|
COMPUTATIONAL MODEL OF HERMISSENDA TYPE-B PHOTORECEPTORS.
|
|
Y. Cai; D.A. Baxter*; T. Crow
|
| Dept. of Neurobiology and Anatomy, The University of Texas Medical School, Houston, TX, USA |
|
The photoreceptors of Hermissenda are an important model system for studying cellular and molecular mechanisms of Pavlovian conditioning. In the present study, a Hodgkin-Huxley type model of type-B photorecpetors was developed. The model consists of several compartments, including rhabdomeric, somatic and axonal. Whenever possible, parameters for the model were derived from available empirical data. The soma compartment included six ionic currents: an A-type K+ current (IK,A), a delayed rectifing K+ current (IK,V), transient and sustained Ca++ currents (ICa,T and ICa,S, respectively), a Ca++-activated K+ current (IK,Ca) and a hyperpolarization-activated inward rectifier current (Ih). The rhabdomeric compartment contained light-activated conductances and the spike-initiating compartment also contained a fast Na+ current in addition to other conductances. The model accurately reproduced the resting spike frequency of dark-adapted B-photoreceptors. The spike frequency was influenced by several currents. For example, decreases in IK,Ca increased the spike frequency of the model and removal of Ih decreased the model's excitability, results that are consistent with experimental findings. The model is sensitive to IK,A kinetics, and decreases in IK,A increased the spike frequency. Morever, ICa,T contributed to spike generation in the model, both directly and indirectly via IK,Ca. Since a number of currents are modulated by 5-HT and Pavlovian conditioning (e.g. IK,A, IK,Ca and Ih), these conductances may contribute to the changes in CS elicited spike frequency produced by Pavlovian conditioning.
Supported by: P01 NS38310.
|
Citation for this abstract:
Cai, Y., D.A. Baxter, and T. Crow (2000). Computational model of Hermissenda type-B photoreceptors. Soc. Neurosci. Abstr. 26, 2032.
|
