Tadasi Sato

Effect of dopamine and haloperidol on the c-wave and light peak of light-induced retinal responses in chick eye.

The relation between dopaminergic cells (and centrifugal fibers), the electroretinogram (ERG) c-wave, and the light peak were electrophysiologically investigated by observing the effects of a retrobulbar conduction block and intravitreal injection of either dopamine or haloperidol on these retinal responses. The retrobulbar conduction block (1% lidocaine) caused a decrease in the amplitude of the c-wave and the light peak in newly hatched chicks. Injections (2–20 μl) containing dopamine (0.1–10 mM) or haloperidol (1.3–13 mM) were given intravitreously while the responses were recorded. Although intravitreous injection of saline for control resulted in no observable change in the responses, dopamine selectively augmented the c-wave of ERGs and the light peak, but not the a-, b-, and d-waves. Haloperidol decreased first the light peak and later the c-wave. The augmentation of the retinal responses by dopamine and their reduction by haloperidol was statistically significant. The estimated threshold concentration of dopamine in the vitreous cavity was 1–3.5 μM.Since in many species the interplexiform cells have been found to contain dopamine, we hypothesize that the modulatory effects on the c-wave and the light peak in this preparation may be due to a centrifugal feed-back loop which includes the interplexiform cells to the horizontal and bipolar cells and the horizontal cells to the cones.

Physiological properties of tooth pulp-driven neurons in the first somatosensory cortex (SI) of the cat.

&NA; Tooth pulp‐driven (TPD) neurons are found in the oral area of the first somatosensory cortex (SI) of the cat. They have been classified according to their discharge patterns in response to electrical stimulation of the tooth pulp: the fast (F) type, slow (S) type, and a fast (Fa) type accompanied by afterdischarges. The characteristics of each type of TPD neuron were investigated in cats anesthetized with nitrous oxide and halothane. In surface distribution, there was no biased localization for any of the types. However, F‐type neurons receiving input from the mandibular tooth tended to be found more medially than F‐types receiving maxillary input. These TPD neurons did not change their firing pattern even when the stimulus was intensified. Mean threshold of the F‐type to tooth pulp stimulation was 7.8 ± 1.6V and tended to be lower than that of the S‐type (16.3 ± 3.0V). Graded increases in tooth pulp stimulation produced progressive increases in discharge frequency of both types of neurons. An analysis of the power function in relation to stimulus vs. response demonstrated that the exponent of the S‐type neuron was about 2.0, being significantly larger compared to the 0.8 value for the F‐type. The mean number of pulps afferent to an F‐type was 1.6, compared to 4.8 for an S‐type or 4.3 for an Fa‐type. The results suggest that F‐type TPD neurons may play a more important part in localizing pulpal pain and in recognizing the intensity than the other types.

Characteristics of the tooth pulp-driven neurons in a functional column of the cat's somatosensory cortex (SI)

SummaryThe columnar arrangement of tooth pulp-driven (TPD) neurons in the first somatosensory cortex (SI) was studied by single unit analysis in the cat anesthetized with nitrous oxide and halo thane. Tactile sensitive neurons in the oral area of SI were arranged functionally in a columnar organization. About 32% of the recorded neurons also responded to tooth pulp stimulation. Thus, the TPD neurons located in area 3b seem to be multireceptive in sensory modality. About 80% of the TPD neurons were F-type which respond with a short latency to tooth pulp stimulation and receive input from a small number of teeth. When a microelectrode penetrated through a single vertical column, most of the F-type TPD neurons encountered received common input from one or two tooth pulps. However, when an electrode was inserted across more than one column, there was no common pulpal input to the TPD neurons encountered in a track. Thus, the TPD neurons in a single column had identical peripheral and pulpal receptive fields, and the same latency of responses to tooth pulp stimulation. These characteristics would support the hypothesis that TPD (presumed nociceptive) neurons are arranged in a vertical column and it may be inferred that the columnar organization of TPD neurons in SI plays an important role in the sensory-discriminative aspects of pulpal pain.

A pH curve of human resting saliva sampled with a small paper slip and its medical application

This paper described physiochemical characteristics of the pH curve of saliva that accompanied escape of CO(2) and that was recorded by a previously reported method. Monthly sample of the resting saliva was collected by a small paper slip from five adults (59.9+/-16.5 years old) over 36 months. The pH curves were examined to represent differences in secretion characteristics among individuals. The following results were obtained: (1) Three variables, pH(1), Delta pH(I), and Delta pH(L), that represent a saliva pH curve indicated secretory characteristics of each individual since the intra-individual variance of them was significantly smaller than the inter-individual variance. (2) These values (mean+/-S.D.) obtained from five adults were 7.03+/-0.54, 0.24+/-0.21, and -0.10+/-0.12, and those obtained from 663 young adults (21.7+/-2.4 years old) were 7.14+/-0.44, 0.26+/-0.23, and -0.08+/-0.13. (3) A characteristic about amplitude of the Delta pH(I) of each individual was maintained over 36 months under the healthy condition. Seasonal variation of the three pH variables and their statistical distribution were also investigated.

