Biomedical subjects

M Hamon

Publications and source records attributed to M Hamon.

At least 145 records · Page 8Linked to original sources

PubMed1997

Immuno-localization of serotonin 5-HT6 receptor-like material in the rat central nervous system.

In order to map the recently cloned serotonin 5-HT6 receptor in the rat brain and spinal cord, polyclonal antibodies were raised against a synthetic octadecapeptide corresponding to a specific portion (Leu398-Val415) of the C-terminal domain of this receptor. Antibodies were detected by enzyme-linked immunosorbent assay as soon as one month after the first injection to rabbits of the peptide coupled to keyhole limpet hemocyanin. Immunoautoradiographic experiments with antibodies affinity-purified on Affi-Gel coupled to the peptide antigen showed that 5-HT6-like immunoreactive material was abundant in the olfactory tubercle (plexiform layer), cerebral cortex (frontal and entorhinal areas), nucleus accumbens, striatum, hippocampus (strata oriens and radiatum of the CA1 area, molecular layer of the dentate gyrus) and the molecular layer of the cerebellum. A specific immunolabeling, but at moderate intensity, was also observed in the thalamus, substantia nigra, superficial layer of the superior colliculus, motor trigeminal nucleus and facial nucleus. In contrast, no 5-HT6-like immunoreactive material was found in white matter areas. As the regional distribution of 5-HT6 receptor-like immunoreactivity matched generally that previously found for the 5-HT6 receptor mRNA, one could infer that this receptor protein is addressed in the vicinity of its synthesis site, i.e. on somas and/or dendrites. Indeed, immunohistochemistry at the light and electron microscope level showed that 5-HT6-like immunoreactivity was associated with dendritic processes in both the striatum and the dentate gyrus of the hippocampus. The relative abundance of 5-HT6 receptor-like immunoreactivity in extrapyramidal and limbic areas suggests that 5-HT6 receptors may participate in the serotoninergic control of motor function and mood-dependent behavior, respectively.

Animals↗

PubMed1997

Stenting within a stent for treatment of residual dissection.

We describe the management of residual dissection protruding through the struts of a Wiktor stent (Medtronic Inc., Minneapolis, MN) implanted in bailout conditions. In general, negotiating a stent through an expanded Wiktor stent is not recommended, but using this strategy, an AVE (Advanced Vascular Engineering, Santa Clara, CA) Micro stent was successfully implanted inside the Wiktor stent, leading to an excellent final angiographic result.

Aortic Dissection↗

PubMed1997

Early versus late coronary stenting following acute myocardial infarction: results of the STENTIM I Study (French Registry of Stenting in Acute Myocardial Infarction).

This study was undertaken to determine the feasibility and safety of coronary stenting in acute myocardial infarction (AMI). In AMI, primary percutaneous transluminal coronary angioplasty (PTCA) is accepted as the preferred method of reperfusion for patients presenting at highly experienced centres. Until recently, however, stenting has been avoided during AMI because of a potential high risk of thrombosis. This prospective observational study carried out in 20 centres and included 648 consecutive patients who underwent PTCA with stent implantation for AMI. Of these 648 patients, 269 (41.5%, Group 1) were dilated early (< 24 hr) after the onset of the symptoms (75% treated by direct PTCA) and 379 (58.5%, Group 2) were dilated between 24 hr and 14 days after AMI. Combined therapy with ticlopidin and aspirin was used after the procedure. Bailout stenting occurred more often in Group 1 than in Group 2 (17% vs. 9.5%)(P < 0.05). Angiographic successful stenting was similar in both groups of patients (96% vs. 97%). During the hospital follow-up period, stent thrombosis occurred in eight patients (3%) in Group 1 and in six patients (1.6%) in Group 2 (NS). There was 14 deaths (5.2%) in Group 1 and 11 deaths (3.9%) in Group 2 (NS). After multivariate analysis bailout stenting was identified as the sole predictor of stent thrombosis (P < 0.0001). Vascular access-site complications occurred in six patients (1%) with no difference between the two groups. This study indicates that patients who receive a coronary stent in AMI can be managed safely with antiplatelet therapy. Randomized studies are needed to determine the precise indication for coronary stenting as an adjunct to primary PTCA.

