Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2016 Sep 13;113(37):E5491-500.
doi: 10.1073/pnas.1610176113. Epub 2016 Aug 29.

Merkel disc is a serotonergic synapse in the epidermis for transmitting tactile signals in mammals

Weipang Chang  1 , Hirosato Kanda  1 , Ryo Ikeda  1 , Jennifer Ling  1 , Jennifer J DeBerry  1 , Jianguo G Gu  2
Affiliations

Merkel disc is a serotonergic synapse in the epidermis for transmitting tactile signals in mammals

Weipang Chang et al. Proc Natl Acad Sci U S A. .

Abstract

The evolution of sensory systems has let mammals develop complicated tactile end organs to enable sophisticated sensory tasks, including social interaction, environmental exploration, and tactile discrimination. The Merkel disc, a main type of tactile end organ consisting of Merkel cells (MCs) and Aβ-afferent endings, are highly abundant in fingertips, touch domes, and whisker hair follicles of mammals. The Merkel disc has high tactile acuity for an object's physical features, such as texture, shape, and edges. Mechanisms underlying the tactile function of Merkel discs are obscured as to how MCs transmit tactile signals to Aβ-afferent endings leading to tactile sensations. Using mouse whisker hair follicles, we show herein that tactile stimuli are transduced by MCs into excitatory signals that trigger vesicular serotonin release from MCs. We identify that both ionotropic and metabotropic 5-hydroxytryptamine (5-HT) receptors are expressed on whisker Aβ-afferent endings and that their activation by serotonin released from MCs initiates Aβ-afferent impulses. Moreover, we demonstrate that these ionotropic and metabotropic 5-HT receptors have a synergistic effect that is critical to both electrophysiological and behavioral tactile responses. These findings elucidate that the Merkel disc is a unique serotonergic synapse located in the epidermis and plays a key role in tactile transmission. The epidermal serotonergic synapse may have important clinical implications in sensory dysfunctions, such as the loss of tactile sensitivity and tactile allodynia seen in patients who have diabetes, inflammatory diseases, and undergo chemotherapy. It may also have implications in the exaggerated tactile sensations induced by recreational drugs that act on serotoninergic synapses.

Keywords: 5-HT receptors; Merkel cells; serotonin; touch; whisker hair follicles.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Tactile SA1 responses can be mimicked by focal application of serotonin to Merkel discs where 5-HT3A receptors are identified at whisker afferent endings. (A) Experimental set-up and basic structures of a whisker hair follicle related to the present study. Whisker afferent impulses were recorded using a suction electrode. Tactile stimuli were delivered by deflecting the whisker hair. MC, Merkel cells; GM, glassy membrane; Rs, ring sinus; RRC, rete ridge collar. MCs are located at two places, underneath the Rs and around the RRC. (B) Sample trace (Upper) shows typical SA1 impulses elicited by a 38-µm displacement to deflect the whisker hair. Instantaneous frequency of SA1 impulse over time is shown in the Lower panel. (C, Left) Image shows MCs labeled by quinacrine vital staining in a fresh whisker hair follicle preparation. A patch-clamp recording electrode and a mechanical stimulation probe are indicated in the image. (Right) Sample traces show MA currents (Upper) and membrane responses (Lower) of a MC recorded in situ in a whisker hair follicle preparation. (D) Two sample traces show focally puffing serotonin (Upper) but not Glu (Lower) to Merkel disc region elicits whisker afferent impulses. Bar graph below the sample traces is summary data of whisker afferent impulses following the focal application of bath solution (control, n = 30), serotonin (1 mM, n = 12), ATP (1 mM, n = 12), Glu (1 mM, n = 6), NE (1 mM, n = 6), Ach (1 mM, n = 6), His (1 mM, n = 6), SP (358 µM, n = 6), VIP (30 µM, n = 6), Enk (0.9 mM, n = 6), CGRP (26 µM, n = 6), and CCK-8 (87 µM, n = 6). (E) Image shows that a 5-HT3AeGFP-positive whisker afferent fiber (arrow indicated) extends its processes (arrowheads indicated) from the Rs to the underneath MC region. (F) A 5-HT3AeGFP-positive whisker afferent fiber (arrow indicated) innervates the RRC Merkel cell region. The boxed region shows 5-HT3AeGFP terminal processes. (G) Image shows the presence of 5-HT-ir cells and 5-HT3AeGFP-whisker afferent endings in Merkel disc region. The surface section of a coronal cut follicle was used and the outer root sheath in this image is seen as a sheet of cells. Arrowhead indicates a 5-HT3AeGFP whisker afferent ending that is in close contact with a serotonin-ir cell in the Merkel disc region of a whisker hair follicle. Data represent the mean ± SEM; ***P < 0.001; compared with bath, one-way ANOVA with Bonferroni post hoc tests.
