Biomedical subjects

M M Morgan

Publications and source records attributed to M M Morgan.

5 recordsLinked to original sources

PubMed1992

Activity of neurons in the rostral medulla of the halothane-anesthetized rat during withdrawal from noxious heat.

The physiological and pharmacological properties of two classes of putative nociceptive modulatory neurons have been extensively characterized in the rostral ventromedial medulla (RVM) of the barbiturate-anesthetized rat. 'On-cells' show a burst of activity, and 'off-cells' a sudden pause immediately preceding the occurrence of nocifensor reflexes. In the present study, we have characterized the reflex-related activity of RVM neurons in halothane-anesthetized rats to determine whether the properties of these neurons are dependent on barbiturate anesthesia. Both on- and off-cells were identified in this preparation. Repeated noxious stimulation was associated with a high level of ongoing activity in on-cells, and a low level in off-cells. These data thus demonstrate that the previously described reflex-related changes in RVM neuron activity are not specific to barbiturate-anesthetized preparations, and that a failure to demonstrate off-cells in some studies may result from these neurons being inactive following repeated testing with noxious stimuli.

Action Potentials↗

PubMed1992

Circuitry linking opioid-sensitive nociceptive modulatory systems in periaqueductal gray and spinal cord with rostral ventromedial medulla.

The interactions among opioid-sensitive nociceptive modulatory systems, which include the midbrain periaqueductal gray, rostral ventromedial medulla and spinal cord, are likely to play a central role in the potent antinociception that results when morphine is administered systemically. The aim of the present study was to investigate the mechanisms through which local application of morphine, either in the periaqueductal gray or at the lumbar spinal cord in the rat, influences the activity of one population of putative nociceptive modulatory neurons in rostral ventromedial medulla, i.e. "on-cells". Previous studies have shown that the spontaneous and tail-flick-related firing of on-cells is invariably depressed when morphine is given systemically in doses demonstrated to inhibit the tail-flick reflex, and that a similar depression of this activity is produced when morphine is applied directly in the periaqueductal gray or intrathecal space. In the present experiments, on-cells were activated pharmacologically using iontophoretically applied glutamate to provide an indication of whether morphine-induced suppression of on-cell firing reflected a postsynaptic inhibition or a disfacilitation resulting from blockade of an excitatory input to the on-cell. Microinjection of morphine into the periaqueductal gray blocked glutamate-evoked activity of on-cells in parallel with its suppression of the tail-flick reflex, suggesting activation of an inhibitory input to these cells. No change in glutamate-evoked activity occurred in rats in which morphine did not produce antinociception. Intrathecal administration of morphine did not alter the glutamate-evoked activity of these neurons despite blocking the tail-flick reflex, suggesting that morphine acting in the spinal cord removes an excitatory input to on-cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Direct and indirect actions of morphine on medullary neurons that modulate nociception.

The rostral ventromedial medulla is part of a neural network through which systemically administered morphine produces antinociception. Two physiologically characterized classes of presumed nociceptive modulating neurons that respond differentially to systemically administered morphine have been identified in this region: the firing of "on-cells" is depressed, whereas "off-cells" become continuously active. On-cells have been proposed to permit or facilitate, and off-cells to inhibit, nociceptive transmission. Because local application of morphine in the rostral ventromedial medulla itself is sufficient to produce antinociception, it is important to determine whether systemically administered morphine exerts its effects on neurons in this region by a direct action. Thus, activity of physiologically characterized neurons was studied before, during and after ionotophoretic administration of morphine. As with systemic administration, iontophoretic application of morphine depresses the activity of on-cells, an effect that is reversed by iontophoretic as well as by systemic administration of naloxone. In contrast, no reliable changes in the firing of off-cells are produced by iontophoretic administration of morphine. Cells of a third class, "neutral cells", are not affected by systemic morphine administration, nor do they respond to iontophoretic application of the drug. The present experiments demonstrate that direct opioid responsiveness in the rostral ventromedial medulla is limited to a single physiologically characterized class of presumed nociceptive modulatory neuron, the on-cell. This implies that the antinociceptive effect exerted by systemically administered morphine involves at least two components within the rostral ventromedial medulla: a direct inhibition of on-cells, and an indirect activation of off-cells. Each of these actions is likely to have a net hypoalgesic effect.

Animals↗

PubMed1978

Quality assurance through automated monitoring and concurrent feedback using a computer-based medical information system.

A computer-based medical information system (COSTAR) has been used to support a quality assurance program where the data collection is an integral part of the patient care recording activity and, therefore, does not require a separate abstracting or encoding process. This program utilizes concurrent audit to detect deficiencies in patient care, and automatic rapid feedback to the responsible provider in time to allow the provider to correct the deficiency. This system has been demonstrated to improve follow-up of throat cultures, positive for Group A Beta hemolytic streptococcus. It is well accepted by the medical staff whose practice is being audited. Because the data are collected as part of the routine operation of COSTAR, the computer monitoring and feedback have only a small incremental cost.

Boston↗

PubMed1977

A computerized prenatal record.

An entirely computerized ambulatory medical record system is operational in a large health maintenance organization. A unique subsystem was designed for use in prenatal care, in which the provider's completion of a single encounter form at the time of visit meets all the information requirements of care delivery, administration, and quality assurance. Instead of using a conventional paper chart, computer-generated summaries and flow charts are automatically provided for scheduled visits and for use as a hospital preadmission record, significantly reducing the provider effort expended on record keeping. On-line inquiry function is also available using terminals at the ambulatory center and the hospital. The computer data base has been used for quality assurance studies in prenatal care. The system is well accepted by providers, is reliable, and is cost effective.

Computers↗