Adult↗

PubMed1997

Fluoxetine-induced desensitization of somatodendritic 5-HT1A autoreceptors is independent of glucocorticoid(s).

Previous in vitro studies showed that glucocorticoid receptor activation (notably by corticosterone) could induce a functional desensitization of somatodendritic 5-HT1A autoreceptors in the dorsal raphe nucleus [Laaris et al. (1995) Neuropharmacology 34:1201-1210], similar to that due to in vivo subchronic treatment with a 5-HT reuptake inhibitor, such as fluoxetine, in rats. In the present study, we investigated whether a link might exist between these effects, i.e., whether glucocorticoid receptor activation could be responsible for the fluoxetine-induced desensitization of 5-HT1A autoreceptors. In vitro recording in the dorsal raphe nucleus of brain-stem slices showed that subchronic treatment with fluoxetine (5 mg/kg intraperitoneally (i.p.), daily for 3-7 days) significantly reduced the potency of the 5-HT1A receptor agonist ipsapirone to inhibit the firing rate of serotoninergic neurons. Parallel experiments in adrenalectomized and sham-operated rats indicated that subchronic fluoxetine treatment produced a similar shift to the right of the ipsapirone inhibition curve in both groups of animals. Furthermore, the subchronic blockade of glucocorticoid receptors by RU 38486 (25 mg/kg subcutaneously (s.c.), daily) in intact rats treated with fluoxetine (5 mg/kg i.p., daily for 3 days) did not affect the ability of the latter treatment to reduce the potency of ipsapirone to inhibit the firing of serotoninergic neurons. These data suggest that glucocorticoid receptors (and their possible activation by corticosterone) are not involved in the functional desensitization of somatodendritic 5-HT1A autoreceptors, which occurs during long-term treatment with a serotonin reuptake inhibitor such as fluoxetine.

Adrenal Glands↗

PubMed1997

Expression, purification, and characterization of rat aromatic L-amino acid decarboxylase in Escherichia coli.

A cDNA encoding rat aromatic L-amino acid decarboxylase (AADC) was successfully expressed in Escherichia coli using a T7 RNA polymerase expression system. Two types of expression vectors were tested and revealed to be equivalent to produce AADC. The enzyme was purified in both cases. The ratio of recovery of the pure active recombinant protein was better when the purification of the protein was made easier by addition of a short His-Tag at the C-terminal moiety of AADC, as achieved in the case of pET-20b+ vector expression. Spectral characteristics of the bound pyridoxal-5'-phosphate were essentially identical to the spectral properties of rat AADC. Kinetic constants Km and Vmax of recombinant AADC for the natural substrates L-dihydroxyphenylalanine and 5-hydroxytryptamine were 0.14 mM and 8444 U/mg, and 0.066 mM and 1813 U/mg, respectively. These values were in good agreement with previously reported values for AADC of the rat and other mammalian species.

5-Hydroxytryptophan↗

PubMed1997

Atypical in vitro and in vivo binding of [3H]S-14506 to brain 5-HT1A receptors.

The tritiated derivative of the potent 5-HT1A receptor agonist S-14506 ¿1[2-(4-fluorobenzoylamino)ethyl]-4-(7-methoxynaphtyl)pipera zine¿ was tested for its capacity to selectively label the serotonin 5-HT1A receptors both in vitro in the rat and the mouse brain, and in vivo in the mouse. In vitro studies showed that the pharmacological profile and the distribution of [3H]S-14506 specific binding sites (Kd = 0.15 nM) in different brain regions matched perfectly those of the prototypical 5-HT1A receptor ligand [3H]8-OH-DPAT. However, in the three regions examined (hippocampus, septum, cerebral cortex), the density of [3H]S-14506 specific binding sites was significantly higher (+66-90%) than that found with [3H]8-OH-DPAT. Whereas the specific binding of [3H]8-OH-DPAT was markedly reduced by GTP and Gpp(NH)p and increased by Mn2+, that of [3H]S-14506 was essentially unaffected by these compounds. In addition, the alkylating agent N-ethylmaleimide was much less potent to inhibit the specific binding of [3H]S-14506 than that of [3H]8-OH-DPAT. Measurement of in vivo accumulation of tritium one hour after i.v. injection of [3H]S-14506 to mice revealed marked regional differences, with about 2.5 times more radioactivity in the hippocampus than in the cerebellum. Pretreatment with 5-HT1A receptor ligands prevented tritium accumulation in the hippocampus but not in the cerebellum. Autoradiograms from brain sections of injected mice confirmed the specific in vivo labeling of 5-HT1A receptors by [3H]S-14506, therefore suggesting further developments with derivatives of this molecule for positron emission tomography in vivo in man.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1997

