Biomedical subjects

J Rivier

Publications and source records attributed to J Rivier.

At least 55 records · Page 3Linked to original sources

PubMed1997

A noncompetitive peptide inhibitor of the nicotinic acetylcholine receptor from Conus purpurascens venom.

A paralytic peptide, psi-conotoxin Piiie has been purified and characterized from Conus purpurascens venom. Electrophysiological studies indicate that the peptide inhibits the nicotinic acetylcholine receptor (nAChR). However, the peptide does not block the binding of alpha-bungarotoxin, a competitive nAChR antagonist. Thus, psi-conotoxin Piiie appears to inhibit the receptor at a site other than the acetylcholine-binding site. As ascertained by sequence analysis, mass spectrometry, and chemical synthesis, the peptide has the following covalent structure: HOOCCLYGKCRRYOGCSSASCCQR* (O = 4-trans hydroxyproline; * indicates an amidated C-terminus). The disulfide connectivity of the toxin is unrelated to the alpha- or the alphaA-conotoxins, the Conus peptide families that are competitive inhibitors of the nAChR, but shows homology to the mu-conotoxins (which are Na+ channel blockers).

Amino Acid Sequence↗

PubMed1997

Stress and autoimmunity: the neuropeptides corticotropin-releasing factor and urocortin suppress encephalomyelitis via effects on both the hypothalamic-pituitary-adrenal axis and the immune system.

Corticotropin-releasing factor (CRF) exerts a major role in the stress response. Both CRF and urocortin, a newly discovered neuropeptide homologous to CRF, suppressed experimental autoimmune encephalomyelitis (EAE). Suppression of paralysis with CRF involved stimulation of the hypothalamic-pituitary-adrenal axis and inhibitory effects on an encephalitogenic T cell line. While CRF increased glucocorticoid production, which is known to block EAE, it also suppressed EAE in adrenalectomized rats, where glucocorticoid stimulation via CRF plays no role. Moreover, the encephalitogenicity of a T cell line exposed to CRF in vitro was reduced. Stress may influence autoimmune disease through the hypothalamic-pituitary-adrenal axis and directly via the immune system.

Animals↗

PubMed1997

NMR structure determination of a novel conotoxin, [Pro 7,13] alpha A-conotoxin PIVA.

A high-resolution solution conformation of a novel conotoxin, [Pro 7,13] alpha A-conotoxin PIVA, GCCGSYPNAACHPCSCKDROSYCGQ-NH2, has been determined by two-dimensional 1H NMR methods and distance geometry calculations. The total of 324 NOE-derived interproton distance restraints including 33 long-range NOE restraints as well as 11 phi and 7 chi 1 torsion angle restraints was used for computation of structures. Back-calculation from the experimental NOE spectrum has provided 49 new NOE restraints and yielded the final R-factors of Ra = 0.641 and Rb = 0.157. The final RMSD values are 0.90 and 1.16 A for the backbone and the heavy atoms, respectively. The C-terminal half of the molecule involving the residues 12-24 is extremely well-defined with a backbone RMSD value of 0.56 A, whereas the N-terminal 3-11 disulfide loop is relatively flexible, possessing a backbone RMSD value of 1.09 A. The [Pro 7,13] alpha A-conotoxin PIVA does not contain any significant secondary structure although the 21S-24G nearly completes one turn of a 3(10) helix. The overall protein fold is largely maintained by the three disulfide bridges of 2-16, 3-11, and 14-23. The presence of the three disulfide bridges imposes geometric constraints that force the molecule to form six continuous bends involving the following residues: 3C-5S, 7P-10A, 12H-14C, 15S-17K, 17K-19R, and 21S-25Q. The overall shape of the [Pro 7,13] alpha A-conotoxin PIVA can be described as an "iron". Residues 15S-19R form a loop that protrudes out of the "bottom plate" formed by the rest of the protein and constitute the handle of the iron. The N-terminal tip of the molecule is relatively immobile due to attractive electrostatic interactions between the gamma-hydroxyl group of 20 Hyp and the phenolic hydroxyl group of 22Y. The flexible 3-11 disulfide loop consists mostly of hydrophobic residues, while the best-defined 14-23 disulfide loop contains the highly charged hydrophilic 15S-19R "handle" domain exposed to the exterior of the protein. Binding to nicotinic acetylcholine receptor can be mediated through two different types of interactions: one involving the aromatic hydrophobic residues such as 6Y and 12H and the other involving the positively charged hydrophilic side chain of the 19R. The side chain of the 19R in the [Pro 7, 13] alpha A-conotoxin PIVA and that of the 9R of the alpha-conotoxin G1, and also the side chains of the 12H and 6Y in the former and those of 10H and 11Y in the latter can be aligned to point to the same direction when the corresponding backbone atoms are superimposed to an RMSD value of 2.5 A.

