Chem. Senses 27: 475-483,
2002
© Oxford University Press 2002
Morphology and Physiology of the Serotonin-immunoreactive Putative Antennal Lobe Feedback Neuron in the Male Silkmoth Bombyx mori
Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
Correspondence to be sent to: Ryohei Kanzaki, Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan. e-mail: kanzaki{at}biol.tsukuba.ac.jp
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Abstract |
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In the male silkmoth Bombyx mori, olfactory information is relayed from olfactory receptor neurons in the antennae to the antennal lobe, and then to a variety of protocerebral neuropils. Currently, very little is known about neuromodulators that may affect the dynamics of this olfactory neural network. Immunocytochemical studies have revealed the presence of a serotonin-immunoreactive (SI) neuron that, in several insect species, is thought to provide feedback to the antennal lobe. To date, no studies have revealed details of this neuron's physiology. Using intracellular recording and staining, the silkmoth SI neuron (in two individuals) was first characterized physiologically and then stained with Lucifer Yellow to reveal morphological details. Immunocytochemical methods were also used to confirm the presence of serotonin. The silkmoth SI neuron branched in many important brain neuropils such as the mushroom body, central body, lateral accessory lobe and antennal lobe. The SI neuron in both individuals fired spontaneous, long duration action potentials, and responded to mechanosensory stimuli to the antennae.
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Introduction |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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The biogenic amine serotonin acts as an important neuro-modulator in the nervous systems of many insects (Nässel, 1988
). In the
hawkmoth Manduca sexta, for example, bath application of serotonin
enhances the responses of neurons in the antennal lobe (AL: the first-order
olfactory center) to pheromonal and electrical stimuli
(Kloppenburg and Hildebrand,
1995; Kloppenburg et
al., 1999). Additionally, serotonin application increases the
amplitude and duration of pheromone-evoked local field potentials, as well as
the amplitude of potential oscillations in the macroglomerular complex (MGC)
of M. sexta (Kloppenburg and
Heinbockel, 2000). Similarly, in the silkmoth Bombyx
mori, high-speed optical imaging experiments using a voltage-sensitive
dye have revealed that both the maximum amplitude and duration of optical
responses (to electrical stimulation of the antennal nerve) in the MGC and in
the ordinary glomeruli (Gs) are enhanced by bath application of serotonin
(Hill et al., 2001).
Furthermore, serotonin inhibits two types of K+ currents as well as
a voltage-activated Ca2+ current in cultured M. sexta AL
neurons (Mercer et al.,
1995). It has been proposed that the effects on the K+
currents underlie the serotonin-induced enhancement of AL neurons' responses
to pheromonal stimuli.
In a variety of insect species, immunocytochemical studies have revealed
the presence of a pair of serotonin-immunoreactive (SI) neurons with branches
throughout one AL as well as in higher order neuropil regions of the brain
(Schürman and Klemm,
1984; Kent et al.,
1987; Rehder et al.,
1987; Homberg and Hildebrand,
1989; Breidbach,
1990; Salecker and Distler,
1990; Sun et al.,
1993). Light and electron microscopic studies of these neurons in
M. sexta and in the American cockroach Periplaneta americana
have revealed that these SI neurons mainly have output synapses in the AL and
it has been proposed that the SI neurons may be involved in a feedback system
from the protocerebrum (PC) to the AL
(Salecker and Distler, 1990;
Sun et al.,
1993).
At present, nothing is known about the physiology of these SI putative AL feedback neurons. Do they fire spontaneous action potentials? Do they respond to olfactory or mechanosensory stimuli, and if so what is the latency of the response? These are questions that can only be answered by intracellular recording from the SI neuron. We have succeeded twice in recording intracellularly from the SI putative AL feedback neuron in the male silkmoth. Additionally, iontophoretic injections of Lucifer Yellow (LY) were performed to allow us to examine in detail the morphology of this neuron. We found that the silkmoth SI neuron branched in many important brain neuropils including the calyces of the mushroom body, the central body and the lateral accessory lobe (LAL). The SI neuron in both individuals fired spontaneous, long duration action potentials and responded to mechanosensory stimuli.
