Evaluation of skin perfusion pressure to assess refractory foot ulcers.

OBJECTIVE: The number of patients with foot gangrene caused by critical ischaemia and severe infection is increasing significantly in developed countries. The measurement of perilesional skin blood flow by skin perfusion pressure (SPP) is useful to select the appropriate treatment of gangrenous lesions, in that it is not affected by calcifications of blood vessels. However, the prognosis of a foot ulcer may also be affected by the level of blood sugar and infections. This study aimed to validate the use of SPP in cases of foot gangrene and ulcers in patients with and without diabetes mellitus (DM) and infection. METHOD: Clinical symptoms, ankle-brachial pressure index (ABPI) and SPP were assessed to evaluate the condition of each foot ulcer. Every foot ulcer was treated as independent, even if a participant had multiple ulcers. All ulcers for which we measured SPP were subject to the analysis. All ulcers were purely ischaemic in nature and were exclusively located on the foot or toes. RESULTS: Data were collected from 117 foot ulcers on 91 toes and feet from 65 patients. Almost all SPP values in healed cases were > 27 mmHg. There were three patients whose ulcers failed to heal by conservative treatments were complicated with severe infection. However, no effect of DM on the relationship between SPP values and prognosis was observed. Logistic regression analysis of all ulcers except for the 5 cases complicated with infection revealed that those with 30 mmHg or lower SPP values are likely to heal by conservative treatment with 23% or lower probability, whereas any ulcer with more than 50 mmHg SPP value and without severe infection may heal without the need for further operations with 80% or higher probability. CONCLUSION: The combination of SPP and careful evaluation of infection may be a good parameter to decide the appropriate treatment for ischaemic skin ulcers, regardless of the complication of DM.

New constraint on the existence of the µ+ → e+ γ decay.

The analysis of a combined data set, totaling 3.6 × 10(14) stopped muons on target, in the search for the lepton flavor violating decay µ(+) → e(+)γ is presented. The data collected by the MEG experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of 5.7 × 10(-13) (90% confidence level). This represents a four times more stringent limit than the previous world best limit set by MEG.

Prognosis of chronic spontaneous urticaria in 117 patients not controlled by a standard dose of antihistamine.

BACKGROUND: Chronic spontaneous urticaria (CSU) is a common skin disorder, but its clinical course reported so far is largely variable, probably due to the heterogeneity of the clinical background of patients and pathogenesis of this disease. METHODS: To reveal the prognosis of refractory CSU, we retrospectively studied the patients who suffered from spontaneous urticaria for six weeks or longer at their first visit to our outpatient clinic, who were insufficiently controlled by a standard dose of antihistamine, and revisited from 2003 to 2009. RESULTS: Among 223 patients with CSU, 117 patients fulfilled the criteria mentioned above. Mean disease duration at first visit and mean duration of follow-up at our hospital were 27.4 ± 4.2 months and 18.7 ± 1.9 months, respectively. By using Kaplan-Meier methods, the estimated improved rates at 12 months, 24 months, and 60 months were 36.6%, 51.2%, and 66.1%, respectively. The overall improvement rate of childhood cases (<19 years) was significantly higher than that of adult cases (P = 0.007, log-rank test). Moreover, the improvement rate of patients with short disease durations (<1 year at the first visit) was significantly (P = 0.003, log-rank test) higher than that of patients with long disease durations (one year or more). CONCLUSION: Our data indicate that the condition of patients with CSU can be gradually improved even in intractable cases. Information about the clinical course and prognostic factors of CSU in this study could help physicians predict the prognosis of patients and ensure medication adherence of patients with CSU.

A large heterozygous deletion including the entire C1 inhibitor gene in a sporadic case of hereditary angio-oedema.

