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L. K. Torgersen

Bio: L. K. Torgersen is an academic researcher from Pfizer. The author has contributed to research in topics: Agonist & Endogenous agonist. The author has an hindex of 2, co-authored 2 publications receiving 64 citations.

Papers
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Book ChapterDOI
01 Jan 1991
TL;DR: The source of the selectivity of CP-93,129 appears to lie in the ability of a pyrrolo[3,2-b]pyrid5-one to act as a rotationally restricted bioisosteric replacement for 5-hydroxyindole.
Abstract: The in vitro and in vivo characteristics of CP-93,129 [Structure 1 in Figure 1, 3-(1,2,5,6-tetrahydropyrid-4-yl)-pyrrolo[3,2-b]pyrid-5-one] are described. This rotationally restricted phenolic analog of RU-24,969 is a potent (15 nm) and selective (200 × vs. the 5-HT1A receptor, 150 × vs. the 5-HT1D receptor) functional agonist for the 5-HT1B receptor. Direct infusion of CP-93, I29 into the paraventricular nucleus of the hypothalamus of rats significantly inhibits food intake, implicating the role of 5-HT1B receptors in regularing feeding behavior in rodents. CP-93,129 has also been shown to be biochemically discriminatory in its ability to selectively inhibit forskolin-stimulated adenylate cyclase activity only at the 5-HT1B receptor. The source of the selectivity of CP-93,129 appears to lie in the ability of a pyrrolo[3,2-b]pyrid5-one to act as a rotationally restricted bioisosteric replacement for 5-hydroxyindole.

7 citations


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Journal Article
TL;DR: The trigeminal nerve transmits headache pain from blood vessels of the pia mater and dura mater, and both neurogenic inflammation and c-fos expression are blocked by sumatriptan and ergot alkaloids via prejunctional mechanisms involving putative 5-HT receptors closely related to the5-HT1, subtype on trigeminovascular fibers.
Abstract: The trigeminal nerve transmits headache pain from blood vessels of the pia mater and dura mater. Triggers for this pain are not well understood, but probably are multiple and largely chemical and develop within the brain parenchyma, the blood vessel wall, and the blood itself. These unknown triggers stimulate the trigeminovascular axons, causing pain and releasing vasoactive neuropeptides from perivascular axons. Released neuropeptides activate endothelial cells, mast cells, and platelets to then increase extracellular levels of amines, arachidonate metabolites, peptides, and ions. Hyperalgesia and prolongation of pain develop as a consequence, mediated by products from activated cells and injured tissue. Within postsynaptic brain stem neurons of the trigeminal nucleus caudalis, trigeminovascular activation stimulates the expression of an early immediate response gene c-fos. Both neurogenic inflammation and c-fos expression are blocked by sumatriptan and ergot alkaloids via prejunctional mechanisms involving putative 5-HT receptors closely related to the 5-HT1D subtype on trigeminovascular fibers. The mechanisms of action of sumatriptan and ergot alkaloids described herein are unrelated to the nature of the migraine trigger or to the contractile state of vascular smooth muscle.

392 citations

Journal ArticleDOI
TL;DR: Quantification of [35S]GTP‐γ‐S binding evoked by potent 5‐HT1 receptor agonists confirmed changes as a decrease in this parameter was noted in the DRN (−66%) and the substantia nigra (−30%) but not other brain areas in 5‐ HTT–/– vs. 5-HTT+/+ mice.
Abstract: By taking up serotonin (5-hydroxytryptamine, 5-HT) released in the extracellular space, the 5-HT transporter (5-HTT) regulates central 5-HT neurotransmission. Possible adaptive changes in 5-HT neurotransmission in knock-out mice that do not express the 5-HT transporter were investigated with special focus on 5-HT1A and 5-HT1B receptors. Specific labelling with radioligands and antibodies, and competitive RT-PCR, showed that 5-HT1A receptor protein and mRNA levels were significantly decreased in the dorsal raphe nucleus (DRN), increased in the hippocampus and unchanged in other forebrain areas of 5-HTT-/- vs. 5-HTT+/+ mice. Such regional differences also concerned 5-HT1B receptors because a decrease in their density was found in the substantia nigra (-30%) but not the globus pallidus of mutant mice. Intermediate changes were noted in 5-HTT+/- mice compared with 5-HTT+/+ and 5-HTT-/- animals. Quantification of [35S]GTP-gamma-S binding evoked by potent 5-HT1 receptor agonists confirmed such changes as a decrease in this parameter was noted in the DRN (-66%) and the substantia nigra (-30%) but not other brain areas in 5-HTT-/- vs. 5-HTT+/+ mice. As expected from actions mediated by functional 5-HT1A and 5-HT1B autoreceptors, a decrease in brain 5-HT turnover rate after i.p. administration of ipsapirone (a 5-HT1A agonist), and an increased 5-HT outflow in the substantia nigra upon local application of GR 127935 (a 5-HT1B/1D antagonist) were observed in 5-HTT+/+ mice. Such effects were not detected in 5-HTT-/- mice, further confirming the occurrence of marked alterations of 5-HT1A and 5-HT1B autoreceptors in these animals.

