2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

superfamily of the ABC transporters plays a major role in the transport of drugs and
drug conjugates. Homologues of the mammalian multidrug resistance protein (MDR),
transporting hydrophobic compounds, and the multidrug resistance-associated
protein (MRP), transporting organic anionic conjugates as well as amphiphillic organic
anions, have been described in a wide variety of organisms. To determine the
presence of MDR and MRP in M. lignano, individuals were exposed to three potential
substrates of the drug- transporters: Fluo-3 AM and Fura-2 AM, both are calcium
indicators, as well Calcein AM, a fluorescent dye indicating cell viability. In the
presence of Verapamil, an MDR inhibitor, the fluorescence signal of Fluo-3 AM, Fura-
2 AM and Calcein am increased significantly in the worms s tissues. After inhibiting
the MRP with MK571 we observed a significant increase in fluorescence intensity of
all three dyes. Also with Probenecid, another MRP inhibitor, we could enhance the
fluorescence signal of Fura-2 AM and Calcein AM. Contrary, inhibition of MDR and
MRP transporters did not increase the cellular fluorescence of Rhodamine B and
other dyes, which are no substrates of these drug transporters. These results suggest
that the flatworms express functional homologues of the mammalian MRP and MDR
transporters shown by pharmacological tools.
�121 Sabine Schleicher A 704 / 16:30
Ca2+-dependent outward currents in identified olfactory neurons of the cockroach
antennal lobe
Authors: Sabine Schleicher 1 , (Cathleen Rotte, Ben Warren, Andreas Klein, Viktor
Bardos, Peter Kloppenburg)
Affiliation: 1 Universität zu Köln
Local interneurons (LNs) mediate complex inhibitory and excitatory interactions
between the glomerular pathways, ultimately restructuring the olfactory information
in the antennal lobe and shaping the tuning profile of projection neurons. In
Periplaneta americana, we found three types of LNs with fundamentally different
intrinsic firing properties, implying that these neurons serve distinct functions in the
olfactory system. Type I LNs fire Na+-driven action potentials in response to odour
stimulation. Type II LNs lack voltage dependent transient Na+ currents and
accordingly could not trigger synaptic release by action potentials. By their
morphology and physiological properties, we further differentiated two subtypes of
non-spiking LNs, namely LN IIa and LN IIb. Considering that the electrophysiological
properties are determined by cell type specific ion channel composition, our long
term goal is to elucidate the distinct sets of ionic currents of each cell type. Recent
studies revealed that in the non-spiking LN II, consistent with graded transmitter
release, the voltage dependence for activation of ICa was shifted to more
hyperpolarized membrane potentials. Here we have started to characterize Ca2+dependent
potassium currents (IKCa). All antennal lobe neurons investigated so far
possess IKCa as shown by its Cd2+-sensitivity. IKCa in different antennal lobe neuron
subtypes had differential Ca2+-dependence. In order to pharmacologically dissect the
different currents, we investigated their sensitivity to specific toxins. Currently we are
studying the role of IKCa in firing properties of projection neurons and LN I.
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