C1 inhibitor (C1-INH) deficiency [hereditary or acquired angio-oedema (HAE or AAE)] is characterized by recurring episodes of subcutaneous or submucosal oedema. Many different mutations in the C1-INH gene have been identified as a cause of HAE. We investigated the molecular basis of the disease in a Japanese woman with sporadic HAE. Direct sequencing of genomic DNA revealed no point mutation in the C1-INH gene. Quantitative real-time PCR showed that the copy number of the C1-INH gene in the patient was half that of a healthy control. Furthermore, we identified a 650-kbp deletion on the chromosome, which included the C1-INH gene. We evaluated the correlation between the patient's attacks and her coagulation activity. The levels of D-dimer were high during the angio-oedema attacks, and often exceeded the normal range even during remission, thus the level of D-dimer reflected the activity of HAE in this patient.

New limit on the lepton-flavor-violating decay µ+→e+γ.

We present a new result based on an analysis of the data collected by the MEG detector at the Paul Scherrer Institut in 2009 and 2010, in search of the lepton-flavor-violating decay µ(+)e(+)γ. The likelihood analysis of the combined data sample, which corresponds to a total of 1.8×10(14) muon decays, gives a 90% C.L. upper limit of 2.4×10(-12) on the branching ratio of the µ(+)→e(+)γ decay, constituting the most stringent limit on the existence of this decay to date.

Coagulation/fibrinolysis and inflammation markers are associated with disease activity in patients with chronic urticaria.

BACKGROUND: The evaluation of disease severity and activity of chronic urticaria (CU) is essential for the adequate treatment of patients. However, there is no reliable biomarker for such evaluations. Recently, markers of blood coagulation and fibrinolysis have been revealed to be elevated in severe cases of CU. In this article, we studied the coagulation/fibrinolysis and inflammation markers and their relationship to disease activity in patients with CU. METHODS: Plasma fibrin degradation products (FDP), d-dimer and serum C-reactive protein (CRP) were measured with the assessment of disease severity and skin reaction to autologous serum in 82 patients with CU and 37 patients with acute urticaria, idiopathic angioedema (AE) or inducible types of urticaria (IU). RESULTS: The levels of FDP in patients with CU were significantly higher than those in patients with IU, but no other differences in FDP, d-dimer and CRP were observed among patients with different types of urticaria. These markers of patients with CU were well correlated with each other and significantly associated with disease severity of CU, but not with skin reactions to autologous serum. In 37 patients with CU, levels of all these parameters reduced as their disease condition improved, while they increased when the disease became aggravated. Regarding FDP, this relationship was observed even if FDP concentrations were within normal range throughout the study. CONCLUSIONS: The measurement of plasma FDP, d-dimer and serum CRP may be useful for the assessment of disease activity of CU.

Characterization of a germline Vk gene encoding cationic anti-DNA antibody and role of receptor editing for development of the autoantibody in patients with systemic lupus erythematosus.

We found previously that cationic anti-DNA autoantibodies (autoAbs) have nephritogenic potential and usage of a specific germline Vk gene, A30, has major influences on cationic charge of the autoAb in human lupus nephritis. In the present study, we have characterized A30 germline Vk gene using cosmid cloning technique in patients with SLE. A30 gene locus locates in less than 250 kb from the Ck region, and the cationic anti-DNA mRNA used the upstream Jk2 gene, indicating that cationic anti-DNA mRNA is a product of primary gene rearrangement. By using PCR technique, we found that A30 gene locus in the genome was defective in eight out of nine SLE patients without nephritis. In contrast, all nine patients with lupus nephritis had intact A30 gene. The presence and absence of A30 gene was associated with the development of lupus nephritis or not (P < 0.01, by Fisher's exact test, two-sided). It was thus suggested that absence of functional A30 gene may rescue from developing lupus nephritis in the patients. A30 is reported to be a potentially functional but rarely expressed Vk gene in humans. It is possible that normal B cells edit primarily rearranged A30 gene with autoreactive potentials by receptor editing mechanism for changing the affinity of the B cell Ag receptor to avoid self-reactivity, whereas SLE B cells may have a defect in this mechanism. Indeed, we found that normal B cells edit A30-Jk2 gene in their genome possibly by inversion mechanism, whereas SLE B cells contain rearranged A30-Jk2-Ck gene in the genome and express A30-associated mRNA, suggesting that receptor editing mechanism is also defective in patients with SLE. Our study suggests that polymorphism of Ig Vk locus, and failure of receptor editing may contribute to the development of pathogenic anti-DNA responses in humans.

