Screening for cerebroprotective agents using an in vivo model of cerebral reversible depolarization in awake rats.

The need to screen cerebroprotective compounds without anesthetic interference prompted the development of a model using hypoxic rats. In this model two outcome measures were used: (1) the time to reach isoelectric electroencephalogram (iEEG), caused by nitrogen gas inhalation in the test chamber, and (2) the time for behavioral recovery measuring the latency of restoration of the head-withdrawal reflex upon vibrissae stimulation. We report here data of blood chemistry, cerebral tissue oxygen measurements, a definition of a proposed scoring system, and the pharmacological results of RGH-2202.

Cerebroprotective drugs shorten the hypoxia-induced onset of electrical silence in unanesthetized rats.

Pharmacological agents that delay the hypoxic arrest of neuronal electrical activity, as indicated by the suppression of electroencephalogram (EEG), have previously been thought to increase brain resistance to oxygen insufficiency. On the other hand, acceleration of the EEG suppression may offer some protection against severe hypoxia by reducing neuronal energy spending on electrogenesis. In unanesthetized rats we examined the effects of several antihypoxic drugs on the time of appearance of isoelectric EEG (tiEEG), caused by normobaric hypoxia.

Classification of drugs based on visually evoked responses in rats.

Quantified parameters of photically evoked afterdischarge and EEG background activity of visual cortex of freely moving rats were used as variables to obtain a t profile for each drug dosage. Behavioural scores were also used. The determination of the dose/time-effect profile of a compound was based on normalization of data and on calculation of the first two factor values in comparison with pooled data of representatives of neuroleptic, anxiolytic, convulsant, petit mal anticonvulsant, antidepressant and psychostimulant drug classes.

Inhibitory effect of hypoxic condition on acetylcholine release is partly due to the effect of adenosine released from the tissue.

Isolated longitudinal muscle strip with Auerbach's plexus attached was used to study the stimulation-evoked release of 3H-acetylcholine (3H-ACh) under normoxic and hypoxic conditions. Hypoxia reduced the release of ACh. Theophylline, a purinoceptor P1 antagonist and vinpocetine, an antiischemic compound partly reversed the effect of hypoxia.

Selective restoration of immunosuppressive effect of cytotoxic agents by thymopoietin fragments.

Swiss male mice were immunosuppressed by cyclophosphamide, cisplatinum, vincristine and methotrexate. The ability of the thymopoietin (TP) fragments TP-3, TP-4 and TP-5 to restore antibody production and phagocytosis was studied. Impaired antibody production after vincristine treatment was partially or totally restored by TP-3, TP-4 or TP-5.

Effects of thyrotropin-releasing hormone and its analogue L-6-ketopiperidine-2-carbonyl-leucyl-L-prolin-amide on behaviour and electroencephalogram.

A comparative dose-response investigation of thyrotropin-releasing hormone (TRH) and L-6-ketopiperidine-2-carbonyl-leucyl-L-proline-amide (RGH-2202) was carried out on rats and cats. RGH-2202 reduced the occurrence of photically evoked after-discharge in rats more significantly than TRH. Neither of the two compounds influenced the parameters of visually evoked potentials.

Synthesis of angiotensin II antagonists with variations in position 5.

Six angiotensin II antagonists containing cyclohexylglycine (Chg) or cyclopentylglycine (Cpg) in position 5 were synthesized by stepwise elongation in solution, using the pentafluorophenyl ester method. The influence of substitution on the inhibitory properties of the analogues was studied in four different bioassays. [Sar1,Chg5,Lac8]AII proved to be the most potent antagonist with low intrinsic activity in both the in vitro and in vivo tests.

The effect of thymopoietin 32-34 (TP3) on suramin-induced inhibition on delayed type hypersensitivity in guinea pigs.

Suramin administration inhibits virus replication and produces impaired immunoregulation. Delayed type hypersensitivity (DTH)-reaction was inhibited by Suramin (200 mg/kg, i.p.

