| Autor: |
Brinkmann, M., Oliver, D., Thurm, U. |
| Zdroj: |
Journal of Comparative Physiology A: Sensory, Neural & Behavioral Physiology; Jan1996, Vol. 178 Issue 1, p125-138, 14p |
| Abstrakt: |
In sensitivity and ultrastructure of their cnidocil apparatus (CA), the nematocytes (stinging cells) of hydrozoans are analogous to hair cells of vertebrates and epidermal mechanoreceptors of insects. Intracellular recordings using current and voltage clamp in the capitate tentacles of the marine hydropolyp Stauridiosarsia producta (Corynidae) now revealed that depolarizing receptor potentials and receptor currents are generated in nematocytes (stenotele type) in response to mechanical stimulation of the CA. The responsive cells were identified by injection of Lucifer Yellow. For recording, the tentacles were isolated from the polyp and held by a suction capillary. Stimuli were applied by a glass probe moved electromagnetically or piezoelectrically. The mechanosensitivity of the nematocytes was found to be strictly limited to the CA. The characteristics of the mechanoelectric transduction were those typical of mechanoreceptor cells: phasic-tonic time course of an increase in membrane conductance; latency between stimulus and receptor response < 50 μs; sigmoid relationship between receptor-response amplitude and stimulus amplitude; maximal increase in conductance of ⩾ 15 nS; reversal potential between + 35 mV and - 10 mV; unspecific cation dependence and reversible blocking by streptomycin. The results suggest a direct mechanical control of unspecific cation channels such as has been found for mechanoreceptor cells. Suprathreshold receptor potentials elicit two forms of regenerative depolarization: non-inactivating, steplike potentials and action potentials. The latter can trigger discharge of the nematocyst. The discharge of nematocysts in the intact animal (without recording) in response to adequate stimuli was blocked by streptomycin and Na depletion in the same way as the receptor potential. Mechanoreceptor potentials are thus the beginning of a stimulus-induced electrical reaction cascade that ends in nematocyst discharge. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
Full text from SpringerLink