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Biomedical subjects

L M Kitahata

Publications and source records attributed to L M Kitahata.

At least 55 records · Page 3Linked to original sources
PubMed1980

Effects of halothane on spinal neuronal responses to graded noxious heat stimulation in the cat.

This study was undertaken to examine the dose-response effects of clinical concentrations of halothane on activity of wide-dynamic-range (WDR) neurons in the dorsal horn of the spinal cord of the decerebrate, spinal cord-transected cat. All cells (n = 40) responded maximally to high-intensity (greater than 45 C) noxious heat stimulation. Following administration of halothane, 0.5, 1.0, and 1.5 per cent, the mean spontaneous discharge frequency was significantly decreased (P < 0.01) by 44, 74, and 87 per cent, respectively. The mean evoked discharge frequencies were also significantly decreased at all temperatures (46, 48.5 51 C) by all concentrations of halothane. The slope of the regression line relating heat intensity and evoked neuronal discharge frequency was significantly decreased (P < 0.01) with both 1.0 and 1.5 per cent halothane by 46 and 75 per cent, respectively. Since the spinal cord was transected, these results indicate that these effects were the result of a direct action at the level of the spinal cord. The neuronal activity that was suppressed was evoked by stimuli that were exclusively noxious. This substantiates the ability of halothane to modify the transmission of noxious information at the spinal cord level, and thus explains a mechanism by which halothane may induce analgesia.

Animals↗
PubMed1980

The hemodynamic tracking system: a method of data management and guide for cardiovascular therapy.

In the operating room or intensive care unit, multiple measurements of circulatory function are almost mandatory in patients with significant cardiovascular disease. Use in these areas requires that the information must be easily organized, rapidly obtained, and inexpensive. A hemodynamic tracking system that meets these criteria is described. This system incorporates a hand-held programmable calculator (cost = $210 to $300) to derive variables computed from standard cardiovascular measurements. The time required to obtain a set of measurements (including thermodilution cardiac output determinations in duplicate), key the numbers into the calculator, and obtain the derived indices is 4 minutes. Two patients, who had acute mitral insufficiency and whose clinical management differed substantially are presented to illustrate the use of data obtained from the hemodynamic tracking system.

Aged↗
PubMed1980

Halothane-induced changes in neuronal activity of cells of the nucleus reticularis gigantocellularis of the cat.

The ability of 0.5% and 1.0% halothane to suppress neuronal activity of cells in the nucleus reticularis gigantocellularis (NRGC) was studied in decerebrate cats. These drug effects were examined in order to substantiate further the potential involvement of the NRGC in the modulation of transmission of pain information. Only cells of the NRGC, which were excited exclusively by electrical stimulation of A-delta fibers in the superficial radial nerve, were studied. Both concentrations of halothane caused a significant, dose-dependent reduction of spontaneous and evoked activity of all cells studied. These findings correlate well with previous reports of other anesthetics suppressing NRGC activity. In light of the selective depression by anesthetics and narcotic analgesics of spinal cord dorsal horn cells associated with noxious stimuli, these findings, when combined with anatomic, physiologic, and behavioral studies of NRGC, provide further evidence of the involvement of NRGC in the signaling of noxious stimuli and the analgesic effects of halothane exerted at this site.

Animals↗
PubMed1979

An analgesic action of intranvenously administered lidocaine on dorsal-horn neurons responding to noxious thermal stimulation.

Using extracellular single-unit recording techniques, effects of intravenously administered lidocaine on dorsal-horn nociceptive neurons were studied in cats made decerebrate whose spinal cords had been transected. Thirty-seven neurons in Rexed lamina V responding to high-threshold mechanical and noxious thermal stimuli (radiant heat, using Hardy-Wolff-Goodell dolorimeter) were studied. Lidocaine hydrochloride, 2.5, 5, and 10 mg/kg, iv, produced dose-related suppression of both spontaneous activity and responses of these neurons to noxious thermal stimulation. Spontaneous discharge frequencies at maximum suppression, observed 3--7 min after administration of each of the three doses of lidocaine were 64 +/- 14 (mean +/- 1 SE), 32 +/- 8, and 25 +/- 9 per cent of control values, respectively; responses to noxious thermal stimuli were 83 +/- 5, 52 +/- 8, and 39 +/- 7 per cent of the control values, respectively. Threshold skin temperature to noxious thermal stimulation increased from 44.7 +/- 0.4 C (control) to 46.3 +/- 0.7 C with lidocaine, 5 mg/kg (P less than 0.05), to 47.8 +/- 0.8 C with lidocaine, 10 mg/kg (P less than 0.01). The times necessary for recovery varied in a dose-related fashion. Plasma lidocaine concentrations 5 min after lidocaine, 5 mg/kg, averaged 3.6 +/- 0.7 microgram/ml. These data support the clinical impression that intravenously administered lidocaine produces analgesia at plasma concentrations of 3--10 microgram/ml. It is suggested that lidocaine may block conduction of nociceptive impulses, at least in part, by suppression of spinal-cord nociceptive neurons.

