[Abstract Title]. - Society for Neuroscience

Topic: B.10.b. Modulation of neuronal firing properties
Support: CIHR
Title: Modulation of sensory proccesing by serotonin in ELL pyramidal cell
Authors: *T. DEEMYAD, M. J. CHACRON;
McGill Univ., Montreal, QC, Canada
Abstract: The serotonergic system is involved in many neural disorders. There is evidence that
serotonin induces burst firing in many area in CNS and capable of altering the neural processing
of sensory information. However, the cellular mechanisms by which this is achieved are not well
understood.
Weakly electric fish, due to relatively simple and well characterized anatomy that shows
important similarities with that of higher vertebrates are a suitable model for investigating this
problem. The electrosensory lateral line lobe (ELL) is the first and only terminal of the
peripheral sensory afferents. The ELL is comprised of three parallel somatotopic representations
of sensory space: lateral (LS), centrolateral (CLS) and centromedial (CMS) segments that all
receive the same afferent input. There are anatomical differences between these maps in terms of
descending input, ion channel distributions, and neuromodulatory inputs. Previous studies have
shown that pyramidal cells, the sole output neurons of the ELL, have a well-defined burst
mechanism that signals particular stimulus features in vivo. The effect of serotonin on pyramidal
cell activity and their processing of sensory input are unknown. Therefore, we studied the effect
of serotonin application on electrical activity of pyramidal cells using sharp-electrode
intracellular recordings. Action potential amplitude and duration were not affected by serotonin.
Serotonin increased burst firing three fold in the lateral segment (LS) and had no significant
effect in the centromedial segment. This augmentation in burst activity in LS pyramidal cells was
achieved by a reduction of the spike afterhyperpolarization (AHP). Moreover, in presence of
serotonin adaptation becomes slower in pyramidal cells. As the calcium activated potassium
channels (SK) are underlies medium component of AHP besides speed of adaptation this finding
suggests that effect of serotonin resulted from down regulation of SK channels. SK channels
show graded patterns of expresion across the ELL maps that mirror those of serotonergic input.
The nature of contribution of SK channels in effect of serotonin on electrical activity of ELL
pyramidal cells in presence of apamin and EBIO, as well as their consequences on sensory
processing, will be discussed.
Disclosures: T. Deemyad , None; M.J. Chacron, None.
Poster
240. Intrinsic Membrane Properties: Modulation of Neuronal Firing Properties by Inputs
and Activity