Biomedical subjects

G Tóth

Publications and source records attributed to G Tóth.

At least 55 records · Page 3Linked to original sources

PubMed2000

Evidence for the involvement of ATP, but not of VIP/PACAP or nitric oxide, in the excitatory effect of capsaicin in the small intestine.

The contractile effect of capsaicin in the guinea-pig small intestine involves an activation of enteric cholinergic neurons. Our present data show that the P(2) purinoceptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS, 30 microM) significantly reduces the contractile response to capsaicin (2 microM) in the presence, but not in the absence, of the tachykinin receptor antagonists [O-Pro(9), (Spiro-gamma-lactam)Leu(10), Trp(11)]physalaemin (1-11) (GR 82334; 3 microM) and (S)-(N)-(1-(3-(1-benzoyl-3-(3, 4-dichlorophenyl)piperidin-3-yl)propyl)-4-phenylpiperidine-4-yl)-N -methylacetamide (SR 142804: 100 nM) (for blocking tachykinin NK1 and NK3 receptors, respectively). PPADS (30 microM) fails to influence submaximal cholinergic contractions evoked by cholecystokinin octapeptide (CCK-8; 2-3 nM) or senktide (1 nM), or the direct smooth muscle-contracting effect of histamine (100-200 nM). A higher concentration (300 microM) of PPADS is also without effect against the stimulatory action of cholecystokinin octapeptide. This means that PPADS can probably be safely used as a purinoceptor antagonist in intestinal preparations. The putative pituitary adenylate cyclase activating peptide (PACAP) receptor antagonist PACAP-(6-38) (3 microM) significantly reduces the contractile effect of PACAP-(1-38) (10 nM) and abolishes that of vasoactive intestinal polypeptide (VIP; 10 nM). PACAP-(6-38) (3 microM) fails to influence the effect of capsaicin (2 microM) both in the absence and in the presence of tachykinin receptor antagonists. The nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine (L-NOARG; 100 microM) also fails to inhibit the capsaicin-induced motor response. We conclude that an endogenous ligand of PPADS-sensitive P(2) purinoceptors (possibly ATP), but not a VIP/PACAP-like peptide or NO, is involved in the nontachykininergic activation of cholinergic neurons in the course of the capsaicin-induced contraction.

Acetylcholine↗

PubMed2000

Receptor binding and G-protein activation by new Met5-enkephalin-Arg6-Phe7 derived peptides.

Met5-enkephalin-Arg6-Phe7 (Tyr-Gly-Gly-Phe-Met-Arg-Phe, MERF) is a naturally occurring heptapeptide that binds to opioid and non-opioid recognition sites in the central nervous system. Four synthetic analogs with single or double amino acid substitutions were prepared by solid phase peptide synthesis to achieve proteolytically more stable structures: Tyr-D-Ala-Gly-Phe-Met-Arg-Phe (I), Tyr-D-Ala-Gly-Phe-D-Nle-Arg-Phe (II), Tyr-D-Ala-Gly-Phe-L-Nle-Arg-Phe (III) and Tyr-Gly-Gly-Phe-L-Nle-Arg-Phe (IV). In this study receptor binding characteristics and G-protein activation of MERF and its derivatives were compared in crude membrane fractions of frog and rat brain. Synthetic MERF-derived peptides were potent competitors for [3H]MERF and [3H]naloxone binding sites with the exception of analog (II) which turned to be substantially less active. The presence of 100 mM NaCl or 100 microM 5'-guanylylimidodiphosphate, Gpp(NH)p, decreased the affinity of the peptides in [3H]naloxone binding assays, suggesting that these ligands might act as agonists at the opioid receptors. Some of the compounds were also used to stimulate guanosine-5'-O-(3-[gamma-[35S]thio)triphosphate ([35S]GTPgammaS) binding in rat and frog brain membranes at concentrations of 10(-9)-10(-5) M. The EC50 values of analog (II) were the highest in both tissues. Analog (I) was as effective as MERF in rat brain membranes, but showed lower maximal stimulation in frog brain preparation. Again, analog (II) seemed to be the least efficacious peptide that stimulated [35S]GTPgammaS binding only by 59%. Specificity of the peptides was further investigated by the inhibition of agonist-stimulated [35S]GTPgammaS binding in the presence of selective antagonists for the opioid receptor types. The mu-selective antagonist cyprodime displayed the lowest potency in inhibiting the effects of the peptides, whereas norbinaltorphimine (kappa-selective antagonist) and naltrindole (delta-selective antagonist) were quite potent in both tissues. We concluded that MERF and its derivatives are able to activate G-proteins mainly via kappa- and delta-opioid receptors.