A radioimmunoassay method for 1-beta-D-arabinofuranosyluracil using antibodies directed against 1-beta-D-arabinofuranosylcytosine.

Above pH 7.0 1-beta-D-arabinofuranosyluracil (ara-U) shows marked pH-dependent cross-reactivity with antibodies directed towards 1-beta-D-arabinofuranosylcytosine. Since this peculiar phenomenon has not been observed with other nucleosides and nucleotides thus far tested, it is probably the result of base-catalyzed tautomerism of ara-U to its enolic form which renders it more structurally similar to 1-beta-D-arabinofuranosylcytosine. By performing the radioimmunoassay at both pH 6.2 and 8.6 we could determine 1-beta-D-arabinofuranosylcytosine and ara-U simultaneously. This method for ara-U assay is simple, fairly reliable, and applicable to blood level studies.

A radioimmunoassay for 1-beta-D-arabinofuranosylcytosine.

A rapid and reliable radioimmunoassay method for 1-beta-D-arabinofuranosylcytosine (ara-C) has been developed using antibody induced in rabbits, [3H]ara-C, and a Millipore filtration technique. The sensitivity of this assay was such that ara-C, 0.02 mug/ml, in plasma could be detected, and the assay was practically free from interference by deoxycytidine, cytidine, 1-beta-D-arabinofuranosyluracil, and other nucleosides, as well as from various antibiotics. Blood levels of ara-C in C57BL X DBA/2F1 mice were determined after injection of 1-(3-O-octanoyl-beta-D-arabinofuranosyl) cytosine. Relatively high ara-C levels could be maintained for a fairly long period. Plasmas of mouse, rat, and rabbit contained high esterase activity which hydrolyzed the 3'-octanoyl group in 1-(3-O-octanoyl-beta-D-arabinofuranosyl)cytosine, whereas this activity was relatively low in dog and human plasmas.

A radioimmunoassay for 1-beta-D-arabinofuranosyluracil with reference to cross-reactivity of 1-beta-D-arabinofuranosylcytosine with an antibody.

Antibodies directed against 1-beta-D-arabinofuranosyluracil have been produced in rabbits by immunization with a conjugate of 1-(5-O-succinyl-beta-D-arabinofuranosyl)uracil with human serum albumin. Two of four antibodies so obtained showed high specificity for 1-beta-D-arabinofuranosyluracil and allowed the development of a sensitive and reliable radioimmunoassay for this substrate. On the other hand, one antibody had a high affinity for 1-beta-D-arabinofuranosylcytosine. The binding of 1-beta-D-arabinofuranosylcytosine to this antibody was practically constant between pH 5.2 and 9.0, whereas 1-beta-D-arabinofuranosyluracil binding was affected drastically by pH. The pH-binding profile for 1-beta-D-arabinofuranosylcytosine and 1-beta-D-arabinofuranosyluracil was reminiscent of the specificity of ara-C-specific antibodies, which we previously obtained after immunization of rabbits with 1-(5-O-succinyl-beta-D-arabinofuranosyl)cytosine as a hapten.

Effects of thyroid hormones on apoptotic cell death of human lymphocytes.

