Spontaneous switching between ortho- and antidromic spiking as the normal mode of firing in the cerebral giant neurons of freely behaving Lymnaea stagnalis.
1. Action-potential generation at sites remote from the cell body leads to antidromic firing and occurs in a wide variety of animals and experimental circumstances. Remote sites of spike generation may play a role in the functional subdivision of the axonal branches of a neuron and are also thought to play a role in synaptic integration. 2. Spontaneous ortho- and antidromic firing was investigated by recording the electrical activity of somata and axons of a pair of identified giant neurons [cerebral giant cells (CGCs)] in freely behaving animals. 3. At the soma of each CGC, the shape of the extracellular action potential was not constant but jumped between two well-defined levels. Subsequent recordings of synchronous firing in both cell bodies showed that the shape of the extracellular action potential depended on the firing sequence of the two CGCs. 4. Simultaneous recordings of the cell body and the main axon of a single CGC showed that spontaneous changes in the direction of spike conduction (orthodromic or antidromic) occurred. These changes in the direction of spike conduction coincided with the changes in the shapes of the extracellular action potentials recorded from the somata. 5. These results show that, under physiological conditions, spontaneous switching occurs between ortho- and antidromic spiking in the CGCs, and that action-potential generation at sites remote from the cell body is a physiologically relevant mechanism.
Jansen
R F
RF
Graduate School Neurosciences Amsterdam, Research Institute Neurosciences Vrije Universiteit, The Netherlands.
Pieneman
A W
AW
ter Maat
A
A
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001369:Axons / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology*; D001921:Brain / Q000166:cytology / Q000502:physiology*; D004567:Electrodes, Implanted; D005071:Evoked Potentials / Q000502:physiology; D015726:Giant Cells / Q000502:physiology* / Q000648:ultrastructure; D008195:Lymnaea; D009474:Neurons / Q000502:physiology* / Q000648:ultrastructure; D012016:Reference Values