Molecular cloning, characterization, and localization of a high-affinity serotonin receptor (5-HT7) activating cAMP formation

By using a strategy based on nucleotide sequence homology, we have cloned a cDNA encoding a functional serotonin (5-HT) receptor. The deduced amino acid sequence of the 5-HT7 receptor displays limited homology with that of other 5-HT receptors. In addition to the seven stretches of hydrophobic amino acids that characterize the superfamily of receptors interacting with guanine nucleotide-binding proteins, the 448-aa sequence of the 5-HT7 receptor contains a hydrophobic domain located at its N-terminal end. Genomic analysis indicated the presence of introns interrupting the coding sequence. The 5-HT7 receptor, stably expressed in transfected CHO cells, bound [3H]5-HT with high affinity (Kd = 1 nM), like receptors of the 5-HT1 subfamily from which, however, it was clearly distinguished by its pharmacology. 5-HT in nanomolar concentrations stimulated cAMP accumulation in these CHO cells by approximately 10-fold, whereas lysergic acid diethylamide displayed low intrinsic agonist activity. These various properties differentiate the 5-HT7 receptor from the four other subfamilies of mammalian 5-HT receptors (i.e., the 5-HT1-, 5-HT2-, 5-HT3-, and 5-HT4-like subfamilies) and, therefore, appear to define another receptor subfamily. Northern blot and in situ hybridization analyses showed the 5-HT7 transcripts to be expressed in discrete areas of the limbic brain (e.g., pyramidal hippocampus cells, tenia tecta, amygdaloid, or mammillary nuclei), suggesting that the receptor mediates serotoninergic controls in functions like mood, learning, or neuroendocrine and vegetative behaviors.

Identification, characterization, and localization of the dopamine D3 receptor in rat brain using 7-[3H]hydroxy-N,N-di-n-propyl-2-aminotetralin

We have identified 7-[3H]hydroxy-N,N-di-n-propyl-2-aminotetralin ([3H]7-OH-DPAT) as a selective probe for the recently cloned dopamine D3 receptor and used it to assess the presence of this receptor and establish its distribution and properties in brain. In transfected Chinese hamster ovary (CHO) cells, it binds to D3 receptors with subnanomolar affinity, whereas its affinity is approximately 100-, 1000-, and 10,000-fold lower at D2, D4, and D1 receptors, respectively. Specific [3H]7-OH-DPAT binding sites, with a Kd of 0.8 nM and a pharmacology similar to those at reference D3 receptors of CHO cells, were identified in rat brain. D3 receptors differ from D2 receptors in brain by their lower abundance (2 orders of magnitude) and distribution, restricted to a few mainly phylogenetically ancient areas--e.g., paleostriatum and archicerebellum--as evidenced by membrane binding are autoradiography studies. Native D3 receptors in brain are characterized by an unusually high nanomolar affinity for dopamine and a low modulatory influence of guanyl nucleotides on agonist binding. These various features suggest that D3 receptors are involved in a peculiar mode of neurotransmission in a restricted subpopulation of dopamine neurons.

BDNF controls dopamine D3 receptor expression and triggers behavioural sensitization

Brain-derived neurotrophic factor (BDNF), like other neurotrophins, is a polypeptidic factor initially regarded to be responsible for neuron proliferation, differentiation and survival, through its uptake at nerve terminals and retrograde transport to the cell body. A more diverse role for BDNF has emerged progressively from observations showing that it is also transported anterogradely, is released on neuron depolarization, and triggers rapid intracellular signals and action potentials in central neurons. Here we report that BDNF elicits long-term neuronal adaptations by controlling the responsiveness of its target neurons to the important neurotransmitter, dopamine. Using lesions and gene-targeted mice lacking BDNF, we show that BDNF from dopamine neurons is responsible for inducing normal expression of the dopamine D3 receptor in nucleus accumbens both during development and in adulthood. BDNF from corticostriatal neurons also induces behavioural sensitization, by triggering overexpression of the D3 receptor in striatum of hemiparkinsonian rats. Our results suggest that BDNF may be an important determinant of pathophysiological conditions such as drug addiction, schizophrenia or Parkinson's disease, in which D3 receptor expression is abnormal.