Apoptosis plays a critical role in the development and homeostasis of tissues, especially those with high cell turnover such as the lymphoid system. We have examined the effects of thyroid hormones, TSH and TRH, on apoptosis of human T lymphocytes. We found that T lymphocytes cultured with T3 and T4, but not TSH nor TRH, in vitro showed enhanced apoptosis, evidenced by DNA ladder formation and characteristic morphological changes. In addition, prolonged cultivation with thyroid hormones of the lymphocytes further enhanced the extent of apoptosis. We also found that treatment with thyroid hormones of T lymphocytes induced reduction of mitochondrial transmembrane potential (delta psi) and production of reactive oxygen species, both of which are intimately associated with apoptotic cell death. In addition, cellular expression of antiapoptotic Bcl-2 protein was clearly reduced by the treatment of lymphocytes with thyroid hormones in vitro. Thus, T lymphocytes treated with thyroid hormones accompany reduction of Bcl-2 protein expression, production of reactive oxygen species, and reduction of mitochondrial delta psi, resulting in apoptotic lymphocyte death. Moreover, we found that lymphocytes in patients with Graves' disease showed enhanced apoptosis compared with those in normal individuals. These results suggest that thyroid hormones have the potential to induce apoptotic cell death of human lymphocytes in vivo and in vitro.

Neuropeptide Y-induced intracellular Ca2+ increases in vascular smooth muscle cells.

The effect of neuropeptide Y (NPY) on cytosolic free Ca2+ concentration ([Ca2+]i) was studied in cultured smooth muscle cells from porcine aorta (PASMC) and compared with the effect of bradykinin (BK) and angiotensin II (ATII) on [Ca2+]i. All peptides induced dose-dependent and transient rises in [Ca2+]i which were not blocked by extracellular EGTA, but the NPY response was different from the others' as follows. First, the [Ca2+]i rise induced by NPY was not as rapid as that induced by BK or ATII. Second, pertussis toxin abolished the [Ca2+]i rise induced by NPY, but not by BK or ATII. Third, following initial treatment with BK, PASMC were able to respond to NPY, but not to ATII. Finally, BK and ATII, but not NPY, significantly increased inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) generation. Although NPY attenuated forskolin-induced accumulation of cyclic AMP, forskolin- and 3-isobutyl-1-methyl-xanthine-induced alterations in intracellular cyclic AMP did not affect the NPY-induced [Ca2+]i rise. These results suggest that NPY increases [Ca2+]i by a pertussis toxin-sensitive GTP binding protein-involved mechanism which is not mediated by the intracellular messengers such as Ins(1,4,5)P3 and cyclic AMP.

A novel non-peptide endothelin antagonist isolated from bayberry, Myrica cerifera.

A potent non-peptide ET receptor antagonist, myriceron caffeoyl ester (50-235), was isolated from the bayberry, Myrica cerifera. This compound selectively antagonized specific binding of [125I]ET-1, but not of [125I]ET-3, to rat cardiac membranes, ET-1-induced increase in the intracellular free calcium concentration in Swiss 3T3 fibroblasts, and ET-1-induced contraction of rat aortic strips. Thus, 50-235 is the first non-peptide ET(A) receptor antagonist. This compound can be useful for studying the physiological role of endothelin and exploring its role in various diseases.

Leukemia inhibitory factor enhances mast cell growth in a mast cell/fibroblast co-culture system through stat3 signaling pathway of fibroblasts.

Leukemia inhibitory factor (LIF) enhanced mast cell growth in a mast cell/3T3 fibroblast co-culture system, however the precise mechanisms have not been defined. Western blot analysis showed that bone marrow-derived mast cells failed to express both LIF receptor (LIFR) and gp130, whereas 3T3 fibroblasts expressed both LIFR and gp130. This result indicates that the activity of LIF for mast cell growth is mediated by 3T3 fibroblasts. Signal transducer and activator of transcription (Stat) 3-transfected 3T3 fibroblasts enhanced mast cell growth. In addition, dominant-negative Stat3-transfected fibroblasts blocked LIF-mediated mast cell growth in the co-culture system. In conclusion, LIF-induced mast cell growth in the co-culture system is mediated by an indirect pathway via 3T3 fibroblasts through activating Stat3 signaling pathway in 3T3 fibroblasts.

