SUMMARY1. Merkel cells were dissociated enzymatically from the footpad epidermis of 10-to 20-day-old rats pretreated with fluorescent dye, quinacrine, for purposes of staining. The fluorescent Merkel cells had an elongated or elliptic shape in situ, yet the dissociated ones were round (7-12 #m in diameter).2. Electrical recordings were performed in the whole-cell configuration using a conventional patch-clamp technique. The mean resting membrane potential of fluorescent Merkel cells was -54 0 mV, the value being greater than the -2641 mV of non-fluorescent epidermal cells. No voltage-dependent channel was observed in non-fluorescent cells.3. The Merkel cells had no Na+ spike in an external standard solution, but tetrodotoxin-resistant long-lasting action potentials were evoked by depolarization with injection of constant currents in an external solution containing Ba2+.4. In Merkel cells under voltage clamp, depolarizing step pulses (800 ms) from a holding potential (VH) of -80 mV elicited predominantly outward K+ currents composed of transient and sustained components: the former was selectively inhibited by 4-aminopyridine (4-AP), while the latter was inhibited by both tetraethylammonium (TEA) and quinacrine. Quinacrine was more effective and selective than TEA in blocking the sustained K+ current but had no effect on the current at the low concentration (10-7or 3 x 10`6 M) used for staining the Merkel cells.5. The sustained outward K+ current (IKD) was activated at potentials more positive than -20 or -10 mV at a VH of -50 mV, at which potential the transient outward K+ channel was completely inactivated. The potential for half-inactivation in the steady-state inactivation curve for IKD was -33 mV.6. The transient outward K+ current (IA) was activated at potentials more positive than -50 mV at a VH of -80 mV. The potential for half-inactivation in the steady-state inactivation curve for IA was -64 mV.7. When the outward K+ currents were blocked by adding both TEA and 4-AP, only a sustained inward Ca2+ current was observed. In an external solution containing 10 mM-Ca2+, ICa was evoked by potentials more positive than -20 mV at a VH of -80 mV, and the maximum inward current appeared around +10 mV. 8. In external solution containing 25 mM-Ba2 , the potential for half-inactivation of the steady-state inactivation curve for IBa was -34 mV.9. The selectivity of the Ca2+ channel for divalent cations was in the order Ba2+ > Sr2+ > Ca2+.10. Organic and inorganic Ca2+ antagonists blocked IBa in a concentrationdependent manner, the potency of inhibition being in the order w-conotoxin > flunarizine = nicardipine > diltiazem > verapamil, and La3+ > Cd2+ > Co2+.11. It is concluded that Merkel cells have at least three distinct voltage-gated currents: a delayed K+ current (IKD), a transient A-current (IA) and a high-threshold (L-type) Ca2+ current (ICa). The electrical and pharmacological properties of these voltage-dependent channels are essentially similar to those of other excitable cells.

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Basal cell carcinoma (BCC) originating from an epidermoid cyst which existed for about 50 years was seen in a 78-year-old Japanese male. Nests of basal cell carcinoma were connected with the epidermoid cyst, partially replacing the cyst wall.

The ring-type electric flash is not an ideal device for recording skin lesions. An illumination device compatible with a standard light source should be employed to yield maximum fidelity.

No abstract