Animal-to-animal variability in temporal pattern and synaptic strength: implications for functional coordination of motor neurons by the heartbeat CPG of leeches.
-
1
California State University San Marcos, Biological Sciences, United States
-
2
Emory University, Biology, United States
Video recordings of the two lateral heart tubes in intact or mostly intact leeches (Hirudo sp.) show a coordinated constriction such that one heart tube beats in a rear-to-front progression (peristaltic mode) and the other tube constricts along its entire length nearly simultaneously (synchronous mode). Approximately every 30-40 beats the two hearts simultaneously switch coordination mode. In recordings from heart (HE) motor neurons in isolated nervous systems, a similar pattern is observed, however there is substantial variability in the timing of the activity of individual motor neurons. For example, during the peristaltic mode, the phase lag between HE(12) and HE(8) can range over approximately 0.2 phase units. Similar phase variation can be observed in the beating of the peristaltic heart tube in intact leeches. Nevertheless, distinct peristaltic and synchronous motor patterns and heart tube constriction patterns can be distinguished. We used a combination of multiple extracellular recordings combined with intracellular voltage clamp to measure the variability in the temporal pattern of the CPG premotor interneurons that produce the heartbeat rhythm, their synaptic strengths onto the motor neurons, and the temporal patterns of the motor neurons. Variations in synaptic strength can range over 4-fold for a given synapse from preparation to preparation and the relative strength of different inputs onto the same motor neurons also varies across preparations. We also observed that the temporal pattern of activity in the premotor interneurons showed variability comparable to the out-put pattern of the motor neurons. We tested whether strengths of different synapses might correlate with motor neuron phase but found no consistent pattern. The results seem to suggest that each animal comes up with a unique solution of temporal patterning and synaptic strengths to produce the required heartbeat pattern. Future work will combine experimental recordings of CPG interneurons and motor neurons with heart constrictions to determine whether animal-to-animal variability in input and output patterns of motor neuron is reflected in the constriction pattern of the heart tubes.
Acknowledgements
Supported by NIH R01 NS024072
Keywords:
Animal-to-Animal Varibility,
CpG,
leech,
neuronal networks
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Invited Symposium (only for people who have been invited to a particular symposium)
Topic:
Motor Systems
Citation:
Norris
BJ,
Wenning
A and
Calabrese
RL
(2012). Animal-to-animal variability in temporal pattern and synaptic strength: implications for functional coordination of motor neurons by the heartbeat CPG of leeches..
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00039
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
30 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Dr. Ronald L Calabrese, Emory University, Biology, Atlanta, GA, Georgia, 30322, United States, ronald.calabrese@emory.edu