285 citations

Journal ArticleDOI
TL;DR: The regional distribution and the pharmacology of the binding sites labelled with the novel 5-hydroxytryptamine (serotonin) 5-HT1B/1D selective radioligand serotonin-O-carboxy-methyl-glycyl-[125I]tyrosinamide (abbreviated [ 125I]GTI) was determined using quantitative autoradiography in rat brain.
Abstract: The regional distribution and the pharmacology of the binding sites labelled with the novel 5-hydroxytryptamine (serotonin) 5-HT1B/1D selective radioligand serotonin-O-carboxy-methyl-glycyl-[125I]tyrosinamide (abbreviated [125I]GTI for the sake of simplicity) was determined using quantitative autoradiography in rat brain. The distribution of [125I]GTI binding sites was largely comparable to that of [125I]iodocyanopindolol ([125I] ICYP) which labels 5-HT1B binding sites (in the presence of 8-OH-DPAT (8-hydroxy-[2N-dipropylamino]tetralin) and isoprenaline, to prevent binding to 5-HT1A and beta-adrenoceptor binding sites), although a detailed analysis revealed differences. The pharmacology of the [125I]GTI binding sites was analysed using compounds known to display high affinity for and/or distinguish between 5-HT1B and 5-HT1D sites: 5-carboxamidotryptamine (5-CT), sumatriptan, CP 93129 (5-hydroxy-3(4-1,2,5,6-tetrahydropyridyl)-4-azaindole), (-)pindolol, PAPP (4[2-[4-[3-(trifluoromethyl)phenyl]-1- piperazinyl]ethyl]benzeneamine), rauwolscine, and 8-OH-DPAT. The displacement of [125I]GTI by 5-CT was monophasic. By contrast, the selective 5-HT1B compound CP 93129 and (-)pindolol produced biphasic curves showing a majority of high affinity sites in the globus pallidus and the substantia nigra, whereas PAPP and sumatriptan (which are somewhat 5-HT1D selective) produced biphasic curves indicating a minority of high affinity sites in these areas. In addition, by blocking the 5-HT1B sites with 100 nM CP 93129, the remaining population of [125I]GTI binding sites could be studied and was found to have high affinity for PAPP, rauwolscine and 8-OH-DPAT. The pharmacological profile of the major binding component was typical of the 5-HT1B type: 5-CT > CP 93129 > or = (-)pindolol > sumatriptan > or = PAPP > rauwolscine. The profile of the minor component of [125I]GTI binding is best characterised as that of a 5-HT1D site: 5-CT > PAPP > or = sumatriptan > rauwolscine > (-)pindolol > or = CP 93129. The localisation of the non 5-HT1B [125I]GTI binding sites was characterised by blocking the 5-HT1B receptors with 100 nM CP 93129. Low densities of the 5-HT1D recognition sites were found to be present in globus pallidus, ventral pallidum, caudate-putamen, subthalamic nucleus, entopeduncular nucleus, substantia nigra (reticular part), nuclei of the (normal and accessory) optic tract, different nuclei of the geniculate body and frontoparietal cortex, although higher densities of 5-HT1B sites were always observed in the same structures.(ABSTRACT TRUNCATED AT 400 WORDS)