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Materials and methods |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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Physiology
Adult silkmoth (Bombyx mori) males were used within 2-4 days of
eclosion. The legs were removed, and then the moth was placed in an
experimental chamber. The head capsule was opened, and most of the muscles and
tracheae were removed. The brain was desheathed using finely sharpened
forceps. A glass microelectrode [4% Lucifer Yellow CH (LY, Sigma, St Louis,
MO) in the tip; resistance 
150 M
] was inserted into the PC in the
region of the LAL in order to record from thick branches of the SI neuron. The
brain was superfused with physiological saline containing (mM): 140 NaCl, 5
KCl, 7 CaCl2, 1 MgCl2, 4 NaHCO3, 5 trehalose
and 5 N-tris (hydroxymethyl)-methyl-2-amino-ethanesulfonic acid (TES) and 100
sucrose (pH 7.3).
Olfactory stimuli were delivered using a puff stimulation system
(Kanzaki et al., 1989)
to both antennae. Two glass stimulant cartridges (Pasteur pipette, 1 mm tip
diameter; air flow of 3-5 ml/s) containing a piece of filter paper (1 x
2 cm) bearing either the major pheromone component (sufficient to trigger the
complete pheromone searching behavior) bombykol
[(E,Z)-10,12-hexadecadienol, 100 ng] or the minor pheromone component
bombykal [(E,Z)-10,12-hexadecadienal, 100 ng] were positioned 2
cm from the antennae. Both bombykol and bombykal were dissolved in
n-hexane to allow application of the odorants to the filter paper;
after application n-hexane was allowed to dry off before the filter
paper was placed in the stimulant cartridge. The blank was n-hexane.
The puff duration was 500 ms. Odorants were removed by gentle suction into an
exhaust tube positioned behind the preparation. Neurons were also tested for
responses to visual stimuli, either light on [from dark (50 lx) to bright (890
lx) or light up gradually (from dark (50 lx) to bright (6100 lx)].
Following the collection of physiological data, LY was injected iontophoretically by 0.2-1.5 nA constant hyper-polarizing current for 1-4 min. After injection of LY, brains were removed surgically from the head capsule and fixed for 2 h in 4% paraformaldehyde at 4°C. Following fixation, brains were dehydrated through an ethanol series and cleared in methyl salicylate. LY fills were then examined as whole mounts with a laser scanning confocal microscope (LSM 510, Carl Zeiss, Jena, Germany). Acquired signals were recorded on a DAT recorder (RD-125 T, TEAC, Tokyo, Japan) at 24 kHz, and later analyzed using various software programs (Quik Vu II, TEAC; Igor, Wave Metrics, Lake Oswego, OR). We wrote a program in Visual BASIC (ver. 6.0) to calculate instantaneous spike frequency.
Immunocytochemistry
After imaging with a confocal microscope, LY-stained brains were returned
to 100% ethanol, and then rehydrated through an ethanol series.
Immunocytochemical double-labeling was then performed on the LY-stained brain.
The brain was permeabilized overnight at 4°C in phosphate-buffered saline
solution containing 0.5% Triton X-100 (0.1 M, pH 7.4) (PBSX). The brain was
embedded in 7% agarose and 250 µm thick sections were made with a vibrating
microtome (Microslicer, Dosaka EM, Kyoto, Japan). Microtome sections were
collected and washed in PBSX for 10 min at 4°C. Subsequently, sections
were incubated with 5% normal goat serum (NGS, Sigma) for 1 h at room
temperature in order to block non-specific staining. The sections were then
incubated for 18 h at 4°C with the primary antibody [1:2000 rabbit
anti-serotonin IgG (Diasorin, Stillwater, MN) in PBSX containing 5% NGS]. The
sections were next rinsed with PBSX and then incubated for 18 h at 4°C in
a solution of fluorescent dye-conjugated anti-rabbit secondary antibody
(1:200, Cy3 conjugated goat anti-rabbit, Chemicon, Temecula, CA). The sections
were then washed at room temperature with PBSX. Finally, sections were
dehydrated through an ethanol series and cleared in methyl salicylate. The
primary antibody used in this study (Diasorin) has been used in previously
published immunocytochemical studies
(Seidel and Bicker, 1996).
They showed that pre-adsorption of the antiserum with serotonin—BSA
(bovine serum albumin) conjugates abolished staining on microtome
sections.
Confocal microscopy
LY-stained neurons were imaged frontally and dorsally with the brain as a whole mount using a laser scanning confocal microscope. Serial optical sections were acquired at 1-2 µm intervals throughout the entire depth of the neuron. Optical sections were stacked upon each other, giving a three-dimensional reconstruction of the stained neuron. Confocal stacks of images were fitted together and adjusted for contrast and brightness using Adobe Photoshop 5.5.
