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Biomedical subjects

H Toyooka

Publications and source records attributed to H Toyooka.

212 records · Page 12Linked to original sources
PubMed1977

Suppressive effect of morphine on single-unit activity of cells in Rexed lamina VII.

Using an extracellular microelectrode recording technique, the effects of intravenously administered morphine sulfate upon the single-unit activities of cells in Rexed lamina VII of the lumbar spinal cord were studied in cats following decerebration and spinal cord transection at L1. These neurons responded principally to high-threshold mechanical and thermal stimuli applied to a receptive field in the ipsilateral hind limbs. Morphine sulfate, 0.25, 0.5, and 1.0 mg/kg, caused dose-related suppression of the spontaneous activities of these neurons. The firing rates at maximum suppression, observed 5-10 min after administration of morphine, were 63.9 +/- 9.2 (mean +/- 1 SE), 43.0 +/- 5.4, and 26.5 +/- 6.0 per cent of the control values, respectively. Since these cells have been shown by others to be associated with the spinothalamic and spinoreticular pathways, the results suggest that the analgesic state may result from the action of morphine on the cells of origin of these major ascending pathways in the spinal cord.

Animals↗
PubMedDate not supplied

Plasma lidocaine, monoethylglycinexylidide, and glycinexylidide concentrations after epidural administration in geriatric patients.

BACKGROUND AND OBJECTIVES: The purpose of this study was to evaluate the effect of age on the pharmacokinetics of lidocaine after epidural administration. METHODS: Two percent lidocaine with epinephrine (5 microg/mL) was administered in two different age groups: an adult group (age 42 +/- 6 years, n = 10) and an elderly group (age 77 +/- 4 years, n = 10). Concentrations of lidocaine and its active metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), were measured in plasma samples obtained after 15, 30, 45, 60, 90, 120, 150, and 180 minutes of administration using high-performance liquid chromatography with ultraviolet detection. RESULTS: No significant differences in plasma concentrations of lidocaine and its metabolites were observed between the two groups during the 3 hours of study. However, the elderly group showed significantly longer mean residence times (MRTs) and lower plasma clearance of lidocaine during the period compared with the adult group (P < .05). Plasma concentration ratios of MEGX/lidocaine were significantly lower in the elderly group after 2 hours of lidocaine administration (P < .05). CONCLUSIONS: The increase in plasma lidocaine concentration after epidural anesthesia in elderly patients was not as high as anticipated. However, the elderly patients showed longer MRTs, lower clearance, and lower ratios of MEGX/lidocaine than did the adult (middle-age) patients.

Adult↗
PubMedDate not supplied

Plasma concentrations of lidocaine and its principal metabolites during continuous epidural infusion of lidocaine with or without epinephrine.

BACKGROUND AND OBJECTIVES: The purpose of this study was to evaluate the effect of epinephrine on the absorption of lidocaine and the accumulation of active metabolites of lidocaine during continuous epidural anesthesia. METHODS: Lidocaine was administered as an initial bolus of 5 mg/kg of 2% lidocaine solution followed by continuous infusion at 2.5 mg/kg/h. Patients in group I (n = 10) received lidocaine alone and patients in group II (n = 10) received lidocaine + epinephrine (5 pg/mL). Concentrations of lidocaine and its active metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), were measured in plasma samples obtained after 15 minutes, 30 minutes, and 1, 2, and 3 hours of infusion using high-performance liquid chromatography with ultraviolet detection. RESULTS: Plasma lidocaine concentrations were higher in group I for the first 30 minutes; however, after 1 hour the levels were the same. Plasma MEGX and GX increased continuously in both groups. MEGX levels the were significantly higher in group I, but there was no significant difference in the sum of lidocaine + MEGX after 2 hours. There was no significant difference in GX levels between the two groups. CONCLUSIONS: With respect to continuous epidural administration, addition of epinephrine to lidocaine solutions is ineffective after 2 hours for reducing the potential for systemic toxicity, because the sum of the plasma concentrations of lidocaine and its principal active metabolite, MEGX, are unaffected.

Absorption↗
PubMedDate not supplied

The formalin test: effects of formalin concentration and short-term halothane inhalation.

BACKGROUND AND OBJECTIVES: In order to evaluate the effects of formalin concentration and inhalational anesthetics in formalin tests, we injected 5 concentrations of formalin into awake and anesthetized rats and investigated their behavior and the c-fos immunoreactivity of their spinal cords. METHODS: Sixty adult male Sprague-Dawley rats were divided into 10 experimental groups. Each rat was either manually restrained or subdued through several minutes of 2% to 2.5% halothane inhalation, and then 1 of 5 concentrations of 0%, 5%, 10%, 27%, or 100% formalin (0%, 1.85%, 3.7%, 10%, or 37% formaldehyde solutions) was injected into its rear paw. Nociceptive behaviors were checked for 1 hour, 6 times for each 5-minute period. Two hours after the formalin injections, the rats were killed and c-fos immunoreactivity was measured. RESULTS: Typical responses were observed in the 5% and 10% formalin (1.85% and 3.7% formaldehyde) groups, and nociceptive behaviors were lower in the 27% and 100% formalin (10% and 37% formaldehyde) groups. The number of c-fos-positive cells increased as the formalin concentration increased. Halothane inhalation affected the results of both the behavior and the c-fos immunoreactivity, especially in the 10% formalin (3.7% formaldehyde) group. CONCLUSIONS: It is desirable to describe both formalin and formaldehyde concentrations simultaneously and to do formalin tests without inhalational anesthetics.

Administration, Inhalation↗