Neurochemical fine tuning of a peripheral tissue: peptidergic and aminergic regulation of fluid secretion by Malpighian tubules in the tobacco hawkmoth M. sexta
N. J. V. Skaer1,
D. R. Nässel2,
S. H. P. Maddrell1,* and
N. J. Tublitz3
1 Department of Zoology, Downing Street, University of Cambridge, Cambridge
CB2 3EJ, UK
2 Department of Zoology, Stockholm University, Svante Arrhenius väg 16,
SE-106 91 Stockholm, Sweden
3 Institute of Neuroscience, University of Oregon, Eugene, Oregon 97403
USA
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Fig. 1. Effects of serotonin and octopamine on fluid secretion by isolated pharate
adult M. sexta Malpighian tubules. (A) Effects of serotonin at three
different concentrations. (B) Effects of octopamine at three different
concentrations. In this and all subsequent figures, fluid secretion data are
normalized to the rate immediately prior to test substance application. Values
are means ± 1 S.E.M. (N=5). Each control trace in A and B
represents data from a single, separate trial.
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Fig. 2. Effects of 1 mmol l-1 cyclic AMP (cAMP) and 1 mmol
l-1 cyclic GMP (cGMP) on fluid secretion by isolated pharate adult
M. sexta Malpighian tubules. Cyclic nucleotides were added at the
time indicated by the vertical line. Values are means ± 1 S.E.M.
(N=5). Control trace represents data from a single trial.
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Fig. 3. Effects of leucokinin I (LK-I) at three different concentrations on fluid
secretion by isolated pharate adult M. sexta Malpighian tubules.
Values are means ± 1 S.E.M. (N=5). LK-I was added at the time
indicated by the vertical line. Control trace represents data from a single
trial.
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Fig. 4. Effects of individual cardioacceleratory peptides (CAPs) on fluid secretion
by isolated pharate adult M. sexta Malpighian tubules. See text for
CAP dosages. The CAPs were added at the time indicated by the vertical line.
Values are means ± 1 S.E.M. (N=5, except for CAP 1a/1b where
N=6). Control trace represents data from a single trial.
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Fig. 5. Effects of tachykinin-related peptides (TRPs) at four different
concentrations on fluid secretion by isolated pharate adult M. sexta
Malpighian tubules. (A) Effects of Locusta TK-1, (B)
Leucophaea TRP-1 and (C) Leucophaea TRP-4. The TRPs were
added at the time indicated by the vertical line. Values are means ± 1
S.E.M. (N=3). In each panel, control traces represent data from a
single, separate trial.
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Fig. 6. Interactions of leucokinin I (LK-I) and cyclic AMP (cAMP) on fluid
secretion by isolated pharate adult M. sexta Malpighian tubules. LK-I
(60 µmol l-1) or cAMP (1 mmol l-1) were applied at
the times indicated by the arrows. Solid line and arrows: cAMP added first
followed by LK-I; broken line and open arrows: LK-I added first followed by
cAMP. Values are means ± 1 S.E.M. (N=8).
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Fig. 7. Tracings of LTKLI neurons in the brain of a fifth instar larva of M.
sexta. (A) Cell bodies of the brain (filled cell bodies are posterior,
unfilled anterior). DN, cell body of the large descending neuron. (B) Tracing
of cell bodies and processes of some of the major posterior LTKLI neurons.
Note the varicose fibres distributed in the brain neuropil and in the four
commissures connecting the hemispheres. The arrow indicates two of the
ascending axons derived from the ventral nerve cord, with arborizations in the
tritocerebrum and protocerebrum. DN, the large descending neuron with
processes in the protocerebrum and axon (also at arrow) to the ventral nerve
cord. Scale bar, 100 µm.
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Fig. 8. Micrographs of LTKLI cells in M. sexta. (A) Whole mount of brain
of fifth instar larva. (B) Other focus and higher magnification shows varicose
branches of LTKLI neurons in larval brain. Note fibres in commissures. (C)
Unfused abdominal ganglion with LTKLI fibres in neuropils and entering from
anterior nerve root (arrow). Cell bodies are in other focal plane. (D)
Terminal abdominal ganglion with LTKLI cell bodies (arrows) and fibres in
neuropil. (E) Surface view of LTKLI endocrine cells of the midgut (e.g. at
arrows). The cells appear irregularly distributed partly because the intestine
became contracted at fixation. (F,G) Immunoreactive endocrine cells seen in
longitudinal view. Gut lumen is at bottom of panels. Scale bars: 100 µm
(A); 50 µm (B-D); 100 µm (E); 25 µm (F,G).
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Fig. 9. Micrographs of cryostat sections of brain from pharate adult M.
sexta labeled with antiserum to LomTK. (A) Fibres in the upper division
of the fan-shaped body of the central body complex (frontal section). Note
also fibres in superior median protocerebrum (above central body). (B) Fibres
in lower part of mushroom body calyx (large arrow) seen in frontal section.
Also in the upper parts there are thinner LTKLI fibres (small arrows). (C)
Antennal lobe with LTKLI fibres in all the glomeruli. Note also cell bodies
(arrow) which are part of a cluster of about 30 neurons supplying LTKLI fibres
to the glomeruli. (D) Also in the macroglomerular complex of the antennal lobe
there are varicose LTKLI fibres. (E-G) Immunoreactive neurons in optic lobes
(overview in G). (E) Large cluster of cell bodies at the anterior base of the
medulla. (F) Fibres in a thin layer of the medulla. (G) An overview of the
medulla (Me), lobula (Lo) and lobula plate (LP) is shown in horizontal
section. Note immunoreactive fibres in medulla and lobula plate (arrows).
Scale bars, 50 µm (A-E); 100 µm (G).
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Fig. 10. Tracing of LTKLI cell bodies in ventral nerve cord of fifth instar larva of
M. sexta. SOG, suboesophageal ganglion; T3, metathoracic ganglion;
A5, fifth unfused abdominal ganglion; TAG, fused terminal abdominal ganglion.
The median neuron in T3 is dorsal, other neurons are ventral. Scale bar, 100
µm.
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© The Company of Biologists Ltd 2002