A novel rat serotonin (5-HT6) receptor: molecular cloning, localization and stimulation of cAMP accumulation

Using a strategy based upon nucleotide sequence homology and starting from the sequence of the rat histamine H2 receptor (Ruat et al., Biochem. Biophys. Res. Commun. 1991, 179, 1470-1478), we have cloned a rat cDNA encoding a functional serotonin receptor (5-HT6). Its coding sequence corresponds to a glycoprotein of 436 amino acids displaying significant homology with other cloned monoaminergic receptors, e.g., various serotonin receptors. Genomic analysis of its gene indicated the presence of at least one intron. The major transcript of the 5-HT6 receptor gene has a size of approximately 4.1 kb but another minor 3.2 kb transcript was also evidenced. The highest expression, detected by Northern blot analysis as well as by in situ hybridization occurs in various serotoninergic areas of rat or guinea pig brain such as striatum, olfactory tubercle, nucleus accumbens and hippocampus, but a faint expression is also detectable in rat stomach. When transiently expressed in transfected COS-7 cells the 5-HT6 receptor appears to be positively coupled to cyclic AMP production.

Phenotypical characterization of neurons expressing the dopamine D3 receptor in the rat brain

We have established the cellular distribution of the dopamine D3 receptor using tritiated 7-hydroxy-N-N-di-n-propyl-2-aminotetralin and a complementary RNA probe to visualize autoradiographically the protein in binding studies and the gene transcripts by in situ hybridization, respectively. Studies with these two markers confirm the restricted expression of the D3 receptor in few brain areas, i.e. mainly the ventral striatal complex, the substantia nigra-ventral tegmental area and the cerebellum. In nucleus accumbens, the D3 receptor was mainly expressed in medium-sized neurons of the rostral pole and ventromedial shell subdivisions, but not of the core or septal pole, i.e. accumbal subdivisions expressing the D2 receptor. In the ventromedial shell, about 60% of the D3 receptor-expressing neurons were neurotensin neurons, presumably projecting to the ventral pallidum. In the islands of Calleja, both D3 receptor binding and messenger RNA were abundant in the entire population of granule cells. These cells are known to make sparse contacts with dopaminergic axons and also to express the D1 receptor. In the mesencephalon, low levels of D3 messenger RNA were detected in few dopamine neurons of substantia nigra pars lateralis and ventral tegmental area. In addition, some D3 receptor binding but not messenger RNA was detected in medial substantia nigra and lateral ventral tegmental area, where the receptor is presumably located presynaptically on afferents. In the archicerebellum, Purkinje cell perikarya in lobules 9 and 10 expressed the D3 receptor messenger RNA, whereas binding sites were found in the molecular layer, where corresponding dendrites but no known dopaminergic projection from mesencephalon are found. The occurrence of D3 receptor gene expression in some brain areas receiving low dopamine innervation supports the hypothesis that this receptor may mediate non-synaptic actions of dopamine.

Induction of dopamine D3 receptor expression as a mechanism of behavioral sensitization to levodopa

In rats with unilateral lesions of the nigrostriatal dopamine pathway with 6-hydroxydopamine, the motor stimulating effects of levodopa, an indirect dopamine receptor agonist, evidenced by contraversive rotations, become enhanced upon repeated intermittent administration. However, the mechanisms of this behavioral sensitization are essentially unknown. We show that development of sensitization is accompanied by a progressive appearance of D3 receptor mRNA and binding sites, visualized by in situ hybridization and 7-[3H] hydroxy-N,N-di-n-propyl-2-aminotetralin autoradiography, respectively, occurring in the denervated caudate putamen, a brain area from which this receptor subtype is normally absent. Development and decay of these two processes occur with closely parallel time courses, whereas there were no marked changes in D1 or D2 receptor mRNAs. D3 receptor induction by levodopa is mediated by repeated D1 receptor stimulation, since it is prevented by the antagonist SCH 33390 and mimicked by the agonist SKF 38393, but not by two D2 receptor agonists. The enhanced behavioral response to levodopa is mediated by the newly synthesized D3 receptor, since it is antagonized by nafadotride, a preferential D3 receptor antagonist, in low dosage, which has no such effect before D3 receptor induction. D3 receptor induction and behavioral sensitization are also accompanied by a sustained enhancement of prodynorphin mRNA level and a progressively decreasing expression of the preprotachykinin gene. We propose that imbalance between dynorphin and substance P release from the same striatonigral motor efferent pathway, related to D3 receptor induction, is responsible for behavioral sensitization.