229 citations

Journal ArticleDOI
TL;DR: The deletion of the 5-HT1B receptor, associated with appropriate behavioral paradigms, thus allowed us to dissociate anxiety from response to novelty, and perseverative behavior from adaptive behavioral inhibition underlying cognitive flexibility (transfer stage in the water maze).
Abstract: In an attempt to characterize the contribution of the 5-HT1B receptor to behavior, 5-HT1B knock-out (KO) mice were subjected to a battery of behavioral paradigms aimed at differentiating various components of cognitive and emotional behaviors. In an object exploration task, wild-type (WT) and 5-HT1B KO mice did not differ in locomotor activity. 5-HT1B KO mice, however, displayed lower thigmotaxis (an index of anxiety) associated with a higher level of object exploratory activity, but no genotype differences were observed in the elevated plus maze. 5-HT1B KO mice also displayed a lack of exploratory habituation. In the spatial version of the Morris water maze, 5-HT1B KO mice showed higher performances in acquisition and transfer test, which was not observed in the visual version of the task. No genotype differences were found in contextual fear conditioning, because both WT and 5-HT1B KO mice were able to remember the context where they had received the aversive stimulus. The deletion of the 5-HT1B receptor, associated with appropriate behavioral paradigms, thus allowed us to dissociate anxiety from response to novelty, and perseverative behavior (lack of habituation) from adaptive behavioral inhibition underlying cognitive flexibility (transfer stage in the water maze). The deletion of the 5-HT1B receptor did not result in significant developmental plasticities for other major 5-HT receptor types but may have influenced other neurotransmission systems. The 5-HT1B receptor may be a key target for serotonin in the modulation of cognitive behavior, particularly in situations involving a high cognitive demand.

227 citations

Journal ArticleDOI
TL;DR: Findings indicate that 5-HT1B receptor stimulation facilitates the reinforcing properties of cocaine and may have important ontogenic implications in the area of drug abuse research.
Abstract: The effects of serotonin1B[5-hydroxytryptamine1B (5-HT1B)] receptor activation on cocaine reinforcement were investigated using intravenous cocaine self-administration by rats. The 5-HT1Breceptor agonists 5-methoxy-3-1,2,3,6-tetrahydro-4-pyridinyl-1H-indole (RU 24969) (0.3–3 mg/kg), 3-(1,2,5,6-tetrahydro-4-pyridyl)-5-propoxypyrrolo[3,2-b]pyridine (CP 94,253) (0.3–3 mg/kg), and 3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo[3,2-b]pyridine (CP 93,129) (3 and 10 μg, i.c.v.) each dose-dependently reduced the self-administration of a cocaine dose on the descending limb of the fixed-ratio 5 (FR-5) cocaine dose–effect function, in a manner similar to the effect produced by increasing the unit dose of cocaine. In addition, each of these 5-HT1B agonists lowered the threshold dose of cocaine that supported self-administration. These results are consistent with a 5-HT1B agonist-induced potentiation of cocaine reinforcement. On a progressive ratio schedule of reinforcement, RU 24969 and CP 94,253 dose-dependently (0.3–3 mg/kg) increased the highest completed ratio for cocaine self-administration, again by producing behavioral alterations similar to those induced by increasing the unit dose of cocaine. The effect of CP 94,253 was dose-dependently blocked by the 5-HT1B/1D receptor partial agonist 2′-methyl-4′-(5-methyl[1,2,4]oxadiazol-3-yl)-biphenyl-4-carboxylic acid[4-methodoxy-3-(4-methyl-piperazin-1-yl)-phenyl]-amide (GR 127,935) (0.3–10 mg/kg) but was unaffected by the 5-HT1A receptor antagonist 4-iodo- N -[2-[4-(methoxyphenyl)-1-piperazinyl]ethyl]- N -2-pyridinyl- benzamide (p-MPPI; 1–10 mg/kg). Self-administration behavior was not maintained when either RU 24969 or CP 94,253 was substituted for cocaine, indicating that these 5-HT1B agonists do not produce significant reinforcing effects alone. Together, these findings indicate that 5-HT1B receptor stimulation facilitates the reinforcing properties of cocaine. These results are in opposition to recent findings with 5-HT1B receptor knock-out mice and may have important ontogenic implications in the area of drug abuse research.

177 citations