Fig. S1.
Fig. S1.
SA1 impulses evoked by whisker hair deflections, mechanical sensitivity, and electrical excitability of MCs in mouse whisker hair follicles, and responses of mouse TG neurons to candidate chemical messengers. (A) Sample traces of SA1 impulses recorded from the whisker afferent bundle of an isolated mouse whisker hair follicle. SA1 impulses were induced by different displacements to deflect whisker hairs. From top to bottom, displacements are 3, 10, 25, and 38 μm. (B) Summary data for the experiments illustrated in A (n = 8). (C) Summary data of the relationship of MC MA current amplitudes and stimulation intensity (displacement distances) in normal bath solution or following serotonin application (100 μM, 20 min, n = 8). (D) Summary data of the V-I relationship of MCs in normal bath solution or following serotonin application (100 μM, 20 min, n = 8). (E) Summary data of AP firing frequency of MCs in responses to membrane depolarization in normal bath solution or following serotonin application (100 μM, 20 min, n = 8). (F) Sample images show Ca2+-imaging measurement of GCaMP3 fluorescent intensity changes in a TG neuron following the bath application of 1 mM ATP. (Upper) Baseline before ATP application. (Lower) Peak response following ATP application. The Ca2+-imaging experiment was performed on a whole-mount TG prepared from a GCaMP3 mouse. (G) Summary data of the changes in GCaMP3 fluorescent intensity (ΔF/F0) in TG neurons under the following conditions: application of bath (control, n = 7), KCl (50 mM, n = 7), serotonin (1 mM, n = 7), ATP (1 mM, n = 7), Glu (1 mM, n = 7), Ach (1 mM, n = 7), His (1 mM, n = 7), NE (1 mM, n = 7), SP (358 µM, n = 7), VIP (30 µM, n = 7), Enk (0.9 mM, n = 7), CGRP (26 µM, n = 7), and CCK-8 (87 µM, n = 7). Data represent the mean ± SEM. NS, no significant difference; **P < 0.01; ***P < 0.001; one-way ANOVA or paired Student’s t test.
Fig. S2.
Fig. S2.
Immunoreactivity of 5-HT3AeGFP, 5-HT3A, 5-HT2A, and 5-HT2B receptors in trigeminal afferent neurons. (A) Image shows 5-HT3AeGFP-positive neurons in a TG section. Some 5-HT3AeGFP-positive and -negative neurons in the field are indicated by arrows and arrowheads, respectively. (B) Cell size distribution of 5-HT3AeGFP-positive (green) and total (gray) TG neurons. (C) Images show immunoreactivity of 5-HT3A (Left), 5-HT2A (Center), and 5-HT2B (Right) in three TG sections. (D) Percent of positive (red) and negative (white) neurons as illustrated in C. (E) Cell size distribution of 5-HT3A-ir (Left, 337 positive cells in 1,246 total cells), 5-HT2A-ir (Center, 413 positive cells in 1,604 total cells), and 5-HT2B-ir (Right, 405 positive cells in 1,426 total cells) neurons in trigeminal sections. (F) Three images on top show FG retrogradely labeled neurons (indicated by arrowheads) in three different TG sections. FG was microinjected into whisker hair follicles 7 d before immunostaining experiments. The Lower three images show immunostaining for 5-HT3A, 5-HT2A and 5-HT2B on the same three TG sections. Arrowheads indicate the FG-labeled neurons that are immunoreactive for 5-HT3A (Left), 5-HT2A (Center), and 5-HT2B (Right). The overlay images are presented in Fig. 2I.
Fig. 2.
Fig. 2.