The Dopamine D3 Receptor: A Therapeutic Target for the Treatment of Neuropsychiatric Disorders

The role of the D(3) receptor has remained largely elusive before the development of selective research tools, such as selective radioligands, antibodies, various highly specific pharmacological agents and knock-out mice. The data collected so far with these tools have removed some of the uncertainties regarding the functions mediated by the D(3) receptor. The D(3) receptor is an autoreceptor that controls the phasic, but not tonic activity of dopamine neurons. The D(3) receptor, via regulation of its expression by the brain-derived neurotrophic factor (BDNF), mediates sensitization to dopamine indirect agonists. This process seems responsible for side-effects of levodopa (dyskinesia) in the treatment of Parkinson's disease (PD), as well as for some aspects of conditioning to drugs of abuse. The D(3) receptor mediates behavioral abnormalities elicited by glutamate/NMDA receptor blockade, which suggests D(3) receptor-selective antagonists as novel antipsychotic drugs. These data allow us to propose novel treatment options in PD, schizophrenia and drug addiction, which are awaiting evaluation in clinical trials.

Polarized expression of Ca2+ channels in pancreatic and salivary gland cells. Correlation with initiation and propagation of [Ca2+]i waves

In polarized epithelial cells [Ca2+]i waves are initiated in discrete regions and propagate through the cytosol. The structural basis for these compartmentalized and coordinated events are not well understood. In the present study we used a combination of [Ca2+]i imaging at high temporal resolution, recording of Ca2+-activated Cl- current, and immunolocalization by confocal microscopy to study the correlation between initiation and propagation of [Ca2+]i waves and localization of Ca2+ release channels in pancreatic acini and submandibular acinar and duct cells. In all cells Ca2+ waves are initiated in the luminal pole and propagate through the cell periphery to the basal pole. All three cell types express the three known inositol 1,4,5-trisphosphate receptors (IP3Rs). Expression of IP3Rs was confined to the area just underneath the luminal and lateral membranes, with no detectable receptors in the basal pole or other regions of the cells. In pancreatic acini and SMG ducts IP3R3 was also found in the nuclear envelope. Expression of ryanodine receptor was detected in submandibular salivary gland cells but not pancreatic acini. Accordingly, cyclic ADP ribose was very effective in mobilizing Ca2+ from internal stores of submandibular salivary gland but not pancreatic acinar cells. Measurement of [Ca2+]i and localization of IP3Rs in the same cells suggests that only a small part of IP3Rs participate in the initiation of the Ca2+ wave, whereas most receptors in the cell periphery probably facilitate the propagation of the Ca2+ wave. The combined results together with our previous studies on this subject lead us to conclude that the internal Ca2+ pool is highly compartmentalized and that compartmentalization is achieved in part by polarized expression of Ca2+ channels.

A meta-analysis of randomized controlled trials of laparoscopic versus conventional appendectomy

BACKGROUND

Despite many randomized controlled trials, the merits of laparoscopic appendectomy remain unclear. A meta-analysis may provide insights not evident from any individual studies.

DATA SOURCES

Systematic literature search yielded 17 trials (1,962 subjects) of true randomized design with usable statistical data comparing laparoscopic and conventional appendectomy in adults. The effect sizes for operating time, hospitalization, postoperative pain, return to normal activity, wound infection, and intra-abdominal abscess were calculated, using the random effects model to allow for heterogeneity. An estimate of the robustness of all positive findings was also calculated.

RESULTS

Modest but statistically significant effect sizes were found for four of the six outcome measures. Laparoscopic appendectomy takes 31% longer to perform, but results in less postoperative pain, faster recovery (by 35%), and lower wound infection rates (by 60%).

CONCLUSION

Laparoscopic appendectomy offers significant improvement in postoperative outcomes at the cost of a longer operation.

Molecular cloning and characterization of the rat fifth melanocortin receptor

Adrenocorticotropic hormone (ACTH) and melanocortin peptides (alpha, beta and gamma MSH) have numerous activities in both central nervous system and peripheral tissues, namely the adrenals. Recently, five melanocortin receptors were cloned and characterized. We report here the cloning, pharmacological characterization and expression of the rat fifth melanocortin receptor (MC5), starting from the dopamine D3 receptor sequence to screen a genomic DNA library. The MC5 comprises a sequence of 325 amino acids, displaying 45-62% identity with other melanocortin receptors and 82% identity with its human counterpart that we cloned thereafter. The sequence of the latter is identical to that of a so-called 'MC2' receptor (Chhajlani et al., 1993, Biochem. Biophys. Res. Comm. 195, 866-873). The MC5, stably expressed in CHO cells, mediates increase in cAMP accumulation with a characteristic pharmacology: alpha MSH is twice as potent as NDP alpha MSH, 10 times as ACTH and 100 times as gamma MSH. Very low expression levels were detected in brain, while high levels were found in adrenals, stomach, lung and spleen. In addition, in situ hybridization studies show the MC5 expressed in the three layers of the adrenal cortex, predominantly in the aldosterone-producing zona glomerulosa cells.

