Calcitonin gene-related peptide (CGRP) is one of the most potent endogenous vasodilators known. This peptide is increased during migraine attacks and has been implicated in the pathogenesis of migraine headache. Here we report on the ®rst small molecule selective CGRP antagonist: BIBN4096BS. In vitro, this compound is extremely potent at primate CGRP receptors exhibiting an a nity (K i ) for human CGRP receptors of 14.4+6.3 (n=4) pM. In an in vivo model, BIBN4096BS in doses between 1 and 30 mg kg 71 (i.v.) inhibited the e ects of CGRP, released by stimulation of the trigeminal ganglion, on facial blood¯ow in marmoset monkeys. It is concluded that BIBN4096BS is a potent and selective CGRP antagonist.

No abstract

Neuropeptide Y (NPY), 1 a 36-residue peptide amide, is a member of the pancreatic polypeptide (PP) hormone family that also includes PP and peptide YY (PYY) (1). NPY is expressed in the central and peripheral nervous systems and is one of the most abundant neuropeptides in the brain. Several important physiological activities, such as induction of food intake, inhibition of anxiety, increase in memory retention, presynaptic inhibition of neurotransmitter release, vasoconstriction, and regulation of ethanol consumption, have been attributed to NPY (2, 3). Especially, the role of NPY in feeding is of major interest because NPY receptor antagonists are potential anti-obesity drug candidates. Many studies have established the strong central influence of NPY in feeding behavior; for example, injection of NPY into the hypothalamus increases food intake (4, 5), and high NPY levels are correlated with leptin deficiency (6), the hormone that is secreted by adipocytes and regulates body weight and energy balance (7,8). Furthermore, NPY knockout can reduce obesity in leptin-deficient mice (named ob/ob mice) (6).Five distinct Y receptor subtypes that bind NPY, PYY, and PP with different affinities have been identified, cloned, and characterized (9). They all belong to the superfamily of the G-protein- Because highly specific tools to investigate the Y 5 receptor activity are still missing, we have focused our work on the design of NPY receptor agonists with both high affinity and selectivity for the Y 5 subtype. It is well established that the C-terminal part of NPY represents the interaction site with the Y receptors and that amino acid exchange is poorly tolerated in the region 33-36 (49); therefore, we induced a conformational change within the peptide region that mediates receptor binding by introducing the ␤-turn-inducing dipeptide Ala-Aib (aminoisobutyric acid) (19) into positions 31-32 of NPY and some peptides that contain segments of NPY and PP (NPY/PP chimeras). The [Ala 31 ,Aib 32 ]-modified peptides showed high selectivity for the Y 5 receptor. Furthermore, in vitro and in vivo studies clearly proved their NPY receptor agonism as well as stimulation of food intake.

1 The novel Y1-selective argininamide derivative BIBO 3304 ((R)-N- [[4-(aminocarbonylaminomethyl)phenyl]methyl]-N 2 -(diphenylacetyl)-argininamide tri¯uoroacetate) has been synthesized and was examined for its subtype selectivity, its in vitro antagonistic properties and its food intake inhibitory properties. 2 BIBO 3304 displayed subnanomolar anity for both the human and the rat Y1 receptor (IC 50 values 0.38+0.06 nM and 0.72+0.42 nM, respectively). The inactive enantiomer of BIBO 3304 (BIBO 3457) had low anity for both the human and rat Y1 receptor subtype (IC 50 41000 nM). BIBO 3304 showed low anity for the human Y2 receptor, human and rat Y4 receptor as well as for the human and rat Y5 receptor (IC 50 values 41000 nM). 3 30 mg BIBO 3304 administered into the paraventricular nucleus inhibited the feeding response induced by 1 mg NPY as well as the hyperphagia induced by a 24 h fast implying a role for Y1 receptors in NPY mediated feeding. The inactive enantiomer had no eect. 4 BIBO 3304 inhibits neither the galanin nor the noradrenaline induced orexigenic response, but it blocked feeding behaviour elicited by both [Leu 31 , Pro 34 ]NPY and NPY (3 ± 36) suggesting an interplay between dierent NPY receptor subtypes in feeding behavior. 5 The present study reveals that BIBO 3304 is a subtype selective nonpeptide antagonist with subnanomolar anity for the Y1 receptor subtype that signi®cantly inhibits food intake induced by application of NPY or by fasting.