1,3-Disubstituted benzazepines as novel, potent, selective neuropeptide Y Y1 receptor antagonists.

A novel series of potent and selective non-peptide neuropeptide Y (NPY) Y1 receptor antagonists, having benzazepine nuclei, have been designed, synthesized, and evaluated for activity. Chemical modification of the R(1) and R(3) substituents in structure 1 (Chart 1) yields several compounds that show high affinity for the Y1 receptor (K(i) values of less than 10 nM). SAR studies revealed that introduction of an isopropylurea group at R(1) and a 3-(benzo-condensed-urea) group, 3-(fluorophenylurea) group, or a 3-(N-(4-hydroxyphenyl)guanidine) group at R(3) in structure 1 afforded potent and subtype-selective NPY Y1 receptor antagonists. 3-(3-(Benzothiazol-6-yl)ureido)-1-N-(3-(N'-(3-isopropylureido++ +))benzyl )-2,3,4,5-tetrahydro-1H-1-benzazepin-2-one (21), which was one of the most potent derivatives, competitively inhibited specific [(125)I]peptide YY (PYY) binding to Y1 receptors in human neuroblastoma SK-N-MC cells (K(i) = 5.1 nM). 21 not only inhibited the Y1 receptor-mediated increase in cytosolic free Ca(2+) concentration in SK-N-MC cells but also antagonized the Y1 receptor-mediated inhibitory effect of peptide YY on gastrin-induced histamine release in rat enterochromaffin-like cells. 21 showed no significant affinity in 17 receptor binding assays including Y2, Y4, and Y5 receptors.

Neurokinin A mimics the slow excitatory postsynaptic current in submucous plexus neurons of the guinea-pig caecum.

Single microelectrode voltage-clamp recordings were made from submucous neurons of the guinea-pig caecum. The slow excitatory postsynaptic current was compared with the currents induced by neurokinin A and substance P. The current induced by neurokinin A (100-300 nM) was associated with a decreased membrane conductance and reversed in polarity between -90 and -100 mV. The neurokinin A current was reduced by Co2+ (1-2 mM), but was not affected by Cs+ (1-2 mM), Ba2+ (10-100 microM) or low Cl- (20-40 mM) solutions. In about 80% of the neurons, the current induced by substance P (100-300 nM) was associated with a decreased membrane conductance and did not reverse with hyperpolarization of the membrane potential up to -130 mV. The current was reduced by Co2+ (1-2 mM) and augmented by low Cl- (20-40 mM) solutions, but was not affected by Cs+ (1-2 mM) or Ba2+ (10-100 microM)-containing solutions. In about 20% of the neurons, the substance P current reversed in polarity between -100 and -120 mV. The slow excitatory postsynaptic current elicited by repetitive nerve stimulation (10-40 Hz, three to five pulses) was accompanied by a decreased membrane conductance, and reversed in polarity between -90 and -100 mV. The slow excitatory postsynaptic current was abolished by Co2+ (1-2 mM) or low Na+ (12 mM) solutions, but was not affected by Cs+ (1-2 mM), Ba2+ (10-100 microM) or low Cl- (20-40 mM) solutions. In such neurons, the neurokinin A current was reversed at approximately the same potential at which the slow excitatory postsynaptic current was reversed, while the substance P current was not reversed even by much stronger hyperpolarizations. It was concluded that the neurokinin A current was mainly due to depression of potassium conductances, while the substance P current resulted from both increased anion conductance and decreased potassium conductances. The conductance change underlying the slow excitatory postsynaptic current is similar to that caused by neurokinin A.

Muscarinic excitation and inhibition of neurons in the submucous plexus of the guinea-pig caecum.