Serotonin evokes inward currents in whisker afferent neurons through activation of both ionotropic and metabotropic 5-HT receptors. (A) Images show two DiI retrogradely labeled whisker afferent neurons (arrowheads indicated) in a whole-mount TG preparation. Both panels are the same field taken under DIC (Upper) and fluorescent (Lower) microscopy. (B) Two sample traces show inward currents evoked by 100 µM serotonin from a whisker afferent neuron of a WT (Upper) and a 5-HT3A−/− (Lower) mouse. The Upper trace shows a mixture of a fast current (Ifast) and a slow current (Islow) but the Lower trace displays only a Islow current. The horizontal bar above each trace indicates the duration (1 min) of serotonin application. (C) Percent of whisker afferent neurons showing mixed Ifast and Islow currents (solid bar) and Islow current only (open bar). WT, n = 16; 5-HT3A−/−, n = 10. (D) Amplitude of Ifast currents in whisker afferent neuron of WT mice (n = 12). No significant Ifast current was observed in any whisker afferent neuron of 5-HT3A−/− mice (n = 10). (E) First set of two bars, Islow currents evoked by the 5-HT2A agonist TCB-2 (10 µM) in whisker afferent neurons of WT mice (solid bar, n = 5) and 5-HT3A−/− mice (open bars, n = 7). Second set of two bars, Islow currents evoked by the 5-HT2B agonist BW ( 10 µM) in whisker afferent neurons of WT mice (solid bar, n = 5) and 5-HT3A−/− mice (open bars, n = 6). (F) Serotonin-evoked Islow currents in whisker afferent neurons of 5-HT3A−/− mice in the absence (open bar, n = 6), presence of 100 µM KT (n = 8) and 100 µM LY (n = 7). Islow currents were evoked by 100 µM serotonin in each test. (G) Single-cell RT-PCR results from two whisker afferent neurons; one shows 5-HT3A, 5-HT2A and 5-HT2B mRNAs (Left) and the other shows only 5-HT2A and 5-HT2B mRNAs (Right). (H) Summary data show the percent of cells that expressed all three 5-HT receptors (solid bar, n = 10) or only expressed 5-HT2A and 5-HT2B receptors (n = 9). (I) Immunoreactivity of 5-HT3A, 5-HT2A, and 5-HT2B receptors detected on retrogradely labeled whisker afferent neurons (arrows indicated). Data represent the mean ± SEM. NS, no significant difference; *P < 0.05; **P < 0.01; ***P < 0.001; unpaired Student t test or one-way ANOVA with Bonferroni post hoc tests.
Fig. 3.
Fig. 3.
Ionotropic and metabotropic 5-HT receptors play differential roles with synergism in driving whisker afferent impulses. (A, Left) Sample traces show whisker afferent impulses elicited by serotonin or 5-HT receptor subtype selective agonists focally applied to whisker hair follicle Merkel disc region of 5-HT3A−/− mice. From top to bottom, the tests are serotonin, the 5-HT3A agonist SR57227, the 5-HT2A agonist TCB-2, and the 5-HT2B agonist BW. (Right) Summary data of the impulse numbers induced by the following tests: serotonin (n = 7), SR57227 (n = 7), TCB-2 (n = 7), and BW (n = 12). (B) Similar to A except WT mice were used for the tests of serotonin (n = 7), SR57227 (n = 7), TCB-2 (n = 7), and BW (n = 12). (C) Similar to B except tests were performed with different agonist combinations as follows, SR57227+TCB-2+BW (n = 7), SR57227+BW (n = 7), SR57227+TCB-2 (n = 7), and TCB-2+BW (n = 7). For all panels, all compounds were puff-applied at the concentration of 1 mM for 400 ms. Data represent the mean ± SEM; *P < 0.05; **P < 0.01; ***P < 0.001; one-way ANOVA with Bonferroni post hoc tests.
Fig. S3.
Fig. S3.
Tests of 5-HT receptor subtype selective agonists for their ability to elicit whisker afferent impulses. The agonists tested were eltoprazine (n = 11, for 5-HT1), TCB-2 (n = 16, for 5-HT2A), BW (n = 11, for 5-HT2B), m-CPP (n = 11, for 5-HT2C), SR57227 (n = 20, for 5-HT3), cisapride (n = 11, for 5-HT4), 5-CT (n = 11, for 5-HT5), EMD (n = 11, for 5-HT6), and AS-19 (n = 11, for 5-HT7). Bath was applied as control (n = 11). Each agonist was tested at the concentration of 1 mM and was puff-applied for 400 ms to the Merkel disc region around the Rs. Data represent the mean ± SEM; *P < 0.05; ***P < 0.001; NS, no significant difference, one-way ANOVA.
