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S Z Langer

Publications and source records attributed to S Z Langer.

At least 19 recordsLinked to original sources
PubMed1992

Partial purification and characterization of the sodium-ion-coupled 5-hydroxytryptamine transporter of rat cerebral cortex.

A procedure for the extensive purification of the Na(+)-coupled 5-hydroxytryptamine transporter of rat cerebral cortex has been developed. The 5-hydroxytryptamine transporter was solubilized with the non-ionic detergent digitonin, and the detergent extracts were subjected to sequential affinity chromatography on a citalopram-based agarose support and wheat-germ-agglutinin-Sepharose. 5-Hydroxytryptamine transporters in the affinity-purified preparation were identified by using the selective 5-hydroxytryptamine-uptake inhibitor [3H]paroxetine, and were shown to display a similar pharmacological profile to those present in particulate preparations. An overall transporter purification of around 2000-fold was achieved with a 9% recovery. SDS/PAGE of affinity-chromatographed material starting from detergent extracts incubated in the presence or absence of 1 mM-citalopram indicated that a polypeptide of M(r) 73,000 corresponded to the 5-hydroxytryptamine-transporter protein.

Animals↗
PubMed1992

The neuroprotective properties of ifenprodil, a novel NMDA receptor antagonist, in neuronal cell culture toxicity studies.

We investigated the effect of ifenprodil on excitotoxic cell death induced by acute exposure to glutamate receptor agonists in primary cultures of foetal mouse cerebral cortex. L-Glutamate and N-methyl-D-aspartate (NMDA) but not kainate and quisqualate-induced toxicity was attenuated in the presence of ifenprodil. In addition, ifenprodil and MK-801 blocked NaCN-induced toxicity. It is concluded that the cerebro-protective properties of ifenprodil in these models are mediated by NMDA receptor antagonism.

Animals↗
PubMed1992

Advances in sodium-ion coupled biogenic amine transporters.

The sodium-ion coupled transporters for 5-hydroxytryptamine (5HT), noradrenaline and dopamine function to reduce extracellular levels of biogenic amines. Over the past fifteen years selective inhibitors of these transport systems have been developed including fluoxetine, citalopram, paroxetine, litoxetine (for 5HT), nisoxetine, desipramine, maprotiline (for noradrenaline) and GBR-12935 (for dopamine). Some of these inhibitors, including drugs selective for noradrenaline transport and particularly those selective for the 5HT transport system are currently widely used in the clinical management of affective disorders. Selective biogenic amine uptake inhibitors have, in addition, provided tools to undertake molecular pharmacological and biochemical studies of their respective transporters. By this means, the rat brain 5HT and dopamine transporters have been identified as polypeptides with relative molecular masses of 73,000 and 80,000, respectively, using affinity-chromatographic purification and photoaffinity-labelling techniques. Recently, the biogenic amine transporters have been cloned and a comparison of their predicted amino acid sequences reveals that these proteins share a considerable degree of similarity with notably 12-13 transmembrane spanning domains. Perspectives for future fundamental and clinical research on biogenic amine transport systems using molecular biological techniques are discussed.

Amino Acid Sequence↗
PubMed1992

Characterization of the 5-hydroxytryptamine receptor modulating the release of 5-[3H]hydroxytryptamine in slices of the human neocortex.

In the rat brain, the presynaptic 5-hydroxytryptamine (5-HT) autoreceptors located on 5-HT terminals correspond to the 5-HT1B subtype. The presence of a 5-HT receptor probably located on 5-HT nerve endings and modulating transmitter release in the human neocortex has been reported, but its detailed pharmacological characterization is not yet available. On the other hand, receptor binding and autoradiographic results indicate that the 5-HT1B receptor subtype is not present in the human brain. We, therefore, studied the modulation of the electrically evoked release of [3H]5-HT by various 5-HT receptor agonists and antagonists in preloaded slices of human neocortex obtained from 18 patients undergoing neurosurgery. The nonselective 5-HT1A/1B/1D receptor agonist 5-carboxamidotryptamine produced a potent inhibition (70% at 0.03 microM) of the electrically evoked release of [3H]5-HT which was blocked by 5-HT receptor antagonists with the following relative order of potency: methiothepin greater than metergoline = methysergide greater than propranolol. The selective 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin at 0.1 microM did not modify the electrically evoked release of [3H]5-HT. The 5-HT1A/1B receptor agonist RU 24969 was 10 times more potent at inhibiting [3H]5-HT overflow in the rat frontal cortex than in the human neocortex. The potent 5-HT1B receptor antagonist cyanopinodolol did not modify the 5-carboxamidotryptamine-induced inhibition of the electrically evoked release of [3H]5-HT in slices of the human neocortex, but produced by itself a small inhibition of [3H]5-HT overflow.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Adrenergic and nonadrenergic cotransmitters inhibit insulin secretion during sympathetic stimulation in dogs.

