Fluctuations in carotid arterial distensibility during the menstrual cycle do not influence cardiovagal baroreflex sensitivity.

AIM: Fluctuations in autonomic nervous functions throughout the menstrual cycle and the underlying mechanism concerning them are not well known. This study was designed to test the hypothesis that fluctuations in cardiovagal baroreflex sensitivity (BRS) throughout the menstrual cycles of young women are due to fluctuations in carotid arterial distensibility. METHODS: In eight eumenorrhoeic healthy young women (18-24 years), we determined the variations in the carotid arterial distensibility coefficient (DC; via simultaneous ultrasonography and applanation tonometry), cardiovagal BRS (phase IV of the Valsalva manoeuvre and the sequence method; up- or down-sequence spontaneous BRS), and serum oestradiol and progesterone concentrations at five points in the menstrual cycle (menstrual = M, follicular = F, ovulatory = O, early luteal = EL, and late luteal = LL). RESULTS: Serum oestradiol and progesterone levels were consistent with the predicted cycle phases. Carotid arterial DC fluctuated cyclically, increasing significantly from the M (52.4 +/- 4.9 x 10(-3) kPa(-1), mean +/- SE) and F (52.7 +/- 4.4) phases to the O (57.6 +/- 4.4) phase and declining sharply in the EL (46.0 +/- 4.0) and LL (45.1 +/- 3.0) phases (F = 6.37, P < 0.05). Contrary to our prediction, however, cardiovagal BRS by the Valsalva manoeuvre (P = 0.73) or sequence method (up-sequence spontaneous BRS; P = 0.84: down-sequence spontaneous BRS; P = 0.67) did not change significantly during the menstrual cycle. CONCLUSION: The results suggest that, although carotid arterial distensibility fluctuates with the changes in ovarian hormone levels that occur during the menstrual cycle, the fluctuations in carotid arterial distensibility do not influence cardiovagal BRS.

Structural determination of novel tetra- and hexasaccharide sequences isolated from chondroitin sulfate H (oversulfated dermatan sulfate) of hagfish notochord.

Oversulfated chondroitin sulfate H (CS-H) isolated from hagfish notochord is a unique dermatan sulfate consisting mainly of IdoAalpha1-3GalNAc(4S,6S), where IdoA, GalNAc, 4S and 6S represent L-iduronic acid, Nacetyl-D-galactosamine, 4-O-sulfate and 6-O-sulfate, respectively. Several tetra- and hexasccharide fractions were isolated from CS-H after partial digestion with bacterial chondroitinase B to investigate the sequential arrangement of the IdoAalpha1-3GalNAc(4S,6S) unit in the CS-H polysaccharide. A structural analysis of the isolated oligosaccharides by enzymatic digestions, mass spectrometry and 1H NMR spectroscopy demonstrated that the major tetrasaccharides shared the common disulfated core structure delta4,5HexAalpha1-3GalNAc(4S)beta1-4IdoAalpha1-3 GalNAc (4S) with 0 approximately 3 additional O-sulfate groups, where delta4,5HexA represents 4-deoxy-alpha-L-threo-hex-4-enepyranosyluronic acid. The major hexasaccharides shared the common trisulfated core structure delta4,5HexAalpha1-3 GalNAc(4S)beta1-4 IdoAalpha1-3 GalNAc(4S)beta1-4IdoAalpha1-3 GalNAc(4S) with 1 approximately 4 additional O-sulfate groups. Some extra sulfate groups in both tetra- and hexasaccharides were located at the C-2 position of a delta4,5HexA or an internal IdoA residue, or C-6 position of 4-O-sulfated GalNAc residues, forming the unique disulfated or trisulfated disaccharide units, IdoA (2S)-GalNAc(4S), IdoA-GalNAc(4S,6S) and IdoA (2S)-GalNAc(4S,6S), where 2S represents 2-O-sulfate. Of the demonstrated sequences, five tetra- and four hexasaccharide sequences containing these units were novel.

