Functional Organization of Mechanoreceptors

Publisher Summary This chapter describes post-hyperpolarizing responses in Pacinian corpuscles recorded by conventional electrophysiological techniques. With post-hyperpolarizing responses, thresholds for impulse activity are found to be lower than otherwise. The elevated concentration of potassium ions in the intracapsular fluid of Pacinian corpuscles may be one of the factors favoring the appearance of post-hyperpolarizing responses. According to microflame photometry, the potassium concentration in the capsular fluid is 6.19 ± 0.72 mEq / litre, that is, 2–2.5 times greater than the potassium concentration either in the blood plasma or in the intertissue fluid surrounding the Pacinian corpuscles in the mesentery. Electrophysiological analysis has demonstrated that application of hyperpotassium solutions, where potassium concentration is 2–3 times higher than that in the blood plasma, results in an enhanced excitability of the corpuscle (by 50–60%) because of a decrease in the firing threshold. The hyperpotassium medium favors the enhancement of sensitivity both in the primary tissue mechanoreceptors and in the secondary mechanoreceptors of the sense organs.