Amino Acid Sequence↗

PubMed1997

Astressin, a novel and potent CRF antagonist, is neuroprotective in the hippocampus when administered after a seizure.

Corticotropin-releasing factor (CRF), the principle hypothalamic regulator of the adrenocortical axis, also functions as a neurotransmitter. In this latter role, CRF causes electrophysiological activation and epileptiform activity in various brain regions. That finding, coupled with the observation that CRF mRNA is induced in endangered brain regions following necrotic insults, suggests that the peptide might contribute to necrotic neuron loss. Supporting that, a number of studies have shown that CRF antagonists decrease ischemic or excitotoxic damage to neurons. In the present report, we demonstrate the considerable neuroprotective potential of a novel and potent CRF antagonist, astressin, against kainic acid-induced excitotoxic seizures. Intracerebroventricular infusion of the peptide both 30 min before and 10 min after seizures decreased damage in some hippocampal cell fields by as much as 84%, a magnitude of protection greater than reported for other CRF antagonists against other models of necrotic neuronal injury. Administration of astressin was done against both local microinfusion (0.035 microgram) or systemic infusion (10 mg/kg body weight) of the excitotoxin; furthermore, the peptide protected even if administered only 10 min following excitotoxin exposure. This fulfills a critical prerequisite for any eventual therapeutic use of CRF antagonists, namely that they need not be administered in anticipation of a neurological insult.

Analysis of Variance↗

PubMed1997

Anxiolytic activity of NPY receptor agonists in the conflict test.

This investigation examined receptor subtype specificity and possible modulation by GABAa receptor ligands of NPY-induced behavioral responses to stressful stimuli. First, a series of NPY receptor agonists were examined for their potential effects on punished responding in a conflict test modified for incremental shock. NPY, peptide YY (PYY) and NPY Y1 receptor agonists [Leu31,Pro34]-NPY and [Gly6, Glu26,Lys26,Pro34]-NPY produced increases in punished responding in the conflict test. No significant effects on unpunished responding were noted. The pattern of responding was similar to that observed with the benzodiazepine agonist chlordiazepoxide. Neither pancreatic peptide (PP) nor the Y2 agonists NPY13-36 or [Glu2,32,Ala6,Dpr27,Lys28]-NPY significantly altered punished or unpunished responding. Of significance, the atypical Y1 agonist [Cys7,21,Pro34]-NPY produced negligible effects on punished responding, consistent with the presence of a subclass of Y1 receptors. Second, the anxiolytic effects of NPY were subjected to treatments that block actions at the GABAa receptor complex. The increase in punished responding produced by NPY was not altered by administration of the benzodiazepine antagonist flumazenil and only partially blocked by the picrotoxinin receptor ligand isopropylbicyclophosphate (10 and 15 microg/kg). These findings further support the hypothesis that the pharmacologic substrates for the anxiolytic-like actions of NPY may be mediated by the Y1 receptor subtype and suggest that these actions are independent of either the benzodiazepine or picrotoxinin binding sites of the GABA/benzodiazepine receptor complex.

Animals↗

PubMed1997

Cardiac inotropic actions of urocortin in conscious sheep.