[A case of diffuse pleural mesothelioma disclosed by a 7 mm tumor shadow on chest X-ray film during a regular physical checkup].

We encountered a patient with diffuse pleural mesothelioma pointed out by a tumor shadow 7 mm in diameter on a chest X-ray film obtained during a regular physical checkup. Computed tomography (CT) scans disclosed several small tumors, slightly thickened pleura, and a small amount of pleural effusion. A cytological examination of the effusion, as well as a bronchoscopic examination, were both unable to detect any evidence of malignancy. The patient was referred to the respiratory medicine department of our hospital, where further bronchoscopic examinations were performed but no conclusive diagnosis was obtained. The patient was therefore referred to our department. CT scans revealed enlarged tumors, markedly thickened pleura, and an increase in pleural effusion. This time a cytological analysis of effusion samples was positive for malignant mesothelioma cells. A pleuropneumonectomy was performed, but tumor cells were partially exposed on the dissected surface. Recurrent tumors were disclosed by CT scans 15 months later. Our conclusion was that a thoracoscopic examination should have been performed for diagnostic purposes at an earlier stage.

Fractures of the base of the middle phalanx of the finger. Classification, management and long-term results.

We classified fractures of the base of the middle phalanx into five types: 1) single palmar fragment; 2) single dorsal fragment; 3) two main fragments; 4) not involving the articular surface, including epiphyseal separation in children; and 5) all others. Types 1 and 2 were subclassified into avulsion, split and split-depression. Surgery is recommended for unstable type-1 avulsion fractures, type-2 avulsions which may develop buttonhole deformities, and all fractures which displace articular cartilage surfaces. Long-term follow-up showed that surgical treatment which produced good stability and congruity gave good results. These should be the primary aims of treatment.

A novel pentasaccharide sequence GlcA(3-sulfate)(beta1-3)GalNAc(4-sulfate)(beta1-4)(Fuc alpha1-3)GlcA(beta1-3)GalNAc(4-sulfate) in the oligosaccharides isolated from king crab cartilage chondroitin sulfate K and its differential susceptibility to chondroitinases and hyaluronidase.

Novel sulfated tetrasaccharide structures containing 3-O-sulfated GlcA were isolated recently from king crab cartilage chondroitin sulfate K [Sugahara, K., Tanaka, Y., Yamada, S., Seno, N., Kitagawa, H., Haslam, S. M., Morris, H. R., & Dell, A. (1996) J. Biol. Chem. 271, 26745-26754]. In this study, we prepared a series of oligosaccharides from the same source after exhaustive digestion with testicular hyaluronidase and determined the structures of a pentasaccharide, two hexasaccharides, and two heptasaccharides by means of fast atom bombardment mass spectrometry and 500-MHz 1H-NMR spectroscopy. All the oligosaccharides had the following hitherto unreported structures including a novel glucuronate 3-O-sulfate: GlcA(3S)(beta1-3)GalNAc(4S)(beta1-4)GlcA(3S)(beta1-3)GalNAc( 4S)(beta1-4)GlcA(beta1-3)GalNAc(4S), GlcA(3S)(beta1-3)GalNAc(4S)(beta1-4)GlcA(3S)(beta1-3)GalNAc( 4S)(beta1-4)GlcA(3S)(beta1-3)-GalNAc(4S), GlcA(3S)(beta1-3)GalNAc(4S)(beta1-4)(Fuc alpha1-3)GlcA(beta1-3)GalNAc(4S), GlcA(3S)(beta1-3)-GalNAc(4S)(beta1-4)(Fuc alpha1-3)GlcA(beta1-3)GalNAc(4S)(beta1-4)GlcA(beta1-3)GalNAc (4S), and GlcA(3S)(beta1-3)GalNAc(4S)(beta1-4)GlcA(3S)(beta1-3)GalNAc( 4S)(beta1-4)(Fuc alpha1-3)GlcA(beta1-3)GalNAc(4S), where 3S or 4S represent 3-O- or 4-O-sulfate, respectively. Furthermore, the three latter structures contained a novel combination of both 3-O-sulfated and 3-O-fucosylated GlcA residues. The pentasaccharide with 3-O-fucosylated GlcA at the internal position remained totally resistant to chondroitinase AC-II, whereas it was degraded by chondroitinase ABC into a disaccharide unit containing GlcA(3S) derived from the nonreducing side and a trisaccharide unit containing fucose from the reducing side.