Following immunocytochemical processing for serotonin, optical sections were imaged with the confocal microscope using appropriate filters to view: first LY and then Cy-3 in the same optical section (excitation: 458 and 543 nm, respectively; emission: longpass 475 and 565 nm, respectively). For scanning of double-labeled sections, optical slices were set at 1.6-1.8 µm. Images were adjusted for contrast and brightness using Adobe Photoshop 5.5.
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Results |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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LY fill
We recorded physiological activity from and stained with LY the silkmoth SI
putative AL feedback neuron in two different preparations. Confocal microscopy
was used to examine in detail the morphology of these two neurons, and we
found that they both resembled morphologically the SI putative AL feedback
neurons reported in M. sexta and P. americana
(Kent et al., 1987;
Salecker and Distler, 1990;
Sun et al., 1993).
Both neurons had their somata in the posterior portion of the lateral cell
cluster of one AL and branched throughout the contralateral AL (both Gs and
MGC) (Figure 1). The neurons
also had processes in both the ipsi- and contralateral superior PC (Figures
1 and
3C), the ipsilateral LAL
(Figures 1 and
4A,B), the calyces of both
mushroom bodies (Figure 4C,D),
and in the central body (Figures
1 and
4E,F). Examination of
individual optical sections revealed that both neurons branched in every
ordinary glomerulus, and in each compartment (cumulus, toroid and horseshoe 1
and 2) of the MGC (e.g. Figures
2 and
3A,B). The primary neurite of
each neuron projected through the ipsilateral AL where it had a few fine
branches in the posterior coarse neuropil region of the AL
(Figure 3D).
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Double labeling demonstrates that these neurons are SI
Immunocytochemical processing for serotonin revealed that one of the LY-stained neurons (SI neuron #1) was in fact SI. Although we did not perform immunocytochemical experiments on the second neuron stained with LY, its morphology was identical to SI neuron #1, therefore we will refer to the second LY stained neuron as SI neuron #2. Most parts of SI neuron #1 showed serotonin immunoreactivity. Figure 2 shows double-labeling in the contralateral MGC (Figure 2A-C), the contralateral Gs (Figure 2D-F) and in the ipsilateral AL (Figure 2G-I) of SI neuron #1. LY images are shown in the left-hand column, serotonin immunostaining in the middle column and double-labeling is shown in the right-hand column. Virtually every LY stained process in the contralateral MGC also showed serotonin immunoreactivity (Figure 2A-C). In the contralateral Gs, again, virtually every LY stained process also showed serotonin immunoreactivity (Figure 2D-F). In the contralateral Gs, a process that was not stained with LY also showed serotonin immunoreactivity (arrows in Figure 2E,F). In the ipsilateral AL, double-labeling of the LY-stained soma can be observed (Figure 2G-I). The primary neurite was only very weakly serotonin immunoreactive (Figure 2H). In the ipsilateral AL, many SI processes that were not stained with LY can be observed (arrows in Figure 2H,I). These processes can be attributed to the counterpart of the LY-stained SI neuron.
In other brain regions, double-labeling was also observed, but in some cases only parts of processes showed serotonin immunoreactivity and some cases, fine LY-stained processes did not show serotonin immunoreactivity (data not shown).
Detailed morphology of the SI neuron revealed by intracellular staining
Examination of the LY-stained SI neuron in two individuals with a confocal microscope revealed that in both cases the SI neuron had extensive branchings in important neuropils including the calyces of both mushroom bodies, the ipsilateral LAL, the central body, the contralateral AL, and both the ipsi- and contralateral superior PC.
The SI neuron's processes in both the contralateral Gs and MGC (Figure 3A,B), and in the ipsilateral LAL (Figure 4A,B) were thicker and more varicose than those seen in other brain regions (Figures 3C,D and 4C-F). Figure 3C shows fine processes in the ipsilateral superior PC (anterior to the calyx of the mushroom body). The SI neuron also had fine processes in the posterior coarse neuropil region of the ipsilateral AL (Figure 3D). In the contralateral AL the SI neuron's branches were restricted to the inner portions of Gs and MGC compartments (Figure 2C,F).