Urocortin (Ucn) is a recently isolated peptide related to the corticotropin-releasing factor (CRF) family, which can produce hemodynamic and hormonal actions in conscious rats. This study examined in detail the cardiovascular actions of Ucn and CRF after intravenous injection in chronically instrumented, conscious sheep. Injection of Ucn produced dose-dependent changes in cardiac contractility [rate of increase of aortic flow (dF/dt)], maximum aortic flow (Fmax), mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), and coronary blood flow (CF). Ucn injected at 100 micrograms produced a potent increase in dF/dt, from 909 +/- 44 to a maximum of 1,849 +/- 901.min-1.s-1, and in Fmax, from 25.5 +/- 0.8 to 36.6 +/- 1.4 l/min. Cardiac contractility increased within 30 min of injection and remained significantly elevated for up to 24 h. MAP increased from 78 +/- 2 to 90 +/- 3 mmHg, and HR increased from 73 +/- 4 to 103 +/- 9 beats/min. CO rose from 5.0 +/- 0.1 to 5.8 +/- 0.2 l/min, whereas central venous pressure, total peripheral conductance, and stroke volume were unchanged. All Ucn-induced cardiovascular effects were inhibited by prior treatment with the CRF antagonist alpha-helical CRF-(9-41). Equimolar doses of CRF produced little change in any hemodynamic parameter. Both peptides increased plasma levels of adrenocorticotropin and cortisol, with Ucn having a more potent effect than CRF. We have shown for the first time that Ucn can produce potent and long-lasting actions to elevate cardiac contractility in conscious animals.

Adrenocorticotropic Hormone↗

PubMed1997

Exon skipping in the gene encoding pituitary adenylate cyclase-activating polypeptide in salmon alters the expression of two hormones that stimulate growth hormone release.

In mammals, GRF and pituitary adenylate cyclase-activating polypeptide (PACAP) are encoded in separate genes. We report here that in the salmon a 4.5-kilobase gene contains five exons that encode the biologically active part of the GRF-like peptide (amino acids 1-32) on exon 4 and PACAP on exon 5. Analysis of two fish messenger RNAs reveals that a long precursor containing GRF and PACAP and a short precursor containing only PACAP are both expressed in the brain of at least five species of salmon, whereas mice express only the long precursor encoded by the PACAP gene. Synthetic salmon PACAP-38 and salmon GRF-like peptide-45 both stimulated GH release from cultured salmon pituitary cells; PACAP stimulated a concentration-dependent release of GH at both 4 and 24 h of incubation, whereas GRF-like peptide did not. Alternative splicing, resulting in the short precursor in which GRF-32 is excised, may provide a means for differential control of GH secretion with higher production of the more potent PACAP. A duplication of the GRF-like/PACAP gene in evolution after the divergence of fish and tetrapods would explain separate genes and regulation for GRF and PACAP in mammals.

Alternative Splicing↗

PubMed1997

Central injection of a new corticotropin-releasing factor (CRF) antagonist, astressin, blocks CRF- and stress-related alterations of gastric and colonic motor function.

The influence of central injection of a new corticotropin releasing factor (CRF) antagonist, astressin, [cyclo(30-33)[D-Phe12,Nle21,38,Glu30,Lys33]r/ hCRF12-41)], on exogenous and endogenous CRF-induced gastric ileus and stimulation of bowel discharges was investigated in conscious rats. Intracisternal (ic) CRF (0.6 microg) reduced gastric emptying of a noncaloric solution to 17.1 +/- 4.9% compared with 50.1 +/- 4.6% in control group injected i.c. with vehicle. Astressin (1,3 and 10 microg, i.c.) dose dependently prevented ic CRF-induced delayed gastric emptying by 33, 100 and 100%, respectively, and had no effect on basal gastric emptying. Abdominal surgery with cecal manipulation (1 min) reduced gastric emptying to 19.8 +/- 5.5% 3 hr postsurgery compared with 59.9 +/- 5.2% after anesthesia alone plus i.c. vehicle. Astressin (1,3 and 10 microg, i.c.) prevented postoperative gastric ileus by 56, 93 and 92%, respectively. Intracerebroventricular CRF (0.6 microg) and water-avoidance stress stimulated pellet output (number/60 min) to 5 +/- 1 and 11 +/- 2, respectively, compared with no fecal pellet output after i.c.v. vehicle and no exposure to stress. Astressin (3 and 10 microg, i.c.v.) blocked exogenous CRF action by 47 and 63%, respectively, and colonic response to stress by 0 and 54%, respectively. These data indicate that astressin injected into the CSF at low doses (1-10 microg) has an antagonistic action against CRF and stress-related alterations of gastrointestinal motor function, without an intrinsic effect in these in vivo systems. Astressin may be a useful tool to explore functional CRF-dependent physiological pathways in specific brain nuclei.

