Evidence for a role of GABA and Mas-allatotropin in photic entrainment of the circadian clock of the cockroach Leucophaea maderae
Bernhard Petri1,
Uwe Homberg2,
Rudolf Loesel2 and
Monika Stengl1,2,*
1 Institut für Zoologie/Biologie I, Universität Regensburg, 93040
Regensburg, Germany
2 Fachbereich Biologie, Tierphysiologie, Philipps-Universität Marburg,
35032 Marburg, Germany
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Fig. 5. Phase response curves obtained in response to 15 pmol of
 -aminobutyric acid (GABA), 0.15 pmol of Mas-allatotropin and control
injections. Data were merged into 2 h bins. Mean ± S.E.M.
transmitter-dependent phase shifts (black squares) and phase shifts following
control injections (grey circles) are plotted (see
Table 1 for values of
N) in the middle of each 2 h bin. Asterisks indicate significant
transmitter-dependent phase shifts (see values marked a in
Table 1).
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Fig. 1. -Aminobutyric acid (GABA) immunostaining in the optic lobe of
Leucophaea maderae. (A) Horizontal section through the optic lobe,
showing immunostaining in the lamina (La), medulla (Me), accessory medulla
(AMe) and lobula (Lo). The arrow points to immunostained accessory lamina at
the posterior proximal edge of the lamina. Asterisks indicate a strongly
stained layer in the medulla. dist, distal; front, frontal. Scale bar, 100
µm. (B) Superimposed images from two frontal sections through the accessory
medulla (AMe) and ventro-median aspects of the medulla (Me).
GABA-immunoreactive processes in the distal tract (DT) separate into two fibre
bundles (arrowheads) and innervate the noduli of the AMe. The thin black
arrows mark primary neurites of GABA-immunoreactive somata. Scale bar, 50
µm. (C) Horizontal view showing the frontal part of the medulla (Me), the
accessory medulla (AMe) and the distal tract (DT). A fascicle of immunostained
axons leaves the distal tract and enters a strongly immunopositive layer of
the medulla (arrow). Scale bar, 50 µm.
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Fig. 2. Frontal reconstructions of -aminobutyric acid (GABA)-immunoreactive
neurons innervating the accessory medulla (AMe). (A) Approximately 25 neurons
send primary neurites into the AMe. From the AMe, immunostained processes
continue in the distal tract (DT) along the anterior surface of the medulla
(Me) and enter the medulla at several sites. The arrowhead points to the cell
body of a neuron with a unique morphology shown in B. (B) The arborizations of
a large immunostained neuron could be reconstructed individually. This neuron
innervates the AMe and has tangential arborizations in the medulla. Six
neuronal processes give rise to extensive ramifications in the lamina (La) and
in small accessory laminae at the posterior inner edge of the lamina (arrows).
Scale bar (applies to both), 100 µm.
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Fig. 4. Scatterplots of -aminobutyric acid (GABA)- and
Mas-allatotropin-dependent phase shifts at different times in the circadian
cycle. (A) GABA injections (15±6 pmol in 1.5±0.6 nl of saline
with blue food dye, mean ± S.D.; N=35) cause maximal phase
delays during the early subjective night (-4.2 h at CT14:50 h) and maximal
phase advances during the middle of the subjective night (3.05 h at CT16:50h).
(B) Irrespective of the time of day, control injections (0.5-2 nl of saline
with blue food dye; N=43) caused only small statistically
non-significant phase delays and phase advances. (C) Injections of
Mas-allatotropin (150±60 fmol in 1.5±0.6 nl of saline with blue
food dye, mean ± S.D., N=36) cause maximal phase delays during
the early subjective night (-4.9 h at CT14:05 h) and maximal phase advances
during the middle of the subjective night (3.2 h at CT17:09 h). Each point
represents the phase shift (in circadian hours) resulting from a single
injection. Phase advances are shown as positive values and phase delays as
negative values.
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© The Company of Biologists Ltd 2002
of 3.05 circadian hours (hCT) after the
injection. (C,D) Injection of 50 pmol of GABA in 0.5 nl of saline with blue
food dye at CT 17:30 h of day 9 (arrowhead) induced a phase advance of 3.15
circadian hours. Neither experiment had any effect on the period 
of the
activity rhythm, after a new stable state, through several transient states
(days 17-28 in A; days 10-18 in C), had been established. CT, circadian
time.