Analgesics↗
PubMed1979

Effects of morphine sulfate on dorsal-horn neuronal responses to graded noxious thermal stimulation in the decerebrate cat.

Effects of morphine sulfate upon activity of the neurons of dorsal-horn lamina V as evoked by graded noxious thermal stimuli applied on the receptive field were studied in spinal cord-transected, decerebrate cats utilizing an extracellular microelectrode recording technique. All single units studied (n = 30) responded to noxious thermal as well as to noxious mechanical stimulation. Their spontaneous discharge frequency was 9.7 +/- 1.5 (mean +/- 1 SE) impulses/sec (IPS), the threshold skin temperature was 44.8 +/- 0.2 C, and a linear correlation existed between skin temperature and discharge frequency at 6.7 +/- 0.6 IPS/degree C. Morphine, 1 and 2 mg/kg, iv, suppressed spontaneous activity by 53 +/- 6 and 84 +/- 6 per cent, respectively; increased threshold skin temperature to 46.5 +/- 0.3 and 47.9 +/- 0.5 C, respectively, and maintained the linear correlation between skin temperature and discharge frequency but depressed the mean slope of the regression line to 4.5 +/- 0.7 and to 2.4 +/- 0.4 IPS/degree C, respectively. Naloxone, 0.02--0.04 mg/kg, iv, reversed all of these changes produced by morphine. The results of the present study are, to the authors' knowledge, the first demonstration of the suppressive effect of morphine on the spinal nociceptive neurons in Rexed lamina V as they respond to graded noxious thermal stimuli. These results may explain the analgesic action of morphine at the spinal level.

Animals↗
PubMed1979

Effects of ketamine on nociceptive cells in the medial medullary reticular formation of the cat.

Anatomic, physiologic and behavioral evidence suggests that the neurons in the nucleus reticularis gigantocellularis of the medial medullary reticular formation may act as a relay station for the transmission of nociceptive information from the spinal cord to higher brain centers. The nucleus reticularis gigantocellularis may also be the site of action of analgesic agents, such as ketamine hydrochloride. Utilizing extracellular microelectrodes in 23 decerebrate cats, the authors measured the effect of ketamine on neurons in the nucleus reticularis gigantocellularis that were excited by electrical stimulation of peripheral nerves. The frequency of spontaneous single-unit firing activity in the nucleus reticularis gigantocellularis was suppressed by 31 +/- 11 (mean +/- 1 SE) and by 62 +/- 7 per cent with ketamine, 1.0 and 2.5 mg/kg, iv, respectively. The frequency of evoked single-unit activity was suppressed by 57 +/- 9 and 79 +/- 5 per cent with ketamine, 1.0 and 2.5 mg/kg, respectively. Ketamine produces significant depression of single-unit activity of the cells in the nucleus reticularis gigantocellularis, suggesting that this may be an important site of its analgesic action.

Animals↗
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↗
PubMed1976

[Failure of acupuncture anesthesia. A psychophysical study (author's transl)].

Four volunteers judged eight levels of thermal stimuli induced by a Hardy dolorimeter, varying in intensity from extremely painful to a low level seldom even perceived. Half of the 406 stimuli were applied during acupuncture and half either before the insertion or after removal of the needles. The experimental design minimized or eliminated factors other than the needles themselves; i.e. no medications were given; the subjects were scientists accustomed to objectivity and, on a preceeding day or days, all became experienced in assigning a number (individually chosen) to the sensation produced by the different stimuli. Galvanic skin resistance was also tested. The results did not show any influence of acupuncture on pain perception or galvanic skin resistance.

Acupuncture Therapy↗