Bistability and its regulation by serotonin in the endogenously bursting
neuron R15 in Aplysia.
Lechner, H. A., D. A. Baxter, J. W. Clark and J. H. Byrne.
Department of Neurobiology and Anatomy, University of Texas Medical School
at Houston, Houston, TX 77030, Department of Electrical and Computer
Engineering, Rice University, Houston, TX 77251-1892.
APStracts 2:0325N, 1995.
SUMMARY AND CONCLUSIONS
1. Previous computational studies of models of neuron R15 in Aplysia have
indicated that several distinct modes of electrical activity may coexist at a
given set of parameters, that this multistability can be modulated by
transmitters such as serotonin (5-HT), and that brief perturbations of the
membrane potential can induce persistent changes in the mode of electrical
activity. To test these predictions, the responses of R15 neurons to
injections of brief (1.5 sec) current pulses were recorded intracellularly in
the absence and presence of 5- HT. 2. In the absence of 5-HT, brief
perturbations induced abrupt transitions in the electrical activity from
bursting to beating. Such transitions were observed in about 20% of the cases.
The duration of beating activity varied from several seconds to tens of
minutes. In the presence of low concentrations (1 [mu] M) of 5-HT, both the
probability of mode transitions and the duration of induced beating activity
increased significantly. 3. These results indicate that at least two stable
modes of electrical activity can coexist in R15 neurons, and that this
bistability can be regulated by 5-HT. In general, these conclusions agree with
the results from analyses of mathematical models of R15. Although the function
of these dynamic properties in R15 is speculative, our results, interpreted on
the background of the model, support the notion that nonlinear dynamical
properties of individual neurons can endow them with richer forms of
information processing than has generally been appreciated.
Received 3 August 1995; accepted in final form 30 October 1995.
APS Manuscript Number J508-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95