Therapeutic possibilities of thymopoietin fragments (TP3 and TP4) based on experimental animal models.

The effects of thymic hormones are focused on the induction of T-cell subpopulations and restoration of the reactivity of an impaired immune system. TP3 and TP4 (corresponding to thymopoietin 32-34 and 32-35) exert a thymic hormone substitution effect. These peptides elicit dissimilar quantitative and qualitative effects.

Immunoregulating peptides II. In vitro effects of TP5 analogs on E-rosette formation and cell division.

The effects of seventeen synthetic analogs of thymopentin (TP-5) have been studied in the active and azathioprine-inhibited E-rosette tests. Thymopentin was gradually shortened from the C terminus to peptides and single amino acids. Thymopoietin 32-34 (Arg-Lys-Asp-RGH-0205-TP-3) (II) and thymopoietin 32-35 (Arg-Lys-Asp-Val-RGH-0206-TP-4) (I) were the most active peptides.

Stimulus-evoked efflux of GABA from preloaded slices of the rabbit oviduct.

The effect of electrical and chemical stimulation on the efflux of [3H]gamma-aminobutyric acid (GABA) from preloaded slices of the rabbit oviduct was examined. Electrical field stimulation significantly increased the outflow of [3H]GABA. This effect could not be prevented by tetrodotoxin or by the removal of Ca2+ from the medium.

Synthesis of thyrotropin-releasing hormone analogues. 2. Tripeptides structurally greatly differing from TRH with high central nervous system activity.

A new series of thyrotropin-releasing hormone (TRH) analogues, obtained by further modifications of our most potent central nervous system (CNS) stimulating neutral tripeptides at both termini, were synthesized by the pentafluorophenyl ester method and tested for CNS and thyrotropin (TSH) releasing activity. Replacement of pyroglutamic acid by pyro-2-aminoadipic acid, 2-oxoimidazolidine-4-carboxylic acid or gamma-butyrolactone-gamma-carboxylic acid and that of proline by pipecolic acid, thiazolidine-4-carboxylic acid, or homoproline in [Leu2]- and [Nva2]TRH led to tripeptides structurally widely different from TRH. In spite of this fact, 7 of the 17 analogues (1, 2, 8-10, 16, and 17) have stronger anticataleptic effect than TRH, with negligible or no hormonal potency.

Antagonism of non-depolarising neuromuscular blockade by aminopyridines in cats.

The antagonism of pipecuronium- and vecuronium-induced neuromuscular blockade by 4-aminopyridine (4AP), 3,4-diaminopyridine (3,4AP) and 3-[(dimethylamino)-carbonyl] amino-4-aminopyridine (LF14) were studied in anaesthetized cats during constant infusion of the relaxants. Aminopyridines were administered cumulatively at steady state 90% block level. The ED50 values of 4AP, 3,4AP and LF14 were 243, 106 and 254 micrograms kg-1 in pipecuronium, and 232, 195 and 235 micrograms kg-1 in vecuronium blockade.

The effect of TP-5 and its analogs on skin grafts in mice.

The immunostimulatory action of oligopeptides RGH-0205 (Arg-Lys-Asp), RGH-0206 (Arg-Lys-Asp-Val) and TP-5 (Arg-Lys-Asp-Val-Try) was measured using the B10LP to C57BL skin graft system and the determination of splenic T cell ratio. While thymectomy increased the period between skin grafting and rejection, each of the oligopeptides increased the number of splenic T cells and in some extent restored the rejection capacity of thymectomised C57Bl mice, presumably by restoration of thymic hormone function.

Comparative characterization of glutamate decarboxylase in crude homogenates of oviduct, ovary, and hypothalamus.

