamine (OA, 5 mM), the octopamine receptor antagonist epinastine (EP, 1 mM), tyramine (TA, 5 mM) and the tyramine receptor antagonist yohimbine (YO, 1 mM).
Numbers in parenthesis (in A) give the number of evaluated preparations for each test group. Columns give the median, ticks the interquartile range and asterisks significant changes (Wilcoxon Signed Rank test *p<0. 05).31.
Figure 11.
Relative changes (%) in the degree of temporal coupling between different motor units (evaluated as in Fig. 6) for wind evoked fictive flight following treatment with (from left to right): octopamine (OA, 5 mM), the octopamine receptor antagonist epinastine (EP, 1 mM), tyramine (TA, 5 mM) and the tyramine receptor antagonist yohimbine (YO, 1 mM).
Data from same preparations as for Fig. 9. A WD-WE latency, B phase of wing elevator in wing depressor cycle (WE/WD-WD), C WD-TD latency (coupling of leg unit TD to the wing unit WD), D phase of leg unit in wing depressor cycle (TD/WD-WD). Columns give the median, ticks the IQR and asterisks significant differences (Wilcoxon Signed Rank test *p<0.05, **p<0.01).