A receptor subtype involved in neuropeptide-Y-induced food intake

Neuropeptide Y (NPY) is a powerful stimulant of food intake and is proposed to activate a hypothalamic 'feeding' receptor distinct from previously cloned Y-type receptors. This receptor was first suggested to explain a feeding response to NPY and related peptides, including NPY2-36, that differed from their activities at the Y1 receptor. Here we report the expression cloning of a novel Y-type receptor from rat hypothalamus, which we name Y5. The complementary DNA encodes a 456-amino-acid protein with less than 35% overall identity to known Y-type receptors. The messenger RNA is found primarily in the central nervous system, including the paraventricular nucleus of the hypothalamus. The extent to which selected peptides can inhibit adenylate cyclase through the Y5 receptor and stimulate food intake in rats correspond well. Our data support the idea that the Y5 receptor is the postulated 'feeding' receptor, and may provide a new method for the study and treatment of obesity and eating disorders.     

5-HT2A receptor subtype is involved in the thermal hyperalgesic mechanism of serotonin in the periphery

Quinupristin/dalfopristin (RP59500) is a novel streptogramin and a semisynthetic derivative of pristinamycins IA and IIB. The following properties of RP59500 were investigated: (i) its in-vitro activity against 164 hospital isolates of Staphylococcus aureus, 101 of which were methicillin-resistant (MRSA); (ii) its killing effect against 24 MRSA and seven methicillin-susceptible (MSSA) isolates; (iii) its interactions with rifampicin and ciprofloxacin against 18 MRSA isolates, six susceptible to both rifampicin and ciprofloxacin and 12 resistant to both, at 1 x MIC, 2 x MIC and 4 x MIC. Rifampicin and ciprofloxacin were applied at a concentration equal to their mean serum levels in order to establish the clinical relevance of the results. The MIC50, MIC90, MBC50 and MBC90 of quinupristin/dalfopristin were, respectively, < or = 0.015, 2, 0.12 and 2 mg/L for MRSA isolates and < or = 0.015, 0.06, < or = 0.015 and 0.25 mg/L for MSSA isolates. All isolates were inhibited by quinupristin/dalfopristin. Its killing effect varied with concentration and time, being optimal at 4 x MIC and after 24 h growth. Strains surviving 24 h exposure to this agent had much higher MICs than the parent strain, but only a limited number of them became resistant. Quinupristin/dalfopristin at 2 x MIC and 4 x MIC showed in-vitro synergy with rifampicin against highly resistant isolates mainly at 6 h and 24 h of growth involving 50-83% of MRSA isolates, and showed synergy with ciprofloxacin at 24 h involving 42-75% of isolates. The MIC increase in colonies surviving at 24 h was restricted by the presence of rifampicin or ciprofloxacin. In contrast, the above combinations acted synergically over the total number of MRSA strains susceptible to both rifampicin and ciprofloxacin. The above findings show that quinupristin/dalfopristin is a very potent antistaphylococcal agent, and that its activity against MRSA isolates is enhanced when it is combined with rifampicin or ciprofloxacin.     

Identification of the receptor subtype involved in the analgesic effect of neurotensin

The neuropeptide neurotensin (NT) elicits hypothermic and naloxone-insensitive analgesic responses after brain injection. Recent pharmacological evidence obtained with NT agonists and antagonists suggests that these effects are mediated by a receptor distinct from the initially cloned high-affinity NT receptor (NTR1). The recent cloning of a second NT receptor (NTR2) prompted us to evaluate its role in NT-induced analgesia. Intracerebroventricular injections in mice of two different antisense oligodeoxynucleotides from the NTR2 markedly decreased NTR2 mRNA and protein and reduced NT-induced analgesia. This effect was specific, because NTR1 levels were unaffected, and sense or scramble oligodeoxynucleotides had no effect. Structure-activity studies revealed a close correlation between the analgesic potency of NT analogs and their affinity for the NTR2 and disclosed potent and selective agonists of this receptor. These data confirm that NTR1 is involved in the NT-elicited turning behavior and demonstrate that the NTR2 mediates NT-induced analgesia.     

cGMP formation in rat atrial slices is ligand and endothelin receptor subtype specific

Involvement of a cGMP pathway in signal transduction stimulated by endothelins(ETs) and sarafotoxins (SRTXs) was examined in rat atrial slices. These peptides activated different receptor-binding sites (ET-1 and SRTX-b reacted with picomolar binding sites of the ET(A) receptor, and ET-3 and SRTX-c reacted with the nanomolar binding sites of the ET(B) receptor) to produce cGMP. ET-1 and SRTX-b stimulated an increase in cGMP levels via a Ca2+-dependent NO pathway involving a pertussis toxin-insensitive G protein, whereas ET-3 and SRTX-c elevated cGMP levels via a Ca2+-independent CO pathway involving a pertussis toxin-sensitive G protein. These results can best be explained in terms of formation of different ligand-receptor-G-protein complexes. The ligands had no effect on ventricular slices, indicating that these signal transduction mechanisms are unique to the atria.     

