Slow-adapting responses of the Pacinian corpuscles of cat planta.

Slow-adapting impulses were recorded from the single nerve fiber innervating the Pacinian corpuscle of the cat planta, which was stimulated by constant pressure. Slow-adapting Pacinian corpuscles responded to both low-frequency (0.1-0.01 Hz) and high-frequency (400-800 Hz) vibrations. Simultaneously performed electron microscopy showed that there were no definite ultrastructural differences between slow- and fast-adapting Pacinian corpuscles.

A novel stretch receptor in the jaw of the rat.

We report here an unusual type of stretch receptor found on each side of the rat jaw. This receptor has unique morphological features: it is quite long (24-28 mm), lies in connective tissue in between masticatory muscles, and extends between the medial pterygoid muscle-tendon on the maxilla and the masseter-tendon on the mandible through a zigzag course, forming a Greek capital letter sigma when viewed from the side. The receptor is neither in parallel nor in series with any masticatory muscles and receives multiple innervation. The receptor increases its length when the jaw closes and shortens when the jaw opens. Electron microscopy revealed axial structures composed of a central cellular core surrounded by tightly packed collagen bundles which are separated from the capsule by a wide capsular space. Most of the sensory endings are found among axial collagen bundles, some in between core cells. The core cells have many finger-like processes on their surface, being coupled by desmosomes. The origin and nature of these cells are unclear. The wide capsular space is filled with Alcian blue positive substrate, probably acid glycosaminoglycans. The structures of outer and inner capsules are similar to those of muscle spindles, the former being composed of three to ten layers of thin flattened cells. The response of the receptor was examined with in vivo as well as in vitro preparations. In in vivo experiments, impulse discharges from this receptor increased with the increase in jaw closing. When the jaw was fully opened the impulse discharge from this receptor disappeared.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood-nerve barrier in the Vater-Pacini corpuscle of cat mesentery.

Correlated thin-section, freeze-fracture and tracer examinations were used to examine the blood-nerve barrier of the Vater-Pacini corpuscles in cat mesentery. A laminar inner core and a multilayered outer core enfolded the terminal nerve fiber of the corpuscle. The lamellar cells of both cores were characterized by numerous vesicular membrane invaginations. Freeze-fracture images and tracer experiments employing lanthanum nitrate proved that these invaginations are static structures mediating in neither active pinocytosis nor the transcellular transport of metabolites. In both inner and outer cores, lamellar cells were connected to one another by tight junctions of either the zonula or the fascia type, that occurred between lamellar-cell processes within the lamella and between the cells of adjacent lamellae. Intravascularly applied lanthanum lay at the outermost regions of the corpuscles without entering their internal zones, apparently because lamellar-cell tight junctions hindered further penetration. The results of our investigations suggest strongly that the Vater-Pacini corpuscle lamellae enfolding the nerve terminal form an effective diffusion barrier against the permeation of tissue fluids, thus preserving the corpuscle internal circumference.

Merkel cell-neurite complexes in touch domes of hamster cheek pouch.

Morphological study has been done in touch domes of hamster cheek pouch as a preparation for further electrophysiological study. The touch domes were examined by light and electron microscopy. There were one or two primary ridges (epithelial ridges) in the center of the touch dome, and each dome was supplied by one to three nerve fibres. Tactile cells (Merkel cells) were localized within primary ridges of touch domes and Merkel cell-neurite complexes were observed in every one. Since Merkel cell-neurite complexes are slow adapting mechanoreceptors, these results suggest that they might be involved in touch sensation.

Distribution of the chain of stretch receptors on masticatory muscles of the rat.

The existence of stretch receptors on the fasciae of masticatory muscles of the rat was demonstrated by means of methylene blue vital staining. A single cord of connective tissue on each side extends over the surfaces of the superficial masseter, temporal, and medial pterygoid muscles. The complex arborizations of unmyelinated nerve terminals originated from branches of the buccal nerve gathered closely within the cord forming the chain of stretch receptors. The chain was lengthened during the jaw closing phase, when the firing rates of stretch receptors probably increased. Results suggested that the chain of stretch receptors signaled position or movement of the mandible. The same stretch receptors were also detected on the masticatory muscles of some other rodents.

Ultrastructure of the encapsulated corpuscles in the lower lip mucosa of the mouse.

Under the light microscope, the encapsulated corpuscles of the mouse lower lip mucosa were only classified into 4 types, simple, ramifying, branched-axon, and clew-like corpuscles. The ultrastructural characteristics of the branched-axon and clew-like corpuscles, however, were not reported. Five male mice, aged 4 to 8 weeks, were used. The mouse lower lip mucosa were examined with a electron microscope. Two types of corpuscles were distinguished. The first type had numerous branched axon terminals and bilaterally symmetrical and/or asymmetrical Schwann cell cytoplasmic lamellae in a few perineural capsules. The second type did not have perineural capsules. We concluded that these two types fell into the categories of branched-axon and/or clew-like corpuscles in the light microscopical observations. We concluded also that first type fit the category of coiled simple corpuscles and second type fit the category of Meissner-like corpuscles according to the electron microscopical observations.

The oscillation from pacinian corpuscles to external stimuli in cat mesentery.

Single Pacinian corpuscles isolated from cat mesentery elicited fast-adapting responses and/or oscillation to displacement and vibratory stimuli at temperatures of 24-43 degrees C. The displacement threshold of oscillation increased by decreasing the temperature of the room or of the corpuscles to below 26 degrees C. Further cooling made the corpuscles elicit only fast-adapting responses to displacement stimuli of identical strength. When a single Pacinian corpuscle was stimulated by the same displacement the impulse patterns depended on the temperature of the experimental plate on which the corpuscle was situated. It is therefore suggested that, in temperatures higher than 28 degrees C and lower than 43 degrees C, constant displacement stimuli or vibratory stimuli (10-0.01 Hz) induced oscillation of the receptor potential from the Pacinian corpuscles.