Animals↗

PubMed2000

Photochemical and chemical oxidation of mexiletine and tocainide. Structure elucidation of the major products.

Mexiletine (mex) and tocainide (toc) are antiarrhythmic drugs of closely related structure. Several degradation products are formed by interaction with both light and oxidizing agents in the case of mex, and only by oxidants with toc. On the basis of the identified structures, the decomposition reactions can be classified into two types (Scheme 1). Type I is an oxidative cyclization reaction producing the oxazepine derivative 1 from mex and the diazepine derivative 3 from toc. In reaction type II side chain oxidized products (2 or 4 and 5) are formed. While tocainide.HCl has proved to be photostable, in solid mexiletine HCl the oxazepine derivative was observed after several days' exposure to direct sunlight. The pharmacopoeias (Ph.Eur.3, USP 23), however, do not prescribe light-protection for mex.HCl.

Anti-Arrhythmia Agents↗

PubMed2000

Tritiated kappa receptor antagonist norbinal torphimine: synthesis and in vitro binding in three different tissues.

Recently a new antagonist with high selectivity for the kappa receptors (norbinaltorphimine) was developed and tested in various systems. This compound was radiolabelled with tritium resulting in high specific radioactivity (47.2 Ci/mmol). [3H]Norbinaltorphimine was characterized by in vitro radioligand binding assays. The radioligand binds to kappa-opioid receptors with a high potency and selectivity in guinea pig, frog and rat brain membranes. Our results suggest the kappa1 specificity of the radioligand.

Animals↗

PubMed2000

Ultrasound in Crohn's disease of the small bowel.

OBJECTIVE: The purpose of this work is to prospectively evaluate high resolution ultrasonography with graded compression in the ability to detect Crohn's disease of the small bowel (CDSB) together with its complications and activity signs, compared with enteroclysis, CT and immunoscintigraphy in the mirror of the final diagnosis. METHODS AND MATERIAL: In a series of 73 consecutive patients, who were referred for enteroclysis with suspected Crohn's disease of the small bowel computed tomography (CT), ultrasound (US), immunoscintigraphy with 99mTc labeled monoclonal antigranulocyte antibody (AGAb) examinations were performed within 10 days from each other. For the final evaluation the diagnosis of CDSB was based on combination of clinical and enteroclysis findings (73 cases) and in 17 cases additional surgical and pathological data were available. The results of other modalities were blinded to the radiologists performing and reading out the exams. The diagnostic values of each modality was assessed also in those 18 patients, who had early Crohn's disease. In the group of 43 patients with proven CDSB who had all the four imaging modalities, the modalities were compared in their ability to demonstrate various pathological conditions related to CD. Increased (>500 ml/min) flow measured by Doppler US in the superior mesenteric artery and increased color signs in the gut wall seen by power Doppler sonography were compared to CDAI. RESULTS: Of the 73 patients the combination of enteroclysis and clinical tests demonstrated CDSB in 47. The sensitivity, specificity and accuracy of ultrasound were 88.4, 93.3 and 90.4%, respectively. Enteroclysis was the most accurate method. CT was more sensitive than US, but less specific. The accuracy of US, CT and scintigraphy were similar. In the group of 18 patients, who had early CDSB, the sensitivity of US decreased to only 67%, CT and scintigraphy had higher values. Intra- and perimural abscesses, and sinus tracts were also more frequently visualized by US, especially if they were small. US was superior than CT in detecting stenoses and skip lesions, but inferior to enteroclysis. US and CT detected more fistulas, than enteroclysis. Compared to CT, US detected more cases with mesenteric lymphadenopathy, equal cases with abscesses and free peritoneal fluids. In detecting mesenteric inflammatory proliferation CT, and in detecting colonic involvement CT and immunoscintigraphy were slightly superior than graded compression US. Patterns of mural stratification detected by ultrasound correlated well with the enteroclysis severity stages. There was only 59% agreement between increased superior mesenteric artery flow detected by Doppler sonography and CDAI, and 60.5% agreement between increased number of Color pixels in the gut wall measured by power Doppler and increased CDAI. CONCLUSION: High resolution graded compression sonography is a valuable tool for detecting small intestinal Crohn's disease. It has similar diagnostic values as CT. However in early disease the sensitivity substantially decreases. In known Crohn's disease for following disease course, evaluating relapses and extramural manifestations US is an excellent tool. Doppler and Power Doppler activity measurements do not correlate well with the more widespread clinical activity index.