Fig. 4.
Fig. 4.
Synergism of ionotropic and metabotropic 5-HT receptors is essential for electrophysiological whisker tactile responses. (A) Sample trace shows SA1 impulses recorded from whisker hair follicles of a WT mouse. Arrowhead-indicated region is expanded on right. (B) Similar to A except SA1 impulses were recorded from a 5-HT3A−/− mouse. (C) Summary of SA1 impulses of WT (n = 30) and 5-HT3A−/− (n = 30) mice. (D) SA1 impulses of WT mice in the absence (control, n = 10) and presence (n = 10) of 2 µM Y25130. (E) Similar to D except using 5-HT3A−/− mice and 20 µM Y25130 (n = 6). (F) SA1 impulses of WT mice in control and the presence of KT+LY (n = 6). (G) Similar to F except the blocker mixture also included Y25130 (n = 7). (H) Similar to F except whisker afferent impulses were recorded from 5-HT3A−/− mice (n = 6). Data represent the mean ± SEM; *P < 0.05; **P < 0.01; ***P < 0.001; two-way ANOVA with Bonferroni post hoc tests.
Fig. S4.
Fig. S4.
Electrophysiological and mechanical transduction properties of MCs in WT and 5HT3A−/− mice. (A) Sample traces show membrane responses and APs in response to depolarizing current steps in a MC of a WT mouse (Left) and a MC of a 5-HT3A−/− mouse (Right). (B, Left) Summary data show V-I relationship of MCs of WT (n = 11) and 5-HT3A−/− mice (n = 9). (Right) Summary data of action potential frequency of WT MCs (open bar, n = 11) and 5-HT3A−/− MCs (closed bar, n = 9). Patch-clamp recordings were performed under the current-clamp mode and depolarizing steps were applied from -60 to +220 pA in increments of 20 pA. (C, Left) Two sets of traces show MA currents recorded from a WT MC (Upper) and a 5-HT3A−/− MC (Lower) in response to displacement steps from 0.5 to 3 µm in increments of 0.5 µm. (Right) Summary data of MA current amplitudes elicited at different displacement distances in WT Merkel cells (n = 7) and 5-HT3A−/− Merkel cells (n = 7). Data represent the mean ± SEM. NS, no significant difference, two-way ANOVA or unpaired Student’s t test.
Fig. S5.
Fig. S5.
Pharmacological block of ionotropic 5-HT3 receptors impairs the earlier phase of whisker SA1 responses. (A) Summary data of SA1 impulses of WT mice at initial (100 ms), middle (1,000 ms), and end (2,600 ms) time points during the course of 2,600-ms whisker displacement (also see Fig. 4D). SA1 impulses were tested in the absence (control, open bars, n = 10), and presence of either 2 µM Y25130 (black bar, n = 10), 20 µM Y25130 (gray bars, n = 10), or 10 µM MDL-72222 (horizontal hatched bars, n = 6). (B) Similar to A except experiments were performed using whisker hair follicles from 5-HT3A−/− mice and tests are control (n = 6, open bars), 2 µM (n = 6, black bars), and 20 µM (n = 6, gray bars) Y25130, and 10 µM MDL (n = 6, horizontal hatched bars). Data represent the mean ± SEM; *P < 0.05; **P < 0.01; ***P < 0.001; NS, no significant difference, comparing with control, one-way ANOVA.
Fig. S6.
Fig. S6.