Antidepressant treatment in helpless rats: effect on the electrophysiological activity of raphe dorsalis serotonergic neurons.

Chronic treatment with antidepressants renders serotonergic neuronal firing less sensitive to the inhibitory effect of serotonin (5-HT) reuptake blockers in the rat, and this has been considered as a major correlate of the therapeutic action of these drugs. We investigated whether the same mechanisms could be evidenced in an experimental model of depression, the learned helplessness paradigm. Rats rendered helpless by a single session of inescapable electrical footshocks exhibit, for several days, depression-like behavioural deficits which can be reversed by sub-chronic, but not acute, treatment with antidepressants. Recording of serotonergic neurons in the dorsal raphe nucleus revealed that, under baseline conditions, the spontaneous firing was similar in helpless rats and in non-helpless controls. However, neurons in the former group exhibited an enhanced sensitivity to the inhibitory action of the 5-HT reuptake blocker, citalopram (ED50 = 0.18 +/- 0.02 mg/kg IV in helpless rats versus 0.27 +/- 0.03 mg/kg IV in controls, P < 0.05). Treatment with zimeldine during 3 consecutive days induced in both helpless and control rats, a decrease in the inhibitory response of serotonergic neurons to the citalopram challenge, which resulted in a normalization of the neuronal reactivity in the helpless group (ED50 = 0.31 +/- 0.03 mg/kg IV). Since this adaptive phenomenon parallels the behavioural improvement induced by the repeated administration of zimeldine and other antidepressants in helpless rats, it might be considered as a crucial event in the mechanism of therapeutic action of these drugs.

Action Potentials↗

PubMed1997

Medial temporal lobe atrophy in memory disorders.

Medial temporal lobe atrophy determined by temporal lobe oriented computed tomography (CT), 1 year before death, is strongly associated with histopathologically confirmed Alzheimer's disease (AD). The aim of this study was to assess the diagnostic accuracy of medial temporal lobe measurement for the diagnosis of AD in patients referred to a memory disorders clinic, especially those at an early stage of the disease. CT oriented to the temporal lobe was performed in 333 subjects aged 41-93 years consecutively recruited in a Memory Disorders Clinic: 124 had probable AD, Mini Mental State score (MMS) = 17 (8); 50 possible AD [MMS = 21 (5)]; and 119 patients had miscellaneous memory disorders [MMS = 22 (7): frontotemporal lobe dementia, subcortical dementia, cortical Lewy body disease, vascular dementia, Korsakoff syndrome, focal atrophy, etc.]. There were also 19 anxious/depressed patients [MMS = 29 (1)] with normal performance on memory tests, and 21 controls. The minimum width of the medial temporal lobe was measured. The best cut-off to distinguish AD patients from non-AD patients was 11.5 mm, in agreement with data in the literature. At this threshold, 84% of probable AD patients had a positive test and 90% of controls and anxious/depressed patients had a negative test. For the diagnosis of probable AD, sensitivity of the measurement was 0.81, specificity 0.95, predictive positive value 0.99, predictive negative value 0.45, and diagnostic accuracy 0.83. The test was positive in half the possible AD patients, and half those with miscellaneous memory disorders. It was negative in all anxious/depressed patients. Therefore, temporal lobe oriented CT might be a valuable tool for assessment of medial temporal lobe atrophy in AD routine practice.

Adult↗

PubMed1997

Vasoactive intestinal polypeptide microinjections into the oral pontine tegmentum enhance rapid eye movement sleep in the rat.