Adult↗

PubMed2000

Carotenoid composition in the fruits of Asparagus officinalis.

The carotenoid pigments of the ripe and unripe fruits of Asparagus officinalis were investigated by means of an HPLC technique. Capsanthin, capsorubin, capsanthin 5,6-epoxide, antheraxanthin, violaxanthin, neoxanthin, mutatoxanthin epimers, zeaxanthin, lutein, beta-cryptoxanthin, beta-carotene, and some cis isomers were found. Carotenoids with 3,5,6-trihydroxy and 3,6-epoxy beta-end groups could not be deleted.

Carotenoids↗

PubMed2000

Specific activation of the mu opioid receptor (MOR) by endomorphin 1 and endomorphin 2.

The recently discovered endomorphin 1 (Tyr-Pro-Trp-Phe-NH2) and endomorphin 2 (Tyr-Pro-Phe-Phe-NH2) were investigated with respect to their direct receptor-binding properties, and to their ability to activate G proteins and to inhibit adenylyl cyclase in both cellular and animal models. Both tetrapeptides activated G proteins and inhibited adenylyl cyclase activity in membrane preparations from cells stably expressing the mu opioid receptor, an effect reversed by the mu receptor antagonist CTAP (D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2), but they had no influence on cells stably expressing the delta opioid receptor. To further establish the selectivity of these peptides for the mu opioid receptor, brain preparations of mice lacking the mu opioid receptor gene were used to study their binding and signalling properties. Endomorphin 2, tritiated by a dehalotritiation method resulting in a specific radioactivity of 1.98 TBq/mmol (53.4 Ci/mmol), labelled the brain membranes of wild-type mice with a Kd value of 1.77 nM and a Bmax of 63.33 fmol/mg protein. In membranes of mice lacking the mu receptor gene, no binding was observed, and both endomorphins failed to stimulate [35S]guanosine-5'-O-(3-thio)triphosphate ([35S]GTPgammaS) binding and to inhibit adenylyl cyclase. These data show that endomorphins are capable of activating G proteins and inhibiting adenylyl cyclase activity, and all these effects are mediated by the mu opioid receptors.

Adenylyl Cyclases↗

PubMed2000

Isolated massive pleural effusion caused by pancreatico-pleural fistula.

BACKGROUND: Massive pleural effusions are uncommon but well-documented complications of chronic pancreatitis, usually caused by the development of a pancreaticopleural fistula. The mechanism of the fistula formation is thought to be rupture of the pancreatic duct or pseudocyst. MATERIAL AND METHODS: In the past 7 years we have treated 5 patients with massive pleural effusion of pancreatic origin in the Surgical Department of Semmelweis University Medical School. 4 patients were males; the average age was 52 years (range: 46-59 years). RESULTS: All 5 patients had a history of alcohol abuse and were admitted to the pulmonary department because of respiratory distress. Other symptoms such as abdominal pain, chest pain, or weight loss were not always present. The diagnosis was confirmed by a markedly elevated amylase level in the aspirated pleural fluid. Abdominal ultrasound, CT scan, and ERCP examinations were carried out in order to determine the cause of the pancreaticopleural fistula. Conservative (nonsurgical) treatment was effective within 3 weeks in only one case. The other 4 patients required surgical management. In 3 cases distal pancreatic resection with splenectomy and cholecystectomy was done. In one case cystojejunostomy was performed. All 5 patients have been cured with complete resolution of their pleural effusions. CONCLUSIONS: Patients with large pleural effusions may have underlying pancreatitis with a pancreaticopleural fistula. It is important to establish this diagnosis because treatment may require operative interventions.

Acute Disease↗

PubMed2000

Microsatellites in different eukaryotic genomes: survey and analysis.

We examined the abundance of microsatellites with repeated unit lengths of 1-6 base pairs in several eukaryotic taxonomic groups: primates, rodents, other mammals, nonmammalian vertebrates, arthropods, Caenorhabditis elegans, plants, yeast, and other fungi. Distribution of simple sequence repeats was compared between exons, introns, and intergenic regions. Tri- and hexanucleotide repeats prevail in protein-coding exons of all taxa, whereas the dependence of repeat abundance on the length of the repeated unit shows a very different pattern as well as taxon-specific variation in intergenic regions and introns. Although it is known that coding and noncoding regions differ significantly in their microsatellite distribution, in addition we could demonstrate characteristic differences between intergenic regions and introns. We observed striking relative abundance of (CCG)(n)*(CGG)(n) trinucleotide repeats in intergenic regions of all vertebrates, in contrast to the almost complete lack of this motif from introns. Taxon-specific variation could also be detected in the frequency distributions of simple sequence motifs. Our results suggest that strand-slippage theories alone are insufficient to explain microsatellite distribution in the genome as a whole. Other possible factors contributing to the observed divergence are discussed.

