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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recurrent inhibition of the dorsal root (DR) evoked responses of frog motoneurons was studied by intracellular recording. Monosynaptic and early polysynaptic action potentials, as well as compound EPSPs initiated by a DR volley in motoneurons were depressed by an antidromic volley in motor axons. The depression had about 10 msec latency, reached maximum at 20-30 msec, and was maintained for 80 msec. The depression was associated with a slow, negative dorsal root potential (VR-DRP) of similar time course. No sign of recurrent postsynaptic inhibition of the motoneuron somata was found. Decrease in excitability of the motoneurons was also observed during the afterhyperpolarization (AHP) associated with either antidromic or direct spikes in the motoneurons. This excitability decrease was detectable at the time of recurrent depression of the DR-evoked responses. The data are explained by the assumption that two mechanisms are involved in the recurrent depression of the DR-evoked responses: the excitability decrease during the AHP in the motoneurons themselves, and the inhibition transmitted by a recurrent pathway which may depress the DR inputs to motoneurons presynaptically.
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PMID:Ventral root elicited depression of the dorsal root evoked response in frog motoneurons. 88 Sep 96

Cord dorsum potentials, dorsal root potentials and field potentials were studied in rats with local depression of inhibitory processes in lumbar spinal segments produced by tetanus toxin. The study was carried out at a stage when excitation of a neuronal population with depressed inhibitory processes (the so-called "determinative dispatch station") evoked generalized excitation of spinal and bulbar motoneurons. In experiments with spinal animals it was shown that the stimulation of a cutaneous nerve on the affected side evokes DRP's P-waves and field potentials of greater amplitude and longer duration than those evoked on the opposite side or in healthy rats. The prolonged P-wave revealed several components which coinsided with prolonged ventral root discharges. This wave could be recorded from an enlarged spinal cord region. The maximal increased and prolonged negative field potentials corresponding in time to the enlarged P-wave were found in the ventral quadrant of the affected side. In this region "spontaneous" rhythmical negative slow waves were recorded. The mechanisms of spreading excitation from the site with depressed inhibitory processes and the localization of this site are discussed.
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PMID:[Spinal cord electrical activity during focal depression of inhibitory processes]. 120 33

Cultures of the solar UV-sensitive cell lines, DRP 36 and DRP 153, and of the parental ICR 2A cell line, were exposed to 150 kJ/m2 of sunlamp UV greater than 315 nm plus photoreactivating light. This treatment resulted in the induction primarily of non-dimer DNA damage. Following either a 0, 3, 6, 12 or 24 h incubation, the cultures were pulse-labelled with [3H]thymidine, and the synthesis of different size classes of replicon intermediates measured using the alkaline step elution assay. For all three cell lines tested, an immediate depression of low molecular weight DNA synthesis was observed. This was followed by an inhibition of all size classes of replicon intermediates. Within 12 h following irradiation, recovery of DNA synthesis was observed, which was generally most apparent for low molecular weight DNA. The ICR 2A cells exhibited a nearly full recovery in all size classes of DNA synthesized by 24 h. However, a much smaller recovery of DNA synthesis was detected for the DRP 36 and DRP 153 cultures. This continued inhibition was primarily in the synthesis of full replicon size DNA, and was most pronounced for the DRP 36 cells. Hence, it appears that replicon chain elongation continues to be inhibited in these solar UV-sensitive cell lines long after irradiation.
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PMID:Inhibition and recovery of semiconservative DNA synthesis in normal and solar UV sensitive ICR 2A frog cell lines following the induction of non-dimer DNA damage by sunlamp UV greater than 315 nm. 256 15

In experiments on spinal narcotized cats perfusion of the lumbosacral cord through the central canal with artificial cerebrospinal fluid containing furosemide (15-48 mmol/l) led to the reversible selective depression of negative DRP and to the depression of prolonged "presynaptic" inhibition of extensor monosynaptic reflexes produced by volleys in flexor muscle afferents of group 1.
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PMID:[Furosemide depression of the dorsal root potentials and of the presynaptic inhibition of monosynaptic reflexes in the cat spinal cord]. 320 Mar 60

In experiments on spinal narcotized cats perfusion of lumbosacral spinal cord through central canal with artificial cerebrospinal fluid containing high concentration (20-46 mM) of magnesium ions led to reversible depression of negative DRP as well as to depression of prolonged "presynaptic" inhibition of extensor monosynaptic reflexes produced by repetitive impulse volleys in group I flexor muscle afferents. Magnesium did not cause a depression of monosynaptic reflex discharges in spinal ventral roots.
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PMID:[Effect of magnesium ions on presynaptic inhibition of monosynaptic reflexes]. 627 37

1 Synaptic potentials and the responses of frog spinal cord to various acidic amino acids were examined by means of the sucrose gap recording technique. 2 Divalent cations (50-250 microM) specifically antagonized responses evoked at N-methyl-D-aspartate (NMDA) receptors by N-methyl D,L aspartic acid (NMDLA). The rank order of potency was Ni2+ greater than Co2+ greater than Mg2+ greater than Mn2+. Responses to glutamate and aspartate were relatively insensitive to these concentrations of divalent cations. 3 The rank order of potency for divalent ions (1 mM) for antagonism of synaptic transmission in bullfrog sympathetic ganglia was Mn2+ greater than Co2+ greater than Ni2+ greater than Mg2+. Thus synaptic transmission in ganglia was especially sensitive to Mn2+ whereas NMDLA responses were especially sensitive to Co2+ and Mg2+. 4 It was possible to depress selectively the dorsal root-dorsal root potential (DR-DRP) and dorsal root-ventral root potential (DR-VRP) of frog spinal cord using low doses of Co2+ or Mg2+ which did not affect VR-DRP (ventral root-dorsal root potential). It was not possible to produce this selective depression of DR-DRP and DR-VRP with Mn2+, as this cation non-selectively depressed all responses. 5 These results suggest that: (i) divalent cations do not antagonize NMDLA responses by blocking Ca2+ channels which may mediate the response; (ii) postsynaptic NMDA receptors are activated by a neurotransmitter involved in the DR-DRP and DR-VRP pathways but not by any neurotransmitters involved in the VR-DRP pathway; (iii) the neurotransmitter activating NMDA receptors in amphibian spinal cord may be an aspartate-like substance rather than aspartate itself or glutamate.
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PMID:The use of low concentrations of divalent cations to demonstrate a role for N-methyl-D-aspartate receptors in synaptic transmission in amphibian spinal cord. 629 90