Rapid eye movement sleep can be elicited in the rat by microinjection of the cholinergic agonist carbachol into the oral pontine reticular nucleus. Intracerebroventricular administration, during the light period, of vasoactive intestinal peptide enhances rapid eye movement sleep in several species. Since this peptide is co-localized with acetylcholine in many neurons in the central nervous system, it was assumed that the oral pontine tegmentum could also be one target for vasoactive intestinal peptide to induce rapid eye movement sleep. This hypothesis was tested by recording the sleep-wakefulness cycle in freely-moving rats injected with vasoactive intestinal peptide or its fragments (1-12 and 10-28) directly into the oral pontine reticular nucleus. when administered into the posterior part of this nucleus, vasoactive intestinal peptide at 1 and 10 ng (in 0.1 microliter of saline), but not its fragments, induced a 2-fold enhancement of rapid eye movement sleep during 4 h, at the expense of wakefulness. At the dose of 10 ng, a significant increase in rapid eye movement sleep persisted for up to 8 h. Moreover, when the peptide was injected into the centre of the positive zone, rapid eye movement sleep was enhanced during three to eight consecutive days. These data provide the first evidence that rapid eye movement sleep can be elicited at both short- and long-term by a single intracerebral microinjection of vasoactive intestinal peptide. Peptidergic mechanisms, possibly in association with cholinergic mechanisms, within the caudal part of the oral pontine reticular nucleus may play a critical role in the long-term regulation of rapid eye movement sleep in rats.

Animals↗

PubMed1997

Distribution pattern and ultrastructural localization of Rxt1, an orphan Na+/Cl(-)-dependent transporter, in the central nervous system of rats and mice.

The cellular and subcellular localization of Rxt1 protein, an orphan Na+/Cl(-)-dependent transporter, was investigated in the central nervous system of rats and mice, with rabbit polyclonal antibodies specifically directed against its C-terminal region. At the light microscope level, the distribution of Rxt1, visualized by the immunoperoxidase method, was found to be similar in rats and mice. Labelled elements were present in numerous gray matter regions of the central nervous system, from the olfactory bulb to the spinal cord. In all labelled regions, immunoreactivity was confined to the neuropil where both a diffuse labelling of low intensity and an intense punctate staining were noted. To further identify the nature of the cellular elements bearing the punctate staining, possible changes in this labelling pattern were investigated: (i) in deep cerebellar nuclei and lateral vestibular nucleus of the Lurcher mutant mouse, in which all cerebellar Purkinje cells are missing and (ii) in the rat cervical spinal cord, 10 days after multiple resections of dorsal roots. The vast majority of the punctate structures, delineating the neuronal perikaryal and stem dendritic contours, had disappeared in the mutant mouse, providing evidence that they belong to Purkinje cell axon terminals. In rhizotomized rats, the intense labelling in laminae I and III had disappeared, demonstrating that it occurred in subclasses of axonal projections of primary afferent fibres. These results strongly suggest that Rxt1 is present in presynaptic axon terminals. The electron microscopic study was carried out in the hippocampus, cerebellum and lateral vestibular nucleus of control mice, where Rxt1-labelled punctate structures were found to be abundant. Immunostaining was confined to axon terminals, particularly in hippocampal and cerebellar mossy fibres and in Purkinje cell axonal terminations of the cerebellar deep nuclei and lateral vestibular nucleus. In the cerebellar cortex, axon terminals belonging to inhibitory local circuit neurons (basket and Golgi cells), were free of labelling. The observations reported in this study have shown that: (1) The Rxt1 transporter is neuron-specific, and is expressed by only some classes or even subclasses of neuronal systems. (2) This transporter can be encountered in excitatory axons using glutamate as neurotransmitter (hippocampal and cerebellar mossy fibres: primary afferent fibres), as well as in inhibitory axons known by their GABAergic nature (Purkinje cell axon terminals) where it might be involved in the re-uptake process of one or several molecules released from corresponding terminals.

Animals↗

PubMed1997

A prospective randomized study of three types of platelet concentrates in patients with haematological malignancy: corrected platelet count increments and frequency of nonhaemolytic febrile transfusion reactions.

