EXCITATION BY HYPERPOL ARl ZING POTENTIALS 



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Fig. 6. Hyperpolarizing potentials developed in intermediate cells of cat retina 

 and depolarizing generator potential and spikes from a ganglion cell. (Upper 

 left) — Hyperpolarizations graded in duration and amplitude resulting from 

 flashes of constant intensity but varying in duration from 1 msec to 1-14 sec. 

 (Upper right) — Gradation of the response by changing the intensity of a light 

 flash of 0-8 sec duration. (Below) — Intracellular recording from a retinal 

 ganglion neuron, showing depolarizing generator potential and augmented 

 spike activity during a light flash of 0-8 sec. (From Brown and Wiesel, 1959.) 



of neurons is "a somewhat unexpected finding which is not compatible with 

 present neurophysiological views" (p. 34). 



The possibihty that sense organs might involve electrically inexcitable 

 activity had already been proposed at that time, however (Grundfest, 1956, 

 1957c, d). The evolutionary relation of the secretory output of neurons, the 

 neurosecretory cells, and glands had also been noted (Grundfest, 1957b, 

 1959b). Indeed, glands may produce hyperpolarizing activity, a fact that was 

 known to Garten (1910) and which was recently confirmed by Lundberg 

 (1956) with intracellular recording (Fig. 8). Garten had likened the electro- 

 salivogram to the electroretinogram, but apparently chiefly because of the 

 long durations of the potentials.* 



An explanation hes in the clarification of the functions which the receptors 

 and intermediate cells are called upon to perform. These cells receive speci- 



* Garten (1910) also explained the deviation from Pacini's rule (Grundfest, 1957a) of 

 the responses of Malaptenirus electroplaques as a sign of hyperpolarizing electrogenesis 

 due to the supposed origin of the electroplaques from gland cells (Fritsch, 1887). In view 

 of the data on salivary gland hyperpolarization this explanation was accepted until recently 

 (Grundfest, 1957a). Subsequent work, however, showed that the electroplaques respond 

 directly to electrical stimuli and produce all-or-none spikes overshooting to internal 

 positivity as do other electrically excitable, conductile cells (cf. Keynes et ai, 1961). 



