Discharge patterns of the slowly adapting mechanoreceptor afferent units innervating the non-warty skin of the frog.

Ogawa, Hisashi; Yamashita, Yoshiro; Nomura, Tomokiyo; Taniguchi, Kohachi

doi:10.2170/jjphysiol.34.255

Cited by 6 publications

(3 citation statements)

References 17 publications

(29 reference statements)

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“…Ft II units are found only in the non-warty skin, but three other types of mechanoreceptive units are present both in the warty and non-warty skin (OGAWA et al, 1984). In the present study, however, we isolated three of the four types of units only from the warty skin.…”

Section: Discussionmentioning

confidence: 60%

“…RA type I and RA type II units in both warty and non-warty skin, and two types of SA units, i.e. frog type I (Ft I) units in warty and non-warty skin and frog type II (Ft II) units in non-warty skin (OGAWA et al, 1981(OGAWA et al, , 1984OGAWA and YAMASHITA, 1982). The purpose of the present study was, therefore, to obtain evidence indicating that different types of cutaneous mechanoreceptor afferent units of frogs encode different aspects of mechanical stimulus.…”

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confidence: 99%

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Threshold response phase to sinusoidal stimulation of frog cutaneous mechanoreceptor afferent units.

1984

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While applying sinusoidal indentations of various frequencies and amplitudes to the receptive field of cutaneous mechanoreceptor afferent units in frogs, we measured latencies of spikes after the time point when sinusoidal stimulation crossed the neutral position from withdrawal to indentation phase. Frog type I (Ft I) and frog type II (Ft II) slowly adapting (SA) units produced spikes only at the indentation phase, and the threshold response phase (TRP), i.e. the phase of the first spike was for ca. 45° at a small amplitude of stimulation. At low frequencies of sinusoidal stimulations, the TRP of Ft II units advanced gradually with an increase in amplitude, conforming to the theoretical expectation as displacement-detectors. But the TRP of Ft I units did not show such an advance with an increase in stimulus amplitude. Rapidly adapting (RA) type I and type II units mostly produced phase-locked discharges at two different phases; the former discharged at ca. 0° and 180° (phase of the highest velocity) and the latter at ca. -90° and 90° (phase of the highest acceleration) at the smallest amplitude used. At a large amplitude, RA type II units showed advance in discharge phase like a theoretical acceleration-detector, but performance of RA type I units did not fit that of the theoretical velocity-detectors. Both types of SA units showed frequency-phase relations which roughly agreed with the performance of the theoretical displacement-detectors in the range below 5 Hz, but RA units of either type did not follow the expectation as the theoretical velocity-detector or acceleration-detector.

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Section: Discussionmentioning

confidence: 60%

mentioning

confidence: 99%

Threshold response phase to sinusoidal stimulation of frog cutaneous mechanoreceptor afferent units.

1984

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“…The stimulus‐adaptation properties of mechanoreceptors have been classified into two categories: slowly adapting and rapidly adapting receptors ( Iggo, 1976 ) . Ogawa and Yamashita (1982) and Ogawa et al (1984 ) have demonstrated that, in the frog, two types of slowly adapting cutaneous mechanoreceptor afferent units are identified by their firing behavior: irregularly discharging frog type I units responding to mechanical stimulation in both warty and non‐warty skins and regularly discharging frog type II units responding to mechanical stimulation in non‐warty skin. Ogawa (1996 ) suggested that frog type I units consist of an MC–N complex and that Merkel cells function as receptive cells.…”

Section: Discussionmentioning

confidence: 99%

Effects of gadolinium and tetrodotoxin on the response of slowly adapting type I mechanoreceptors to mechanical stimulation in frog dorsal skin

Takeda

Nishikawa

Sato

et al. 2003

J Peripheral Nervous Sys

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To elucidate the excitatory mechanism of mechanoreceptors innervating the frog skin, we examined the effects of gadolinium (Gd3+) and tetrodotoxin (TTX) on the response of single-unit activity of slowly adapting type I mechanoreceptors to mechanical stimulation topically applied to the receptive field (RF). Recordings were made from 46 fibers responding to mechanical stimulation with von Frey hairs, which caused an irregular firing pattern with slow adaptation. Application of a mechanically gated channel blocker, Gd3+ (30 microM), and a Na+ channel blocker, TTX (3 microM), caused the suppression of discharge rates, which was characterized by the conversion of a slowly adapting to a rapidly adapting discharge pattern. The administration of a high-voltage-activated (HVA) Ca2+ channel blocker, Cd2+ (100 microm), inhibited the unit discharge and caused the conversion of a slowly adapting to a rapidly adapting discharge pattern. Tonic discharges evoked by anodal electrical stimulation were inhibited by the application of Gd3+ or TTX. Electron microscopic examination showed that the cytoplasm of Merkel cells seen in the RF contained numerous Merkel granules. These results suggest that the excitatory mechanism of frog cutaneous mechanoreceptors may be mediated by the activation of Gd(3+)-sensitive stretch-activated channels in the Merkel cell-neurite complex, which are related to the Na+ influx via voltage-gated Na+ channels and/or the Ca2+ influx through HVA Ca2+ channels.

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Differential effects of manganese and magnesium on two types of slowly adapting cutaneous mechanoreceptor afferent units in frogs

1986

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While perfusing a frog leg with various solutions, the mechanical responsiveness of slowly adapting (SA) cutaneous mechanoreceptor afferent units innervating the plantar surface of the hindfoot was examined. Perfusion with normal Ringer solutions enhanced the mechanical responsiveness of two types of the SA units, irregularly discharging Frog type I units and regularly discharging Frog type II units, in comparison with that by normal blood supply. On the other hand, when the perfusion was made with Ringer solutions containing Ca blockers, i.e., Mn and Mg, the response magnitudes of both units were reversibly and dose-dependently decreased. Ringer solutions containing 3 mM Mn or 20 mM Mg almost abolished the maintained responses of the Frog type I units to ramp stimulation of the skin, while Ringer solutions of 10 mM Mn significantly decreased those of the Frog type II units. It is suggested that Ca in the medium is a prerequisite to mechanoelectric transduction and the spike generation process at the terminal regions of these slowly adapting cutaneous mechanoreceptor afferent units. Findings that the Frog type I units were quantitatively more sensitive to these Ca blockers than the Frog type II units suggest that an additional process of higher Ca-sensitivity, e.g., chemical synaptic transmission, may be involved on the way from mechanoelectric transduction to the spike generation of the Frog type I units.

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Discharge patterns of the slowly adapting mechanoreceptor afferent units innervating the non-warty skin of the frog.

Cited by 6 publications

References 17 publications

Threshold response phase to sinusoidal stimulation of frog cutaneous mechanoreceptor afferent units.

Threshold response phase to sinusoidal stimulation of frog cutaneous mechanoreceptor afferent units.

Effects of gadolinium and tetrodotoxin on the response of slowly adapting type I mechanoreceptors to mechanical stimulation in frog dorsal skin

Differential effects of manganese and magnesium on two types of slowly adapting cutaneous mechanoreceptor afferent units in frogs

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