We prospectively randomized 51 patients with haematological malignancy requiring platelet concentrates (PCs) to receive either single donor platelet-pheresis products (SD-PC), PCs made from pooled buffy coats (BC-PC) or pooled units of platelets made by the platelet-rich plasma method (PRP-PC). The leucocyte content of each type of PC was 0.33 (0.03-13.5), 5.68 (0.19-99.0) and 365 (65-910) x 10(6); median (range), respectively; P < 0.0001. All red cell transfusions were leucodepleted by filtration. Statistical comparison of the probability of the occurrence of a nonhaemolytic febrile transfusion reaction (NHFTR) following transfusion of PCs in patients in each group showed a significant decrease for the SD-PC and BC-PC groups (0.031 and 0.038, respectively) when compared with PRP-PC (0.171); P = 0.0001. The actual corrected platelet count increments (CCI) at 1-6 and 18-24 h post-transfusion for all three types of PC did not differ significantly. We conclude that transfusion of PRP-PC is associated with a significant increase in NHFTR.

Adult↗

PubMed1997

Stress-induced alterations of somatodendritic 5-HT1A autoreceptor sensitivity in the rat dorsal raphe nucleus--in vitro electrophysiological evidence.

Somatodendritic 5-HT1A autoreceptors play a key role in the control of the electrical and metabolic activity of serotoninergic neurons in the dorsal raphe nucleus. These neurons also possess intracellular glucocorticoid receptors which may be involved in the well established modulation of serotonin (5-hydroxytryptamine, 5-HT) metabolism by corticosterone in stressed animals. The possible mediation by somatodendritic 5-HT1A autoreceptors of such corticosterone-dependent changes in serotoninergic neuron activity was investigated using an in vitro electrophysiological approach. 5-HT1A autoreceptor-mediated inhibition of the firing of serotoninergic neurons was examined in brain stem slices from rats whose serum corticosterone concentrations had been markedly increased (+100-200%) by two different stressful conditions. Immobilization for 30 or 90 min (restraint stress) did not modify the concentration-dependent inhibition of the firing of serotoninergic neurons by the 5-HT1A receptor agonist ipsapirone. In contrast, placing the rats in novel uncontrolled environmental conditions for 16 h significantly reduced the cell response to ipsapirone, indicating a decreased sensitivity of somatodendritic 5-HT1A autoreceptors. Such a change was not observed in adrenalectomized rats subjected to the same stressful conditions. These data show that some forms of stress can reduce the 5-HT1A autoreceptor-dependent inhibitory control of the electrophysiological activity of serotoninergic neurons in the dorsal raphe nucleus. Both the nature and duration of stress seem to be critical factors for triggering the (corticosterone-dependent) mechanism(s) responsible for the functional desensitization of 5-HT1A autoreceptors in stressed rats.

Adrenalectomy↗

PubMed1997

Association of angiotensin converting enzyme and angiotensin II type 1 receptor genotypes with left ventricular function and mass in patients with angiographically normal coronary arteries.

OBJECTIVE: To analyse the potential association of the angiotensin converting enzyme (ACE) and angiotensin II type 1 receptor (AT1R) gene polymorphisms on left ventricular function and mass in patients with normal coronary arteries. DESIGN: Consecutive sample. SETTING: University hospital. SUBJECTS: 141 consecutive white patients referred for coronary angiography and with angiographically normal coronary arteries. Patients with valvar diseases, cardiomyopathies, or a history of myocardial infarction were excluded. MAIN OUTCOME MEASURES: Left ventricular variables were measured for all patients. The ACE and AT1R genotypes were determined with a polymerase chain reaction based protocol using DNA prepared from white blood cells. A general linear model was used to compare data according to the ACE and to the AT1R genotypes. RESULTS: A strong association was observed between left ventricular mass and systemic hypertension (mean (SD) hypertension: 114 (31) g/m2; no hypertension 98 (23) g/m2; P < 0.003). However, no influence of ACE and AT1R polymorphisms on left ventricular mass was found, regardless of systemic hypertension. The subjects homozygous for the AT1R CC mutation had a significantly lower ejection fraction than those with allele A (AC+AA) (mean (SD) 62(12)% and 68(10)%, respectively, P < 0.05). No synergistic interaction of ACE and AT1R gene polymorphisms on left ventricular function and mass was found. CONCLUSIONS: These data do not support an association of the ACE and AT1R genotypes on left ventricular hypertrophy in white patients with normal coronary arteries.