The SI neuron had extensive processes in the ipsilateral LAL. These processes were located in the dorsal region of the LAL (Figure 4A). In Figure 4B, varicose processes can be seen in a dorsal view of the LAL. Both SI neurons had many fine processes throughout the calyces of both mushroom bodies. Numerous fine processes can be seen in both the ipsilateral (Figure 4C) and contralateral (Figure 4D) calyces. Interestingly, the fine processes were not stained by serotonin immunocytochemistry (data not shown). Therefore, the presence of fine processes throughout the calyces of both mushroom bodies could only have been detected by intracellular staining of the SI neuron. The SI neuron had fine processes throughout the central body. In Figure 4E,F, two confocal stacks throughout the central body are shown. In both anterior (Figure 4E) and posterior (Figure 4F) stacks thick processes are seen entering the dorsal part of the central body, with finer processes extending throughout the neuropil.
Physiology
In both individuals, bombykol and blank stimuli elicited very similar
responses from the SI neuron in terms of spike frequency and number of spikes
fired. A mechanosensory response is a response to the air puff associated with
an odor and not to the odor itself. Therefore we believe that the responses of
the SI neuron in both individuals are actually mechanosensory in nature. SI
neuron #1 responded to bombykol and blank stimulation
(Figure 5A) with a burst of
6-10 action potentials with a peak frequency between 35 and 55 Hz (n
= 6), which was higher than the background frequency level of 4 Hz. SI
neuron #2 responded to bombykol, bombykal and blank stimulation
(Figure 5B) with a brief
increase in spike frequency. The responses had a peak spike frequency of
10 Hz, which was higher than the background frequency of 2.5 Hz.
Neither SI neuron responded to visual stimuli (data not shown). The average
latency of the responses of SI neuron #1 was 157.1 ± 12.5 ms
(n = 6), and the average latency of the responses of SI neuron #2 was
204.3 ± 7.0 ms (n = 6). In both cases, there were no
significant differences in the latencies of the responses to bombykol,
bombykal or the blank.
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The action potentials recorded in the SI neuron in both individuals had considerably longer durations than those of typical silkmoth PC neurons (PCNs). In Figure 6A, action potentials recorded from the SI neuron are shown. The action potentials in SI neuron #1 had an average duration of 9.3 ± 0.5 ms (n = 25) and those in SI neuron #2 had an average duration of 4.5 ± 0.3 ms (n = 25), whereas the action potentials recorded from three other typical silkmoth PCNs had much shorter durations (PCN #1: 1.6 ± 0.1 ms (n = 25), PCN #2: 1.4 ± 0.08 ms (n = 25), PCN #3: 2.6 ± 0.2 ms (n = 25) (Figure 6B). PCNs were identified as such by confocal examination of LY fills.
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Discussion |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
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The silkmoth neuron from which we, in two individuals, recorded physiological activity and stained with LY resembles a SI putative AL feedback neuron that has been reported in several insect species using immunocyto-chemical methods (Schürman and Klemm, 1984
; Kent et
al., 1987; Rehder et
al., 1987; Homberg and
Hildebrand, 1989; Breidbach,
1990; Salecker and Distler,
1990; Sun et al.,
1993). Furthermore, double-labeling with serotonin
immunocytochemistry confirmed the presence of serotonin in one of these
neurons (SI neuron #1). In both individuals, the SI neuron responded to
mechanosensory stimuli and not to visual stimuli. Examination of the LY stains
of the SI neuron with a confocal microscope revealed extensive branches in
areas of the brain that had not been reported in immunocytochemical studies of
similar SI neurons in other insects (Kent
et al., 1987;
Salecker and Distler, 1990;
Sun et al.,
1993).
Where does the SI neuron receive synaptic input and where does it output? A
definitive answer to this question can only be obtained using electron
microscopy and is beyond the scope of this study. However, based on the
appearance of LY-stained processes we can make inferences as to potential pre-
and postsynaptic regions similar to those made in previously published studies
(Kondoh and Hisada, 1986;
Mishima and Kanzaki, 1999;
Lei et al., 2001). In
these studies the authors proposed that thick or blebby processes could
represent presynaptic processes and that thin or smooth processes could be
postsynaptic processes. Furthermore, similar inferences have been drawn in
determining the possible synaptic polarity of crayfish neurons
(Kondoh and Hisada, 1986).