SDZ ENA 713 facilitates central cholinergic function and ameliorates spatial memory impairment in rats.

We have clarified the effects of SDZ ENA 713 (ENA), a new phenyl-carbamate derivative, on the spatial learning impairment and neurochemical indices of central cholinergic neurons in rats. Basal forebrain (BF) lesioning with ibotenic acid markedly impaired acquisition ability in the water maze task without changing swimming rates and decreased choline acetyltransferase (ChAT) activity in the frontal cortex of rats. ENA (0.1, 0.2 mg/kg, p.o.) significantly ameliorated the impairment in acquisition ability in a dose-dependent manner. At 0.2 mg/kg, ENA prevented the reduction in ChAT activity. In normal rats, ENA (1 mg/kg, p.o.) increased extracellular ACh concentration of the prefrontal cortex. On the other hand, tissue concentrations of norepinephrine, serotonin, dopamine and their metabolites were not changed in the frontal cortex, hippocampus and striatum of normal rats. These results suggest that ENA ameliorates spatial learning disability by not only facilitating the cholinergic transmission, but normalizing impaired ChAT activity in the learning-impaired rat model.

Ameliorating effects of SDZ ENA 713 on age-associated decreases in learning performance and brain choline acetyltransferase activity in rats.

In the present study, we have investigated the effects of SDZ ENA 713 on spatial learning deficits in aged rats. Using the same animals, the effect of SDZ ENA 713 on choline acetyltransferase was simultaneously studied to obtain a basis for the behavioral study. In the aged rats, the spatial learning and choline acetyltransferase activity in the frontal cortex were significantly deteriorated compared with young adult rats. SDZ ENA 713 (0.2 mg/kg) significantly shortened the time to reach a hidden platform without affecting swim rates in the water maze task. SDZ ENA 713 (0.1 and 0.2 mg/kg) inhibited aging-induced decreases in choline acetyltransferase activity in the frontal cortex. These results suggest that SDZ ENA 713 ameliorates aging-induced learning deficits and cholinergic dysfunction in rats.

[A case of mediastinal seminoma undergoing extremely cystic degeneration].

A-25-year-old male had an abnormal shadow on chest X-ray. CT and MRI films revealed a cystic lesion, with irregular nodules in the right anterior mediastinum. A cystic teratoma was suggested. Antero-axillary thoracotomy revealed a cystic lesion originating from the right lobe of the thymus. The lesion was extirpated, along with the right lobe of the thymus. The cystic part of the lesion, filled with brown fluid, was occupied by several masses originating from the wall of the tumor. Pathologically, the lesion was diagnosed as a seminoma undergoing cystic degeneration. The patient was given post-operative irradiation of 20Gy. No apparent recurrence has been detected 33 months after surgery. Mediastinal seminomas generally occur as a solid tumor consisting of stroma and tumor cells. However, this case report suggests that mediastinal seminomas may undergo extremely cystic degeneration.

Novel sulfated oligosaccharides containing 3-O-sulfated glucuronic acid from king crab cartilage chondroitin sulfate K. Unexpected degradation by chondroitinase ABC.