Polarized expression of Ca2+ pumps in pancreatic and salivary gland cells. Role in initiation and propagation of [Ca2+]i waves

The present study was aimed at localization of plasma membrane (PMCA) and intracellular (SERCA) Ca2+ pumps and characterizing their role in initiation and propagation of Ca2+ waves. Specific and polarized expression of Ca2+ pumps was observed in all epithelial cells examined. Immunolocalization revealed expression of PMCA in both the basolateral and luminal membranes of all cell types. SERCA2a appeared to be expressed in the luminal pole, whereas SERCA2b was expressed in the basal pole and the nuclear envelope of pancreatic acini. Interestingly, SERCA2b was found in the luminal pole of submandibular salivary gland acinar and duct cells. These cells expressed SERCA3 in the basal pole. To examine the significance of the polarized expression of SERCA and perhaps PMCA pumps in secretory cells, we compared the effect of inhibition of SERCA pumps with thapsigargine and partial Ca2+ release with ionomycin on Ca2+ release evoked by agonists and Ca2+ uptake induced by antagonists. Despite their polarized expression, Ca2+ uptake by SERCA pumps and Ca2+ efflux by PMCA resulted in uniform reduction in [Ca2+]i. Surprisingly, inhibition of the SERCA pumps, but not Ca2+ release by ionomycin, eliminated the distinct initiation sites and propagated Ca2+ waves, leading to a uniform increase in [Ca2+]i. In addition, inhibition of SERCA pumps reduced the rate of Ca2+ release from internal stores. The implication of these findings to rates of Ca2+ diffusion in the cytosol, compartmentalization of Ca2+ signaling complexes, and mechanism of Ca2+ wave propagation are discussed.

Impaired brain growth in neonatal rats exposed to ethanol

Infant rat pups, fed through intragastric cannulas from postnatal day 4 through day 18, showed a 19 percent reduction in total brain weight when ethanol was included in their diet on days 4 through 7. This reduction in brain weight occurred even though body growth in the experimental rats was equal to that of their littermate controls. The ethanol-exposed animals were markedly hypoactive during the period of drug administration, then displayed gross body tremors for 3 to 5 days. Throughout the study, the animals treated with ethanol had poor motor coordination and were hyperresponsive. These brain and behavioral effects appear similar to those seen in fetal alcohol syndrome.

Possible implications of the dopamine D(3) receptor in schizophrenia and in antipsychotic drug actions

The D(3) receptor may represent an important target for antipsychotic drugs which all bind with high affinity and do not induce upon repeated administration either tolerance or receptor upregulation. The D(3) receptor is localized in brain areas, namely the nucleus accumbens and cerebral cortex, implicated in neural circuits believed to display defective functioning in schizophrenia. Overexpression of the D(3) receptor, which accounts for the behavioral sensitization to levodopa in a rodent model of Parkinson's disease, might also be responsible for the sensitization to dopamine agonists observed in schizophrenia. The appearance of the D(3) receptor during brain development, early in proliferating neuroepithelia and later in neurons from limbic areas, suggests further studies to assess its participation in the neurodevelopmental disorders of schizophrenia. Finally, meta-analysis of approximately 30 studies comprising over 2500 patients indicate that a polymorphism in the coding sequence of the D(3) receptor is associated with a small but significant enhancement of vulnerability to the disease.

Long-term contraception with the levonorgestrel 20 mcg/day (LNg 20) and the copper T 380Ag intrauterine devices: a five-year randomized study

An intrauterine device, releasing approximately 20 micrograms/day of levonorgestrel (LNg 20), used by 1124 women, was studied in a randomized trial of five years duration in comparison with the Copper T, model TCu 380Agm in 1121 women. At five years, the gross cumulative pregnancy rate of 1.1 +/- 0.5 per 100 among users of the LNg 20 devices was not significantly different from the rate of 1.4 +/- 0.4 per 100 experienced by users of the Copper T 380Ag. The steroid-releasing IUD had significantly higher termination rates for expulsion and amenorrhea, a significantly lower termination rate for other menstrual problems and pain, and a lower continuation rate. The five-year continuation rate among women using the TCu 380Ag was 40.6 per 100 as compared with that of 33.0 per 100 among women randomized to the LNg 20 device (P less than .001). Terminations attributed to amenorrhea with the LNg device primarily account for differences in continuation. These two intrauterine devices are the most effective long-term, reversible IUDs yet reported in the literature. No other contraceptive methods have exhibited such low long-term pregnancy rates in randomized comparative trials.