Animals↗

PubMed1996

Appetite-suppressing effects of urocortin, a CRF-related neuropeptide.

The neuropeptide corticotropin-releasing factor (CRF) is well known to act on the central nervous system in ways that mimic stress and result in decreases in exploration, increases in sympathetic activity, decreases in parasympathetic outflow, and decreases in appetitive behavior. Urocortin, a neuropeptide related to CRF, binds with high affinity to the CRF2 receptor, is more potent than CRF in suppressing appetite, but is less potent than CRF in producing anxiety-like effects and activation. Doses as low as 10 nanograms injected intracerebroventricularly were effective in decreasing food intake in food-deprived and free-feeding rats. These results suggest that urocortin may be an endogenous CRF-like factor in the brain responsible for the effects of stress on appetite.

Animals↗

PubMed1996

Identification of ligand binding determinants in the somatostatin receptor subtypes 1 and 2.

The somatostatin (SRIF) receptors (SSTRs) 1 and 2 bind SRIF and SRIF 28 with high affinity, although a number of synthetic hexapeptide and octapeptide analogs of SRIF bind selectively to SSTR2. Extracellular loop three and its adjoining trans-membrane-spanning regions contain elements essential for the binding of such analogs to murine SSTR2. In particular, a stretch of amino acids from residues 294-297 (FDFV) in murine SSTR2 in trans-membrane domain seven can determine affinity for the SSTR2-selective analogs. Within this region, Phe294 has previously been predicted to be essential for the binding of octapeptides (Kaupmann, K., Bruns, C., Raulf, F., Weber, H., Mattes, H., and Lubbert, H. (1995) EMBO J. 14, 727-735) based on the observation that SSTR1 can bind the octapeptide SMS-201-995 with reasonable affinity after a Ser-to-Phe conversion in the analogous region of this receptor (SSTR1S305F). We find that SSTR1S305F has low affinity for a number of SSTR2-selective hexapeptides, suggesting that these analogs have different binding requirements than SMS-201-995. A correlation is seen between the ability of SSTR1S305F to bind hexapeptide analogs and the presence of a phenylalanine, but not tyrosine, at position two in these small cyclic molecules. Thus, a single hydroxyl group in hexapeptides can play a critical role in determining receptor binding to these receptor mutants. We also find that the second extracellular loop of SSTR1 is important for the selectivity of certain SRIF agonists for binding to SSTR1. Taken together, our data indicate that there are multiple elements in the somatostatin receptors that can determine the binding affinity and selectivity of peptide analogs.

Amino Acid Sequence↗

PubMed1996

Importance of pituitary and brain receptors for corticotrophin-releasing factor in modulating alcohol-induced ACTH secretion in the rat.

Alcohol (EtOH) releases ACTH through mechanisms that ultimately depend on the presence of endogenous corticotropin-releasing factor (CRF), but we still do not know where alcohol acts within the hypothalamic-pituitary-adrenal (HPA) axis. The present study was designed to determine the respective importance of the activation of pituitary and/or hypothalamic CRF receptors in mediating the stimulatory effect of EtOH on ACTH secretion. We used two CRF antagonists: (1) alpha-helical CRF9-41 (alpha-hel ant.), which is very effective in interfering with biological responses mediated by brain CRF receptors, but relatively impotent in blocking pituitary CRF receptors; and (2) astressin, {cyclo(30-33)[DPhe12,Nle21,38,Glu30,Lys33]r/h CRF12.41}, a member of the newest generation of antagonists capable of significantly blocking both brain and pituitary CRF receptors. The role of pituitary CRF receptors was shown by the ability of i.v. injected astressin, at doses shown to completely block CRF-induced ACTH release, to significantly (P < 0.01) reduce the ACTH response to EtOH (1.5 or 3 g/kg, i.p.). The importance of hypothalamic CRF receptors was tested by injecting alpha-hel ant. intracerebroventricularly (i.c.v.). We reasoned that if this antagonist leaked to the pituitary following administration into the ventricle, it would not be able to act directly on the corticotrophs. The ACTH response to EtOH was modestly and not significantly (P > 0.05) blunted by i.c.v. alpha-hel ant. Similarly, the stimulatory effect of alcohol on hypothalamic neuronal activation, measured by increases in the immediate early gene NGFI-B mRNA levels, was only slightly altered by blockade of hypothalamic CRF receptors. Collectively, these results suggest that during acute alcohol treatment, few brain pathways mediating the stimulatory effect of EtOH on ACTH release depend on the activation of CRF synapses. The induction of immediate early gene transcripts by alcohol similarly relies on hypothalamic circuits that stimulate CRF neurons relatively independently of the activation of CRF receptors. In contrast, functional pituitary CRF receptors are essential for the ACTH response to the drug.

