[Abstract Title]. - Society for Neuroscience

Abstract: Using an adaptation of published behavioral protocols, we have determined that acute
exposure to the cholinergic compounds nicotine and carbamylcholine (an acetylcholine analog)
decreased planarian motility in a concentration-dependent manner, with IC50 values of 75 +/- 9
µM and 151 +/- 14 µM for nicotine and carbamylcholine respectively. The tobacco cembranoid
(1S,2E,4R,6R,7E,11E)-cembra-2,7,11-triene-4,6-diol (4R), also decreased planarian motility
with an IC50 of 20 +/- 5 uM. At concentrations at or below 1 µM, 4R alone did not decrease
planarian motility nor had any apparent behavioral or toxic effects in this organism. Experiments
in the presence of 1 µM 4R did not change the IC50 for carbamylcholine-induced decrease in
planarian motility (p = 0.350, F-test). In contrast, 1 µM 4R significantly increased the IC50 for
the nicotine-induced decrease in planarian motility (p < 0.0001, F-test). When planarians were
exposed for 24 hours to either nicotine or carbamylcholine at concentrations near their respective
IC50 values and then transferred to plain media, nicotine-exposed, but not carbamylcholineexposed
worms displayed distress behaviors resembling withdrawals symptoms. In experiments
where planarians were pre-exposed to 100 µM nicotine for 24 hours in the presence of 1 µM 4R,
the withdrawal-like effects were significantly reduced. These results parallel published data
describing the relative higher potency of 4R to inhibit nicotine- vs. acetylcholine-induced
currents through α4β2 neuronal nicotinic acetylcholine receptors.
Disclosures: O.R. Pagan , None; A. Rowlands, None; A. Fattore, None; T. Coudron,
None; K. Urban, None; A. Bidja, None; V.A. Eterovic, None.
Poster
259. Cochlear Mechanoreceptors
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 259.1/AA25
Topic: D.02.a. Mechanoreceptors and cochlea
Support: USyd R&D grant 2007
Title: Efferent innervation is present to both low- and high-frequency regions of the auditory
basilar papilla of lizards
Authors: E. WIBOWO, J. BROCKHAUSEN, *C. KOEPPL;
Sch. of Med. Sci., Univ. Sydney, Sydney, Australia
Abstract: The inner ear of vertebrates contains hair cells for sensory transduction. Hair cells are
generally innervated by afferent neurons to transmit the sensory information to the brain as well
as efferent neurons to receive feedback from the brainstem. The function of this efferent
feedback system is poorly understood and may have changed during evolution as different