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Biomedical subjects

P Giusti

Publications and source records attributed to P Giusti.

At least 73 records · Page 4Linked to original sources
PubMed1991

Electrophysiological effects of a pumiliotoxin-B-like alkaloid derived from the skin of the Australian frog Pseudophryne coriacea.

Skin extracts of the Australian frog Pseudophryne coriacea (PsC) potentiate and prolong the bioelectric activity of various excitable tissues. When studied by electrophysiological means in a preparation of mouse diaphragm, PsC skin extracts did not affect the spontaneous acetylcholine (ACh) release. However, the indirect stimulation of the preparation in the presence of PsC skin extracts gave rise to a different profile of rhythmic activity showing afterpotentials and variable oscillatory activity. The action potential and the total sodium current recorded in the muscle fibre with the loose patch clamp method were not modified significantly by the alkaloid. Concentrations of PsC skin extract that did not cause repetitive activity, seemed to reduce slightly the quantal content of the evoked release of ACh. The resting potential of muscle fibres was not modified even by the highest PsC skin extract concentrations. These results suggest that the facilitation effects of PsC skin extracts could be due to intracellular mechanisms probably related to the control of the cytosolic calcium concentrations or to an increased excitability of the presynaptic biomembranes.

Acetylcholine↗
PubMed1991

The preferential antagonism of pentylenetetrazole proconflict responses differentiates a class of anxiolytic benzodiazepines with potential antipanic action.

With the use of the shock-induced suppression of water drinking in thirsty rats (Vogel's conflict paradigm) and the pentylenetetrazole-enhanced shock-induced suppression of drinking (proconflict paradigm) as animal models to test anxiolytic and antipanic agents, it was possible to distinguish two major classes of benzodiazepines (BZDs) and congeners on the basis of their antiproconflict index (ratio of anticonflict/antiproconflict potencies). Thus, typical low potency BZDs and congeners (diazepam, midazolam, zolpidem, alpidem) with anxiolytic/hypnotic properties have a low antiproconflict index (close to 1), whereas typical high potency BZDs (clonazepam, alprazolam, bretazenil) with reported antipanic properties have an antiproconflict index approximately 10-fold higher. The anticonflict and antiproconflict actions of BZDs with low or high antiproconflict indices are blocked by flumazenil but are potentiated differentially by the gamma-aminobutyric acid (GABA) reuptake blocker 1-2-[bis(trifluoromethyl)-phenyl]-methoxyethyl-1,2,5,6-tetrahydro-3- pyridine-carboxylic acid. Protracted administration of antianxiety and antipanic antidepressant drugs that do not act on GABAA receptors, directly, resulted in anticonflict and antiproconflict effects. However, the efficacy of these drugs is clearly inferior (20-30%) to that of BZDs. These data suggest that specific GABAA receptor subtypes mediate the pharmacological action of BZDs possessing low and high antiproconflict indices.

Animals↗
PubMed1991

gamma-Aminobutyric acidA receptor heterogeneity in rat central nervous system: studies with clonazepam and other benzodiazepine ligands.

The properties of [3H]clonazepam, [3H]diazepam and [3H]zolpidem (N,N,6[trimethyl-2-(4-methyl-phenyl)imidazo[1,2-a]pyridine-3-acetamide hemitratrate) binding to synaptic membranes of cerebellum, cortex, olfactory bulb, striatum and spinal cord of rat were compared to the binding properties of [3H]flunitrazepam, [3H]flumazenil and [3H]midazolam. In the cerebellar, cortical and olfactory bulb membranes, the density of high-affinity binding sites of all these tritiated benzodiazepine (BZ) ligands is almost identical. In contrast, in the striatum, the density of [3H]clonazepam and [3H]zolpidem binding sites is approximately 60 and 30%, respectively, of the density of [3H]diazepam, [3H]flunitrazepam or [3H]flumazenil sites. In spinal cord membranes, the number of high-affinity binding sites of [3H]clonazepam and [3H]zolpidem is less than 20% of the number of binding sites for [3H]diazepam, [3H]flunitrazepam, [3H]flumazenil and [3H]midazolam. Moreover, the displacement of [3H]flunitrazepam from spinal cord membranes by clonazepam and zolpidem was characterized by high IC50 values and Hill slopes significantly less than 1. Because [3H]BZ ligand binding in the spinal cord is enhanced by gamma-aminobutyric acid (GABA), these data suggest that different regions of the rat central nervous system may contain different GABA-BZ receptor subtypes. The different pharmacological properties of clonazepam, diazepam and zolpidem (i.e., regarding their ability to enhance bicuculline seizure threshold, to decrease locomotor activity, to induce ataxia or to elicit anticonflict action) further support the concept that in the rat central nervous system preferential occupancy of heterogeneous GABAA receptors by these drugs can be related to their effects on behavior.

Animals↗
PubMed1990

[Stress hormones liberated by fangotherapy. ACTH and beta-endorphin levels under heat stress].

In 6 healthy subjects submitted to fango therapy in the Euganean thermal baths (Italy), the plasma concentrations of beta-endorphin and ACTH increased transitorily but significantly. These results correlate with the release of these peptides by the pituitary in response to thermal stressing. The analgesic and hypothermic action responsible for good toleration of thermal stress induced by fango therapy, can be explained by this increase in plasma beta-endorphin. The repeated brief increases in plasma beta-endorphin during thermal treatment result in progressive improvement in articular and muscular symptomatology. The results of our study on plasma levels of ACTH confirm that the thermal stress associated with fango therapy activates the pituitary gland. Immunomodulatory effects are discussed.