Animals↗

PubMed2000

Enteroclysis and spiral CT examination in diagnosis and evaluation of small bowel Crohn's disease.

INTRODUCTION: During the last few decades introducing many of new radiologic methods, diagnostic conditions and facilities of Crohn's disease has became markedly improved. Appropriate using of these technics definitely modifies the management of patients with known or suspected Crohn's disease serving reliable information about extent, severity and possible complications of disease. Enteroclysis and Computed tomography are the two major and basic methods to disclose or confirme diagnosis of Crohn's disease, obtain appropriate inforination about disease either with mucosal, transmural or extraintestinal manifestation. METHODS AND PATIENTS: We evaluated 281 patients who were referred in our institution under suspition of Crohn's disease. Enteroclysis and abdominal spiral CT in all cases were carried out usually within 1 week. The 172 patients underwent abdominal spiral CT as the primary examination to evaluate diagnostic value of spiral CT in this entity, while 109 patiens had enteroclysis followed by abdominal CT. In 11 cases we also perforined CT enteroclysis with administration of 0.5% methylcellulose solution thorough nasojejunal tube controlled by electric motor driven contrast pump. Results were compared with final clinical, pathological or surgical data were available. RESULTS: From the 281 patients eventually 74 proved Crohn's disease; sensitivity and specificity of enteroclysis proved to be 96 and 98%, while spiral CT sensitivity and specificity was 94 and 95%, respectively. Enteroclysis was superior to the spiral CT in demonstration of early lesions and functional disorders, while spiral CT proved to be essential in evaluation of transmural and extraintestinal complications. CONCLUSIONS: Regarding enteroclysis and spiral CT as complementary methods, they provide excellent results in diagnosis of Crohn's disease.

Adult↗

PubMed2000

Half-a-century of the "Körmend Growth Study".

The authors give a sketch about the "Körmend Growth Study" which is series of cross-sectional growth studies, carried out in Körmend, a small town in Western Hungary. The first investigation was carried out in 1958 (K-58) and it has been repeated every ten years (K-68, K-78, K-88, and K-98). All 3-18 year-old healthy boys and girls in nurseries and schools in Körmend were involved in the study. Twenty-three body measurements were taken. This paper focuses on changes in height, weight, and BMI. Means of these two body measurements show an increase from time to time (as a phenomenon of positive secular trend), however, the secular trend for increasing height and weight is declining. BMI follows a similar pattern.

Adolescent↗

PubMed1999

Trinucleotide repeat polymorphism at five disease loci in mixed Hungarian population.

In apparently healthy, unrelated Hungarians we examined triplet repeat length polymorphism at Huntington disease (HD), spinal and bulbar muscular atrophy (SBMA), spinocerebellar ataxia type 1 (SCA-1), dentatorubral-pallidoluysian atrophy (DRPLA), and myotonic dystrophy (MD) loci. The distribution of alleles of the SCA-1 locus was markedly different compared with Asians and Caucasian samples examined by Watkins WS, Bamshad M, and Jorde LB [1995: Hum Mol Genet 4:1485-1491]. The unimodal distribution of peaks was shifted towards the shorter repeats on the average with 4-5 repeats. Alleles under 21 repeats at the SBMA locus were significantly less frequent in Hungarians than in Asians and Caucasians. We also found significant difference in the distribution of DRPLA allele size at repeat length over 15 repeats; these alleles were less frequent in Hungarians compared with Asians and Caucasians. No significant differences were found in alleles at the MD and also at the HD loci compared with the other groups. These findings suggest that these trinucleotide sites in combination with other markers are particularly useful for determination of the genetic origin of a population, if they can be compared with similar subset of data of other populations. The present results could not confirm the large genetic distance between Hungarian and Oriental races and the relatively short distance between Hungarian and other European populations suggested in earlier reports [Czeizel A, Benkmann H-G, Goedde HW, editors. 1991: Genetics of the Hungarian population. Budapest: Akadémiai Kiadó. p 82-334].