Intracellular recordings were made from neurons in dorsal root ganglia (DRG) of rats, isolated in vitro. The depolarization of DRG cells caused by the application of gamma-aminobutyric acid (GABA) diminished reversibly when penicillin (0.08--2.0 mM) was added to the bathing fluid. The decrease of the input resistance of DRG cells measured during GABA perfusion was also depressed in the presence of penicillin, but no evidence of a shift of the reversal potential of the GABA-induced depolarization was found. Nor did penicillin (up to 10 mM) cause a change in the voltage-current function, in electrical excitability, in the inclination to repetitive firing, bursting discharge, or after discharge. In decapitate cat preparation the amplitude of the negative dorsal root potential (DRP or DR V) diminished by 0--50% after the i.v. administration of 0.5--1.0 X 10(6) I.U./kg (the convulsant dose) of penicillin. Post-tetanic depression of the DRP was aggravated by penicillin. The degree of depression of the DRP bore no relationship to the promptness of the eruption, and to the intensity, of the seizure activity induced by penicillin. The rates of rise and fall of the negative DRP (DR V) were consistently slowed, the positive DRP (DR VI) reduced, and the dorsal root reflex (DRR) blocked by penicillin. Inhibitory reflex effects presumed to be presynaptic were either enhanced or unchanged, never depressed by penicillin. This was seen when inhibitory function was gauged by monosynaptic reflex amplitude, and also from the inhibition of ventral root electrotonic excitatory postsynaptic potentials (VP EPSPs). Possible explanations of these seemingly paradoxical findings are discussed, with arguments in favor and against each.
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PMID:The effects of convulsant doses of penicillin on primary afferents, dorsal root ganglion cells, and on 'presynaptic' inhibition in the spinal cord. 737 99

1. In the immature rat in vitro hemisected spinal cord preparation the dorsal root-evoked depolarizing potential recorded from an adjacent dorsal root DR-DRP had a mean peak amplitude (+/- s.e.mean, n = 27) of 2.9 +/- 0.2 mV and a mean latency to peak amplitude of 106 +/- 3 ms. The DR-DRP amplitude was maximal with a stimulus intensity of four times the threshold intensity required to activate the lowest threshold fibres. The peak amplitude and/or integral over a time-source of 0.5 s were used to assess the effects of applied drugs. 2. The DR-DRP was abolished by baclofen (mean IC50 190 +/- 46 nM, n = 7). The depressant effect of baclofen was reversed by CGP35348 (1 mM). The mean apparent Kd value calculated from dose-ratios was 16.7 +/- 6.4 microM (n = 3). 3. At a maximally effective concentration, tizanidine (1 microM) produced at the most only a 14% depression of the DR-DRP (n = 4). Clonidine (0.3 microM) had an effect similar to that of tizanidine. These depressant effects were reversed by idazoxan (1 microM). 4. The DR-DRP was potentiated by diazepam in a flumazenil (1 microM)-reversible manner. A maximal potentiation of 23.2 +/- 2.7% (n = 5) was produced by 1 microM diazepam. 5. Diazepam (1 microM) induced a mean bicuculline- (10 microM, n = 2) and flumazenil- (1 microM, n = 8) sensitive depolarization in the dorsal root of 0.25 +/- 0.03 mV (n = 8). However, diazepam failed to depolarize dorsal roots (n = 3) which had been excised from the spinal cord. 6. Comparison of the above effects with previously reported depressant effects of these drugs on the synaptic output from ventral roots suggests that actions on presynaptic inhibition, as reflected in the DR-DRP, are of subsidiary importance in explaining the muscle relaxant actions of tizanidine or diazepam.
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PMID:The effects of central myorelaxants on synaptically-evoked primary afferent depolarization in the immature rat spinal cord in vitro. 791 16

This study was done to investigate the frequency of co-morbidity and to demonstrate the best method for assessing depression among cancer patients. The subjects were 50 (25 male and 25 female) cancer patients and 50 (25 male and 25 female) medically ill patients. All subjects were interviewed by psychiatrists and were administered psychological tests such as SAS (self-rating anxiety scale), SDS (self-rating depression scale), POMS (Profile of Mood States), HADS (Hospital Anxiety and Depression Scale) and DRP (Depression-related personality traits). The psychiatric interview revealed that 44% of cancer patients and 38% of the medical patients had mental disorders according to DSM-IV. The most frequently observed disorder was depression, which was seen in 28% of the cancer patients and 30% of the medical patients. The cancer patients with depression scored significantly higher on the DRP and the Anger mood state of POMS than did the medically ill patients with depression. In addition, most psychological tests employed had no discrimination between depressed and normal subjects among the cancer and the medical patients. However, it was found that the Depression scale in HADS (HADS-D) split depressed patients from normal subjects since the HADS-D was composed of items that were not concerned with physically ill conditions.
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PMID:Depression among cancer patients. 901 27