No abstract

Aged memory-impaired (AI) and unimpaired (AU) 24–25-month-old Long- Evans rats were used to investigate the integrity of various cholinergic markers during normal aging and to establish if alterations can possibly relate to cognitive disabilities. AI and AU rats were classified on the basis of their performance in the Morris swim maze task. Choline acetyltransferase activity (ChAT) was not differentially altered in various cortical and hippocampal areas between these two groups. Similarly, quantitative receptor autoradiography did not reveal significant differences in 3H-pirenzepine/muscarinic M1 and 3H- hemicholinium-3/high-affinity choline uptake binding sites in AI versus AU rats. In contrast, 3H-AF-DX 384/putative muscarinic M2 binding was significantly increased in certain cortical and hippocampal areas of the age-impaired animals. These increments were correlated with decreased in vivo acetylcholine (ACh) release capacity in the AI rats. Most interestingly, the muscarinic M2 antagonist BIBN-99 reversed, in a dose-dependent manner, the impaired ACh release as well as the cognitive deficits observed in the AI group. Similarly, BIBN-99 reversed scopolamine-induced amnesia in young animals. The efficacy of BIBN-99 likely relates to its antagonistic properties on negative muscarinic M2 autoreceptors that are apparently increased in the AI animals, leading to altered ACh release. Taken together, these findings strengthen the role of ACh in learning and memory and may have implications for the treatment of degenerative disorders associated with impaired cholinergic functions, such as Alzheimer's disease.

1 Calcitonin gene-related peptide (CGRP) is believed to play a pivotal role in the pathogenesis of migraine via activation of CGRP receptors in the trigeminovascular system. The CGRP receptor antagonist, BIBN4096BS, has proven efficacy in the acute treatment of migraine attacks and represents a new therapeutic principle. 2 We used an improved closed cranial window model to measure changes of the middle meningeal artery (MMA) and cortical pial artery/arteriole diameter (PA) and changes in local cortical cerebral blood flow (LCBF Flux ) in anaesthetised artificially ventilated rats. 3 The ability of BIBN4096BS (i.v.) to prevent the vasodilatatory actions of rat-aCGRP, bCGRP and endogenously released CGRP following transcranial electrical stimulation (TES) was investigated. 4 BIBN4096BS was per se without vasoactive effect on any of the measured variables and significantly inhibited the hypotension induced by both types of CGRP (Po0.001). 5 The aCGRP induced MMA dilatation was reduced from 97.4714 to 2.171.3% (Po0.001) and the bCGRP induced dilatation was fully blocked by BIBN4096BS. ID 50 was 5.471.6 mg kg À1 for aCGRP and 16.371.6 mg kg À1 for bCGRP. 6 Transcranial electrical stimulation induced a 119.176.9% increase in MMA diameter. BIBN4096BS (333 mg kg À1 ) attenuated this increase (19.872.1%) (Po0.001). 7 Systemic CGRP and TES induced an increase in PA diameter that was not significantly inhibited by BIBN4096BS. The CGRP induced increase in LCBF Flux was similar not prevented by the antagonist. 8 We suggest that systemic BIBN4096BS exerts its inhibitory action mainly on large dural blood vessels (MMA).

1 This study examined the eects of the peptide CGRP receptor antagonist CGRP and the newly-developed non-peptide CGRP receptor antagonist BIBN4096BS for their potential to both inhibit the development and reverse tolerance to the antinociceptive action of morphine. 2 Repeated administration of intrathecal morphine (15 mg), once daily, produced a progressive decline of antinociceptive eect and an increase in the ED 50 value in the tail¯ick and paw pressure tests. Co-administration of CGRP 8-37 (4 mg) or BIBN4096BS (0.05, 0.1 mg) with morphine (15 mg) prevented the decline of antinociceptive eect and increase in ED 50 value in the tail¯ick test. Intrathecal administration of the CGRP receptor antagonists did not alter the baseline responses in either tests. Acute CGRP 8-37 also did not potentiate the acute actions of spinal morphine. 3 In animals rendered tolerant to intrathecal morphine, subsequent administration of CGRP (4 mg) with morphine (15 mg) partially restored the antinociceptive eect and ED 50 value of acute morphine, re¯ecting the reversal of tolerance. 4 Animals tolerant to intrathecal morphine expressed increased CGRP and substance P-like immunostaining in the dorsal horn of the spinal cord. The increase in CGRP, but not substance Plike immunostaining, was blocked by a co-treatment with CGRP 8-37 (4 mg). In animals already tolerant to morphine, the increase in CGRP but not substance P-like immunostaining was partially reversed by CGRP 8-37 (4 mg). 5 These data suggest that activation of spinal CGRP receptors contributes to both the development and expression of spinal opioid tolerance. CGRP receptor antagonists may represent a useful therapeutic approach for preventing as well as reversing opioid tolerance.