Adrenocorticotropic Hormone↗
PubMed1990

Sodium-activated potassium current in mouse diaphragm.

The mouse diaphragm muscle fiber was studied using the loose patch clamp technique. The voltage gated sodium currents were evoked by step pulses from a holding potential of about - 70 mV. Following the activation of the sodium current, a very large and fast outward current was evoked. The sensitivity of this current to 4-aminopyridine and tetraethylammonium indicates the potassium ion as the possible carrier for the channel. Furthermore, the sensitivity to tetrodotoxin and extracellular sodium demonstrated the sodium dependence of this current.

Action Potentials↗
PubMed1990

Influence of glycine on morphine-induced antinociception in mice.

The effects of glycine on morphine-induced antinociception were investigated in mice, using a cutaneous thermal test (hot-plate), a visceral chemical test (acetylcholine writhing test), and a locomotor activity test. When glycine (200 mg/kg p.o.) and morphine (5 mg/kg s.c.) were given together during the first 30 min, glycine first antagonized the morphine-induced antinociception then this was followed by a synergistic effect. The two-phase influence of glycine on morphine-induced antinociception may be due to the interaction of glycine with different receptors.

Acetylcholine↗
PubMed1989

Synthesis and quantitative structure-activity relationships of analeptic agents related to dimefline.

Some new dimefline-type derivatives have been synthesized and their pharmacological activity, as well as their distribution coefficients have been determined. The distribution coefficients of a number of previously published analogue compounds have also been measured and the QSAR analysis of the whole set has been carried out. The results of such analysis allow to point out which factors are influencing the biological activity of this group of compounds.

Animals↗
PubMed1989

Computerized estimation of spontaneous and evoked acetylcholine release at the neuromuscular junction.

A new and automated on-line analysis of the parameters related to the neuromuscular activity is shown. The procedure used to obtain in real time the statistical evaluation of the recorded electrical signals is presented and discussed. The hardware is composed of a PDP-11/73 microcomputer equipped with an analog input/output board. The software is written principally in FORTRAN 77 and also uses MACRO/ASSEMBLY language.

Acetylcholine↗
PubMed1987

Imipramine receptors in human platelets: effect of age.

Imipramine receptors were studied in platelets from six healthy young subjects (age between 24 and 38 years), five newborns, and six healthy elderly persons (age between 70 and 81 years). Binding parameters, the maximum binding capacity (Bmax) and the apparent dissociation constant (Kd), were determined by Scatchard's analysis. Level of differences between young subjects and the other groups was determined by Student's t-test. Bmax (mean +/- SD) was 1162 +/- 138 (young persons), 564 +/- 65 (newborn), and 508 +/- 98 (elderly persons) fmol/mg protein. The figure for the young was different from that of the newborn (p less than 0.001) and the elderly (p less than 0.01). Kd (means +/- SD) was 1.78 +/- .69 (young persons), 0.68 +/- 0.13 (newborn), and 0.80 +/- 0.27 nM in the elderly. Kd in the volunteers was different from that in the newborn or the elderly subjects (p less than 0.01). Imipramine receptors in platelets appear to be influenced by development and aging.

Adult↗
PubMed1985

Antinociceptive effect of some carboxypeptidase A inhibitors in comparison with D-phenylalanine.

It had previously been shown that D-phenylalanine and hydrocinnamic acid, two in vitro inhibitors of carboxypeptidase A, possess an analgesic action when injected i.p. in mice. We have studied the in vivo effects of indole-3-acetic acid, another carboxypeptidase A inhibitor, and of the following analogs of D-phenylalanine substituted in position 4: D-tyrosine, p-fluoro-D-phenylalanine and trifluoroacetyl-p-fluoro-D-phenylalanine. Whereas indole-3-acetic acid caused a higher and shorter analgesia in comparison with D-phenylalanine, p-fluoro-D-phenylalanine and its N-trifluoroacetyl derivative yielded both a greater and a much longer lasting analgesic effect. Since the latter compound showed only slight inhibitory activity on carboxypeptidase A in vitro, we suggest that inhibition of this enzyme and analgesia might not be directly correlated.

Analgesics↗
PubMed1985

Adaptation of a prefabricated post to dentin.

The adaptation of an inventive prefabricated post and core to dentin is presented as part of a series of research reports. The authors suggest that the imaginative design of the split shaft and its telescoping or collapsible apex reduces stress and the finely threaded shaft improves retention.

Crowns↗
PubMed1985

Are calcitonins analgesic and/or hyperalgesic?

The acetylcholine writhing test and the hot plate test were used in mice to evaluate peripheral and central analgesia after porcine, salmon and human calcitonin administrations. ICV and IV injection of calcitonins caused a peripheral analgesia that persisted for at least 2 hr. SC injection of calcitonins did not produce peripheral analgesia. However, when administered by IP route, an increasing peripheral analgesia was observed. Although it had a slow onset, it was as powerful as after ICV or IV administration. Employing the hot plate test to determine the entity of a central analgesic response, the IP administration of calcitonin surprisingly revealed a hyperalgesic effect. It started soon after the injection, reaching its maximum after about 2 hr. At this point the hyperalgesic effects were fully antagonized by EDTA.2 Na ICV, or by Ca++ICV. Moreover only the latter produced a strong and long acting analgesia. Applying a central or peripheral test, calcium seems to play different roles on the algesia variations induced by calcitonins.

Analgesics↗