PMC

Microscopic structure of a normal Pacinian corpuscle showing the inner bulb (transverse section of branches of terminal unmyelinated nerve endings) and lamellae (concentric layers of collagenous connective tissue and flattened fibroblasts)

Histological appearance of Ruffini-like corpuscle (A), Pacini-like corpuscle (B), and unclassified neural ending (C and D). Ruffini-like endings are thinly encapsulated; terminal branches that coil and arborize within the corpuscles are displayed after staining for S-100. Pacini-like corpuscle contains a central axon (arrow) and a lamellated capsule, stained for p75. Unclassified neural endings are visualized by staining for PGP 9.5. Magnification,×100.

(A) The Pacinian corpuscle is comprised of a single neurofilament+ (NFH) Aβ RAII-LTMR (pink) axon that travels in an unbranching manner throughout the entirety of the corpuscle before terminating in the bulbous ultraterminal region. Proximal to the ultraterminal region is the terminal region of the corpuscle. Though the Aβ RAII-LTMR is initially myelinated upon entry of the main, terminal region, the axon is unmyelinated throughout the majority of the terminal and ultraterminal region of the corpuscle where it instead forms extensive associations with S100+ lamellar cells (blue). The S100+ lamellar cells form the tightly packed inner core of the Pacinian corpuscle and organize into two sets of semi-annular, cytoplasmic lamellae that extend processes to surround the central axon. Adapted with permission from .
(B) The Aβ RAII-LTMR is unique among LTMR afferents in its insensitivity to innocuous forces delivered at low frequencies. The Aβ RAII-LTMR’s threshold for spiking decreases as frequency increases with the afferent able to entrain to light forces delivered at 500–600 Hz. Responses shown are schematic illustrations of typical responses, see: Mountcastle et al. (1967) and Talbot et al. (1968).
(C) The receptor potential of an intact Pacinian corpuscle in response to a mechanical stimulus is rapidly adapting. The potential rises during the dynamic phase of indentation and rapidly declines during the static phase of indentation, allowing only one or two impulses during the onset and offset of indentation (left). Loewenstein and colleagues showed that removal of the outer core region lead to the prolongation of the receptor potential (right), suggesting that adaptation rate is partly determined by mechanical properties of the corpuscle. Responses shown are schematic illustrations of typical responses, see: Loewenstein, W. and Mendelson, M. (1965).

(A) Schematic representation of human digital Meisser. a, axon; c, capsule; lc, lamellar cells, Sc, Schwann cells. Lamellar cells in Meissner corpuscles are closely related to the axon and form a “coin stack.” (B) Schematic representation of human Pacinian corpuscle. a, axon; c, capsule; ic, inner core; il, intermediate layer; lc, lamellar cells; oc, outer core; Sc, Schwann cells. (C) Arrangement of the terminal glial cells in the terminal and ultraterminal zones of the inner core.