Vascular and biochemical responses to pancreatic sympathetic nerve stimulation were investigated in the blood-perfused pancreas of anesthetized dogs. During sympathetic nerve stimulation, pancreatic perfusion pressure and norepinephrine release increased, whereas insulin secretion decreased. The latter effect did not occur after pretreatment with the alpha 2-adrenoceptor antagonist idazoxan. However, after beta-adrenoceptor blockade with propranolol, neither single administration of idazoxan nor the alpha 1-adrenoceptor antagonist prazosin or glibenclamide, a blocker of ATP-modulated K+ channels, affected the decrease in insulin secretion induced by sympathetic nerve stimulation. In contrast, the combination of glibenclamide with idazoxan markedly antagonised the decrease in insulin release evoked by the latter procedure. After depletion of catecholamines with syrosingopine, the stimulation-induced inhibition of insulin secretion remained unchanged even though no increases in pancreas perfusion pressure or norepinephrine release were observed. In this preparation, glibenclamide inhibited the decrease in insulin release by 50%. In animals pretreated with the neuronal blocking agent bretylium, all of the responses to sympathetic nerve stimulation were abolished. These results indicate that the inhibitory effects exerted by the sympathetic nervous system on insulin secretion are mediated not only by the classical neurotransmitter norepinephrine acting on alpha 2-adrenoceptors but also by a nonadrenergic cotransmitter that can maintain transmission under conditions of catecholamine deficiency. The postulated nonadrenergic cotransmitter(s) acts, at least partly, via the opening of ATP-modulated K+ channels blockable by glibenclamide, and its release can be prevented by the neuronal blocking agent bretylium.

Animals↗
PubMed1992

SL 84.0418: a novel, potent and selective alpha-2 adrenoceptor antagonist: in vitro pharmacological profile.

One novel, potent and selective alpha-2 adrenoceptor antagonist is 2-(4,5-dihydro-1H-imidazol-2-yl)-1,2,4,5-tetrahydro-2- propylpyrrolo[3,2,1-hi]-indole hydrochloride (SL 84.0418). It inhibits with high affinity the radioligand binding to rat cortical alpha-2 adrenoceptors, as well as to human platelet alpha-2 adrenoceptors labeled with [3H]idazoxan (Ki = 7 nM). SL 84.0418 has low affinity for alpha-1 adrenoceptors labeled with [3H]prazosin (Ki = 3.3 microM). In vitro, SL 84.0418 has no alpha agonist properties, whereas it is a potent alpha-2 adrenoceptor antagonist at both pre- and postsynaptic alpha-2 adrenoceptors. In contrast, it possesses low potency as an antagonist at postsynaptic alpha-1 adrenoceptors demonstrating a more than 1000-fold selectivity toward alpha-2 compared with alpha-1 adrenoceptors. In the same tests, the alpha-2 adrenoceptor antagonist idazoxan had a selectivity ratio of 200. SL 84.0418 is the racemic mixture of two enantiomers, SL 86.0715 [(+) enantiomer] and SL 86.0714 [(-) enantiomer]. The alpha-2 adrenoceptor blocking activities reside with SL 86.0715. Similar to idazoxan, SL 84.0418 increases in a concentration-dependent manner the electrically evoked release of [3H]norepinephrine from rat hypothalamic slices through the blockade of the presynaptic inhibitory alpha-2 adrenoceptors. In isolated hamster adipocytes, SL 84.0418 potently antagonizes the inhibition of lipolysis induced by UK 14,304. In addition, SL 84.0418 inhibits epinephrine-induced aggregation of rabbit platelets, effects mediated by postsynaptic alpha-2 adrenoceptors. SL 84.0418 does not inhibit (IC50 > 1,000 nM) radioligand binding to other receptors or recognition sites, nor does it inhibit calcium, sodium or potassium channels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1991

Pre- and postsynaptic alpha-2 adrenoceptors as target for drug discovery.