We prepared a series of oligosaccharides from king crab cartilage chondroitin sulfate K after exhaustive digestion with testicular hyaluronidase, and determined the structures of four tetrasaccharides and a pentasaccharide by fast atom bombardment mass spectrometry, high performance liquid chromatography analysis of chondroitinase AC-II digests, and 500-MHz 1H NMR spectroscopy. The tetrasaccharides shared the common core structure GlcAbeta1-3GalNAcbeta1-4GlcAbeta1-3GalNAc with various sulfation profiles. One structure was GlcAbeta1-3GalNAc(4S)beta1-4GlcAbeta1-3GalNAc(4S), whereas three of them have the following hitherto unreported structures including a novel glucuronate 3-O-sulfate: GlcA(3S)beta1-3GalNAc(4S)beta1-4GlcAbeta1-3GalNAc(4S), GlcAbeta1-3GalNAc(4S)beta1-4GlcA(3S)beta1-3GalNAc(4S), and GlcA(3S)beta1-3GalNAc(4S)beta1-4GlcA(3S)beta1-3GalNAc(4S), where 3S or 4S represents 3-O- or 4-O-sulfate, respectively. The structure of the pentasaccharide was determined as GlcA(3S)beta1-3GalNAc(4S)beta1-4GlcA(3S)beta1- 3GalNAc(4S)beta1-4GlcA. Chondroitinase ABC digestion of the tetrasaccharides with GlcA(3S) at the internal position destroyed the disaccharide unit containing GlcA(3S) derived from the reducing side and resulted in only the disaccharide unit from the non-reducing side. In contrast, these tetrasaccharides remained totally resistant to chondroitinase AC-II. The results indicated that it is necessary to reevaluate the disaccharide composition of chondroitin sulfate poly- or oligosaccharides purified from various biological sources, since they were usually determined after chondroitinase ABC digestion. It is probable that the structures containing GlcA(3S) would not have been detected.

[Intrapulmonary lymph node diagnosed by thoracoscope: a case report].

A 62-year-old man was admitted to our hospital because of abnormal shadow on chest X-ray. Chest X-ray and CT showed a subpleural tumor 12 mm in diameter in the S8 segment of the right lung. Thoracoscopic observation revealed a subpleural black nodule. Wedge resection of the S8 segment was performed. Pathologically, the nodule was diagnosed as an intrapulmonary lymph node. It should be noted that thoracoscope was very useful for differentiation of intrapulmonary lymph node from other small malignancy.

The content and distribution of glycosaminoglycans in the ejaculates of normal and vasectomized men.

The glycosaminoglycans (GAGs) of sperm and seminal plasma of normal men and seminal plasma of vasectomized individuals have been identified and quantified by two dimensional (2D) electrophoresis. The sperm contains predominantly CSC and HS as well as significant amounts of DS which achieves a high level in the sperm of the youngest man, while HA and LSC are either undetectable or present in small quantities. In normal seminal plasma, characteristically, DS is essentially lacking whereas CSC is the major GAG and HA and LSC account for relatively high percentages. Interestingly, in the ejaculates of vasectomized men the DS content is relatively prominent and the HA concentration varies widely. The oversulfated chondroitin sulfates CSD/CSE were detected in 7 of the 37 specimens. Their presence in a normal human body fluid is reported for the first time and the previous observation of the youthful DS/CSC switch is expanded to this study.

Effects of continual intravenous posttreatment with D-CPP-ene, a potent competitive N-methyl-D-aspartate receptor antagonist, on rat brain edema induced by injection of triethyltin into the cerebral hemisphere.

Brain edema was produced by injecting triethyltin (TET) into the right cerebral hemisphere via the internal carotid artery in rats. TET induced a dose-related increase in mortality rate and brain water content. Immediately after TET-injection (2 mg/head), saline, glycerol (125 mg/ml) or the N-methyl-D-aspartate receptor antagonist (R)-4-(3-Phosphono-2-propenyl)-2-piperazine carboxylic acid (D-CPP-ene; 0.083 and 0.25 mg/ml) was continually infused via the right internal jugular vein at 20 microliters/min for 6 h. The mortality rate and brain water content were significantly decreased after infusion of 0.25 mg/ml D-CPP-ene, but only somewhat reduced after glycerol infusion when compared with the saline group. The results suggest that continual intravenous posttreatment with D-CPP-ene is useful for treatment of brain edema.