Branches in the contralateral AL and in the LAL of the SI neuron in both
individuals appear thicker and more varicose than processes in all other
regions of the brain. Previous electron microscopic studies
(Salecker and Distler, 1990;
Sun et al., 1993) of
similar SI neurons in P. americana and M. sexta reported
that these neurons make mostly output synapses in the contralateral AL.
Therefore, the thick, varicose appearance of processes in the contralateral AL
is consistent with this hypothesis and suggest that the SI neuron in B.
mori may also have mainly presynaptic processes in the contralateral AL.
The varicose appearance of the processes in the LAL leads us to speculate that
these may also represent output synapses.
Some local interneurons (LNs) in B. mori have branchings in the AMMC (antenno-mechanosensory motor center), the Gs, and in the posterior coarse neuropil region of the AL (Y. Seki, personal communication). These LNs may provide a link between the AMMC and the AL, causing AL neurons to respond to mechanosensory as well as olfactory stimuli. It is interesting to note that the fine processes of the SI neuron are also located in the posterior coarse neuropil region of the ipsilateral AL. The fine appearance of the SI neuron's processes in this region suggests that these may be postsynaptic in nature.
A similar SI neuron in P. americana was also reported to have
branches in the calyx of the mushroom body
(Salecker and Distler, 1990),
however no such branches were reported in the M. sexta SI neuron
(Kent et al., 1987).
The fine appearance of the branches of the B. mori SI neuron in the
calyces suggests that they may serve a postsynaptic function. We found that
these fine processes were either only weakly serotonin immunopositive or did
not show serotonin immunoreactivity at all. Coupled with the fact that
brilliant serotonin immunoreactivity was observed throughout the calyces of
both mushroom bodies (data not shown), it would have been impossible to
confirm the presence of the SI neuron's branches in the calyces of the
mushroom body relying solely upon immunocytochemical methods. This may explain
why no report of processes in the calyces of the mushroom body was made in
M. sexta in studies relying solely, or mainly, upon
immunocytochemical methods to characterize the SI neuron
(Kent et al., 1987;
Sun et al., 1993).
Additionally, this may also explain why previous studies of a similar SI
neuron in M. sexta reported no branches in the coarse neuropil region
of the ipsilateral AL or in the ipsilateral LAL. Alternatively,
species-specific differences could also account for the differences in the
branching areas between B. mori and M. sexta.
The present data are the first report of the SI neuron having branches in
the LAL, thought to be a convergence center for multi-modal neural processing
in which many descending interneurons, which link the brain to the thoracic
motor center, have branches (Kanzaki et al.,
1991a,
b,
1994;
Kanzaki and Shibuya, 1992;
Mishima and Kanzaki, 1999;
Lei et al., 2001).
The varicose appearance of LY-stained processes in the LAL leads us to
speculate that these may be presynaptic in nature. Consequently, the
possibility that the SI neuron may output in both the contralateral AL and in
the ipsilateral LAL arises. Intracellular recording studies have demonstrated
that serotonin enhances the olfactory responses of both AL neurons and PC
neurons with branches in the LAL
(Kloppenburg et al.,
1999; Hill and Kanzaki,
2000). The enhancement of olfactory responses of interneurons in
these two important neuropils would have a multiplicative effect, and the
sensitivity of the moth to olfactory stimuli would be increased much more than
if interneurons in only one (i.e. the AL) of the two neuropils were affected.
On the other hand, until an electron microscopic study of the processes in the
LAL is performed, the possibility that the processes are postsynaptic in
nature remains. In such a scenario, neural information would be relayed from
the last olfactory processing neuropil in the insect brain (the LAL) to the
first (the AL).
Electron microscopic studies of similar SI neurons in P. americana
and M. sexta have demonstrated the presence of both input and output
synapses in the AL (Salecker and Distler,
1990; Sun et al.,
1993), suggesting that the SI neuron may participate in local
processing in the AL, in addition to centrifugal processing. Until electron
microscopic analyses of the protocerebral branches of the SI neuron are
performed, the possibility that the SI neuron also participates in local
processing in various protocerebral neuropils must be considered. For
instance, it is conceivable that rather than acting as a centrifugal neuron,
the SI neuron could be involved in local processing (input-output) in each of
the neuropils in which it branches.