Intracellular recordings were made from neurons in the submucous plexus of the guinea-pig caecum. Muscarinic agonists (acetylcholine, bethanechol and muscarine) depolarized about 70%, and hyperpolarized about 30% of the submucous plexus neurons. Low concentrations of pirenzepine reversibly antagonized both responses. The measured dissociation constants (KD) of 10-30 nM for the depolarizations and 1-3 nM for the hyperpolarizations suggest that each response was mediated by muscarinic M1 cholinoceptors. The muscarinic depolarization and hyperpolarization were associated with a decreased and an increased conductance, respectively, and the reversal potential for the muscarinic responses varied as the potassium concentration varied, always being around the potassium equilibrium potential. In cells depolarized by muscarinic agonists these agents appeared to decrease a potassium conductance that could also be inactivated by substance P. In approximately 30% of the submucous neurons, the slow inhibitory postsynaptic potential, elicited in response to single or repetitive focal stimuli (1-10 pulses at 20-40 Hz), appeared to consist of a large component which was sensitive to the blocking action of idazoxan (100-300 nM) and a small component which was idazoxan-insensitive. The latter (muscarinic slow inhibitory postsynaptic potential) was completely abolished by pirenzepine. The concentrations of pirenzepine which caused a 50% depression ranged from 5 to 20 nM. The muscarinic slow inhibitory postsynaptic potential was increased in amplitude and duration by physostigmine (100-300 nM). The muscarinic slow inhibitory postsynaptic potential was accompanied by a decrease in membrane input resistance, and was reversed in polarity near the potassium equilibrium potential. When muscarine induced a hyperpolarization and/or focal stimulation elicited a muscarinic slow inhibitory postsynaptic potential in the presence of idazoxan (100-300 nM), the intracellular injection of guanosine 5'-O-(3-thiotriphosphate) produced a progressive membrane hyperpolarization during which the muscarinic hyperpolarizing responses were attenuated. It is concluded that the muscarine-induced reduction in potassium conductance is mediated through a muscarinic M1 receptor which has a relatively low affinity for pirenzepine. The muscarine-induced increase in potassium conductance is probably produced by the association of a guanine nucleotide-binding regulatory protein with another muscarinic M1 receptor that has a relatively high affinity for pirenzepine.

Slow postsynaptic potentials in neurones of submucous plexus of guinea-pig caecum and their mimicry by noradrenaline and various peptides.

Intracellular recordings of membrane potential and membrane currents were made from neurones in the submucous plexus of the guinea-pig caecum in vitro. Fast and slow excitatory postsynaptic potentials and slow inhibitory postsynaptic potentials were recorded from the majority of neurones following focal stimulation of presynaptic fibres in the plexus. The slow inhibitory postsynaptic potential was associated with an increase in membrane conductance and reversed its polarity at -90 mV; it was reversibly blocked by yohimbine. The slow excitatory postsynaptic potential and its underlying current was associated with a decrease in membrane conductance. Two kinds of voltage-dependence both of the slow excitatory postsynaptic potential and current were observed; in 80% of cells, the excitatory postsynaptic potential and current became smaller with membrane hyperpolarization and reversed polarity at -90 mV (reversing type) but in 20% of cells both the excitatory postsynaptic potential and current simply disappeared when the membrane potential reached -70 mV (non-reversing type). The effects of acetylcholine, adenosine 5'-triphosphate, bombesin, 5-hydroxytryptamine, neurotensin, noradrenaline, substance P and vasoactive intestinal polypeptide were examined. The only substance which mimicked the slow inhibitory postsynaptic potential was noradrenaline; brief applications of noradrenaline caused hyperpolarizations which had the same time-course, reversal potential and sensitivity to yohimbine as the slow inhibitory postsynaptic potential. The non-reversing type of slow excitatory postsynaptic potential was mimicked only by adenosine 5'-triphosphate. The reversing type of slow excitatory postsynaptic potential was mimicked by bombesin, neurotensin, substance P and vasoactive intestinal polypeptide. 5-Hydroxytryptamine and vasoactive intestinal polypeptide (in some neurones) caused a depolarization with an increase in membrane conductance. All three synaptic potentials were reversibly depressed by superfusion of noradrenaline but noradrenaline did not affect the potential changes evoked by brief application of exogenous acetylcholine or substance P. It is concluded that, in guinea-pig submucous plexus neurones, the slow inhibitory postsynaptic potential is mediated by noradrenaline and results from a potassium conductance increase.(ABSTRACT TRUNCATED AT 400 WORDS)