Adrenocorticotropic Hormone↗

PubMed1996

Peptide chemistry: development of high performance liquid chromatography and capillary zone electrophoresis.

The development of relatively non-compressible supporting media of small particle size as well as pumps that deliver constant flow rates at high pressures has enabled investigators to perform rapid, high resolution liquid chromatography for more than two decades. Studies initiated in this laboratory in 1975, evaluating the compatibility of unprotected peptides with commercially available chromatographic supports and development of solvent systems ultimately led to separations not previously observed with both synthetic peptides and native peptides from tissue extracts. It was rapidly realized however, that recovery of certain molecules could be problematic. To meet the challenges presented by the isolation of natural hormones (such as corticotropin releasing factor and growth hormone releasing hormone) and proteins (such as inhibin and activin) and the need for large quantities of highly purified peptides for clinical investigations, our group invested heavily in identifying new supports (high carbon loading and 300 A pore sizes) and solvent systems (triethylammonium phosphate and trifluoroacetic acid) compatible with reverse phase, size exclusion and ion exchange chromatographies from a practical and economical perspective. More recently, we have contributed to the identification of unusual buffer systems (inclusive of organic modifiers) compatible with capillary zone electrophoresis that will both modulate the capillaries' selectivity, increase resolution and serve as an orthogonal approach to determining peptide purity. From a pragmatic point of view, in this paper we highlight the original and timely contributions (technical and strategical) of this laboratory in the field of analytical and preparative high performance liquid chromatography and capillary zone electrophoresis of synthetic and native biologically active peptides and proteins over the past twenty years.

Amino Acid Sequence↗

PubMed1996

Dose relationship between GnRH antagonists and pituitary suppression.

While the clinical significance of gonadotrophin-releasing hormone (GnRH) agonists is well recognized, the potential use of GnRH antagonists in humans awaits the availability of potent analogues with no untoward side-effects. We have designed, synthesized and tested several hundred linear and cyclic analogues (agonists and antagonists) of GnRH in different rat models; some have high histamine releasing activity and others have poor solubility in aqueous buffers with a pH > 6.0. Furthermore, we have identified analogues exhibiting short (< 12 h), intermediate (12-72 h) and long (> 72 h) duration of action in the rat (50 micrograms s.c. dose/rat). We have concluded that the basis for such resistance to degradation and elimination must be specific. In order to gain further information on the optimal nature and sterical requirements of side-chains, preliminary experiments were carried out using betidamino acids. Finally, mono- and dicyclic analogues of GnRH with potencies comparable with that of the most potent linear analogues were also obtained. Our approach to the development of such analogues included the use of nuclear magnetic resonance and computational techniques as well as that of state-of-the-art synthetic approaches. We intend to use the information derived from these structure/activity relationship studies to design conformationally-similar peptido-mimetics.

Amino Acid Sequence↗

PubMed1996

Reversal by NPY, PYY and 3-36 molecular forms of NPY and PYY of intracisternal CRF-induced inhibition of gastric acid secretion in rats.

