Motor Control of Heartbeat Coordination in the Medicinal Leech Open Access

Kim, Jay (2014)

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Animals of the same species produce stereotyped motor patterns for movements such as breathing and heartbeat despite animal-to-animal variability in underlying neuronal networks and muscle performance. The Calabrese laboratory studies all aspects of the heartbeat system of the leech, from the central pattern generator (CPG) to the heart constrictions (Calabrese et al., 1995; Kristan et al., 2005). In the isolated nervous system, there is a large variability from animal-to animal in the temporal and synaptic output of the CPG corresponding to similar variability in the fictive motor pattern (i.e. the motor pattern produced by the heart motor neurons in the isolated nervous system) (Norris et al., 2011). Despite this variability, the fictive motor patterns were all functional; they were recognizable as fictive heartbeats. Here we report studies on the variability of the heart constriction patterns in intact and semi-intact leeches as well as in a novel isolated ganglia chain-innervated heart, reduced preparation.

In the intact animal preparation, we use transparent leeches to visualize flow in the anterior segments. However, since such leeches are quite rare (<5%), only a select few produced analyzable video recordings (N=3). Optical recordings in semi-intact preparations were not possible due to loss of blood, so we measured the constriction pattern with a force transducer in multiple segments. We focused on the heart segments 8 and 12 in both semi-intact animals and reduced preparations recording bilaterally from force transducers. A custom MATLAB program quantifies the maximum rate of rise in constriction patterns of these heart segments across individual animals in the three different preparations. Our goal is to compare these constriction patterns with the motor patterns recorded in vivo (Wenning et al., 2014). Together, these experiments will help us understand whether variability in the constriction patterns and in the fictive motor pattern is similar.

Table of Contents

Table of Contents
I. Introduction...1
II. Materials and Methods...5

a. Animal and bathing solutions...5
b. Intact preparation and imaging of hearts in situ...5
c. Semi-intact preparation...6
d. Tension measurement...7
e. Reduced preparation...7
f. Electrophysiology and recording techniques...8
g. Data acquisition and analysis...9

III. Results...11

a. Phase distribution and relation of segmental hearts in the front...11
b. Tension measurement of hearts in the semi-intact preparation...11
c. Physiological controls of the reduced preparation...12
d. Phase relation of ipsilateral segments in the reduced preparation...13
e. HE analysis of ipsilateral segments in the reduced preparation...13

IV. Discussion...14

a. Characterization of constriction patterns in frontal segments...14
b. Limitations of the trans-illumination approach...14
c. Comparison of semi-intact segmental phase relations...15
d. Comparison of phase distributions in the reduced preparation...16

V. Conclusion...17
VI. Figures...18
VII. Appendix...34
VIII. References...65

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