Prospective comparison of admission computed tomographic scan and plain films of the upper cervical spine in trauma patients with altered mental status

OBJECTIVE

The accurate evaluation of patients with multiple injuries is logistically complex and time sensitive, and must be cost-effective. We hypothesize that computed tomographic (CT) scan of the upper cervical spine (occiput to C3 [Co-C3]) would add little to the initial evaluation of patients with multiple injuries who have altered mental status.

METHODS

The study consisted of a prospective, unblinded, consecutive series. Patients met entry criteria if they had sustained a blunt mechanism of injury and had an altered mental status requiring CT scan of two or more body systems. All patients received CT scan of Co-C3 with 2-mm cuts and subsequent reconstructions as well as five-view cervical spine plain films. Cervical spine injury was defined as any radiographically identified fracture or subluxation that required treatment. Patients were excluded if they died or were cleared clinically before plain film series were obtained. CT scan of Co-C3 and cervical spine films were reviewed by two different attending radiologists.

RESULTS

Of the 2,690 consecutive admissions between December 1998 and November 1999, 1,356 patients met entry criteria. Seventy patients (5.2%) had a total of 95 injuries to the upper cervical spine. CT scan of Co-C3 identified 67 of 70 patients and plain films identified 38 of 70 patients with injuries to the upper cervical spine. Twelve patients (17%) had neurologic deficits attributable to Co-C3 injuries. Three patients had false-negative CT scans of Co-C3, and one patient was quadriplegic. There were 32 patients with false-negative plain films, including four patients with motor deficits (one with quadriplegia). Use of the guidelines developed by the Eastern Association for the Surgery of Trauma identified all patients with upper cervical spine injuries; to date, no patient in the study group was readmitted or has initiated a lawsuit for missed injury of the upper cervical spine.

CONCLUSION

CT scan of Co-C3 was superior to plain films in the early identification of upper cervical spine injury. Plain films failed to identify 45% of upper cervical spine injuries; four of these missed injuries resulted in motor deficits. Our study supports the practice guidelines developed by the Eastern Association for the Surgery of Trauma for clearance of the upper cervical spine in patients with altered mental status, as all patients with injuries were identified using these guidelines.

A paradoxical regulation of the dopamine D3 receptor expression suggests the involvement of an anterograde factor from dopamine neurons

The effects of interruption of dopaminergic transmission or sustained blockade of dopamine receptors by neuroleptics on the dopamine D3 receptor in the shell of the nucleus accumbens were investigated in rats. In this brain area the D3 receptor is abundant and may mediate antipsychotic drug effects. The D3 receptor density and mRNA abundance were evaluated with 7-[3H]hydroxy-N,N-di-n-propyl-2-aminotetralin and by quantitative PCR or image analysis of in situ hybridization signals, respectively. Unilateral dopamine neuron degeneration by 6-hydroxydopamine or sections triggered, after a few days, a marked decrease (up to 50%) in D3 receptor binding and mRNA in the nucleus accumbens. In contrast, a 2-week treatment with the neuroleptic haloperidol (20 mg/kg) had no effect on D3 receptor density and mRNA but enhanced D2 receptor density and mRNA level by > 50%. In addition, tolerance to the haloperidol-induced change of neurotensin mRNA mediated by the D2 receptor developed, but there was no tolerance to the opposite change mediated by the D3 receptor. Reserpine, a monoamine-depleting drug with antipsychotic activity, did not modify D3 receptor mRNA. These observations reinforce the idea that the D3 receptor may be an important target for neuroleptics whose antipsychotic actions, but not extrapyramidal motor actions, do not display tolerance. The D3 receptor mRNA level was also decreased by a unilateral injection in dopamine cell body areas of colchicine, a drug blocking the anterograde axonal transport, or by baclofen, a type A gamma-aminobutyric acid receptor agonist reducing dopamine neuron activity, but not by sustained blockade of D1-like and D2-like, neurotensin, or cholecystokinin receptors. We therefore propose that an anterograde factor present in mesolimbic dopaminergic neurons, but distinct from dopamine and known peptide cotransmitters, plays a positive role on transcription of the D3 receptor gene.