MC electrophysiological properties and mechanical transduction are not affected by the 5-HT2A antagonist KT (10 µM), the 5-HT2B antagonist LY (10 µM), and the 5-HT3 antagonist Y25130 (100 µM). (A) Sample traces show membrane responses and AP in response to depolarizing current steps in a MC. The tests were performed in the absence (control, Left) and presence (Right) of 10 µM KT + 10 µM LY + 100 µM Y25130. Depolarizing steps were from −60 to +220 pA in increments of 20 pA for both traces. (B, Left) Summary data (n = 10) show V-I relationship under current-clamp recordings in the absence (control) and presence of 10 µM KT + 10 µM LY + 100 µM Y25130. (Right) Summary data (n = 10) of AP frequency in the absence (control, open bar) and presence (closed bar) of 10 µM KT + 10 µM LY + 100 µM Y25130. (C, Left) Two sets of MA currents elicited from MCs in the absence (control) and presence of 10 µM KT + 10 µM LY + 100 µM Y25130. Displacement steps were applied from 0.5 to 3 µm in increments of 0.5 µm. (Right) Summary data (n = 6) of MC MA current amplitudes elicited at different displacements in the absence (control) and presence of 10 µM KT + 10 µM LY + 100 µM Y25130. All MCs were from WT mice. Data represent the mean ± SEM. NS, no significant difference, two-way ANOVA or paired Student’s t test.
Fig. S7.
Fig. S7.
High concentrations of KT and MDL-72222 used in previous studies produce nonspecific effects. Previous studies showed that the 5-HT3 receptor antagonist MDL-72222 at the concentrations of 100 and 500 μM almost completely blocked SA1 responses and that the 5-HT2A antagonist KT at the concentration of 500 μM also greatly suppressed SA1 responses (–17). However, our results shown in the figure indicate that the previous studies are a result of the nonspecific effects of these two drugs at very high concentrations. (A and B) The 5-HT3 receptor antagonist MDL-72222 at the concentration of 100 μM blocked SA1 responses in both WT (A, n = 8) and 5-HT3−/− (B, n = 6) mice. In A and B, the Left panel shows sample traces of SA1 responses in the absence (Upper, control) and presence (Lower) of 100 μM MDL-72222. The Right panel shows summary data of SA1 impulse frequency over time in control (black circles) and in the presence of MDL-72222 (red circles). SA1 impulses were completely blocked by MDL-72222 in both WT (A) and 5-HT3−/− (B), indicating that the inhibitory effects on SA1 responses by MDL-72222 at this or higher concentrations are not mediated by 5-HT3 receptors. (C) The 5-HT2A antagonist KT at the concentration of 500 μM inhibits Piezo2-mediated mechanotransduction in MCs, the upstream key event for driving SA1 responses. (Left) Two sample traces show MA currents in MCs in the absence (control, black trace) and presence (red trace) of 500 µM KT. (Right) Summary data show MC MA currents were significantly suppressed in the presence of 500 µM KT (red circles, n = 6). Data represent the mean ± SEM; *P < 0.05; **<0.01; ***P < 0.001, two-way ANOVA (A and B) or paired Student’s t test (C).
Fig. 5.
Fig. 5.
Tactile stimulation releases serotonin from MCs in whisker hair follicles. (A) Two sets of sample traces on Left show whisker afferent SA1 responses recorded from whisker hair follicles of WT mice in normal bath (control, Upper) and in the presence of 0.5 nM BoNTA for 2 h (Lower). (Right) Summary data of the changes of whisker afferent SA1 impulses recorded over time in normal bath solution (control, n = 6, black circles) and in the presence of 0.5 nM BoNTA (n = 8, red circles). (B) Serotonin detected in bath solution by ELISA following mechanical stimulation that deflects whisker hairs. Bars from left to right are serotonin concentrations detected following increased tactile stimulation numbers. In each experiment, 10 follicles were used and a tactile stimulus is a displacement at 38 µm. Eight sets of tests (n = 8) were performed for each condition. (C, Upper) RT-PCR shows the expression of tryptophan hydroxylase 1 (Tph1) mRNAs in MCs. Similar results were observed in two other sets of RT-PCR experiments. (Lower) Image shows the present of 5-HT-ir cells (arrowheads indicated) in Merkel disc region of the out root sheath. The middle section of a coronal cut follicle was used and the out root sheath (MC region) is a thin layer at the border below the Rs. (D) Image shows a Merkel disc region of a fresh whisker hair follicle used for real-time detection of serotonin release from MCs. MCs were vital-stained by quinacrine and a MC is indicated by an arrowhead. The MC is in close contact with the tip of a carbon fiber electrode (star indicated) and the same carbon fiber electrode was used for both mechanical stimulation and amperometric detection of serotonin release. (E) Sample trace of oxidation current events detected by a carbon fiber electrode following mechanical stimulation of a Merkel cell by a 10-μm displacement. Two traces on the bottom are at an expanded scale for the two parts indicated by dashed lines. (F) Percent of MCs showing multiple release events (n = 75) or only a single release event (n = 47). (G) Peak amplitude (serotonin concentrations) of the first event of multiple release event cells (n = 40) and single release event cells (n = 32). (H) Event-amplitude distribution of multiple release events. The first event is excluded from the plots. Greater than 65% of the release events were in the size range of 0.4–0.6 μM serotonin. (I, Left) Sample traces show the detection of mechanical stimulation-evoked serotonin release in normal bath (control, Top), in a low Ca2+ bath solution (Middle), and recovery after returning to normal bath (Bottom). (Right) Summary data (n = 10) of serotonin release in control, low Ca2+ bath solution and recovery. The value of the biggest event in each test was used for the summary data. Data represent the mean ± SEM; *P < 0.05; ***P < 0.001; one-way ANOVA with Bonferroni post hoc tests or paired Student’s t test.