The presynaptic terminal autoreceptors which modulate the release of noradrenaline through a negative feed-back mechanism correspond to the alpha 2-subtype of adrenoceptors. These receptors are also present post-synaptically in the pancreatic islets were they mediate inhibition of the glucose-induced release of insulin. The sympathetic innervation of the pancreatic islets involves alpha 2-adrenoceptors both presynaptically as well as postsynaptically. SL 84.0418 is a novel alpha 2-adrenoceptor antagonist with preferential effects in the periphery and with at least a 10-fold higher selectivity ratio between alpha 2 and alpha 1-adrenoceptors when compared with idazoxan. SL 84.0418 antagonizes the hyperglycemia and the inhibition of insulin release induced by the alpha 2-adrenoceptor agonist UK 14304. The administration of SL 84.0418 significantly reduces the glucose evoked hyperglycemia in several species including man. It is proposed that SL 84.0418 may represent a useful and novel hypoglycemic drug in the treatment of type II diabetes.

Adrenergic alpha-Agonists↗
PubMed1991

Characterization and purification of the neuronal sodium-ion-coupled 5-hydroxytryptamine transporter.

The selective 5-hydroxytryptamine (5-HT) uptake inhibitor, [3H]paroxetine, has been used as a specific probe in a series of experiments aimed at characterizing the substrate and 5-HT uptake inhibitor binding domains on the neuronal sodium-ion-coupled 5-HT transporter. In addition, an affinity-chromatographic protocol which provided a greater than 3000-fold purification of this neuronal transporter protein is outlined.

Animals↗
PubMed1990

Antagonism of presynaptic dopamine receptors by phenothiazine drug metabolites.

Electrically evoked release of dopamine from the caudate nucleus is reduced by the dopamine receptor agonists, apomorphine and bromocriptine, and facilitated by neuroleptic drugs, which act as dopamine autoreceptor antagonists. The potencies of chlorpromazine, fluphenazine, levomepromazine and their hydroxy-metabolites in modulating electrically evoked release of dopamine were examined by superfusion of rabbit caudate nucleus slices pre-incubated with 3H-dopamine. O-Desmethyl levomepromazine, 3-hydroxy- and 7-hydroxy metabolites of chlorpromazine and levomepromazine facilitated electrically evoked release of 3H-dopamine, having potencies similar to that of the parent compounds. 7-Hydroxy fluphenazine was less active than fluphenazine in this system. These results indicate that phenolic metabolites of chlorpromazine and levomepromazine, but not of fluphenazine, may contribute to effects of the drugs mediated by presynaptic dopamine receptors.

Animals↗
PubMed1990

Selectivity for omega-receptor subtypes as a strategy for the development of anxiolytic drugs.

The names omega 1-, omega 2-, and omega 3-receptor subtypes have recently been proposed to replace the nomenclature of BZ1, BZ2 and BZp receptors in order to avoid a nomenclature exclusively linked to the benzodiazepine (BZ) structure or to a regional localization. The multiplicity of pharmacological actions of currently available anxiolytics may be due to their lack of selectivity for omega-receptor subtypes. The idea that a receptor-subtype selective drug will offer a more specific therapeutic profile is widely accepted. In the field of preferential anxiolytic or hypnotic drugs, imidazopyridines represent a new chemical and therapeutic class possessing selectivity for omega-receptor subtypes. Of these, alpidem (6-chloro-2-(4-chloro-phenyl)-N,N-dipropylimid-azo[1,2-a] pyridine-3-acetamide) behaves preferentially as an anxiolytic drug in both animal models and man. Receptor-binding studies using alpidem either as a displacer or as a radioligand indicate that the compound has a high affinity for omega 1- and for omega 3- but not for omega 2-receptors. In the human brain, the binding of [3H]-alpidem to omega 1- and omega 3-receptors occurs with a Kd of 1.67 nM and 0.33 nM respectively. The binding of [3H]-alpidem to omega 1-receptors in the rat cerebral cortex with a Kd of 1.5 nM is enhanced by GABA, and in contrast to anxiolytics of the benzodiazepine type, is unaffected by chloride ions and pentobarbital. In conclusion, the affinity of alpidem for the omega 1-receptor is allosterically influenced by the activation of the GABAA receptor but not by other components of the same receptor complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Involvement of alpha-2 adrenergic receptor subtypes in hyperglycemia.