The SI neuron in both individuals exhibited low frequency (2.5-4 Hz)
spontaneous firing of long duration action potentials and responded to
mechanosensory stimuli. The long duration of the action potentials recorded in
the SI neuron is similar to those observed in B. mori neurosecretory
neurons (Ichikawa, 2001). While
the SI neuron in both individuals responded to mechanosensory stimuli with
increases in spike frequency, the responses of SI neuron #1 were much greater
in terms of peak spike frequency and number of spikes in the burst. These
discrepancies could be due to differences in the air-flux of the stimuli, or
it is possible that there may be some individual differences in the responses
of the SI neuron. Since the SI neuron in both cases responded to
mechanosensory stimuli, we speculate that the SI neuron may mediate an
increase in serotonin levels in neuropils in which it outputs in response to
mechanosensory stimuli. Such increases in serotonin levels would potentially
lead to an increased sensitivity to subsequent exposure to pheromonal or
general odor stimuli. Mechanosensory stimuli are abundant during the course of
the male silkmoth's pheromone searching behavior. Due to the fact that odors
are carried to the moth's antennae by wind, there is the `passive'
mechanosensory stimulus of the air movements. Next, the wing fluttering
associated with B. mori pheromone-triggered upwind walking is an
example of an `active' mechanosensory stimulus. Both of these stimuli could,
in theory, cause the SI neuron to increase its firing rate briefly, thus
increasing transiently the levels of serotonin in certain neuropils. Such
increases in serotonin levels would potentially increase the moth's
sensitivity to the pheromone source it is tracking.
The presence of a similar SI neuron in a variety of insects suggests that serotonergic modulation, and the flexibility it confers upon neural processing, is of great importance for insect olfaction.
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Acknowledgments |
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This work was supported by the Program for the Promotion of Basic Research Activities for Innovative Biosciences and the Ministry of Education, Culture, Sports, Science and Technology of Japan.
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References |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Breidbach, O. (1990) Serotonin-immunoreactive brain interneurons persist during metamorphosis of an insect: a developmental study of Tenebrio molitor, L. (Coleoptera). Cell Tissue Res.,259 , 345-360.
Hill, E.S. and Kanzaki, R. (2000) Analyzing the roles of GABA and serotonin in the protocerebral generation of the flipflop neural code of the male silkmoth Bombyx mori. Soc. Neurosci. Abstr., 26,1208 .
Hill, E.S., Okada, K. and Kanzaki, R. (2001) Serotonergic modulation in the antennal lobe of the male silkmoth Bombyx mori revealed by high-speed optical imaging with a voltage-sensitive dye. Zool. Sci. Abstr.,18 , 115.
Homberg, U. and Hildebrand, J.G. (1989) Serotonin-immunoreactive neurons in the median protocerebrum and subesophageal ganglion of the sphinx moth Manduca sexta. Cell Tissue Res., 258,1 -24.[Web of Science][Medline]
Ichikawa, T. (2001) Ultradian firing rhythm of neurosecretory cells producing an insulin-related peptide in the silkmoth Bombyx mori. Zool. Sci.,18 , 151-158.
Kanzaki, R. and Shibuya, T. (1992) Long-lasting excitation of protocerebral bilateral neurons in the pheromone-processing pathways of the male moth Bombyx mori. Brain Res., 587,211 -215.[Web of Science][Medline]
Kanzaki, R., Arbas, E.A. and Hildebrand, J.G. (1991a) Physiology and morphology of protocerebral olfactory neurons in the male moth Manduca sexta. J. Comp. Physiol. A, 168,281 -298.[Medline]
Kanzaki, R., Arbas, E.A. and Hildebrand, J.G. (1991b) Physiology and morphology of descending neurons in pheromone-processing olfactory pathways in the male moth Manduca sexta.J. Comp. Physiol. A , 169,1 -14.[Medline]
Kanzaki, R., Arbas, E.A., Strausfeld, N.J. and Hildebrand, J.G. (1989) Physiology and morphology of projection neurons in the antennal lobe of the male moth Manduca sexta.J. Comp. Physiol. A , 165,427 -453.[Medline]
Kanzaki, R., Ikeda, A. and Shibuya, T. (1994) Morphological and physiological properties of pheromone-triggered flipflopping descending interneurons of the male silkworm moth Bombyx mori. J. Comp. Physiol. A,175 , 1-14.
Kent, K.S., Hoskins, S.G. and Hildebrand, J.G. (1987) A novel serotonin-immunoreactive neuron in the antennal lobe of the sphinx moth Manduca sexta persists throughout postembryonic life. J. Neurobiol.,18 , 451-465.[Web of Science][Medline]
Kloppenburg, P., Ferns, D. and Mercer, A.R.
