First published online September 16, 2005
Journal of Experimental Biology 208, 3711-3720 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01827
Integration of hydrodynamic and odorant inputs by local interneurons of the crayfish deutocerebrum
DeForest Mellon, Jr
Department of Biology, 286 Gilmer Hall, University of Virginia,
Charlottesville, VA 22903, USA
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Fig. 1. (A) Diagram of the isolated, cannulated head preparation, including the
olfactometer arrangement. (B) Organization of the solenoid switches
controlling water and odorant flow to the antennular olfactometers. See text
for details.
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Fig. 2. Intracellular records from a Type I-like neuron recorded in the OL in
response to (A) a 100 ms pulse of tetramin imbedded in a 10-s water pulse; (B)
a 200 ms pulse of tetramin imbedded in a 10-s water pulse and (C) a 2 s pulse
of tetramin imbedded in water. Freshwater flow past the lateral antennular
flagellum was begun approximately 5 s prior to interruption by the odorant
pulse in each case. In this and all other figures, water onset is indicated by
upward deflection of the broken line, and odorant onset is indicated by upward
deflection of the solid line.
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Fig. 3. Responses of a Type I-like neuron to water onset and to 2-s odorant pulses
of standard tetramin and three serial 10-fold dilutions thereof, delivered as
indicated by the routine shown below trace D. (A) Standard tetramin diluted
1000-fold; (B) standard tetramin diluted 100-fold; (C) standard tetramin
diluted 10-fold; (D) standard tetramin. (E) Relationship between spike
responses and the relative odor concentration. Each point is the mean ±
1 S.E.M. of five stimulus presentations. The straight line
relationship is a graph of the equation
y=a(log10x)+b, where a=1.55 and b=8.3. The
correlation coefficient of the relationship is 0.95.
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Fig. 4. Records from a Type I cell, illustrating its responses to water onset and a
2-s pulse from the odorant reservoir. When the reservoir contained 0.05%
tetramin, the cell responded with a short burst of spikes (top trace); when
the reservoir contained only water, there was no spike response. The initial
onset of water produced the standard E-I-E response sequence.
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Fig. 5. Record from a Type I-like cell to illustrate the lability of the response
to hydrodynamic stimulation. The initial stimulus sequence generated both a
response to water onset (arrow) and to a 2-s odor pulse. When the sequence was
repeated about 1 s following the end of the previous stimulus routine, the
response to hydrodynamic input was greatly diminished (arrow).
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Fig. 6. Latency measurements from the Type I cell of
Fig. 3. Filled bars are latency
measurements to the EPSP generated by water onset, while the open bars are
latency measurements from the immediately following response to a 2-s odor
pulse. The odor response latency was, in every case, at least 25% longer than
that for the hydrodynamic latency but was progressively shorter as the
concentration of tetramin was increased. Each bar is the mean of at least five
separate measurements ± 1 S.E.M.
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Fig. 7. Comparison of response latencies following water onset (filled bars) or
odor (open bars) in seven additional Type I-like neurons. With the exception
of one instance, the latencies to olfactory input were at least twice as long
as those for hydrodynamic input. Error bars are ± 1
S.E.M.
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Fig. 8. Electrical records from a Type I-like neuron to water onset and to standard
tetramin in response to stimulus regimes presented to the lateral flagellum
(A) and to the medial flagellum (B) of the ipsilateral antennule. With the
exception of a minimal response to water onset, the stimuli to the medial
flagellum were ineffective.
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Fig. 9. (Ai,ii) Respective responses from a Type I-like interneuron to different
stimulus routines, shown below each electrical trace. Responses to the odorant
stimulus were doubled when it occurred prior to the water pulse. (B) Bar
graphs documenting the potentiation of the neuronal response to two
concentrations of odorant with different routines of hydrodynamic and/or
odorant stimuli. Odorant pulses were 2 s in length. See text for further
details.
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Fig. 10. Bar graphs of responses to water-first (open bars) or odor-first (filled
bars) in two additional Type I-like neurons. Each bar is the mean of at least
four observations ± 1 S.E.M. A t-test analysis
between pairs of responses indicates that they are significantly different
(P<0.01).
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Fig. 11. Records from a Type I-like neuron in response to two different stimulus
routines, as indicated beneath each electrical trace. In A, the arrow
indicates the latency of the peak of the third (depolarizing) phase of the
E-I-E response to the onset of fluid (water) movement past the antennule. In
B, the arrow is at the identical latency to fluid (odor) onset and indicates
that the third response phase would occur within the odor-response envelope,
presumably allowing for summation. Odorant pulses lasted 2 s.
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Fig. 12. (A) Records showing differences in the rate of rise of the response to
odorant (gray trace and gray stimulus routine) and to a combination of odorant
and hydrodynamic stimuli (black trace and routine). Odorant pulses lasted 2 s.
(B) Bar graph showing differences in the slopes as mV s-1. Each bar
is the mean ± 1 S.E.M. of at least eight measurements. A
t-test analysis showed the two means to be significantly different at
the 0.005 level of confidence.
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Fig. 13. Records from a Type I cell that showed no potentiation of the response to
2-s pulses of odorant in the different stimulus routines. In the lower trace,
note the intensity of the second, hyperpolarizing phase of the response to
hydrodynamic input and the absence of a third, depolarizing phase.
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Fig. 14. Electrical responses from a Type II-like neuron recorded in the OL. Water
onset was accompanied by spiking activity, which was inhibited in a
dose-dependent manner by (A) 1-s and (B) 2-s pulses of 0.05% tetramin.
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© The Company of Biologists Ltd 2005
