RACK1 (receptor for activated C-kinase 1) interactions with spectrin repeat elements.

Receptor for activated C-kinase 1 (RACK1) is an intracellular scaffolding protein involved in a multitude of signalling pathways. The cytoskeleton is fundamental for intracellular cell signalling as it forms an interconnected network of regulatory proteins. Here, spectrin is a central component as it forms the actin-spectrin network that serves as docking surfaces for cellular components. The interaction between RACK1 and components of spectrin, the single spectrin repeats R16, R17 and the double spectrin repeat R1617 from the α-spectrin chain were investigated by biosensor technology and docking analysis. RACK1 associated only weakly to R16 (KD = 1.0 ± 0.5 × 10(-6) M), about 20 times stronger to R1617 (KD = 5.3 ± 0.7 × 10(-8) M) and 100 times stronger to R17 (KD = 0.9 ± 0.3 × 10(-8) M). Docking analysis showed that while R16 alone preferentially docked with its B-helix, R17 docked through its A-helix and BC loop. The double repeat and RACK1 mainly formed two different complex conformations. R1617 docked tangentially to the N/C-terminal of RACK1 or radially along a groove on the outer surface of RACK1. These configurations could account for the slight increase in entropic and the decrease in enthalpic interactions for the R1617-RACK1 interaction, compared with the interactions of RACK1 to the two single repeats. Our results suggest a mode of interaction that allows spectrin to attach to the N/C part of RACK through the inter-helical AB and BC loops and adopt a multitude of configurations in between the two limiting configurations.

Slaughter of Atlantic salmon (Salmo salar L.) in the presence of carbon monoxide.

The different stunning methods for Atlantic salmon can still be improved with regard to animal welfare. Salmon exposed to carbon monoxide expressed no aversive reactions towards CO as such. CO exposed fish showed an earlier onset of rigour mortis and a faster decrease in muscle pH due to depletion of oxygen during the treatment. Exposure to CO did increase the level of cortisol compared to undisturbed control fish, but the increase was less than in the water only control group. Neuroglobin, a CO binding globin, was found in salmon brain and Saccus vasculosus, a richly vascularized sac connected to the fish brain. Binding of CO to neuroglobin during sedation might possibly improve animal welfare.

Cloning, expression and purification of Atlantic salmon (Salmo salar, L.) neuroglobin.

Neuroglobin (Ngb) exists only in small amounts in salmon brain. In order to study the protein in more detail salmon neuroglobin (sNgb) was cloned, heterologously expressed in Escherichia coli and purified. The protein had red color and showed the characteristic peaks at 411nm (metNgb), 415nm (carboxyNgb) and 424nm (deoxyNgb). Western analysis showed that sNgb reacted weakly against a rabbit anti human neuroglobin (hNgb) and strongly to a sNgb specific antibody. Our 3D-homology model of the sNgb indicated modifications adjacent to and in the O(2)/CO binding site. This may correlate to differences in substrate affinities for the sNgb compared to the hNgb. Also sNgb contained shorter helixes and longer interhelical loops typical for psychrophilic proteins.

Thermal stability of chicken brain α-spectrin repeat 17: a spectroscopic study.

Spectrin is a rod-like multi-modular protein that is mainly composed of triple-helical repeats. These repeats show very similar 3D-structures but variable conformational and thermodynamical stabilities, which may be of great importance for the flexibility and dynamic behaviour of spectrin in the cell. For instance, repeat 17 (R17) of the chicken brain spectrin α-chain is four times less stable than neighbouring repeat 16 (R16) in terms of ∆G. The structure of spectrin repeats has mainly been investigated by X-ray crystallography, but the structures of a few repeats, e.g. R16, have also been determined by NMR spectroscopy. Here, we undertook a detailed characterization of the neighbouring R17 by NMR spectroscopy. We assigned most backbone resonances and observed NOE restraints, relaxation values and coupling constants that all indicated that the fold of R17 is highly similar to that of R16, in agreement with previous X-ray analysis of a tandem repeat of the two domains. However, (15)N heteronuclear NMR spectra measured at different temperatures revealed particular features of the R17 domain that might contribute to its lower stability. Conformational exchange appeared to alter the linker connecting R17 to R16 as well as the BC-loop in close proximity. In addition, heat-induced splitting was observed for backbone resonances of a few spatially related residues including V99 of helix C, which in R16 is replaced by the larger hydrophobic tryptophan residue that is relatively conserved among other spectrin repeats. These data support the view that the substitution of tryptophan by valine at this position may contribute to the lower stability of R17.