Angiotensin III and IV activation of the brain AT1 receptor subtype in cardiovascular function

The present investigation determined that native angiotensins II and III (ANG II and III) were equipotent as pressor agents when ICV infused in alert rats, whereas native angiotensin IV (ANG IV) was less potent. An analogue of each of these angiotensins was prepared with a hydroxyethylamine (HEA) amide bond replacement at the N-terminus, yielding additional resistance to degradation. These three angiotensin analogues, HEA-ANG II, HEA-ANG III, and HEA-ANG IV, were equivalent with respect to maximum elevation in pressor responses when ICV infused; and each evidenced significantly extended durations of effect compared with their respective native angiotensin. Comparing analogues, HEA-ANG II had a significantly longer effect compared with HEA-ANG III, and HEA-ANG IV, whereas the latter were equivalent. Pretreatment with the AT1 receptor subtype antagonist, Losartan (DuP753), blocked subsequent pressor responses to each of these analogues, suggesting that these responses were mediated by the AT1 receptor subtype. Pretreatment with the specific AT4 receptor subtype antagonist, Divalinal (HED 1291), failed to influence pressor responses induced by the subsequent infusion of these analogues. These results suggest an important role for Ang III, and perhaps ANG IV, in brain angiotensin pressor responses mediated by the AT1 receptor subtype.     

Comparison of D2 and D3 dopamine receptor affinity of dopaminergic compounds in rat brain

This study used quantitative autoradiography to simultaneously evaluate the relative affinities of dopaminergic compounds for dopamine D2 and D3 receptors in rat brain. PD 152255, PD 128907, and l-nafadotride exhibited significantly higher affinity for cerebellar dopamine D3 sites than [3H]quinpirole-labeled sites in caudate/putamen (6.3-, 6.0-, and 2.3-fold, respectively). In contrast, chlorpromazine, risperidone, and domperidone were more potent at striatal dopamine D2 receptors (3.8-, 31-, and 40-fold, respectively). Dopamine, quinelorane, (+)-UH 232, and RS-trans-7-OH-PIPAT exhibited relatively little D2/D3 selectivity.     

Alpha 1-adrenoceptor subtype involved in the positive and negative inotropic responses to phenylephrine in rat papillary muscle

OBJECTIVE: Neoadjuvant androgen ablation (NAAA) causes significant cytoarchitectural changes in both benign and malignant prostatic epithelial cells that may contribute to underdetection of prostate cancer capsular involvement and positive surgical margins. METHODS: The aim of this study is to determine the ability of cytokeratin immunohistochemistry to enhance the determination of pathologic stage of prostate cancer following NAAA. RESULTS: Cytokeratin AE1/AE3 immunohistochemistry identified 6 (27.3%), 15 (68.2%), 5 (22.7%), and 5 (22.7%) cases of organ-confined disease, capsule penetration, positive surgical margin, and seminal vesicle involvement, respectively, as compared with 10 (45.5%), 10 (45.5%), 3 (13.6%), and 5 (22.7%) cases by hematoxylin-eosin (H&E) staining, respectively. Two cases without detectable tumor by H&E staining had demonstrable residual tumor by cytokeratin immunohistochemical staining. CONCLUSIONS: Cytokeratin immunohistochemistry revealed more extensive intracapsular, capsular, and extracapsular tumor involvement and higher rate of positive surgical margin than did conventional H&E staining. Therefore, the beneficial pathologic effects of NAAA observed may, in part, be attributable to the artifact of observation.     

Corticotropin-releasing hormone receptor subtype 1 is significantly up-regulated at the time of labor in the human myometrium

Circulating concentrations of CRH rise late in human pregnancy, reaching a peak at labor. The presence of functional CRH receptors, CRH-R1 and CRH-R2, in the human myometrium suggests that CRH may modulate uterine activity. We hypothesized that the number of CRH receptors would be higher in myometrium than fetal membranes (FM) and would change during labor. Myometrial samples were collected from the lower segment (LS) in nonpregnant, preterm (32 +/- 2 weeks), and term (39 +/- 1.6 weeks) pregnant patients before and at labor. Fundus and LS samples were also collected from nonpregnant, pregnant, laboring, and postpartum women. FM were collected at term and at labor. We identified CRH receptors in myometrium and FM by semiquantitative RT-PCR and immunohistochemistry. CRH-R1 messenger ribonucleic acid (mRNA) in the LS was decreased in pregnancy and increased significantly in both preterm and term labor (P < 0.05), but remained unchanged in the fundus. CRH-R2 mRNA was present in 28% of LS myometrium with no change at labor. CRH-R1 and CRH-R2 protein was localized to myometrial smooth muscle in nonpregnant and laboring patients, with lower levels at term. CRH-R1 mRNA was present in chorion and decidua, but CRH-R2 was undetectable in these tissues. We conclude that CRH-R1 is expressed preferentially in myometrium and FM. Changes in CRH receptors during labor are consistent with CRH mediating effects on myometrial activity.     

