Fain G L, Matthews H R
Department of Ophthalmology, Jules Stein Eye Institute, UCLA School of Medicine 90024.
Trends Neurosci. 1990 Sep;13(9):378-84. doi: 10.1016/0166-2236(90)90023-4.
Vertebrate photoreceptors transduce the absorption of light into a hyperpolarizing change in membrane potential. The mechanism of transduction is becoming fairly well understood and has been shown to occur via a G protein-coupled decrease in cyclic GMP. Attention is now turning to the way the enzymatic machinery in the outer segment of the photoreceptor cell is modulated during light adaptation. Recent studies show that light adaptation cannot occur if changes in the concentration of cytoplasmic free calcium in the outer segment are prevented, suggesting that calcium functions as a second messenger in sensitivity regulation.
脊椎动物的光感受器将光的吸收转化为膜电位的超极化变化。转导机制已被相当深入地理解，并且已证明是通过G蛋白偶联导致环鸟苷酸减少而发生的。现在人们的注意力转向光感受器细胞外段的酶促机制在光适应过程中是如何被调节的。最近的研究表明，如果阻止外段细胞质游离钙浓度的变化，光适应就无法发生，这表明钙在敏感性调节中作为第二信使发挥作用。