Morphine selectively suppresses the slow response of tooth pulp-driven neurons in first somatosensory cortex (SI) of the cat

Tooth pulp-driven (TPD) neurons are found in the oral area of the first somatosensory cortex (SI) and they have been classified into fast (F-) type, slow (S-) type and fast type accompanied by afterdischarges (Fa). Effects of morphine on single unit responses of the F- and S-type neurons to pulp stimulation were examined by recording the discharges from a single neuron using a microelectrode. Intraperitoneal administration of morphine at 1.5 mg/kg markedly suppressed the response of S-type TPD neurons that fire with a long latency. This effect was completely reversed by naloxone at 0.2 mg/kg. On the other hand, the discharges of F-type neurons that fire with a short latency were not affected by application of morphine at 3 mg/kg. These findings suggest that S-type neurons in SI are concerned with pain perception.

Characteristics of tooth pulp-driven neurons in the posterior group of the cat thalamus

This investigation was designed to determine the responses of neurons in the posterior group of nuclei (PO) to tooth pulp stimulation. Eighteen tooth pulp-driven (TPD) neurons were recorded in 9 cats anesthetized with nitrous oxide and halothane, 14 of them in the medial part (POM) and the remainder in the lateral part (POL) of the posterior nuclei. These TPD neurons also responded to non-noxious tactile stimuli of the orofacial region of the body. Most TPD neurons responded with a short latency of less than 20 ms to tooth pulp stimulation (mean 13.5 +/- 5.9). The number of teeth having afferents to these neurons was 4-8 (mean 6.7 +/- 1.3).

Recovery of a patient with a recurrent dysgeusia monitored by salivary variables and serum zinc content

A patient with dysgeusia of phantom sweetness was monthly monitored by a recently developed measurement of resting saliva besides of psychosomatic therapy since there were indications to be suspected declines in the serum zinc content and carbonic anhydrase activity at the first saliva inspection. The decline of serum zinc content was later supported by a chemical analysis of the blood, which was 83 &mgr;g dl(-1). After the patient enhanced her nutritional intake of zinc rich foods, her serum zinc content rose to 88 &mgr;g dl(-1) and her symptoms improved. However, when the concentration of her saliva Na(+) increased over 10 mM, the disappearance and reappearance of the phantom sweetness symptom repeated. Thus she was advised to maintain a medium level of Na(+) concentration by maintaining amount of weekly exercise, which contributed to obtain continuous disappearance of the phantom sweetness over 10 months. Her serum zinc content was between 94 and 101 &mgr;g dl(-1) in the latter period, and Na(+) concentration was maintained around average value of young adults (6.3 mM). This paper also reports the correlation between subjective intensity of phantom sweetness and Na(+) concentration of saliva with a phase delay of 1 month.

Electroretinogram c-wave and slow PIII of the rabbit: Changes in peak time and amplitude under various stimulus durations

Changes in peak time and amplitude of the direct current registered c-wave of the electroretinogram of the albino rabbit were investigated with various stimuli of duration ranging from 0.25 to 10 sec. The stimulus intensity was 500 lux at the surface of the cornea. Slow PIII was isolated by administrations of sodium iodate and sodium aspartate.The peak time of the c-wave was longer than that of the slow PIII in the range of stimulus duration less than 3.5 sec, but peak times were almost the same in the range above 3.5 sec. The amplitude of the c-wave at peak was larger than the corresponding amplitude of the slow PIII in the range less than 1 sec, but the slow PIII became larger than the c-wave at more than 1 sec. For stimuli less than 4 sec, the smaller the stimulus duration, the smaller was the negative slow PIII which affected the height of the c-wave.We conclude that in order to minimize the influence of the slow PIII on the c-wave, the duration of stimuli with intensity of 500 lux for recording the c-wave of the rabbit should be less than 4 sec.

Osmotic pressure of the interstitial fluid obtained from neonatal chick eyes and its variation under light and dark adaptation

In experiments by Yoneyama et al. (1985) a hypertonic perfusing solution was used to record the c-wave from the isolated chick retina. We investigated whether the chick retina was surrounded by such hypertonic liquids. The following results were found: (1) the osmolarity of the subchoroidal humor was markedly higher than that of fluids from other areas of the eye; (2) the relative difference in osmolarity between both sides of the retina was 110–170 mOsmol in the light-adapted condition, whereas it was about 270 mOsmol in the dark-adapted condition; and (3) in the dark-adapted state the volume of the subchoroidal humor decreased about 40% but increased in osmolarity about 30–40%, whereas osmolarity of the subviteous humor decreased about 15–20 mOsmol. Results suggest the presence of an inward-directed pump mechanism for watersoluble components in the retina in addition to the proposed outward-directed pump mechanism of the pigment epithelium. The inward-directed pump may be more active in the dark-adapted state.

Retrospective investigation on management of salivary hypofunction concerning with serum zinc content

Monthly measurement of the resting saliva was performed in addition to psychosomatic therapy for patients visiting our clinic who were suspected of having decreased activity of carbonic anhydrase. According to the serum zinc content, patients were divided into a low serum zinc group (n=22) and a mid-high serum zinc group (n=12). Patients in the former group were advised to improve mastication efficiency and to consume more food with a high zinc content. After 6.6+/-5.6 months, serum zinc increased from 75.6 to 90.9 mug/dl in the former group, whereas no change was found in the latter group, though symptoms improved in the both groups. Improvement in salivary secretion was noticed in DeltapH(I) in the former group, and a decrease in K(+) concentration was found in the latter group.