Coexpression of dopamine D1 and D3 receptors in islands of Calleja and shell of nucleus accumbens of the rat: opposite and synergistic functional interactions

Using double in situ hybridization, we found extensive coexpression of dopamine D1 and D3 receptor (D1R and D3R) mRNAs in neurons of the island of Calleja major (ICjM) and ventromedial shell of nucleus accumbens (ShV), respectively. Thus, at least 79 and 63% of D3R mRNA-expressing neurons in ICjM and ShV also expressed the D1R mRNA. Coexpression of D1R and D3R mRNAs was found to occur in substance P (SP) mRNA-expressing neurons in both areas, suggesting SP mRNA as a marker of the activity of coexpressing neurons. Administration of SKF 38393, a D1R receptor agonist, increased c-fos mRNA in ICjM, whereas administration of quinpirole, a D2R/D3R agonist, decreased it; SCH 23390, a D1 R antagonist and nafadotride, a preferential D3R antagonist, given alone, had effects opposite to those of the corresponding agonists. These data indicate that basal c-fos expression in ICjM is maintained by endogenous dopamine acting tonically upon two receptor subtypes subserving opposite effects on the same cell. However, in ShV, whereas SKF 38393 also increased c-fos mRNA, quinpirole had no effect, a difference presumably reflecting the lower fraction of neurons coexpressing D1R and D3R in this area. In contrast, in ShV from reserpine-treated rats, SKF 38393 increased SP mRNA and quinpirole potentiated this effect. These contrasting interactions of D1R- and D3R-mediated signalling events, i.e. in either opposite or synergistic directions, most likely occurring at the single cell level, may serve to increase the dopamine response threshold of the target cells in ICjM and to maintain a strong tonic activity of ShV neurons.

Immuno and functional characterization of CFTR in submandibular and pancreatic acinar and duct cells

Cystic fibrosis results from defective Cl- channel activity mediated by the cystic fibrosis transmembrane conductance regulator (CFTR) gene product. In the gastrointestinal tract this is manifested in abnormal salivary secretion and pancreatic insufficiency. This is generally attributed to defective Cl- transport by the ductal system of the glands. We provide the first immunocytochemical and functional evidence for expression of CFTR protein and Cl- current in rat and mouse submandibular gland (SMG) and pancreatic acinar cells, a site proximal to the ductal system of these secretory glands. Monoclonal and polyclonal antibodies recognizing COOH-terminal epitopes of CFTR show that duct and acinar cells from the two glands express CFTR in the luminal membrane. Specificity of the polyclonal antibody was verified by absence of staining in duct and acinar cells of the SMG of cf-/cf- and delta F/delta F mice. Identification of CFTR in acinar cells was aided by demonstrating coexpression of CFTR and type 3 inositol 1,4,5-trisphosphate receptors in the luminal pole of acini and absence of type 3 inositol 1,4,5-trisphosphate receptors in ducts. Electrophysiological characterization in single SMG duct and acinar cells shows the presence of a protein kinase A-activated, voltage- and time-independent, ohmic Cl- current and absence of repolarization-dependent tail currents, all of which are kinetic properties of the CFTR-dependent Cl- channel. In addition, the channel was activated by the nonhydrolyzable ATP analog 5'-adenylylimidodiphosphate and the benzimidazalone NS-004. Channels activated by all activators were inhibited by glibenclamide and a known inhibitory antiserum [anti-CFTR-(505-511)]. Combined immunologic, functional, and pharmacological evidence allows us to conclude that acinar cells of the SMG and pancreas express functional CFTR-dependent Cl- channels. Because this site is proximal to the duct, modification of activity of this channel in acinar cells is likely to contribute to abnormal salivary secretion and pancreatic insufficiency typical of cystic fibrosis.

Selective increase of dopamine D3 receptor gene expression as a common effect of chronic antidepressant treatments

The mesolimbic dopaminergic system is a neuroanatomical key structure for reward and motivation upon which previous studies indicated that antidepressant drugs exert a stimulatory influence, via still unknown neurobiological mechanisms. Here we examined the effects of chronic administration of antidepressants of several classes (amitriptyline, desipramine, imipramine, fluoxetine and tranylcypromine) and repeated electroconvulsive shock treatments (ECT) on dopamine D3 receptor expression in the shell of the nucleus accumbens, a major projection area of the mesolimbic dopaminergic system. Short-term drug treatments had variable effects on D3 receptor mRNA expression. In contrast, treatments for 21 days (with all drugs except fluoxetine) significantly increased D3 receptor mRNA expression in the shell of nucleus accumbens; D3 receptor binding was also significantly increased by amitriptyline or fluoxetine after a 42-day treatment. ECT for 10 days increased D3 receptor mRNA and binding in the shell of nucleus accumbens. D1 receptor and D2 receptor mRNAs were increased by imipramine and amitriptyline, but not by the other treatments. The time-course of altered D3 receptor expression, in line with the delayed clinical efficiency of antidepressant treatment, and the fact that various antidepressant drugs and ECT treatments eventually produced the same effects, suggest that increased expression of the D3 receptor in the shell of nucleus accumbens is a common neurobiological mechanism of antidepressant treatments, resulting in enhanced responsiveness to the mesolimbic dopaminergic system.

The effect of phenytoin on the magnitude and duration of neuromuscular block following atracurium or vecuronium

Patients chronically receiving anticonvulsants have been reported to be resistant to the long-acting competitive neuromuscular blockers. This study examines the effects of atracurium and vecuronium on 100 neurosurgical patients; 50 receiving chronic phenytoin therapy (group I) and 50 controls (group II). During O2/N2O/halothane anesthesia, five patients in each group were given a bolus of vecuronium 0.1 mg/kg, and a different five patients in each group were given atracurium 0.5 mg/kg, to produce neuromuscular blockade in excess of 95%. The time to maximum blockade and the recovery from atracurium was unaffected by phenytoin therapy. Recovery from vecuronium was enhanced in the phenytoin group, as demonstrated by the recovery index, defined as the time required for recovery from 25-75% of the control neuromuscular response (7.9 +/- 2.2 min compared with 17.8 +/- 5.1 min in controls, P less than 0.005). Similarly, the total duration of neuromuscular blockade, defined as recovery to 90% of control response, was significantly shorter in the phenytoin group (31.9 +/- 6.0 min compared with 69.7 +/- 12.9 min in controls, P less than 0.001). The remaining 40 patients from each group were given a preselected dose of either vecuronium (0.02-0.06 mg/kg) or atracurium (0.10-0.25 mg/kg) during anesthesia with O2/N2O/fentanyl, to generate dose-response curves for the relaxants. Using analysis of covariance, the slopes and elevations for atracurium were found to be essentially identical in the two groups; as were the calculated ED50 and ED95. Patients receiving chronic phenytoin therapy were resistant to vecuronium-induced neuromuscular blockade. With vecuronium, the dose-response curves for the two groups were parallel; the curve for phenytoin patients was shifted to the right.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional implications of multiple dopamine receptor subtypes: the D1/D3 receptor coexistence

The D3 dopamine receptor, a D2-like receptor, is selectively expressed in the ventral striatum, particularly in the shell of nucleus accumbens and islands of Calleja, where it is found in medium sized substance P neurons. The latter co-express the D1 receptor whose interaction with the D3 receptor was studied by treating rats with selective agonists and antagonists. In agreement with the opposite cAMP response, they mediate in cultured neuroblastoma cells, the D1 and D3 receptors exerted opposite influences on c-fos expression in islands of Calleja. However, in agreement with the synergistic influence of cAMP on D3 receptor-mediated mitogenesis on the same cultured cells, D1 and D3 receptor stimulation in vivo synergistically enhanced preprotachykinin mRNA in the shell of accumbens. This indicates that the two receptor subtypes may affect neurons in either synergy or opposition according to the cell or signal generated. Levodopa-induced behavioral sensitization in hemiparkinsonian rats is another example of D1/D3 receptor interaction. Hence repeated levodopa administration induces the ectopic appearance of the D3 receptor in substance P/dynorphin, striatonigral neurons of the dorsal striatum. This induction is secondary to D1 receptor stimulation in neurons of the denervated side and fully accounts for the sensitization, i.e. the increased behavioral responsiveness to levodopa. During brain development, a similar process could operate to control the late appearance of the D3 receptor in D1-receptor bearing neurons of the ventral striatum at a time at which they start to be innervated by dopamine neurons. Finally, taking into account a variety of genetic, developmental, neuroimaging and pharmacological data, we postulate that imbalances between the levels of D1 and D3 receptors in the same neurons could be responsible for schizophrenic disorders.

Factors influencing physicians' prescribing behaviour in the treatment of childhood diarrhoea: knowledge may not be the clue

Proper diarrhoea treatment has received greater attention during the last 10 years. However, the unjustified use of medicines to treat simple episodes of acute diarrhoea continues to divert attention and available resources away from appropriate treatment. A study to identify the factors determining prescribing practices for diarrhoea treatment was carried out in a peri-urban part of Lima, Peru in 1991. Physicians were interviewed, and then their practice was assessed by visits of confederates with healthy children described as ill, by interviews with mothers of sick children leaving the clinic, or by both of these methods. Physicians' reported practices in treating diarrhoea cases were compared to their actual practices. Although physicians' knowledge of drug management seemed to influence the low frequency of prescription of antidiarrhoeal drugs, it did not have the same influence on prescription of antimicrobials. Our results suggest that the diagnostic process and consequently the treatment decision do not follow a scientific rationale for this illness. The physicians' prescribing practices seemed to be more related to agreement with social expectations and the caretakers' perception of the physicians' role than they were to the standard biomedical rules of diarrhoea management.

The Fanconi anemia protein FANCC binds to and facilitates the activation of STAT1 by gamma interferon and hematopoietic growth factors

Hematopoietic progenitor cells from Fanconi anemia (FA) group C (FA-C) patients display hypersensitivity to the apoptotic effects of gamma interferon (IFN-gamma) and constitutively express a variety of IFN-dependent genes. Paradoxically, however, STAT1 activation is suppressed in IFN-stimulated FA cells, an abnormality corrected by transduction of normal FANCC cDNA. We therefore sought to define the specific role of FANCC protein in signal transduction through receptors that activate STAT1. Expression and phosphorylation of IFN-gamma receptor alpha chain (IFN-gammaRalpha) and JAK1 and JAK2 tyrosine kinases were equivalent in both normal and FA-C cells. However, in coimmunoprecipitation experiments STAT1 did not dock at the IFN-gammaR of FA-C cells, an abnormality corrected by transduction of the FANCC gene. In addition, glutathione S-transferase fusion genes encoding normal FANCC but not a mutant FANCC bearing an inactivating point mutation (L554P) bound to STAT1 in lysates of IFN-gamma-stimulated B cells and IFN-, granulocyte-macrophage colony-stimulating factor- and stem cell factor-stimulated MO7e cells. Kinetic studies revealed that the initial binding of FANCC was to nonphosphorylated STAT1 but that subsequently the complex moved to the receptor docking site, at which point STAT1 became phosphorylated. The STAT1 phosphorylation defect in FA-C cells was functionally significant in that IFN induction of IFN response factor 1 was suppressed and STAT1-DNA complexes were not detected in nuclear extracts of FA-C cells. We also determined that the IFN-gamma hypersensitivity of FA-C hematopoietic progenitor cells does not derive from STAT1 activation defects because granulocyte-macrophage CFU and erythroid burst-forming units from STAT1(-/-) mice were resistant to IFN-gamma. However, BFU-E responses to SCF and erythropoietin were suppressed in STAT(-/-) mice. Consequently, because the FANCC protein is involved in the activation of STAT1 through receptors for at least three hematopoietic growth and survival factor molecules, we reason that FA-C hematopoietic cells are excessively apoptotic because of an imbalance between survival cues (owing to a failure of STAT1 activation in FA-C cells) and apoptotic and mitogenic inhibitory cues (constitutively activated in FA-C cells in a STAT1-independent fashion).

Phenobarbital-induced brain growth retardation in artificially reared rat pups

Phenobarbital was administered daily to rat pups during the period of their brain growth spurt. A new technique for artificially rearing rat pups, using chronic intragastric feeding cannulas, was used to prevent drug-induced undernutrition. Rats, receiving neonatal phenobarbital, experienced a marked interruption of early brain growth, although their body weights reflected normal growth.

Neuroleptic malignant syndrome in children and adolescents

OBJECTIVE

Neuroleptic malignant syndrome (NMS) is a serious iatrogenic condition. This report reviews the world literature to characterize the syndrome and evaluate factors that promote early detection and effective intervention.

METHOD

The review identified 77 NMS cases (49 males, 27 females, 1 gender unknown); ages ranged from 0.9 to 18 years (mean 14.8 +/- 3.96). Univariate and multiple regression analyses were applied to 38 variables to identify early signs of the disorder, to identify correlates of outcome, and to evaluate treatments.

RESULTS

The duration of NMS spanned from 1 to 119 days. Nine percent of patients died and 20% resolved with serious sequelae. Patients receiving low-potency neuroleptics had a poorer outcome (p = .01). Fever was related to longer duration of illness (p = .03). Anticholinergics and bromocriptine were effective and without fatalities, but dantrolene was not useful in this sample of children and adolescents.

CONCLUSIONS

Early detection and appropriate interventions appear important in moderating the course and outcome of NMS.