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Biomedical subjects

R W Cutler

Publications and source records attributed to R W Cutler.

At least 19 recordsLinked to original sources
PubMed1983

Factors influencing the vitreous potassium concentration in the rat.

The vitreous of the intact eye of the rate was perfused with artificial medium to study factors that influence the vitreous potassium concentration. The vitreous potassium concentration in anesthetized rats was 5.07 mM. Perfusion with media containing higher or lower potassium concentrations led to passive diffusion of potassium out of or into the vitreous, respectively. Ouabain caused a release of potassium from the retina into the vitreous. Photic stimulation reduced the vitreous potassium concentration, presumably as a result of neuronal hyperpolarization. Glutamate raised and glycine lowered the vitreous potassium concentration, effects that also may be related to retinal depolarization and hyperpolarization, respectively.

Animals↗
PubMed1981

The release of endogenous amino acids into the vitreous of the intact eye of the albino rat: effect of light, potassium, and ouabain.

The vitreal space of the intact eye of albino rats was perfused in vivo. The concentration of several endogenous amino acids in the vitreal effluent was measured by the [3H]microdansylation procedure. GABA was never detected despite a sensitivity of the method of 0.5 pmol. In contrast to previous results obtained in pigmented rats, photic stimulation with flashing white light did not alter the release of glycine or any of the other amino acids. Potassium (60 mM) and ouabain (0.1 mM) evoked a specific release of glycine. The potassium-evoked release was blocked by magnesium suggesting a neuronal site of origin of glycine. Ouabain-evoked release was not blocked by magnesium. The results were contrasted with experiments on radiolabeled amino acid release from retinas preloaded and superfused in vitro, a condition in which glial localization of exogenous amino acids predominates.

Amino Acids↗
PubMed1980

Bidirectional movement of gamma-aminobutyric acid in rat spinal cord slices.

The bidirectional movement of GABA (gamma-aminobutyric acid) was studied in slices of rat spinal cord which were incubated in small volumes of medium. The appearance in the medium of endogenous GABA and the disappearance from the medium of [14C]GABA were used to calculate the rates of unidirectional uptake and unidirectional release of GABA. Under these conditions, no net uptake of GABA was observed when slices were incubated in media containing concentrations of gABA as high as 25 microM. Elevated potassium (60 mM) stimulated the unidirectional release of endogenous GABA from spinal cord slices by a calcium-dependent process. Ouabain (0.1 mM) more than doubled the unidirectional release of endogenous GABA in a calcium-independent manner, while unidirectional uptake was inhibited by 44%. Nipecotic acid (1.0 mM) stimulated unidirectional release and inhibited unidirectional uptake of GABA.

Animals↗
PubMed1979

The effect of penicillin on the release of gamma-aminobutyric acid from cerebral cortex slices.

Penicillin is known to block the depressant action of GABA on cortical and spinal neurons. In this study we examined the effect of penicillin on the release of endogenous amino acids from rat cerebral cortex slices. The principal finding was that penicillin blocked the potassium-stimulated release of GABA, a calcium-dependent process. It did not block the veratridine-stimulated release of GABA, a calcium-independent process. It did not affect the release of other putative transmitter amino acids. Inhibition of GABA release from nerve endings may explain in part the ability of penicillin to depress synaptic inhibitory mechanisms.

Amino Acids↗
PubMed1979

Bidirectional movement of gamma-aminobutyric acid in cerebral cortex slices incubated in small volumes of medium.

Rat cerebral cortex slices were incubated in small volumes of medium in order to study the bidirectional movements of gamma-aminobutyric acid (GABA) between tissue and medium, and to measure the extent of release of endogenous amino acids of interest as potential neurotransmitters. The apparent uptake, real uptake, and net change of GABA were calculated from the changes in [14C]GABA and endogenous GABA in the medium. The extent of release of endogenous amino acids was dependent upon the amino acid the duration of incubation, and the volume of incubating medium. Substantial amounts of endogenous amino acids may accumulate in the medium under conditions commonly employed in amino acid uptake studies. The accumulation of endogenous GABA may affect the calculation of GABA uptake when this is based on the initial specific activity of exogenous [14C]GABA. The difference between apparent uptake and real uptake was particularly prominent in the presence of the depolarizing agents, potassium or veratridine, which caused a marked increase in GABA release. Exchange or net release of GABA was found when slices were incubated briefly in media containing 1.3 micrometer or 12.5 micrometer exogenous GABA; net uptake accounted for 50% of observed uptake when slices were incubated in media containing 25 micrometer GABA.

Amino Acids↗
PubMed1979

Effect of barbiturates on release endogenous amino acids from rat cortex slices.

The potassium-stimulated, calcium-dependent release of endogenous GABA and glutamic acid was suppressed by pentobarbital. The ouabain and veratridine-stimulated fluxes of the amino acids, calcium-independent processes, were not suppressed by pentobarbital. Release of GABA and glutamic acid was not suppressed by pentobarbital in the presence of the calcium ionophore A23187. Of eight barbiturates studied at equimolar concentrations six were found to inhibit GABA release. Thiopental was the most potent, and phenobarbital and secobarbital were inactive.

Amino Acids↗
PubMed1978

Inhibition of gamma-aminobutyric acid release from rat cerebral cortex slices by barbiturate anesthesia.

Amobarbital and pentobarbital anesthesia inhibited the potassium-stimulated, Ca-dependent release of gamma-aminobutyric acid (GABA) from rat cerebral cortex slices during incubation in vitro. Inhibition of GABA release was not found when slices were prepared from rats shortly after they awakened from amobarbital anesthesia. Phenobarbital anesthesia did not affect the release of GABA.

Amino Acids↗
PubMed1977

Maturational changes of amino acid concentration in cerebrospinal fluid of the rat.

The cisternal spinal fluid (CF), plasma, and brain stem concentrations of 6 amino acids were measured in suckling rats between birth and one months of age. Each of the amino acids studied had its distinctive maturational pattern of CF concentration. Presumably these amino acids have separate mechanisms of transport from CF, which mature at different times.

Aging↗
PubMed1975

Release of (3H)GABA and (14C)glutamic acid from rat cortex slices: the relationship between the tissue pool size and rates of spontaneous and electrically induced release.

A constant fraction of the existing tissue pool of (3H)GABA or (14C)glutamic acid was released during electrical stimulation of rat cortex slices. The sum of the amounts of labeled amino acids released spontaneously and by electrical stimulation was constant when stimulated slices were superfused with normal medium or media containing ouabain or a high K+ concentration. The fraction of the total amount released that was attributable to electrical stimulation varied inversely with the amount released spontaneously. Pentobarbital inhibited the accelerated spontaneous release produced by ouabain or high K+ and restored the ability of the slice to respond to electrical stimulation. Electrically induced release was felt to be limited by a theoretical maximum transport velocity of efflux of approximately 5.5% per min.

Aminobutyrates↗