HIV-1 p6-Another viral interaction partner to the host cellular protein cyclophilin A.

The 52-amino acid human immunodeficiency virus type 1 (HIV-1) p6 protein has previously been recognized as a docking site for several cellular and viral binding factors and is important for the formation of infectious viruses. A particular structural feature of p6 is the notably high relative content of proline residues, located at positions 5, 7, 10, 11, 24, 30, 37 and 49 in the sequence. Proline cis/trans isomerism was detected for all these proline residues to such an extent that more than 40% of all p6 molecules contain at least one proline in a cis conformation. 2D (1)H nuclear magnetic resonance analysis of full-length HIV-1 p6 and p6 peptides established that cyclophilin A (CypA) interacts as a peptidyl-prolyl cis/trans isomerase with all proline residues of p6. Only catalytic amounts of CypA were necessary for the interaction with p6 to occur, strongly suggesting that the observed interaction is highly relevant in vivo. In addition, surface plasmon resonance studies revealed binding of full-length p6 to CypA, and that this binding was significantly stronger than any of its N- or C-terminal peptides. This study demonstrates the first identification of an interaction between HIV-1 p6 and the host cellular protein CypA. The mode of interaction involves both transient enzyme-substrate interactions and a more stable binding. The binding motifs of p6 to Tsg-101, ALIX and Vpr coincide with binding regions and catalytic sites of p6 to CypA, suggesting a potential role of CypA in modulating functional interactions of HIV-1.

The host-pathogen interaction of human cyclophilin A and HIV-1 Vpr requires specific N-terminal and novel C-terminal domains.

BACKGROUND: Cyclophilin A (CypA) represents a potential key molecule in future antiretroviral therapy since inhibition of CypA suppresses human immunodeficiency virus type 1 (HIV-1) replication. CypA interacts with the virus proteins Capsid (CA) and Vpr, however, the mechanism through which CypA influences HIV-1 infectivity still remains unclear. RESULTS: Here the interaction of full-length HIV-1 Vpr with the host cellular factor CypA has been characterized and quantified by surface plasmon resonance spectroscopy. A C-terminal region of Vpr, comprising the 16 residues 75GCRHSRIGVTRQRRAR90, with high binding affinity for CypA has been identified. This region of Vpr does not contain any proline residues but binds much more strongly to CypA than the previously characterized N-terminal binding domain of Vpr, and is thus the first protein binding domain to CypA described involving no proline residues. The fact that the mutant peptide Vpr75-90 R80A binds more weakly to CypA than the wild-type peptide confirms that Arg-80 is a key residue in the C-terminal binding domain. The N- and C-terminal binding regions of full-length Vpr bind cooperatively to CypA and have allowed a model of the complex to be created. The dissociation constant of full-length Vpr to CypA was determined to be approximately 320 nM, indicating that the binding may be stronger than that of the well characterized interaction of HIV-1 CA with CypA. CONCLUSIONS: For the first time the interaction of full-length Vpr and CypA has been characterized and quantified. A non-proline-containing 16-residue region of C-terminal Vpr which binds specifically to CypA with similar high affinity as full-length Vpr has been identified. The fact that this is the first non-proline containing binding motif of any protein found to bind to CypA, changes the view on how CypA is able to interact with other proteins. It is interesting to note that several previously reported key functions of HIV-1 Vpr are associated with the identified N- and C-terminal binding domains of the protein to CypA.

The intriguing cyclophilin A-HIV-1 Vpr interaction: prolyl cis/trans isomerisation catalysis and specific binding.

BACKGROUND: Cyclophilin A (CypA) represents a potential target for antiretroviral therapy since inhibition of CypA suppresses human immunodeficiency virus type 1 (HIV-1) replication, although the mechanism through which CypA modulates HIV-1 infectivity still remains unclear. The interaction of HIV-1 viral protein R (Vpr) with the human peptidyl prolyl isomerase CypA is known to occur in vitro and in vivo. However, the nature of the interaction of CypA with Pro-35 of N-terminal Vpr has remained undefined. RESULTS: Characterization of the interactions of human CypA with N-terminal peptides of HIV-1 Vpr has been achieved using a combination of nuclear magnetic resonace (NMR) exchange spectroscopy and surface plasmon resonance spectroscopy (SPR). NMR data at atomic resolution indicate prolyl cis/trans isomerisation of the highly conserved proline residues Pro-5, -10, -14 and -35 of Vpr are catalyzed by human CypA and require only very low concentrations of the isomerase relative to that of the peptide substrates. Of the N-terminal peptides of Vpr only those containing Pro-35 bind to CypA in a biosensor assay. SPR studies of specific N-terminal peptides with decreasing numbers of residues revealed that a seven-residue motif centred at Pro-35 consisting of RHFPRIW, which under membrane-like solution conditions comprises the loop region connecting helix 1 and 2 of Vpr and the two terminal residues of helix 1, is sufficient to maintain strong specific binding. CONCLUSIONS: Only N-terminal peptides of Vpr containing Pro-35, which appears to be vital for manifold functions of Vpr, bind to CypA in a biosensor assay. This indicates that Pro-35 is essential for a specific CypA-Vpr binding interaction, in contrast to the general prolyl cis/trans isomerisation observed for all proline residues of Vpr, which only involve transient enzyme-substrate interactions. Previously suggested models depicting CypA as a chaperone that plays a role in HIV-1 virulence are now supported by our data. In detail the SPR data of this interaction were compatible with a two-state binding interaction model that involves a conformational change during binding. This is in accord with the structural changes observed by NMR suggesting CypA catalyzes the prolyl cis/trans interconversion during binding to the RHFP35RIW motif of N-terminal Vpr.

Effects of bifeprunox and aripiprazole on rat serotonin and dopamine neuronal activity and anxiolytic behaviour.

The atypical antipsychotic bifeprunox is a partial dopamine D(2) and 5-HT(1A) receptor agonist. Using in-vivo electrophysiological and behavioural paradigms in the rat, the effects of bifeprunox and aripiprazole were assessed on ventral tegmental area (VTA) dopamine and dorsal raphe serotonin (5-HT) cell activity and on foot shock-induced ultrasonic vocalisation (USV). In VTA, bifeprunox and aripiprazole decreased (by 20-50%) firing of dopamine neurons. Interestingly, bursting activity was markedly reduced (by 70-100%), bursting being associated with a larger synaptic dopamine release than single spike firing. Both ligands reduced inhibition of firing rate induced by the full dopamine receptor agonist apomorphine, whereas the D(2) receptor antagonist haloperidol prevented these inhibitory effects, confirming partial D(2)-like agonistic properties. On 5-HT neurons, bifeprunox was more potent than aripiprazole to suppress firing activity. The 5-HT(1A) receptor antagonist WAY-100,635 prevented their effects. In the USV test of anxiolytic-like activity, bifeprunox had higher potency than aripiprazole to reduce vocalisations. Both WAY-100,635 and haloperidol reversed the effects of both agonists. The present in-vivo study shows that bifeprunox is a potent partial D(2)-like and 5-HT(1A) receptor agonist reducing preferentially the phasic activity of dopamine neurons. Thus, bifeprunox would be expected to be an effective compound against positive and negative symptoms of schizophrenia.

Strict conservation of the ITS regions of the ribosomal RNA genes in Atlantic cod (Gadus morhua L.).

The nucleotide sequence of the internal transcribed region (ITS) of ribosomal RNA genes from Atlantic cod (Gadus morhua L.) was determined. The complete ITS region spanned approximately 1113 base pairs. The ITS1 region comprised 532 base pairs, the 5.8S region 159, and the ITS2 region contained 422 base pairs. Sequence data were obtained from a total of 12 samples, one pool from six cod and 11 individuals. The sequencing was carried out in two separate experimental periods employing slightly different methodology. The samples were from two different cod stocks, Norwegian costal cod and North East Arctic cod. The sequence analysis showed that in the 12 samples, the ITS region, including the 5.8S RNA, was identical. The ITS region is thus totally conserved in these two cod stocks. The extreme conservation of the ITS regions in the cod rDNA could reflect the small genome size of cod and/or indicate a specific critical role in the processing of the ribosomal units in cold-adapted species.

Expression and purification of receptor for activated C-kinase 1 (RACK1).