Structures of the N-linked oligosaccharides on human plasma vitronectin.

The structures of N-linked oligosaccharides present on human plasma vitronectin were elucidated. Oligosaccharides were released from the vitronectin by N-glycosidase F digestion and tagged with 2-aminopyridine; the pyridylamino-oligosaccharides were then fractionated by anion-exchange and reverse-phase HPLC. Ten major pyridylamino-oligosaccharides were isolated. The linkages and locations of sialic acid residues were determined by desialylation with Salmonella sialidase in combination with acid. The asialo forms were then analyzed by two-dimensional sugar mapping, component sugar analysis and 400-MHz 1H-NMR spectroscopy. The major oligosaccharides of human vitronectin were of the diantennary N-acetyllactosamine type, with a lesser amount of the tri- and a small amount of the mono-antennary type, to which 1-3 mol sialic acid residues were linked, mostly through alpha 2-6 linkages, although alpha 2-3 linkages were also present. The possibility that several binding activities of vitronectin can be ascribed to its glycan moiety was discussed, based on the specific features of the N-linked oligosaccharides on human vitronectin revealed here.

[Study of cystic mediastinal lesions--diagnostic usefulness of magnetic resonance imaging].

We have recently operated 17 cases of cystic mediastinal lesions. A study was made here on their findings of magnetic resonance imaging (MRI). The MRI findings of all the cases revealed oval shaped mediastinal lesions. T2-weighted images showed the lesions to have extremely high signal intensity. Findings characteristic of each disease could also be observed. 1. Pericardial cyst. The cystic lesion was pericardial diverticulum located in cephalad recess of azygos vein (CRAzV) in 5 out of 6 cases. T1-weighted images revealed a mass lesion of low signal intensity with thin wall and enhancement effect by Gd-DTPA wasn't observed. 2. Bronchogenic cyst. In 2 out of 4 cases the cystic lesion was located in CRAzV and 2 cases in the posterior mediastinum. T1-weighted images revealed a mass lesion of high signal intensity and enhancement effect by Gd wasn't observed. 3. Thymic cyst. In all 3 cases the cystic lesion was located in the anterior mediastinum and even when large continuity with fatty tissue of the anterior mediastinum was observed. T1-weighted image revealed a mass lesion of low or iso-intensity and some parts of the wall were enhanced by Gd. 4. Cystic teratoma. In all 3 cases the cystic lesion was located in the anterior mediastinum. Even when the large part showed a cystic pattern, the wall had solid protuberant parts. This parts showed high signal intensity on T1-weighted images and were enhanced by Gd. 5. Cystic thymoma. We experienced a case of cystic thymoma. It presented a high signal intensity on T1-weighted images with a thick section in a part of the wall.(ABSTRACT TRUNCATED AT 250 WORDS)

Thalamocortical and corticocortical excitatory postsynaptic potentials mediated by excitatory amino acid receptors in the cat motor cortex in vivo.

Intracellular recordings were made from neurons in the motor cortex of an anaesthetized cat, together with iontophoretic application of excitatory amino acid receptor agonists and antagonists, in order to evaluate the role of such receptors in excitatory postsynaptic potentials evoked from stimulation of afferent and recurrent pathways in vivo. Excitatory postsynaptic potentials which were evoked by stimulation of the ventrolateral thalamus were found to be largely insensitive to antagonism by N-methyl-D-aspartate receptor antagonists, although they were susceptible to blockade by the non-N-methyl-D-aspartate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione. Increasing the ventrolateral thalamus stimulation frequency from 0.5 or 1 to 5 Hz caused an increase of evoked excitatory postsynaptic potential amplitudes and number of action potentials. These augmented excitatory postsynaptic potentials remained insensitive to application of N-methyl-D-aspartate antagonists. In contrast, recurrent excitatory postsynaptic potentials evoked by stimulation of the pyramidal tract were found to be sensitive to N-methyl-D-aspartate receptor antagonists and/or non-N-methyl-D-aspartate receptor antagonists in some neurons. These results demonstrate the involvement of both N-methyl-D-aspartate- and non-N-methyl-D-aspartate receptors in synaptic responses of cat motor cortex neurons in vivo, and that the synaptic pharmacology of the thalamic input may differ from that of the local recurrent pathways.