Fig. S8.
Fig. S8.
Detection of serotonin release from MCs using the amperometry with carbon fiber electrodes. (A) Calibration for the measurement of transient serotonin following a brief puff-application. A set of transient oxidation currents detected by a carbon fiber electrode following brief puff applications of serotonin onto the electrode tip in a bulk bath solution. For detecting serotonin transiently present at the electrode tip, an oxidation voltage step of 550 mV was applied for 10 s. Serotonin was puff-applied with a glass electrode for a short duration of 100 ms (arrow indicated) during the continuous oxidation voltage of 550 mV. (B) Summary data of the averaged calibration values of oxidation currents with serotonin concentrations up to 5 μM (n = 6). (C) Top and Middle traces show examples of oxidation currents following mechanical stimulation of a MC of a WT mouse and a MC of a 5-HT3A−/− mouse, respectively. Bottom trace shows no detectable oxidation currents following the same mechanical stimulation to a non-MC of a WT mouse. (D) Summary data of the peak concentrations of serotonin release from MCs of WT mice (n = 12) and 5-HT3A−/− mice (n = 10), and the lack of serotonin release from non-MCs of WT mice (n = 9). In this set of experiments, MCs were prelabeled by vital staining with quinacrine. Detections were performed from MCs underneath the Rs and from non-MCs in the region between the RRC and Rs. Data represent the mean ± SEM. NS, not significantly different, unpaired Student’s t test.
Fig. 6.
Fig. 6.
Ionotropic and metabotropic 5-HT receptors in whisker hair follicles are involved in behavioral whisker tactile responses. (A) Diagram illustrates tactile behavioral tests. Dashed arrow indicates the direction of tactile stimulation to move the whisker hair using a tactile stimulation filament. (B) Behavioral responses of WT mice to whisker hair tactile stimulation following hair follicle microinjection of saline (control), KT+LY, Y25130, or KT+LY+Y25130. (C) Behavioral responses of 5-HT3A−/− mice to whisker hair tactile stimulation following microinjection of saline or KT+LY, n = 6 for each experiment in B and C. The testing drugs were administered at 100 μM with a total volume of 1 µL. Data represent the mean ± SEM; *P < 0.05, Student’s t test.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Zimmerman A, Bai L, Ginty DD. The gentle touch receptors of mammalian skin. Science. 2014;346(6212):950–954. - PMC - PubMed
    1. Johnson KO. The roles and functions of cutaneous mechanoreceptors. Curr Opin Neurobiol. 2001;11(4):455–461. - PubMed
    1. Halata Z, Grim M, Bauman KI. Friedrich Sigmund Merkel and his “Merkel cell”, morphology, development, and physiology: review and new results. Anat Rec A Discov Mol Cell Evol Biol. 2003;271(1):225–239. - PubMed
    1. Merkel F. Tastzellen and Tastkoerperchen bei den Hausthieren und beim Menschen. Arch Mikrosc Anat. 1875;11:636–652.
    1. Iggo A, Muir AR. The structure and function of a slowly adapting touch corpuscle in hairy skin. J Physiol. 1969;200(3):763–796. - PMC - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources