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D Morin

Publications and source records attributed to D Morin.

At least 109 records · Page 6Linked to original sources
PubMed1993

Amino-acid sequence of rusticyanin from Thiobacillus ferrooxidans and its comparison with other blue copper proteins.

Rusticyanin, a copper protein characterized by a high redox potential (+680 mV) and a high stability at acidic pH, is involved in iron oxidation in Thiobacillus ferrooxidans. It has been characterized from a new strain and its amino-acid sequence has been determined and compared to two other rusticyanin sequences isolated from different strains. It comprises 155 amino acids and the alignment of the three rusticyanins shows a high degree of homology. Comparing the rusticyanins with six blue copper proteins which have a copper-I site in common, a consensus sequence containing Cys, His and Met in the C-terminal part of the protein and His-85 is proposed to be involved in the copper coordination. Secondary structure predictions are compared to three structures of copper proteins obtained by X-ray crystallography.

Amino Acid Sequence↗
PubMed1993

Distinct molecular origins for Denys-Drash and Frasier syndromes.

The direct involvement of the Wilm's tumor suppressor gene (WT1) in Denys-Drash syndrome through mutations within exons 8 or 9 has recently been established. The absence of such alterations in three patients with Frasier syndrome provides a molecular basis for distinguishing these two syndromes that are associated with streak gonads, pseudohermaphroditism and renal failure.

Base Sequence↗
PubMed1993

Changes in serotonin metabolism may elicit obstructive apnoea in the newborn rat.

1. Experiments were performed on anaesthetized newborn rats (aged 3-10 days) to know whether an increase in central serotonin levels might favour the occurrence of obstructive apnoeas as previously suggested by in vitro results from our group. 2. The levels of serotonin (5-HT), its precursor 5-hydroxytryptophan (5-HTP) and its metabolite, 5-hydroxyindole-acetic acid (5-HIAA), were analysed in cerebrospinal fluid samples collected at the level of the obex prior to and after intraperitoneal injection of L-tryptophan (50 mg kg-1) in sixty-eight anaesthetized newborn rats (control rats prior to injection and injected rats 15, 30 and 45 min after the injection). A significant increase in 5-HT and 5-HTP levels occurred 30 min after the injection, attesting to the activation of 5-HT biosynthesis. 3. The EMG activity of both the genioglossus and the diaphragm was recorded before and after L-tryptophan load (50 mg kg-1) in twenty-two newborn rats. After the injection of L-tryptophan, the amplitude of the integrated genioglossus activity decreased, or was even abolished, either during a few respiratory cycles or for long periods in twenty-one out of twenty-two animals. Recovery of the genioglossus activity occurred within 45-60 min. 4. The thoracic respiratory movements and the resulting upper airway pressure changes were recorded before and after L-tryptophan injection (50 mg kg-1) in sixty-two animals. In some litters (n = 7), most of the animals (21/25) displayed, within 20-40 min of the injection, recurrent episodes of obstructive apnoea often followed by central ones. These respiratory difficulties became severe and drastic, and led in two instances to respiratory distress and death. Lower doses of L-tryptophan (10 mg kg-1) did not induce any respiratory disorders unless these were potentiated by pargyline treatment (50 mg kg-1, n = 7). The obstructive apnoeas liable to occur after an L-tryptophan load (50 mg kg-1) were prevented by blocking the 5-HT receptor with methysergide (50 mg kg-1, n = 5) or by blocking the 5-HT biosynthesis by applying p-chlorophenylalanine (PCPA) pretreatment at birth (300 mg kg-1, n = 7). In other litters (n = 6), none of the eighteen newborn rats tested were affected by L-tryptophan, however, In five young adult rats, L-tryptophan again had no effect.4+ ĕ

5-Hydroxytryptophan↗
PubMed1993

Postnatal changes in the expression and distribution of pulmonary cytochrome P450 monooxygenases during Clara cell differentiation in rabbits.

Previous studies have indicated that both cytodifferentiation of Clara cells and the onset of pulmonary cytochrome P450 activity are postnatal events. However, the relationship between these two events during lung development remains poorly understood. To determine how these events interrelate, we examined rabbit Clara cells during postnatal differentiation, with the following goals in mind: 1) to identify the patterns of intracellular expression of cytochrome P450 monooxygenase isozymes 2B and 4B and cytochrome P450 reductase, 2) to describe the biogenesis of the organelles with which these isozymes are associated, namely smooth and rough endoplasmic reticulum, and 3) to compare the patterns of expression with cytochrome P450 activity in the whole lung over the same period. Lungs of rabbits ranging in age from 24 days gestational age (DGA) to 25 weeks postnatally were studied. Ultrastructural morphometry showed that smooth endoplasmic reticulum averaged < 5% of the Clara cell volume in late gestational (24-30 DGA) and neonatal rabbits [0-7 days postnatally (DPN)], grew to 20-30% of the cell volume in 14-21-DPN animals, and approximated adult levels (> 40%) in 28-DPN rabbits. In contrast, rough endoplasmic reticulum decreased from > 10% of the cell volume at 27 DGA to < 5% in adults. All postnatal animals showed considerable heterogeneity in the abundance of smooth endoplasmic reticulum among individual cells. Immunohistochemistry revealed that cytochrome P450 reductase appeared in Clara cells earlier (28 DGA) than did either isozyme 2B or 4B (1 DPN). Each antigen was detected first in the apical borders of the cells, then throughout the cytoplasm in a few cells by 7 DPN, and finally in adult abundance by 28 DPN. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting showed that cytochrome P450 protein concentrations increased postnatally. Cytochrome P450 heme protein was not detected spectrophotometrically in the lungs of animals younger than 3 DPN but increased to approximately 70% of adult levels by 28 DPN. Likewise, cytochrome P450 activity (measured as ethoxy- and pentoxyresorufin O-dealkylation) was not detected in animals younger than 2 DPN but increased to approximately 75% of adult levels by 28 DPN.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Evaluation of central adrenergic receptor signal transmissions after an antidepressant administration to the rat.

The effects of several antidepressants, amitriptyline, citalopram, desipramine, fluoxetine, maprotiline, mianserin, nialamide, nomifensine, tranylcypromine and viloxazine, on the accumulation of cyclic AMP and inositol monophosphates were studied in rat cerebral cortical slices. The two enzymatic systems were stimulated either by adrenergic agonists or by forskolin. Cyclic AMP and inositol monophosphates (IPs) formed were determined by a double label method. In vitro all drugs, except inhibitors of monoamine oxidase, nialamide and tranylcypromine, inhibited alpha 1-agonist-mediated production but did not modify the cyclic AMP accumulation. Otherwise, chronic desipramine but not citalopram administration decreased the accumulation of cyclic AMP (-39%) elicited by beta-adrenoceptor agonists; no change was observed in inositol phosphate metabolism after administration of these two drugs. These data support previous investigations showing a decrease in cyclic AMP production after chronic treatment with norepinephrine uptake blockers but do not confirm the hypothesis of a modification of alpha 1-adrenoceptor-stimulated inositol phosphate metabolism.

Animals↗
PubMed1992

Serotonergic modulation of the respiratory rhythm generator at birth: an in vitro study in the rat.

In order to investigate the mechanisms through which serotonin (5-HT) modulates the activity of the respiratory rhythm generator, respiratory activity was recorded from cervical ventral roots of the superfused isolated brainstem-spinal cord preparation of the newborn rat. Replacing the normal bathing medium by a medium containing 5-HT (30 microM) increased the respiratory frequency by 70% of the control value. Intact pontomedullary structures are necessary for this effect to take place, however, since the 5-HT-induced increases in respiratory frequency were no longer observed after elimination (section and electrolytic lesion) of the caudal ventro-lateral pons containing the A5 areas. Local applications of 5-HT (dual bath, microdialysis and microinjection experiments) revealed, however, that 5-HT acts at the medullary level and that its effects are not due to a diffuse action on all the neurons of the medullary respiratory centers but to a specific action focusing on structures located in the rostral ventro-lateral medulla.

Animals↗
PubMed1992

Serotonin enhances the beta-adrenergic response in rat brain cortical slices.

Serotonin increased the isoproterenol-induced cyclic AMP accumulation in rat brain cortical slices but did not itself stimulate the production of cyclic AMP in this area. This effect appeared to be inhibited by the 5-HT2 receptor antagonist, ritanserin. This potentiation was not observed in the hippocampus. These data reinforce the hypothesis of a coupling between the noradrenergic and serotonergic systems, which may be involved in the mechanism of action of antidepressant drugs.

Animals↗
PubMed1992

Compared effects of serotonin on cervical and hypoglossal inspiratory activities: an in vitro study in the newborn rat.

1. Experiments were performed on the brain stem-spinal cord preparation of newborn rats, in which the phrenic and hypoglossal nerves continue to show rhythmic respiratory activity in vitro, in order to compare the effects of serotonin (5-HT) on both activities and to analyse the mechanisms responsible for the depression by 5-HT of the hypoglossal activity. 2. Under control conditions, simultaneous recordings of the inspiratory discharges of hypoglossal and cervical roots showed that the two bursts did not start simultaneously and had different patterns (time-to-peak and peak values); this suggests that both pools of motoneurons did not share the same central drive(s). 3. Adding 5-HT and related agents to the bathing medium delayed and depressed the hypoglossal inspiratory discharge via activation of 5-HT2 receptors since these effects were elicited by 5-HT2 agonists (alpha-methyl-5-HT and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane-HCl (DOI)) but not by 5-HT1 agonists (RU 24969 and (+/-)-8-hydroxy-2-(di-N-propylamino)tetralin hydrobromide (8-OH-DPAT)). The 5-HT depression of the hypoglossal discharge was prevented by applying a pretreatment with a specific 5-HT2 antagonist (ketanserin). Parallel to the hypoglossal discharge decrease, 5-HT elicited a permanent cervical root discharge along with a persistent inspiratory bursting. Adding the 5-HT precursor L-tryptophan to the bathing medium depressed the hypoglossal (XII) discharge without affecting the cervical one. 4. Local application of 5-HT within the hypoglossal motor nucleus decreased the hypoglossal output, revealing that the 5-HT depression of the hypoglossal discharge was at least partly mediated by the 5-HT effects at the level of the motoneurons. Local application of 5-HT within the cervical motor nucleus elicited a permanent firing in the cervical root with a persistent inspiratory bursting. 5. Intracellular analysis confirmed the existence of differences in central respiratory drive between cervical and hypoglossal motoneurons under control conditions, as well as differences in response to 5-HT. All the hypoglossal motoneurons became silent under 5-HT bathing, and showed no change in the input membrane resistance, a moderate depolarization, and a delayed central respiratory drive with a decreased amplitude. The cervical motoneurons became more active during inspiration, despite a decrease in the amplitude of the central respiratory drive, which was compensated for by a large depolarization and an increased input membrane resistance. Some cervical motoneurons even fired at a low rate during expiration.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Molecular analysis of the sex-determining region from the Y chromosome in two patients with Frasier syndrome.

In the Frasier syndrome there is an association between XY gonadal dysgenesis and chronic renal failure. Owing to an observed sex reversal, the Y chromosomes of two girls with this syndrome have been analyzed. Using molecular-biology techniques, no major alterations of the known sex-determining area of the Y chromosome were found. Furthermore, the sequence did not reveal impairment of the recently described testis-determining factor SRY. These data suggest that in the Frasier syndrome, XY sex reversal and renal failure could be the result of either faulty gene(s) located downstream in the sex differentiation pathway during embryogenesis, or impaired SRY regulation. Preliminary results on the Wilms' tumor suppressor gene WT1, a candidate for acting downstream to SRY, are also provided.

Adolescent↗
PubMed1992

Mechanisms and pathology of monocrotaline pulmonary toxicity.

Monocrotaline (MCT) is an 11-membered macrocyclic pyrrolizidine alkaloid (PA) that causes a pulmonary vascular syndrome in rats characterized by proliferative pulmonary vasculitis, pulmonary hypertension, and cor pulmonale. Current hypotheses of the pathogenesis of MCT-induced pneumotoxicity suggest that MCT is activated to a reactive metabolite(s) in the liver and is then transported by red blood cells (RBCs) to the lung, where it initiates endothelial injury. While several lines of evidence support the requirement of hepatic metabolism for pneumotoxicity, the mechanism and relative importance of RBC transport remain undetermined. The endothelial injury does not appear to be acute cell death but rather a delayed functional alteration that leads to disease of the pulmonary arterial walls by unknown mechanisms. The selectivity of MCT for the lung, as opposed to that of other primarily hepatotoxic PAs, appears likely to be a consequence of the differences in hepatic metabolism and blood kinetics of MCT. A likely candidate for a reactive metabolite of MCT is the dehydrogenation product monocrotaline pyrrole (MCTP). Secondary or phase II metabolism of MCT through glutathione (GSH) conjugation has been characterized recently and appears to represent a detoxification pathway. The role of inflammation in the progression of MCT-induced pulmonary vascular disease is uncertain. Both perivascular inflammation and platelet activation have been proposed as processes contributing to the response of the vascular media. This review presents the experimental evidence supporting these hypotheses and outlines additional questions that arise from them.

Animals↗
PubMed1992

Labelling of rat brain beta-adrenoceptors: (3H)CGP-12177 or (125I)iodocyanopindolol?

Binding of (125I)iodocyanopindolol (ICYP) and (3H)CGP-12177 to rat brain homogenates was characterized and compared. ICYP was shown to bind to both beta-adrenergic and serotonin1B (5HT1B) receptors whereas (3H)CGP-12177 only labelled the first ones. The addition of 10 microM serotonin (5HT) prevented ICYP binding to 5HT receptors and under these experimental conditions both ligands labelled a similar total number of beta-adrenoceptors in the different rat brain regions. ICYP displayed a higher affinity for cerebellar (mainly beta 2-subtype) than for cerebral cortex beta-adrenoceptors (mainly beta 1-subtype) suggesting a subtype selectivity. A multiple displacement binding approach using CGP-20712A, a beta 1-subtype ligand, as competitor revealed a 2.6 fold selectivity of ICYP for the beta 2-adrenoceptor subtype. On the other hand, (3H)CGP-12177 binds only to beta-adrenoceptors and is not subtype selective in the rat brain homogenate. Considering both its high specificity and its lack of subtype selectivity (3H)CGP-12177 seems to be a more suitable ligand than ICYP to non-selectively label beta-adrenoceptors in rat brain.

Adrenergic beta-Antagonists↗
PubMed1992

[Piezoelectric extracorporeal lithotripsy in children: first results and reflections after 18 sessions].

From 1988 to 1990, we treated 13 children between the ages of 2 and 15 years with stones of the upper urinary tract. These stones were treated by means of 18 sessions of piezoelectric extracorporeal lithotripsy: 14 under general anaesthesia and 4 without even any analgesia. We obtained an 84.5% success rate with no particular adverse effects. These results are similar to those reported for hydroelectric or electromagnetic shock wave lithotripsy, which are associated with a higher morbidity. The efficacy of extracorporeal lithotripsy in paediatrics is remarkable, but clinical studies in adults as well as animal experimentations have demonstrated severe renal contusion and do not formally exclude the possibility of delayed complications. At the present time, this technique should therefore be used very cautiously and must be accompanied by systematic prevention of recurrent stones.

Adolescent↗
PubMed1992

Relationship of cytochrome P-450 activity to Clara cell cytotoxicity. I. Histopathologic comparison of the respiratory tract of mice, rats and hamsters after parenteral administration of naphthalene.

The purpose of this study was to define the sites of cytotoxicity within the respiratory tract (nasal cavity and tracheobronchial airway tree) resulting from administration of naphthalene, an organic chemical whose cytotoxic properties require metabolic activation via the cytochrome P-450 monooxygenase system. Three species were compared: mouse, hamster and rat. Naphthalene was administered in corn oil at these doses: mouse (0-400 mg/kg), hamster (0-800 mg/kg) and rat (0-1600 mg/kg), and the animals were sacrificed 24 hr later. In mice, naphthalene produced Clara cell cytotoxicity at 50 mg/kg. The primary alteration was swelling and vacuolation of Clara cells in terminal bronchioles. At 100 mg/kg, the number of terminal bronchioles with vacuolated Clara cells and the number of Clara cells within terminal bronchioles which showed vacuolation increased. At 200 and 300 mg/kg, almost all of the nonciliated cells lining terminal bronchioles in mice were exfoliated and necrotic. In contrast, there was no apparent effect on Clara cells or ciliated cells of terminal bronchioles in rats treated with up to 1600 mg/kg. At 800 mg/kg, minor alterations in Clara cells in some terminal bronchioles were observed in hamsters. At 300 mg/kg, lobar bronchus and trachea showed swelling 'and vacuolation of nonciliated cells in mice, but no detectable change at 200 mg/kg or below. The trachea and lobar bronchus were unaffected in rats, but showed cytotoxic changes in hamsters. In the nasal cavity of mice, cytotoxicity was observed only in the olfactory epithelium and only in animals treated with 400 mg/kg. There were minimal alterations in the respiratory epithelium. The only epithelial population showing cytotoxicity in the rat was the olfactory epithelium. Complete necrosis was observed at 200 mg/kg and higher. In the hamster there was no discernible alteration in the olfactory epithelium at 100 and 200 mg/kg. At 400 mg/kg, the olfactory epithelium was necrotic. Naphthalene injury to the tracheobronchial epithelium of the mouse is: 1) Clara cell specific; 2) dose-related in the terminal bronchiole; and 3) involves more proximal airways in a dose-dependent fashion. The tracheobronchial epithelium of the rat is refractory to Clara cell injury even at the LD50, but proximal airways are more susceptible than distal airways in the hamster. The nasal cavity shows specific injury in one zone (olfactory epithelium) in a dose and species specific manner. The susceptibility to naphthalene-induced injury in the olfactory epithelium does not correlate with the susceptibility of Clara cells in more distal portions of the respiratory tract.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Relationship of cytochrome P450 activity to Clara cell cytotoxicity. II. Comparison of stereoselectivity of naphthalene epoxidation in lung and nasal mucosa of mouse, hamster, rat and rhesus monkey.

Naphthalene, a murine Clara cell cytotoxicant, is metabolized by cytochrome P450 monooxygenases to unstable, chiral epoxide metabolites which can conjugate with glutathione in the presence of glutathione transferases. Analysis of the three diasteriomeric glutathione adducts produced from conjugation of naphthalene oxides was used in these studies to characterize the stereochemistry of naphthalene epoxidation in preparations of nasal mucosa, lung and liver of the mouse, rat, hamster and monkey. The highest rates of naphthalene metabolism were observed in mouse lung and liver microsomal incubations. Rat, hamster and monkey lung microsomal preparations metabolized naphthalene at 12, 37, and 1%, respectively, of the rate observed in mouse lung. The ratio of chiral epoxides produced in microsomal incubations was dependent upon the concentration of naphthalene. At high substrate concentrations (0.25-1.0 mM), the ratio of 1R,2S- to 1S,2R-naphthalene oxide, as assessed by the glutathione adducts generated (adduct 2/adducts 1 + 3), in murine lung microsomal incubations was 10:1 and at low concentrations (0.062 mM and below) varied from 13.8:1 to 30:1. In contrast, the ratio of 1R,2S- to 1S,2R-naphthalene oxide produced in murine liver microsomes varied from 1:1 at high substrate concentrations to 5:1 at low substrate concentrations. The ratio of naphthalene oxides was unaffected by the concentration of glutathione in the incubation. In contrast to the preferential formation of 1R,2S-naphthalene oxide observed in mouse lung microsomal preparations, lung microsomes derived from the rat, hamster and monkey yielded 1R,2S- to 1S,2R-epoxide ratios of 0.48, 0.61 and 0.12, respectively, at 0.5 mM naphthalene.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Red blood cells augment transport of reactive metabolites of monocrotaline from liver to lung in isolated and tandem liver and lung preparations.

Monocrotaline (MCT) is a pyrrolizidine alkaloid that causes pulmonary hypertension in rats by mechanisms which remain largely unknown. MCT is thought to be activated in the liver to a reactive intermediate that is transported to the lung where it causes endothelial injury. Our previous pharmacokinetic work demonstrated significant sequestration of radioactivity in red blood cells (RBCs) of rats treated with [14C]MCT. To determine whether this RBC sequestration might be important in the transport of reactive MCT metabolites, we compared the effect of inclusion of RBCs in the perfusion buffer on the extent of covalent binding of [14C]MCT to rat lungs in tandem liver-lung preparations. The potential effect of RBCs in stabilizing reactive intermediates was evaluated by preperfusion of isolated liver preparations with [14C]MCT with and without RBCs, separation and washing of the RBC fraction, and subsequent (90 min later) perfusion of washed RBCs or buffer alone in isolated perfused lungs. Covalent binding to lung tissues was determined by exhaustive methanol/chloroform extractions of unbound label from homogenized lung tissue followed by scintillation counting of residual 14C. Covalent binding was expressed as picomole MCT molecular weight equivalents/mg protein. Comparison of the relative capability of these isolated organ preparations for conversion of MCT to polar metabolites was done by extraction and HPLC analysis of perfusate at the end of the experiment. Isolated livers converted 65-85% of MCT to polar metabolites compared with less than 5% conversion in the isolated lungs. Inclusion of RBCs in the buffer of tandem lung liver preparations perfused with 400 microM [14C]MCT increased the covalent binding to the lung from 97 +/- 25 (buffer alone) to 182 +/- 36 (buffer + RBC) pmol/mg protein. At the end of these perfusions, RBCs contained 1552 +/- 429 pmol/mg hemoglobin of which 333 +/- 98 pmol/mg hemoglobin resisted exhaustive solvent extraction. After 90 min at room temperature, buffer with 400 microM [14C]MCT preperfused in isolated livers resulted in covalent binding to isolated perfused lung of 0.8 +/- 0.4 pmol/mg protein while washed RBCs isolated from buffer of similar liver preperfusions preparations resulted in 53 +/- 7 pmol/mg protein bound to lung. Control groups perfused with 400 microM [14C]MCT in buffer or buffer + RBCs through isolated lungs only resulted in covalent binding of 2 +/- 1 or 1 +/- 0.6 pmol/mg protein respectively. We conclude: (1) RBCs significantly augment the transport of lung reactive MCT metabolites from the liver to the lung.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

5-Hydroxytryptamine modulates central respiratory activity in the newborn rat: an in vitro study.

Respiratory activity was recorded in cervical ventral roots during in vitro experiments performed on superfused brainstem-cervical cord preparations from newborn rats aged 0-3 days. The effects of 5-HT agents added to the bathing medium on respiratory frequency were analysed. Adding 5-hydroxytryptamine (5-HT, 30 microM) or 5-HT precursors (either L-tryptophane, L-Trp, 50 microM, or 5-hydroxytryptophane, 5-HTP, 50 microM) elicited increases in respiratory frequency. Precursor effects were blocked by a 5-HT antagonist (methysergide, 70 microM) and significantly reduced by pretreatment with a 5-HT synthesis inhibitor (p-chlorophenylalanine, PCPA, i.p. 300 mg/kg at birth). Adding drugs known to block (methysergide, 40 microM) or to potentiate (fluoxetine, 100 microM) any endogenous 5-HT effects decreased or increased respiratory frequency, respectively. These results suggest that the 5-HT biosynthesis mechanisms remain functional in vitro and that a continuous release of endogenous 5-HT exerts excitatory modulation on the respiratory rhythm generator.

Animals↗
PubMed1991

Serotonin and cervical respiratory motoneurones: intracellular study in the newborn rat brainstem-spinal cord preparation.

Previous experiments performed in the in vitro newborn rat brainstem-spinal cord preparation reported that the addition of serotonin (5-HT, 30-50 microM) to the bathing medium induced increases in the respiratory frequency and a large tonic discharge on all the cervical ventral roots. The aim of the present work was to define whether the 5-HT-induced tonic discharge involved respiratory or non-respiratory motoneurones. Intracellular recordings demonstrated that cervical (C2) motoneurones (n = 27) were depolarized by 5-HT but that the 5-HT-induced tonic discharge was mainly due to recruitment of silent motoneurones (n = 18) which fired permanently (15/18; 17 +/- 3 Hz) under 5-HT. The respiratory motoneurones (n = 9) retained a phasic inspiratory discharge (5/9), even if some (4/9) occasionally exhibited a few spikes during expiration. Therefore, it is concluded that the 5-HT-induced tonic discharge is unlikely to have functional significance in respiration.

Animals↗