Opioids increase potassium conductance in submucous neurones of guinea-pig caecum by activating delta-receptors.

Intracellular records were made from neurones in the submucous plexus of the guinea-pig caecum. [Met5]enkephalin, [Leu5]enkephalin, [D-Ala2,D-Leu5]enkephalin (DADLE) and [D-Ser2,Leu5]enkephalin-Thr (DSLET) hyperpolarized the membrane when applied in concentrations of 30 nm-10 microM. Normorphine, [D-Ala2, MePhe4,Gly5]enkephalin-ol (DAGO), [D-Ala2,MePhe4,Met(0)5]enkephalin-ol (FK33824), dynorphin A and tifluadom had no effect at concentrations up to 10 microM. The hyperpolarization resulted from an increase in the membrane potassium conductance. Hyperpolarizations induced by [Met5]enkephalin were antagonized competitively by naloxone and by N-bisallyl[aminoisobutyrate2,3, Leu5]enkephalin (ICI 174864). The Schild plots for these antagonisms had slopes not different from one, and the dissociation equilibrium constants among individual neurones were 5-50 nM for naloxone and 5-60 nM for ICI 174864. The results indicate that the opioid receptors on guinea-pig submucous neurones which are coupled to potassium channels are of the delta-type.

Y2-receptor-mediated selective inhibition of slow, inhibitory postsynaptic potential in submucous neurones of guinea-pig caecum.

1. The subtype of neuropeptide Y receptor mediating the selective inhibition of the slow inhibitory postsynaptic potential (i.p.s.p.) of submucous neurones in guinea-pig caecum was investigated by use of conventional intracellular electrophysiological recording techniques. 2. Neuropeptide Y (NPY) (1-300 nM) was found to depress or abolish reversibly the slow i.p.s.p. evoked by focal stimulation of internodal fibre tracts. At low concentrations (1-30 nM), a reduction in the duration of the slow i.p.s.p. was often apparent before any inhibition of the amplitude of this synaptic potential. 3. These inhibitory effects of NPY were mimicked by peptide YY (PYY; 0.3-100 nM), NPY13-36 (1-300 nM) and NPY22-36 (10-100 nM); [Leu31,Pro34]NPY ([Pro34]NPY) and bovine pancreatic polypeptide (bPP) were without pre- or postsynaptic effects at concentrations of up to 300 nM. The IC50 +/- s.e. mean values for PYY, NPY, and NPY13-36 were 2.7 +/- 0.3, 7.8 +/- 2.1 and 30 +/- 4.8 nM, respectively, and were significantly different from each other. Thus, the apparent rank order of potency was PYY > NPY > NPY13-36 >> [Pro34]NPY and bPP. 4. In concentrations of up to 300 nM, NPY and its analogues had no depressant effects on the active and passive properties of the impaled neurone and did not affect the amplitude or duration of either cholinergic fast synaptic potentials or non-cholinergic, slow excitatory postsynaptic potentials (e.p.s.ps). Furthermore, none of these peptides altered the amplitude or time-course of changes in membrane potential induced by focal application of acetylcholine or noradrenaline. 5. It is, therefore, concluded that the selective inhibition of the slow i.p.s.p. is mediated by Y2-receptors,located presynaptically on noradrenergic nerve terminals.