Angiotensin II↗

PubMed1997

bFGF restores endothelium-dependent responses of hypercholesterolemic rabbit thoracic aorta.

In animal models, a hypercholesterolemic diet induces areas of deendothelialization and impairs endothelium-dependent vasorelaxation. Angiogenic growth factors increase endothelial cell growth in vivo. This study was thus designed to test the hypothesis that chronic administration of basic fibroblast growth factor (bFGF) in hypercholesterolemic rabbits might restore normal physiological responses to endothelium-dependent agonists. After feeding on a 2% cholesterol diet for 6 wk, 14 New Zealand White rabbits received twice-weekly intravenous boluses of either 2.5 microg bFGF (hypercholesterolemic bFGF group, n = 6) or placebo (hypercholesterolemic control group, n = 8) for 3 wk and were killed for assessment of in vitro vasoreactivity and for histological analysis. Six animals fed with standard rabbit diet were used to assess normal responses. Endothelium-dependent responses to acetylcholine and to the calcium ionophore A-23187 were reduced in the hypercholesterolemic control group compared with normal rabbits. Hypercholesterolemic animals treated with bFGF had significantly better endothelium-dependent responses than hypercholesterolemic rabbits not treated with bFGF. Endothelium-independent responses did not differ significantly among the three groups. A similar degree of plaque formation was observed in control- and bFGF-treated hypercholesterolemic rabbits. These results show that, in this model of atherosclerosis, bFGF has a highly beneficial effect on the functional responses of atherosclerotic vessels and does not have a deleterious effect on the degree of plaque formation.

Acetylcholine↗

PubMed1997

Role of serotonin3 receptors in the nucleus tractus solitarii on the carotid chemoreflex.

The effects of serotonin3 (5-HT3)-receptor stimulation in the nucleus tractus solitarii (NTS) on the cardiovagal, sympathetic, and respiratory responses to activation of carotid body chemoreceptors were investigated in anesthetized rats. The chemoreflex responses were triggered by an intravenous administration of KCN (40 microg/kg) in spontaneously breathing urethan-chloralose-anesthetized rats or by an intracarotid administration of saline saturated with 100% CO2 in pancuronium bromide-paralyzed and artificially ventilated urethan-anesthetized rats. Microinjections of 5-HT (2.5-5 nmol) or the 5-HT3 agonist 1-(m-chlorophenyl)-biguanide (CPBG, 300-1,200 pmol) into the commissural NTS blocked in a dose-dependent manner the atropine-sensitive chemoreflex bradycardia elicited by KCN. However, neither 5-HT nor CPBG affected the KCN-induced increase in respiratory volume and the CO2-induced increases in blood pressure and lumbar sympathetic nerve discharge. The inhibitory effect of 5-HT or CPBG on KCN-induced bradycardia was blocked by prior intra-NTS microinjection of a 5-HT3 antagonist, such as zacopride (100 pmol) or ondansetron (100 pmol), or the A-type gamma-aminobutyric acid (GABA(A)) antagonist bicuculline (10 pmol). In contrast, local microinjections of antagonists acting at 5-HT1 and 5-HT2 receptors, such as methysergide (100 pmol) and ketanserin (10 pmol), respectively, did not prevent the actions of 5-HT or CPBG. These data show that the stimulation of 5-HT3 receptors in the NTS exerted an inhibitory influence, probably through the activation of a local GABAergic system, on the cardiovagal component of the chemoreflex. Because similar effects of 5-HT3-receptor stimulation in the NTS were previously found on the baroreflex and Bezold-Jarisch reflex responses, it can be inferred that NTS 5-HT3 receptors play a key modulatory role in the reflex control of the heart rate.

Animals↗

PubMed1997

[Pituitary radiotherapy. Current data and future prospects].