1. The Y receptor subtype involved in the antagonism by neuropeptide Y (NPY) of intracisternal corticotropin-releasing factor (CRF)-induced inhibition of gastric acid secretion was studied in urethane-anaesthetized rats by use of peptides with various selectivity for Y1, Y2 and Y3 subtypes: NPY, a Y1, Y2 and Y3 agonist, peptide YY (PYY), a Y1 and Y2 agonist, [Leu31, Pro34]-NPY, a Y1 and Y3 agonist, NPY(3-36) and PYY(3-36), highly selective Y2 agonists and NPY(13-36) a weak Y2 and Y3 agonist. Peptides were injected intracisternally 10 min before intracisternal injection of CRF (10 micrograms) and gastric acid secretion was measured by the flushed technique for 1 h before and 2 h after pentagastrin-(10 micrograms kg-1 h-1, i.v.) infusion which started 10 min after CRF injection. 2. Intracisternal injection of CRF (10 micrograms) inhibited by 56% gastric acid secretion stimulated by pentagastrin. Intracisternal injection of NPY and PYY (0.1-0.5 microgram) did not influence the acid response to pentagastrin but blocked CRF-induced inhibition of pentagastrin-stimulated acid secretion. NPY(3-36) (0.5 microgram) and PYY(3-36) (0.25 and 0.5 microgram) also completely blocked the inhibitory action of CRF on pentagastrin-stimulated acid secretion. 3. [Leu31, Pro34]-NPY (0.5-5 micrograms) and NPY(13-36) (0.5-5 micrograms) injected intracisternally did not modify gastric acid secretion induced by pentagastrin or CRF inhibitory action. 4. The sigma antagonist, BMY 14802 (1 mg kg-1, s.c.) did not influence the acid response to pentagastrin but prevented the antagonism by PYY(3-36) (0.5 microgram) of the CRF antisecretory effect. 5. These results show that both PYY and NPY and the 3-36 forms of PYY and NPY are equipotent in blocking central CRF-induced inhibition of pentagastrin-stimulated gastric acid secretion. The structure-activity profile suggests a mediation through Y2 receptor subtype and the involvement of sigma binding sites.

Animals↗

PubMed1996

Neuronal pathways involved in abdominal surgery-induced gastric ileus in rats.

The 20-min rate of gastric emptying of a noncaloric solution and c-fos expression detected by immunohistochemistry in the brain were monitored 3 h after abdominal surgery performed under 10-min enflurane anesthesia in rats. Abdominal surgery (laparotomy and 1-min manipulation of the cecum) decreased gastric emptying from 60.8 +/- 3.4 to 25.9 +/- 3.4%. Capsaicin applied to the celiac/superior mesenteric ganglia 2 wk before the experiment reduced the delay in gastric emptying induced by abdominal surgery (46.3 +/- 3.4%), whereas perivagal capsaicin application had no effect (23.6 +/- 7.9%). The corticotropin-releasing factor (CRF) antagonist [D-Phe12, Nle21,38,C alpha MeLeu37]CRF-(12--41) injected intracisternally (10-20 micrograms) prevented postoperative gastroparesis induced by surgery, while having no effect on basal gastric emptying. Abdominal surgery increased the number of Fos-positive cells in brain nuclei regulating autonomic outflow: the nucleus of the solitary tract, locus ceruleus, paraventricular nucleus, and supraoptic nucleus of the hypothalamus. These data indicate that capsaicin-sensitive splanchnic afferent fibers and activation of CRF receptors in the brain are part of the neuronal circuitry mediating gastric stasis 3 h after abdominal surgery.

Abdomen↗

PubMed1996

Nature of ligand affinity and dimerization of corticotrophin-releasing factor-binding protein may be detected by circular dichroism.

As the association of corticotrophin-releasing factor (CRF) with its binding protein (BP) to form a dimer complex (CRF2/BP2) appears to be dependent on the nature of the ligand we have compared the circular dichroism difference spectra after association of the BP with ovine (o) CRF, human (h) CRF and the alpha-helical CRF (9-41) antagonist. All three ligands caused a negative change in molar ellipticity above 210 nm, with oCRF having the least and hCRF the greatest effect. Below 210 nm there was a marked divergence of difference spectra, with the reaction with the natural peptides, hCRF and oCRF, resulting in a positive change in ellipticity, whilst that with the antagonist produced a negative change. In view of the BP spectrum indicating predominantly beta-sheet and the peptides showing mainly alpha-helix these results were interpreted as the changes above 210 nm being due to dimerization and below 210 nm to a change in the conformation of ligand on binding. The opposite change in alpha-helicity of the antagonist observed on binding compared with the two natural CRF peptides could have fundamental pharmacological implications.