Alleles↗

PubMed1999

Mu-opioid receptor specific antagonist cyprodime: characterization by in vitro radioligand and [35S]GTPgammaS binding assays.

The use of compounds with high selectivity for each opioid receptor (mu, delta and kappa) is crucial for understanding the mechanisms of opioid actions. Until recently non-peptide mu-opioid receptor selective antagonists were not available. However, N-cyclopropylmethyl-4,14-dimethoxy-morphinan-6-one (cyprodime) has shown a very high selectivity for mu-opioid receptor in in vivo bioassays. This compound also exhibited a higher affinity for mu-opioid receptor than for delta- and kappa-opioid receptors in binding assays in brain membranes, although the degree of selectivity was lower than in in vitro bioassays. Cyprodime has recently been radiolabelled with tritium resulting in high specific radioactivity (36.1 Ci/mmol). We found in in vitro binding experiments that this radioligand bound with high affinity (K(d) 3. 8+/-0.18 nM) to membranes of rat brain affording a B(max) of 87. 1+/-4.83 fmol/mg. Competition studies using mu, delta and kappa tritiated specific ligands confirmed the selective labelling of cyprodime to a mu-opioid receptor population. The mu-opioid receptor selective agonist [D-Ala(2),N-MePhe(4),Gly(5)-ol]enkephalin (DAMGO) was readily displaced by cyprodime (K(i) values in the low nanomolar range) while the competition for delta- ([D-Pen(2), D-Pen(5)]enkephalin (DPDPE)) and kappa- (5alpha,7alpha, 8beta-(-)-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro(4, 5)dec-8-yl]-benzene-acetamide (U69,593)) opioid receptor selective compounds was several orders of magnitude less. We also found that cyprodime inhibits morphine-stimulated [35S]GTPgammaS binding. The EC(50) value of morphine increased about 500-fold in the presence of 10 microM cyprodime. These findings clearly indicate that cyprodime is a useful selective antagonist for mu-opioid receptor characterization.

Animals↗

PubMed1999

Nociceptin binding sites in frog (Rana esculenta) brain membranes.

The recently discovered natural heptadecapeptide nociceptin (orphanin FQ) shares some homology with the opioid peptides but it binds to a distinct receptor type, termed nociceptin receptor. This study demonstrates the presence of specific nociceptin recognition sites in brain membrane fractions of an amphibian, Rana esculenta. Para-iodo-Phe(1)-nociceptin-amide was radiolabelled by catalytic dehalotritiation, resulting in p[(3)H]Phe(1)-nociceptin-amide of 25 Ci/mmol specific radioactivity. Specific binding of [(3)H]nociceptin-amide to frog brain membranes was found to be saturable and of high affinity with equilibrium K(d) values in the low nanomolar range. A single set of binding sites with about 180 fmol/mg protein maximal binding capacity was obtained in saturation and competition experiments. [(3)H]Nociceptin-amide binding could easily be inhibited by synthetic nociceptin compounds but not by opioid ligands. Both sodium ions and 5'-guanylylimidodiphosphate decreased the binding of the radioligand by transferring the receptor to a lower affinity state. Nociceptin dose-dependently stimulated the binding of the nonhydrolysable, radiolabeled GTP-analogue guanosine-5'-O-(3-thio)triphosphate ([(35)S]GTPgammaS) to G-proteins in frog brain membranes. Addition of 1 microM naloxone caused no significant change in the curves, indicating that nociceptin-mediated activation of G-proteins occurred through nonopioid mechanism.

Amides↗

PubMed1999

Liquid chromatographic study of the enzymatic degradation of endomorphins, with identification by electrospray ionization mass spectrometry.

The recently discovered native endomorphins play an important role in opioid analgesia, but their metabolic fate in the organism remains relatively little known. This paper describes the application of high-performance liquid chromatography combined with electrospray ionization mass spectrometry to identify the degradation products resulting from the incubation of endomorphins with proteolytic enzymes. The native endomorphin-1, H-Tyr-Pro-Trp-Phe-NH2 (1), and endomorphin-2, H-Tyr-Pro-Phe-Phe-NH2 (2), and an analog of endomorphin-2, H-Tyr-Pro-Phe-Phe-OH (3), were synthetized, and the levels of their resistance against carboxypeptidase A, carboxypeptidase Y, aminopeptidase M and proteinase A were determined. The patterns of peptide metabolites identified by this method indicated that carboxypeptidase Y first hydrolyzes the C-terminal amide group to a carboxy group, and then splits the peptides at the Trp3-Phe4 or Phe3-Phe4 bond. The remaining fragment peptides are stable against the enzymes investigated. Carboxypeptidase A degrades only analog 3 at the Phe3-Phe4 bond. Aminopeptidase M cleaves the peptides at the Pro2-Trp3 or Pro2-Phe3 bond. The C-terminal fragments hydrolyze further, giving amino acids and Phe-NH2-s while the N-terminal part displays a resistance to further aminopeptidase M digestion. Proteinase A exhibits a similar effect to carboxypeptidase Y: the C-terminal amide group is first converted to a carboxy group, and one amino acid is then split off from the C-terminal side.