Some technical improvements have allowed to minimize the frequency of severe complications following fractionated pituitary conventional radiotherapy, without altering its efficiency. "Conformational" radiotherapy is currently under development, aiming at the best fitting of the tumor borders to the irradiation zone, by the means of stereotactic imaging. More recently, radiosurgery has been proposed for pituitary adenomas. It consists in a single high radiation dose to the tumor, by the means of either cobalt minibeams (Gamma Unit) or photon beams from a linear particle accelerator. These techniques require the use of a stereotactic frame and precise 3D imaging in order to tightly superimpose the target volume to the reference isodose. They must not be viewed as an alternative to conventional radiotherapy. They can be applied only to small lesions (less than 20 mm in their maximal axis) which are distant (> 5 mm) from the optic chiasma and nerves. Their efficiency is similar to the one of fractionated conventional radiotherapy, with a shorter response time. In conclusion, radiotherapy can be used safely for pituitary adenomas. It remains however a second line treatment, when surgery has been incomplete and when a simple, effective and inexpensive medical treatment is not possible.

Adenoma↗

PubMed1996

Ultrastructural localization of 5-hydroxytryptamine1A receptors in the rat brain.

5-Hydroxytryptamine1A (5-HT1A) receptors have been visualized at the electron microscopic level in selected areas (dorsal raphe nucleus, hippocampus, septum) of the rat brain using specific anti-peptide antibodies. 5-HT1A receptor immunoreactivity was found almost exclusively in the somatodendritic compartment of neurons and was very rarely observed within processes possibly belonging to glial cells. The immunoenzymatic reaction product was associated exclusively with dendritic spines in the dorsal hippocampus, whereas in the dorsal raphe nucleus and the septal complex, immunoreactivity was found in both dendritic processes and somata. Although some immunolabeling was observed within the cytoplasm of cell bodies, 5-HT1A receptor immunoreactivity was essentially confined to the plasma membrane where it was unevenly distributed. It was frequently associated with synapses (except in the dorsal raphe nucleus), but was also found extrasynaptically in both somata and dendrites. These data suggest that the action of serotonin via 5-HT1A receptor could occur through junctional as well as nonjunctional transmission.

Animals↗

PubMed1996

Interaction of S 21007 with 5-HT3 receptors. In vitro and in vivo characterization.

The interaction of S 21007 [5-(4-benzyl piperazin-1-yl)4H pyrrolo [1,2-a]thieno[3,2-e]pyrazine] with serotonin 5-HT3 receptors was investigated using biochemical, electrophysiological and functional assays. Binding studies using membranes from N1E-115 neuroblastoma cells showed that S 21007 is a selective high affinity (IC50 = 2.8 nM) 5-HT3 receptor ligand. As expected of an agonist, S 21007 stimulated the uptake of [14C]guanidinium (EC50 approximately 10 nM) in NG 108-15 cells exposed to substance P, and this effect could be prevented by the potent 5-HT3 receptor antagonist ondansetron. In addition, like 5-HT and other 5-HT3 receptor agonists (phenylbiguanide and 3-chloro-phenylbiguanide), S 21007 (EC50 = 27 microM) produced a rapid inward current in N1E-115 cells. The 5-HT3 receptor agonist action of S 21007 was also demonstrated in urethane-anaesthetized rats as this drug (120 micrograms/kg i.v.) triggered the Bezold-Jarisch reflex (rapid fall in heart rate), and this action could be prevented by pretreatment with the potent 5-HT3 receptor antagonist zacopride. Finally, in line with its 5-HT3 receptor agonist properties, S 21007 also triggered emesis in the ferret. Evidence for 5-HT3 receptor antagonist-like properties of S 21007 was also obtained in some of these experiments since previous exposure to this compound prevented both the 5-HT-induced current in N1E-115 cells and the Bezold-Jarisch reflex elicited by an i.v. bolus of 5-HT (30 micrograms/kg) in urethane-anaesthetized rats. These data suggest that S 21007 is a selective 5-HT3 receptor agonist which can exhibit antagonist-like properties either by triggering a long lasting receptor desensitization or by a partial agonist activity at 5-HT3 receptors in some tissues.

Animals↗