Animals↗

PubMed1996

Corticotropin-releasing factor (CRF) antagonist [D-Phe12,Nle21,38,C alpha MeLeu37]CRF attenuates the acute actions of the highly potent cannabinoid receptor agonist HU-210 on defensive-withdrawal behavior in rats.

The present study evaluated the modulatory role of central corticotropin-releasing factor (CRF) systems in the mediation of the effects of acute exposure to the brain cannabinoid receptor agonist HU-210 [3-(1,1-dimethylheptyl)-(-)-11-hydroxy-delta 8-tetrahydrocannabinol] on defensive withdrawal behavior in male rats. The apparatus used for the defensive withdrawal test consisted of a small chamber, set on one side of a one-square meter open field. The actions of the potent CRF antagonist [D-Phe12,Nle21,38,C alpha MeLeu37]CRF (D-Phe CRF12-41) were examined on defensive behavior under both novel and familiar conditions. The acute i.c.v. administration of D-Phe CRF12-41 (0.2-5 micrograms/injection) antagonized the defensive behavior response to stressing conditions such as novelty or swim stress in field-habituated animals. The acute i.p. administration of HU-210 (4, 20 and 100 micrograms/kg) produced a clear dose-dependent stress-like effects in field-habituated animals, as reflected in the HU-210-induced increase in both the emergence latency and the mean time spent in the small chamber. The i.c.v. administration of 5 micrograms of D-Phe CRF12-41, 5 min before the administration of the cannabinoid prevented the stressing actions of HU-210 (20 micrograms/kg, but not 100 micrograms/kg). Acute administration of HU-210 also induced a dose-dependent increase in plasma corticosterone levels which was not antagonized by pretreatment with 5 micrograms of D-Phe CRF12-41. The present study suggests a role of central CRF systems in the mediation of the anxiogenic effects of brain cannabinoid receptor agonists. This finding is consistent with a direct hypothalamic effect of cannabinoids on the activation of the pituitary-adrenal axis.

Animals↗

PubMed1996

Development of a selective agonist at the somatostatin receptor subtype sstr1.

Somatostatin (SRIF) induces its biological actions by interacting with a family of five recently cloned receptors. SRIF receptor subtype, SSTR1, has high affinity for SRIF, but no ligand has been available that selectively binds to this receptor. Desamino acid(1,2,5) [DTryptophan8, N-p-isopropl-4-aminomethyl-l-phenylalanine9]SRIF(des-AA1,2,5 [DT rp8, IAmp9]SRIF inhibits the binding of [125ITyr11]SRIF to the cloned human SSTR1 with an affinity of 1.8+0.7nM, but does not bind to the other cloned SRIF receptors. des-AA1,5[125ITyr2,DTrp8,IAmp9]SRIF bound selectively, potently and saturably to SSTR1 with a Kd of 0.5 + 0.1 nM and a maximal binding density of 226 +/- 56 fmol/mg of protein. The binding of des-AA1,5[125ITyr2,DTrp8,IAmp9]SRIF to SSTR1 was potently inhibited by SRIF, [DTrp8]SRIF, des-AA1,2,5[DTrp8,IAmp9,DSer13]SRIF and SRIF 28 with K, values of 0.7+0.3, 0.2+0.2, 4.3+0.7 and 0.6+0.1 nM, respectively. SRIF analogs that selectively bind to SSTR2 and SSTR5 were impotent in displacing des-AA1,5[125ITyr2,DTrp8,IAmp9]SRIF from human SSTR1. des-AA1,5[125ITyr2,DTrp8,IAmp9]SRIF binding to SSTR1 expressed in COS-7 cells was reduced by GTPgS, and this effect was prevented by pertussis toxin treatment. In contrast, the binding of[125ITyr11]SRIF to SSTR1 was not affected by these treatments. These findings indicate that des-AA1,5[125ITyr2,DTrp8,IAmp9]SRIF may bind to SSTR1 in a defferent manner than SRIF. des-AA1,2,5[DTrp8,IAmp9]SRIF and its tyrosine analog are the first ligands that selectively bind to SSTR1 with high affinity and should be useful in localizing and determining the functional properties of this receptor.

Animals↗