Evaluation of a monoclonal antibody-based colony blot test for rapid identification of virulent Rhodococcus equi.

We recently generated a monoclonal antibody immunoglobulin G1 (MAb 10G5), which can recognize 15- to 17-kDa antigens, virulence-associated antigens of Rhodococcus equi, and developed a colony blot enzyme-linked immunosorbent assay with MAb 10G5 for the rapid identification of virulent R. equi. In this epidemiologic study, we evaluated the results of the colony blot test in the identification of virulent isolates of R. equi from feces of horses and soil and compared them with those from a conventional procedure (plasmid profiles of isolates by agarose gel electrophoresis). Environmental isolates (778 isolates from feces of foals, 170 isolates from feces of dams, and 1,267 isolates from soil on horse-breeding farms in Hokkaido) were tested by the colony immunoblot test, and 238 of the 778 isolates, 6 of the 170 isolates, and 85 of the 1,267 isolates showed positive signals. Positive isolates were then analyzed for the presence of virulence plasmid DNA, and 235 (98.7%) of the 238 isolates from foals, 6 (100%) of the 6 isolates from dams, and 75 (88.2%) of the 85 isolates from soil showed the presence of virulence plasmids. On the other hand, 50 isolates from each source, which were randomly selected from the isolates that showed negative signals by colony immunoblot, did not contain virulence plasmids. These results demonstrated that the colony blot test that uses a monoclonal antibody specific for virulence-associated antigens is a rapid and reliable test for the identification of virulent R. equi.

[Three cases of arteriovenous malformation of the lung].

Three cases of arteriovenous malformation (AVM) of the lung are presented. The first patient was 36-year-old female and the second was 25-year-old male, and both with asymptomatic bilateral multiple small AVMs. We used coil spring occlusion in therapeutic transcatheter embolization of the AVMs. A pulmonary arteriogram confirmed the completely occluded AVMs. The another patient was 21-year-old female whose lips and nails were cyanotic. She had clubbing fingers and vascular murmur was audible on her chest wall. The laboratory examination revealed polycythemia and hypoxemia. A pulmonary angiogram revealed a single large AVM which was composed of a feeding artery (A9) and a draining vein (dilated basal pulmonary vein). We performed a left basal segmentectomy and postoperative course was uneventful. Transcatheter embolization is useful for the case of multiple or peripheral or small AVM of the lung, but the case of large solitary AVM with rapid blood flow is thought to be an indication for the operation. These two therapeutic modality should be selected case by case.

Acutely isolated neurons of the rat globus pallidus exhibit four types of high-voltage-activated Ca2+ current.

