Neuroscience 2000 Abstract
| Presentation Number: | 518.15 |
|---|---|
| Abstract Title: | Distinct modulatory states of a cation channel in excised patches from <I>Aplysia</I> bag cell neurons. |
| Authors: |
Magoski, N. S.*1
; Kaczmarek, L. K.1
1Department of Pharmacology, Yale School of Medicine, New Haven, |
| Primary Theme and Topics |
C. Excitable Membranes and Synaptic Transmission - 30. Presynaptic mechanisms |
| Secondary Theme and Topics | C. Excitable Membranes and Synaptic Transmission<br />- 33. Synaptic plasticity |
| Session: |
518. Presynaptic mechanisms: physiology I Poster |
| Presentation Time: | Tuesday, November 7, 2000 3:00 PM-4:00 PM |
| Location: | Hall G-J |
| Keywords: | Modulation, Mollusc, Phosphorylation, Single-Channel |
Egg laying behavior in Aplysia is controlled by the bag cell neurons. In response to stimulation, these neurons afterdischarge and release egg laying hormone. A nonselective cation channel provides the depolarizing drive for the afterdischarge. Using cultured bag cell neurons and inside-out patches, we now show that the effect of ATP on these cation channels differs depending on whether on not PKC is associated with the channel. Previously, we demonstrated that when PKC is associated with the channel, applying ATP enhances Po (PNAS 95:10938; SFN Astr 25:503.9). In the present study, for 50% of patches (n=71) application of ATP to the cytoplasmic face increased cation channel Po, while for the other 50% of patches (n=71) ATP either had no effect or decreased Po slightly. The nature of the response was determined by the animal from which the neurons were isolated, i.e., all channels in neurons cultured from a single animal responded to ATP in the same way (increased Po in 29 animals or no effect on Po in 33 animals). Animals whose neurons yielded channels lacking an ATP response were observed year round, with a slight trend towards the winter. Treatment with GTP (n=7 patches), GTPγS (n=4 patches), or Conus textile venom (an afterdischarge stimulating agent; n=3 neurons/patches) failed to rescue the ATP response. Similarly, src-kinase failed to restore the ATP response, rather, it decreased Po likely via a direct tyrosine phosphorylation of the channel (n=5 of 6 patches). However, exposing neurons to phorbol ester rescued the ATP response in 6 of 10 patches, while in untreated neurons from the same animals only 1 of 11 patches had ATP-responsive channels. Therefore, the effects of ATP are likely due to a lack of association of PKC with the cation channel. Following an afterdischarge bag cell neurons are refractory, and fail to respond to subsequent stimulation. The lack of PKC-dependent modulation of the cation channel may represent a molecular homologue of such a refractory period.
Supported by NIH (USA), HFSP (France), and MRC (Canada).
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2000 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2000. Online.
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