Some biochemical characteristics of L-glutamate decarboxylase (GAD) were compared using crude homogenates of the rat oviduct, ovary, and hypothalamus. As estimated by the measurement of CO2 production, the specific activities of oviductal and ovarian GAD were about 10 and 3% of the hypothalamic value, respectively. Stoichiometric formation of gamma-aminobutyric acid (GABA) and CO2 from L-glutamate could be observed in oviduct and hypothalamus, while in ovarian homogenates the production of CO2 was more than nine times that of GABA.

Synthesis of thyrotropin-releasing hormone analogues. 1. Complete dissociation of central nervous system effects from thyrotropin-releasing activity.

Twenty-four thyrotropin-releasing hormone (TRH) analogues containing mainly aliphatic amino acids in position 2 were synthesized and tested for central nervous system (CNS) and hormonal (TSH) activity. Application of the pentafluorophenyl ester method in the syntheses resulted in optimal yields and high purity of the products. The neutral tripeptides pGlu- Nva -Pro-NH2 (9), pGlu-Nle-Pro-NH2 (10), and pGlu-Leu-Pro-NH2 (3) with a three- or four-membered straight or branched alkyl side chain in the position of the central amino acid had 2.

GABAB receptor-mediated stimulation of the contractility of isolated rabbit oviduct.

The effects of gamma-aminobutyric acid (GABA) and related compounds were examined on longitudinal and circular muscle preparations isolated from oviducts of virgin rabbits. GABA and baclofen stimulated the spontaneous motility in each type of preparation, which action could not be antagonized by bicuculline, phentolamine, atropine or tetrodotoxin. Muscimol was virtually ineffective.

Gastrointestinal cytoprotection by indomethacin + sodium salicylate combination in rat.

Non-steroidal antiinflammatory agents are well known to cause gastrointestinal damage in many species including the rat and human. Pelsonin a combination of indomethacin and sodium salicylate (1:10 ratio) has a cytoprotective effect against acidic-alcohol induced gastric necrosis, and it does not induce intestinal ulceration. Pelsonin is capable of blocking the formation of intestinal ulcers induced by oral indomethacin 10 mg/kg (curative cytoprotection).

High density of specific GABA binding sites in the human fallopian tube.

The concentration of gamma-aminobutyric acid (GABA) in the human Fallopian tube and the ability of a membrane preparation from the same organ to bind [3H]GABA specifically were examined. A GABA concentration of 177 nM/g frozen tissue was determined and a single population of high-affinity receptor binding sites has been identified in the human oviduct. The density of binding sites demonstrated was as high as in the brain.

Immuno-regulating peptides, I. Synthesis and structure-activity relationships of thymopentin analogs.

Seventeen peptides, related to thymopoietin pentapeptide, L-arginyl-L-lysyl-L-aspartyl-L-valyl-L-tyrosine (thymopentin) were synthesized by the stepwise strategy in solution. Of these, L-arginyl-L-lysyl-L-aspartic acid and L-arginyl-L-lysyl-L-aspartyl-L-valine, shortened from the C-terminus of the pentapeptide, exhibit significant immuno-stimulating potencies, exceeding those of thymopentin, both in vitro and in vivo immunological tests. Studies on the structure-activity relationships suggest that the potencial active site of thymopoietins is very sensitive to the N- and C-terminal elongations of the peptide chain.

The occurrence of GABA in vas deferens, prostate, epididymis, seminal vesicle and testicle of the rat.

The concentration of gamma-aminobutyric acid (GABA) was determined in vas deferens, prostate, epididymis, seminal vesicle and testicle of the adult rat. Among the organs examined, vas deferens was found to be the richest in GABA and the lowest concentration was measured in testicle. Although the GABA levels appear to be 10-50 times lower in the sex organs examined than in the brain tissue, even the low GABA contents are suggestive of a role of this amino acid in the reproductive organs of the male rat.

Higher GABA concentrations in fallopian tube than in brain of the rat.

The GABA content was determined simultaneously in two peripheral organs, i.e., ovary and Fallopian tube.