Amino Acid Sequence↗

PubMed1999

Diprotin A, an inhibitor of dipeptidyl aminopeptidase IV(EC 3.4.14.5) produces naloxone-reversible analgesia in rats.

The dipeptidyl aminopeptidase IV (DP IV) inhibitor Diprotin A produces a full, dose-dependent, short-lasting and naloxone-reversible analgesia in the rat tail-flick test when given intracerebroventricularly, with an ED50 of 295 nmol/rat but it has no direct opioid agonist activity in the longitudinal muscle strip of guinea-pig ileum bioassay. Two of the potential DP IV substrates, morphiceptin and endomorphin 1, identified recently in bovine brain were also analgesic given by similar route. The action of endomorphin 1 was more potent (ED50 = 7.9 nmol/rat) and slightly but significantly more sustained than that of Diprotin A. Diprotin A neither potentiated nor prolonged the effect of a marginally analgesic dose of endomorphin 1. The distinct time course and the lack of potentiation indicate that in the analgesic effect of Diprotin A in rats the protection of a brain Tyr-Pro-peptide other than endomorphin 1 is involved.

Analgesia↗

PubMed1999

Neurotransmitter-mediated open-field behavioral action of CGRP.

The effects of central administration of calcitonin gene-related peptide (CGRP) on open-field activity were examined in male rats. Three doses (250 ng, 500 ng and 1 microg) of CGRP given intracerebroventricularly (i.c.v.) were tested on the ambulatory, rearing and grooming activities of the animals. One microg of peptide significantly decreased the ambulatory activity and increased the rearing and grooming activities 30 min after the treatment. The animals were pretreated with different receptor antagonists in doses which by itself did not affect the behavioural paradigm. The decrease in ambulation induced by CGRP was antagonized by acetylcholine-, opioid-, 5HT-receptor and beta-adrenoceptor antagonists. CGRP induced increase in rearing activity was blocked by naloxone, phenoxybenzamine and propranolol. The CGRP-induced increase in grooming behavior was prevented by atropine, haloperidol, naloxone, methysergide and propranolol. The results suggest that different neurotransmitter systems are involved in the action of CGRP on open-field behavior in rats.

Animals↗

PubMed1999

Characterization of [3H]Met-enkephalin-Arg6-Phe7 binding to multiple sites in rat and guinea pig cerebellum.

[3H]Met-enkephalin-Arg6-Phe7 (MERF) has been shown to label opioid (kappa2 and delta) and sigma2 sites in rat and frog brain membrane preparations, and no specific binding to kappa1 opioid receptors could be established (refs. 6 and 8). In this study the binding was examined in rat cerebellar membranes which are relatively rich in kappa2-sites, and in guinea pig cerebellar preparations where kappa1 opioid receptors are almost exclusively present. In accordance with our previous results, [3H]MERF binding could not be displaced in guinea pig cerebellar membranes neither with U-69,593 nor with naloxone or levorphanol suggesting no interaction with opioid sites, nevertheless a Kd of 2.8 nM was calculated in cold saturation experiments. In rat cerebellar membrane fractions about the half of the specific [3H]MERF binding sites was inhibited by opiate alkaloids such as naloxone, ethylketocyclazocine, or bremazocine. This portion of the heptapeptide binding sites was stereoselective as demonstrated by the difference in the affinities of the enantiomeric compounds levorphanol and dextrorphan, therefore it would represent an opioid site. In both tissues (-)N-allyl-normetazocine (SKF-10,047), which is also considered as sigma2 ligand, displayed the highest affinities. Among opioid peptides beta-endorphin and dynorphin(1-13) showed the highest potencies, displacing [3H]MERF also from its non-opioid sites. It was concluded therefore that [3H]MERF does not bind to kappa1 sites, and besides kappa2-opioid sites substantial binding to peptide preferring non-opioid sites, and/or sigma2 receptors also occurs.

Animals↗