1. Large, projection-like neurons from the adult (> 3 wk post-natal) rat globus pallidus (GP) were acutely isolated and subjected to whole-cell voltage-clamp (n = 37). Ca2+ currents were isolated pharmacologically in cells with whole-cell capacitances of 15-34 pF. 2. With 5 mM Ba2+ as a charge carrier, whole-cell currents began to activate near -40 mV and peaked near 0 mV. Based on activation threshold and inactivation kinetics, currents appeared to be of the high-voltage-activated type. 3. Cd2+ blocked whole-cell currents with an IC50 near 2 microM. Currents activated at negative potentials were not relatively resistant to Cd2+, supporting the inference that low-voltage-activated currents were not prominent in these neurons. 4. The dihydropyridine, L-channel antagonist, nifedipine (5 microM), reduced peak current by 21 +/- 4% (SD) (n = 10). The dihydropyridine agonist, BayK 8644 (1-2 microM) enhanced peak current and slowed current deactivation (n = 4). 5. The N-channel antagonist, omega-conotoxin GVIA (omega-CgTx, 2 microM) blocked 25 +/- 7% of the peak whole-cell current (n = 10). The blocks produced by omega-CgTx and nifedipine were additive, blocking an average of 46 +/- 8% of the current (n = 10). 6. The current resistant to the selective N- and L-channel antagonists was partially blocked by the P-channel antagonist omega-agatoxin IVA (omega-AgTx, 100 nM). omega-AgTx blocked about one-half of the current not attributable to N- and L-type channels (22 +/- 5% of the total current, n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Structures of the N-linked oligosaccharides on porcine plasma vitronectin.

The structures of N-linked oligosaccharides, especially the distribution of sialic acid species, present on porcine plasma vitronectin were elucidated. Oligosaccharides were released from the vitronectin by N-glycosidase F digestion and tagged with 2-aminopyridine, and the pyridylamino-oligosaccharides were fractionated by anion-exchange and reverse-phase HPLC. Nine major pyridyl-amino-oligosaccharides were isolated. The linkages and locations of sialic acids were determined by a novel approach involving desialylation with Salmonella sialidase in combination with acid desialylation. After desialylation, the asialo-forms were analyzed by two-dimensional sugar mapping, component sugar analysis and 400-MHz 1H-NMR spectroscopy. The major oligosaccharides of porcine vitronectin were of the fucosylated biantennary type, with a small amount of the triantennary N-acetyllactosamine type, to which 1-3 mol sialic acids was linked. Sialic acids were linked predominantly through alpha 2-6 linkages, although alpha 2-3 linkages were also present, and fucose was linked to the innermost N-acetylglucosamine through an alpha 1-6 linkage. It was found that every pyridylamino-oligosaccharide population contained N-glycolylneuraminic acid and N-acetylneuraminic acid in a molar ratio of 1:2-9, and that N-glycolylneuraminic acids were located predominantly on the Man alpha 1-6 arm.

Capsaicin-induced activation of fine afferent fibres from rat skin in vitro.

A preparation of the hindpaw-skin together with the saphenous nerve from the adult rat was maintained in vitro. This was used to characterize the properties of sensory receptors with slowly conducting nerve fibres (C- and A delta) and to evaluate the effects of capsaicin and the capsaicin antagonist, capsazepine. Mechano-heat sensitive C-fibres were the most sensitive to capsaicin (threshold < 0.3 microM) applied to the receptive field. Other types of C-fibres were less sensitive (mechano-cold sensitive fibres threshold 1 microM) or insensitive (high- and low-threshold mechano-sensitive fibres). Mechano-heat and mechano-cold sensitive A delta-receptors were also activated by capsaicin but high- and low-threshold mechano-sensitive A delta-fibres were insensitive to capsaicin (maximum concentration 3 microM). The capsaicin-induced activation of mechano-heat sensitive C-fibres was concentration dependent with an EC50 = 350 nM. Responses to capsaicin, administered at submaximal concentrations were highly reproducible when administrations were separated by 30 min. Administrations at greater frequency reduced responsiveness to capsaicin. This was accompanied by a slowing of conduction velocity or production of a conduction blockade which was reversible after a few minutes. The activation of mechano-heat sensitive C-fibres by capsaicin could be prevented by capsazepine, indicating the involvement of specific capsaicin receptor-sites. These data show that fine afferents in the rat hindpaw-skin retain receptive properties when maintained in vitro. These fibres exhibit differential sensitivity to capsaicin; mechano-heat sensitive C-fibres being the most sensitive. The activation of this class of fibre was mediated via a specific capsaicin-receptor.