The investigation of the spontaneous activity and evoked potentials at cellular level in the central nervous system of fresh-water mussel (Anodonta cygnea L.)

Varanka, István (1974) The investigation of the spontaneous activity and evoked potentials at cellular level in the central nervous system of fresh-water mussel (Anodonta cygnea L.). A Magyar Tudományos Akadémia Tihanyi Biológiai Kutatóintézetének évkönyve, 41. pp. 91-109. ISSN 0365-3005

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Abstract

Single cell responses evoked by the stimulation of the nervus pallialis posterior maior have been investigated through extracellular microelectrode recording from the visceral ganglion of Anodonta cygnea L. It has been established that: 1. The majority of the neurones are spontaneously silent. The averagefrequency of the neurones possessing spontaneous activity is 0.78 cps and the activity may be of different pattern. 2. At the investigation of the effectiveness of square wave impulse applied asymmetrically, it was established that this kind of stimulation results in a primary response in the silent and spontaneously active neurones, and in the majority of cases the anodic stimulus is more effective than the cathodic one. 3. The primary response of the 1st type evoked by a single shock may consist of one or more (extremely 25) spikes and its latency is longer than th a t of the 2nd type. 4. Generally, the increase of latency and the decrease of the response (its habituation-like feature), occasionally, the facilitation of the response were experienced after the application of stimulus trains. 5. The stimulus-frequency-following of the responses is also limited, in th e case of low frequency (0.1 cps) stimulation, too (also a habituation-like phenomenon). This phenomenon is increased in the case of a stimulus-frequency of 1—5 cps. 6. After the stimulation of the nppm the spontaneously active neurones may respond with a secondary response, and with a short or long time inhibition, too, showing the plasticity of their discharge pattern. 7. Peculiarity referring to a functional structure was not found in the VG. The neurones giving the same response are diffusely localized, suggesting an extensive synaptic arborization (divergence).

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