碩士 / 國立清華大學 / 分子醫學研究所 / 98 / The caudal photoreceptors (CPR) in the sixth abdominal ganglion of the crayfish are complex and multi-modal interneurons. These cells respond directly to light with tonic spike discharges, and they integrate synaptic input from an array of filiform mechanoreceptors on the tailfan, moreover, they have spontaneous spikes. Thus, the photoreceptor output represents the integrated activity of photosensitive, mechanosensory and spontaneity.
After removing the afferent nerve, CPRs alter their response. In comparison with the intact CPRs not hydrodynamically stimulated, the spiking frequency of the CPRs lack of mechanosensory input decreases and exhibits a regular pulse train. Namely, CPRs have different responses merely because of losing the mechanosensory input from the tailfan. It also suggests that mechanosensory input plays an important role for CPRs.
The CPRs without mechanosensory input still can respond to light of different intensity and their photosensitivity is improved. Therefore, the mechanosensory input might inhibit CPRs’ photosensitivity. Whether there is an inhibition or not, the spiking frequency of the CPRs increases under the continuous illumination intensity greater
3
than 92 lux. Moreover, a circadian rhythm system has three main organization levels. The second level, a synchronization system of external stimuli composed of receptors and sensorial pathways, can mediate between the ensemble of oscillators and ambient conditions. The photosensitivity characteristic relates to the fact that CPR participates in the circadian rhythm system.
According to the experimental results of the three different types of illumination stimulation, the mechanosensory input from the tailfan would inhibit CPRs’ sensitivity to light. In the experiment of the continuous illumination, CPRs show the characteristic that they can react to the environmental illumination intensity. The characteristic suggests that CPRs participate in the pathway of regulation and modulation in crayfish's circadian rhythm system.
| Identifer | oai:union.ndltd.org:TW/098NTHU5538007 |
| Date | January 2010 |
| Creators | 吳旻芝 |
| Contributors | 葉世榮 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 45 |
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