(1999) Serotonin enhances central olfactory neuron responses
to female sex pheromone in the male sphinx moth Manduca sexta. J.
Neurosci., 19,8172
-8181.
Kloppenburg, P. and Heinbockel, T. (2000) 5-hydroxytryptamine modulates pheromone-evoked local field potentials in the macroglomerular complex of the sphinx moth Manduca sexta. J. Exp. Biol., 203,1701 -1709.[Abstract]
Kloppenburg, P. and Hildebrand, J.G. (1995) Neuromodulation by 5-hydroxytryptamine in the antennal lobe of the sphinx moth Manduca sexta. J. Exp. Biol.,198 , 603-611.[Abstract]
Kondoh, Y. and Hisada, M. (1986) Regional specialization in synaptic input and output in an identified local nonspiking interneuron of the crayfish revealed by light and electron microscopy. J. Comp. Neurol., 251,334 -348.[Web of Science][Medline]
Lei, H., Anton, S. and Hansson, B.S. (2001) Olfactory protocerebral pathways processing sex pheromone and plant odor information in the male moth Agrotis segetum.J. Comp. Neurol. , 432,356 -370.[Medline]
Mercer, A.R., Hayashi, J.H. and Hildebrand, J.G. (1995) Modulatory effects of 5-hydroxytryptamine on voltage-activated currents in cultured antennal lobe neurons of the sphinx moth Manduca sexta. J. Exp. Biol.,198 , 613-627.[Abstract]
Mishima, T. and Kanzaki, R. (1999) Physiological and morphological characterization of olfactory descending interneurons of the male silkworm moth Bombyx mori. J. Comp. Physiol. A, 184,143 -160.
Nässel, D.R. (1988) Serotonin and serotonin-immunoreactive neurons in the nervous system of insects.Prog. Neurobiol. , 30,1 -85.[Web of Science][Medline]
Rehder, V., Bicker, G. and Hammer, M. (1987) Serotonin-immunoreactive neurons in the antennal lobes and suboesophageal ganglion of the honeybee. Cell Tissue Res., 247,59 -66.
Salecker, I. and Distler, P. (1990) Serotonin-immunoreactive neurons in the antennal lobes of the American cockroach Periplaneta americana: light-and elecron-microscopic observations. Histochemistry, 94,463 -473.[Medline]
Seidel, C. and Bicker, G. (1996) The developmental expression of serotonin-immunoreactivity in the brain of the pupal honeybee. Tissue Cell, 28,663 -672.[Medline]
Schürmann, F.W. and Klemm, N. (1984) Serotonin-immunoreactive neurons in the brain of the honeybee. J. Comp. Neurol., 225,570 -580.[Medline]
Sun, X.J., Tolbert, L.P. and Hildebrand, J.G. (1993) Ramification pattern and ultrastructural characteristics of the serotonin-immunoreactive neuron in the antennal lobe of the moth Manduca sexta: a laser scanning confocal and electron microscopic study. J. Comp. Neurol.,338 , 5-16.[Web of Science][Medline]
Accepted March 20, 2002
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 A. M. Dacks, T. A. Christensen, and J. G. Hildebrand Modulation of Olfactory Information Processing in the Antennal Lobe of Manduca sexta by Serotonin J Neurophysiol, May 1, 2008; 99(5): 2077 - 2085. [Abstract] [Full Text] [PDF]
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 L. Gatellier, T. Nagao, and R. Kanzaki Serotonin modifies the sensitivity of the male silkmoth to pheromone J. Exp. Biol., June 15, 2004; 207(14): 2487 - 2496. [Abstract] [Full Text] [PDF]
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E. S. Hill, K. Okada, and R. Kanzaki Visualization of modulatory effects of serotonin in the silkmoth antennal lobe J. Exp. Biol., March 2, 2003; 206(2): 345 - 352. [Abstract] [Full Text] [PDF]
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R. Kanzaki, K. Soo, Y. Seki, and S. Wada Projections to Higher Olfactory Centers from Subdivisions of the Antennal Lobe Macroglomerular Complex of the Male Silkmoth Chem Senses, February 1, 2003; 28(2): 113 - 130. [Abstract] [Full Text] [PDF]
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