Cholinergic modulation of electrosensory processing in the electrosensory lateral line lobe of Apteronotus leptorhynchus
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1
McGill University, Biology Department, Canada
The response properties of sensory neurons have to be tuned constantly continuously to enable animals to extract important information from highly variable sensory stimuli. A key player in the control of state-dependent sensory processing is acetylcholine (Ach). ACh has been shown to modulate information transmission in various sensory systems. In the weakly electric fish, Apteronotus leptorhynchus, anatomical and physiological evidence points towards an important role of ACh in modulating electrosensory processing in the hindbrain via muscarinic ACh receptors. To characterize the stimulus conditions that activate the cholinergic pathway as well as the consequences for sensory processing, we exposed the fish to a set of behaviourally relevant electrosensory stimuli while recording extracellularly from pyramidal neurons in the electrosensory lateral line lobe (ELL). The muscarinic antagonist, atropine, was focally applied in the dendritic trees of recorded pyramidal cells using a micropressure ejection technique. The immobilized animals were stimulated with random amplitude modulations (RAMs) of the fish’s own electric organ discharge (EOD). The stimuli were presented with different geometries: local (mimicking prey-like stimuli), global (mimicking encounters with conspecifics), and a third type that consisted of simultaneous global and local RAMs to test the response in a situation where both prey and conspecifics are present. The application of the muscarinic antagonist atropine, by itself, did not change the basal firing rate or the firing rate of the neuron in the presence of RAMs. For each stimulation geometry, we calculated the stimulus-response (SR) coherence as a measure of how well the neuron responded to the stimulus. During global stimulation, the application of atropine tended to decrease the SR coherence of cells with low basal firing rates, without changing the response of cells with higher firing rates. For local stimulation, the changes in SR were more pronounced than for global stimulation, but highly variable between cells. When atropine was applied in the presence of both global and local RAMs, changes (reductions/increases) in coherence seen with local stimulation alone were still present with approximately the same amount of change. These results point towards an effect of ACh in the processing of local stimuli in the ELL. There was no difference in the effects seen between E-type and I-type pyramidal cells. These results suggest that ACh may not have a role in discrimination of competitive sensory stimuli at the ELL level.
Keywords:
Acetylcholine,
Atropine,
electrosensory system,
Neuromodulation,
weakly electric fish
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for student poster award)
Topic:
Sensory: Electrosensory
Citation:
Toscano-Márquez
B and
Krahe
R
(2012). Cholinergic modulation of electrosensory processing in the electrosensory lateral line lobe of Apteronotus leptorhynchus.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00392
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Received:
01 May 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Miss. Brenda Toscano-Márquez, McGill University, Biology Department, Montreal, Quebec, H3A1B1, Canada, brenda.toscanomarquez@mail.mcgill.ca