The glycine site of the NMDA receptor contributes to neurokinin1 receptor agonist facilitation of NMDA receptor agonist-evoked activity in rat dorsal horn neurons

Resistance measurements are the most useful parameters for assessing acute changes in airway caliber associated with bronchodilation or bronchial provocation. Used in addition to spirometry, Raw can provide a better differentiation of the causes of airflow impairment as well as the presence of concurrent processes. A simple, noninvasive Raw measurement can provide definitive answers in the absence of other changes. Finally, the addition of practical, nonplethysmographic measurements opens a new application for bedside, office, and home monitoring.     

Involvement of the 5-HT1A subtype receptor in the neonatal organization of agonistic behaviour in the rat

5-hydroxytryptamine (5-HT) interacts with testosterone (T) in the development of a number of neuronal systems controlling sexually dimorphic adult behaviours. In this report, we investigated this interaction on the organization of agonistic behaviour in males, females, androgenized females (250 micrograms/pup of T proprionate on the day of birth), and males castrated on the day of birth. We have shown previously that manipulating 5-HT2 activity over the 2nd week of life modulates adult agonistic behaviour, depending on genetic sex and the presence of T. In this report, we investigated the effects seen in adulthood of a 5-HT1A agonist [8-OH-DPAT, 0.25 mg/kg, intraperitoneally (i.p.)] and antagonist (WAY100135, 0.25 mg/kg, i.p.) given over days 8-16 postpartum. The test for agonistic behaviour was carried out in a neutral territory against a matched conspecific, and introductory, offensive and defensive activities were note. Results show that neonatal administration of the 5-HT1A antagonist WAY100135 increases introductory activity and defense in the presence of neonatal T, independent of genetic sex, because these effects were seen in sham-castrated males and androgenized females. Offence followed a similar pattern, in that it was increased by WAY100135, but only in males. In the case of defence, the effects of the antagonist were reinforced by the action of the agonist (8-OH-DPAT) in both males and females, indicating an inhibitory role of 5-HT1A perinatal activity on defence in the presence of malelike levels of circulating T and a facilitatory role when levels of T are low or negligible. These findings indicate that 5-HT1A activity is involved in the development of agonistic behaviour and the effects are influenced by T. The results also show that the offensive and defensive facets of agonistic activity are controlled differently.     

Role of dopaminergic neuronal system in dizocilpine-induced acetylcholine release in the rat brain

The effects of dopaminergic receptor antagonists on dizocilpine-induced increase in extracellular acetylcholine (ACh) levels in the rat parietal cortex were examined in freely-moving rats, using an in vivo brain microdialysis method. Dizocilpine (0.5 mg/kg) significantly increased extracellular ACh levels in the rat parietal cortex and hippocampus, but not in the striatum. Pretreatment with alpha-methyl-p-tyrosine methyl ester (alpha MpT) delayed the onset but prolonged the duration of the dizocilpine-induced increases in extracellular ACh levels. The dopamine D2 receptor antagonist, haloperidol, showed dual effects similarly to alpha MpT, while the dopamine D1 receptor antagonist, SCH23390, prolonged, but did not delay, the onset of the dizocilpine-induced increases in ACh levels. These results suggest that the dopaminergic system is involved in the dizocilpine-induced increase in the extracellular ACh level in the parietal cortex in two ways, through both dopamine D1 and D2 receptors.     

Selective enrichment with alpha 1A- and alpha 1B-adrenoceptor subtypes in rat brain cortical membranes

In this controlled, prospective and partially blind study two groups of patients with temporal lobe epilepsy were evaluated, respectively with good and bad prognosis. Measurements of epileptogenesis were based on frequency of seizures, and on epiletogenic electroencephalographic abnormalities obtained from scalp electrodes over the temporal lobes. The results were analysed by non-parametric analysis of variance, comparison of groups and analysis of correlation. The results indicated the temporal lobe groups were similar to at least one of the control groups in age, sex, educational and social level, therapeutic regime, age at onset and length of history of epilepsy. The quantitative measurements showed a global difference between the group of temporal lobe with bad and good prognosis, reaching statistical significance in clinical epileptogenesis, and a trend towards greater epileptogenesis on the electroencephalogram, in the same group of patients. The results indicate the experimental usefulness of some of the original measurements used in the study, but also their problems. A review of the literature is carried out.     

