2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

����171 Hannah Wasser
Quantification of antennal afferent regeneration in the locust brain after nerve
crush
Authors: Hannah Wasser 1 , Michael Stern 1
Affiliation: 1 Division of Cell Biology, University of Veterinary Medicine Hannover
We study neuronal regeneration in the olfactory pathway of the locust (Locusta
migratoria). Olfactory afferents are axotomized in adult locusts and 5th instar
nymphs by crushing the base of one antenna, leaving the other antenna as an
internal reference. We quantify the resulting degeneration and subsequent
regeneration in the first olfactory processing center, the antennal lobe, by means of
anatomical size measurements, quantitative immunofluorescence of cell surface
markers, anterograde labeling, and intracellular recording.
In the antennal lobe of postembryonic locusts, the cell adhesion molecule Fasciclin I
is exclusively expressed by olfactory receptor neurons. Thus, after degeneration of
axotomized distal segments of sensory neurons, Fasciclin I staining vanished in the
antennal lobe within two days following the deafferentation. The reappearance of
Fasciclin I during the following days proved a valuable quantitative marker for the
regeneration process. Olfactory receptor neurons of 5th instar nymphs regenerated
faster than those of adults.
To describe the neuroanatomical changes during regeneration the ingrowing
afferents were labeled anterogradely with neurobiotin through the scraped-off
olfactory sensilla on individual antennal segments (annuli). Normally, fibers from
individual annuli grow together as discrete bundles in the antennal nerve and
innervate the antennal lobe in a conspicuous ring-shaped pattern. Such an ordered
pattern of growth and innervation is not observed in regenerated fibers, despite their
precise confinement to the antennal lobe.
Intracellular recording from olfactory interneurons in the antennal lobe revealed the
first regenerated synaptic connections seven days after axotomy.
����172 Georg Welzel
Direct analysis of activity-dependend changes in gap junction conductivity in the
leech
Authors: Georg Welzel 1 , Stefan Schuster 1
Affiliation: 1 Department of Animal Physiology, University of Bayreuth
It is well established, that gap junctional conductance can be affected by a variety of
mechanisms. However, activity-dependent modifications, such as LTP, have been
much less studied in electrical than in chemical synapses and have mostly been
assayed in rather indirect ways. Here we directly measure the electric coupling
between the two Retzius-cells of the leech Hirudo medicinalis by using a dual-cell
voltage-clamp technique. We show that the prolonged depolarization of any one of
the two cells causes a lasting increase in gap junction conductivity. These findings
make the well-accessible electrical synapses of the leech an attractive model to study
mechanisms of plasticity in electric synapses.
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