Alpha-2 adrenoceptor stimulation induces in the mouse a hyperglycemic response which is accompanied by a concomitant inhibition of insulin secretion. To test the possibility that one of the postulated subtypes of alpha-2 adrenoceptors is preferentially implicated in this response, we compared the interaction of several drugs with known selectivity toward alpha-2A or alpha-2B adrenoceptor subtypes in our model. The alpha-2A preferential agonist oxymetazoline induced in the mouse a hyperglycemic response similar to that of the nonselective alpha-2 adrenoceptor agonist UK 14.304. This hyperglycemic response to oxymetazoline was accompanied by a concomitant inhibition of insulin release. Both the effect on glycemic level and the inhibition of insulin release by oxymetazoline were antagonized by the alpha-2 adrenoceptor antagonist idazoxan. The alpha-2B preferential antagonists ARC-239, prazosin or chlorpromazine failed to block the modifications in both glycemic and insulin levels induced by alpha-2 adrenoceptor stimulation. The nonselective antagonists rauwolscine, yohimbine, WY 26703, phentolamine and corynanthine, as well as the receptor antagonists with alpha-2A selectivity like WB 4101, idazoxan and tolazoline, dose-dependently antagonized both the glycemic and the insulin responses to UK 14.304. A positive correlation was obtained between the potencies of these drugs in antagonizing the hyperglycemic response to UK 14.304 and their affinities for alpha-2A adrenergic receptors (r = 0.918, P less than .001) but no correlation was obtained with their affinities for alpha-2B adrenergic receptors (r = 0.048, P = N.S.)(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Agonists↗
PubMed1990

Pharmacological characterization of alpha-2 adrenergic receptor subtype involved in the release of insulin from isolated rat pancreatic islets.

Alpha-2 adrenoceptors are involved in the inhibition of insulin release induced by sympathetic nerve stimulation. To test the possibility that one of the postulated subtypes of alpha-2 adrenoceptors is differentially implicated in the inhibition of insulin release, we compared the effects of several agonists and antagonists with preferential selectivity for the alpha-2 adrenoceptor subtypes on the release of insulin induced by glucose in rat isolated islets. Similar to the inhibition of glucose-evoked release of insulin by the alpha-2 agonist (nonsubtype selective) UK 14.304, the alpha-2A preferential agonist oxymetazoline, concentration-dependently inhibited the release of insulin. Glucose-evoked insulin release was similarly inhibited by other alpha-2 adrenoceptor agonists such as clonidine, p-aminoclonidine, epinephrine and norepinephrine. However, neither the alpha-1 selective agonist cirazoline, nor the beta adrenoceptor agonist isoproterenol affected glucose-evoked insulin release, thus suggesting that this inhibitory effect is mediated by alpha-2 adrenoceptors, possibly of the alpha-2A subtype. The inhibition of glucose-evoked insulin release induced by the alpha-2 adrenoceptor agonists was concentration-dependently inhibited by the alpha-2 antagonists yohimbine, phentolamine, rauwolscine and idazoxan. However, neither the alpha-1 selective antagonist prazosin, nor the beta selective antagonist propranolol attenuated the inhibition of insulin release induced by alpha-2 adrenoceptor agonists. Furthermore, the inhibition of insulin release induced by UK 14.304 was concentration-dependently antagonized by the alpha-2A preferential antagonist WB-4101.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Agonists↗
PubMed1990

Interaction between serotonin uptake inhibitors and alpha-2 adrenergic heteroreceptors in the rat hypothalamus.

The effectiveness of presynaptic receptor agonists to inhibit the electrically evoked release of [3H]monoamines from brain slices is attenuated in the presence of blockade of neuronal uptake for the serotonin (5-HT) and the norepinephrine (NE) systems. There is controversy, however, as to the existence of a functional link between the presynaptic receptors and the neuronal uptake carriers. An alternative hypothesis involves competition for the presynaptic receptor sites between the exogenous agonist and the released neurotransmitter. In order to examine the proposed functional interaction, we studied the alpha-2 adrenoceptor-mediated inhibition of the electrically evoked release of [3H]-5-HT from slices of the rat hypothalamus, a model in which endogenous NE does not activate the alpha-2 heteroreceptors located on 5-HT terminals. The inhibitors of 5-HT uptake, citalopram (0.01-1 microM) and paroxetine (1 microM), which by themselves did not modify [3H]-5-HT release, antagonized the inhibition of [3H]-5-HT overflow produced by UK 14.304, an alpha-2 adrenoceptor agonist. The inhibition of the electrically evoked release of [3H]-5-HT by exogenous NE (0.1-1 microM) was also attenuated in the presence of citalopram. In contrast, citalopram did not modify the electrically evoked release of [3H]-NE or the inhibition of [3H]-NE release mediated by UK 14.304. When the 5-HT autoreceptor was blocked by cyanopindolol, the inhibitory effect of UK 14.304 on [3H]-5-HT release was unaltered in the presence of citalopram.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