AT1 receptor subtype mediates the inhibitory effect of central angiotensin II on cerebrospinal fluid formation in the rat

The effect of central administration of angiotensin II (AII) on cerebrospinal fluid (CSF) formation was studied in pentobarbital-anesthetized, artificially-ventilated rats. CSF production was measured by the ventriculocisternal perfusion method with Blue Dextran 2000 as the indicator. Baseline value of CSF production was 3.35 +/- 0.08 microliters/min. Intracerebroventricular (i.c.v.) infusion of AII at rates of 0.5 and 5 pg/min significantly lowered (P < 0.01) CSF formation by 23% and 16%, respectively. In comparison, high peptide doses (50 and 500 pg/min) did not alter this parameter. The inhibitory effect of low AII doses on CSF formation was blocked by the i.c.v. AT1 receptor subtype antagonists, losartan and SK&F 108566 (2.4 and 2.7 ng/min, respectively), but not by the AT2 receptor subtype-specific agent, PD 123319 (3.8 ng/min). Peptide AII antagonists, [Sar1,Ile8]AII (5 ng/min), which binds to both AT1 and AT2 receptors, had a similar effect to those of AT1-specific blockers. It is concluded that AII, by controlling CSF formation, may influence the water and electrolyte balance in the brain.     

The N-methyl-D-aspartate receptor pathway is involved in hypoxia-induced c-Fos protein expression in the rat nucleus of the solitary tract

In chloroplast photosystem II, the extrinsic polypeptide of 33 kDa is involved in the stabilization the Mn cluster in charge of water splitting and in the fulfilment of the Ca(2+)-cofactor requirement for oxygen evolution. The conformational analysis of the purified 33 kDa extrinsic polypeptide was carried out using FTIR spectroscopy with its self-deconvolution and second derivative resolution enhancement as well as curve-fitting procedures. The FTIR spectroscopic results showed that the isolated polypeptide is characterized by a major proportion beta-sheet conformation (36%) with 27% alpha-helix, 24% turn, and 13% beta-antiparallel structures.     

Repeated diazepam administration influences 5-HT1A receptor binding in the rat brain

Repeated administration of diazepam for 14 days (5 mg/kg daily) resulted in a significant increase of 5-HT1A receptor density in the midbrain of the rat. Bmax values were increased from 239.6 to 684.9 fmol/mg. The affinity constants (KD) were also increased, from 0.97 to 3.01 nM/l.     

Immunohistochemical and cytochemical localization of the somatostatin receptor subtype sst1 in the somatostatinergic parvocellular neuronal system of the rat hypothalamus

Somatostatin is known to mediate its actions through five G-protein-coupled receptors (sst1-sst5). We have studied the expression of the sst1 receptor in the rat hypothalamus by using a subtype-specific antiserum. In Western blotting, the antiserum reacted specifically with a band with an apparent molecular weight of 80,000 in membranes prepared from hypothalamic tissue. The localization of the sst1 receptor was investigated by immunohistochemistry in hypothalamus sections. Additionally, an immunofluorescent double-labeling was performed for the sst1 receptor and somatostatin. Light microscopy revealed that the sst1 receptor is located in perikarya and nerve fibers in the rostral periventricular area surrounding the third ventricle as well as in nerve fibers projecting from the perikarya to the external layer of the median eminence. In these neuronal structures, sst1 immunoreactivity was found to be colocalized with somatostatin. Furthermore, the location of sst1 receptors was studied by immunoelectron microscopy in the median eminence. In the external layer, receptor immunoreactivity was confined to nerve terminals. Immunoreactive nerve terminals were seen to make synapse-like junctions with other both stained and unstained nerve terminals. Thus, the sst1 receptor is present in the classic somatostatinergic hypothalamic parvocellular system inhibiting hormone secretion from the anterior pituitary gland. These findings indicate that the sst1 receptor may act as an autoreceptor and inhibit the release of somatostatin from periventricular neurons projecting to the median eminence.     

Maternal and viral factors in vertical transmission of HIV-1 subtype E

Lipids in the synovial fluid of patients with active rheumatoid arthritis are elevated compared to normal synovial fluid and that of other inflammatory arthropathies. Various assumptions about the role of these lipids have been made. This study offers evidence that these lipids may contribute to the synovitis in rheumatoid arthritis through participation in the arachidonic pathway within the joint space. Phospholipase A2 activity, phospholipids, prostaglandin E2, and leukotriene B4 have been correlated in the synovial fluid and plasma of untreated rheumatoid patients and compared with that of patients with osteoarthritis.