Receptor for activated C-kinase (RACK1) binds to protein kinase C and functions as an anchor for several other cellular components. Most in vitro studies of RACK1 have been carried out with RACK1 fused to a soluble fusion protein partner, such as GST or MBP. Here, we show that fusion complexes may exist as large soluble aggregates and thereby lead to false conclusions about the biological activity of RACK1. We developed a purification procedure that gave soluble monodisperse molecules of the protein. The RACK1 gene was cloned and expressed in a pMAL vector. After purification of the resulting MBP-RACK1 fusion protein, RACK1 was excised from MBP by thrombin, rendering RACK1 in a soluble monodisperse form as monitored by fluorimetric static light scattering, gel filtration, and ultracentrifugation. Circular dichroism analysis revealed that RACK1 was properly folded with a T(m) of approximately 62 degrees C and contained the predicted portions of secondary structures. The biological activity of the purified protein was verified by binding to activated protein kinase C. The production of soluble, high-purity RACK1 will allow structural studies and functional in vitro studies to identify interacting partners to this important scaffold protein.

Actin binding of a minispectrin.

A "minispectrin" has been constructed from the tail end of the alpha/beta heterodimer, and its actin-binding properties have been characterised. It is a complex of the N-terminal fragment of the beta-subunit consisting of the actin-binding domain plus the two first triple-helical repeats beta 1 and beta 2, and the C-terminal fragment of the alpha-subunit containing the repeats alpha 19 and alpha 20 plus the calmodulin-like domain. This minispectrin exists in a dimeric form that contains one copy of each polypeptide and binds to actin in a cooperative manner with an apparent K(d) of 2.5 microM. Calcium seems not to have any effect on its binding to actin. Electron microscopic analysis shows that the minispectrin decorates actin filaments as clusters, and induces formation of actin bundles. This study shows that the actin-binding region of the spectrin alpha/beta heterodimer retains its functional properties in a truncated form and establishes basis for further research on spectrin's structure and function.

Effects of the 5-HT(6) receptor antagonist, SB-271046, in animal models for schizophrenia.

The 5-HT(6) receptor is targeted by several new antipsychotics such as clozapine, olanzapine, and sertindole. We studied the effect of SB-271046 [5-chloro-N-(4-methoxy-3-piperazin-1-yl-phenyl)-3-methyl-2-benzothiophenesulfonamide], a specific 5-HT(6) receptor antagonist, in three models for the positive symptoms of schizophrenia---D-amphetamine-induced hyperactivity, and D-amphetamine- or phencyclidine (PCP)-disrupted prepulse inhibition (PPI). We also tested this compound in a model for the negative symptoms of schizophrenia, PCP-disrupted social interaction (SIT) in rats. Induction of side effects by this compound was evaluated by testing its potency to reduce spontaneous motility, and to induce catalepsy in rats. The effect of SB-271046 was compared to clozapine in all models tested. This study showed that SB-271046 had no beneficial effect in PCP-disrupted SIT. However, SB-271046 dose-dependently normalised D-amphetamine-disrupted PPI, but did not reverse PCP-disrupted PPI. In addition, SB-271046 did not antagonise D-amphetamine-induced hyperactivity. Thus, this specific 5-HT(6) receptor antagonist was associated with a clear positive outcome in only one model for the positive symptoms of schizophrenia, and had no beneficial effect in the model for negative symptoms. Consequently, it is clear that SB-271046 is not expected to have an antipsychotic efficacy, at least when given as monotherapy.

Effects of the 5-HT(7) receptor antagonist SB-258741 in animal models for schizophrenia.

The 5-HT(7) receptor is targeted by several new antipsychotics such as clozapine and risperidone. We studied the effect of R-(+)-1-(toluene-3-sulfonyl)-2-[2-(4-methylpiperidin-1-yl)ethyl]-pyrrolidine (SB-258741), a specific 5-HT(7) receptor antagonist, in three models for positive symptoms, D-amphetamine-induced hyperactivity and D-amphetamine- and phencyclidine (PCP)-disrupted prepulse inhibition (PPI) in rats, with the aim of investigating the role of this receptor in the clinical effect of antipsychotics. We also tested this compound in a model for negative symptoms, PCP-disrupted social interaction (SIT) in rats. Induction of side effects by this compound was evaluated by testing its potency to reduce spontaneous motility and to induce catalepsy in rats. The effect of SB-258741 was compared to risperidone in all models. This study showed that SB-258741 had no beneficial effect on PCP-disrupted SIT. SB-258741 did not reverse D-amphetamine-disrupted PPI; however, it dose-dependently normalised PCP-disrupted PPI. SB-258741 antagonised D-amphetamine-induced hyperactivity but reduced motility of rats at similar doses. Thus, this specific 5-HT(7) receptor antagonist brought a clear positive outcome in only one model for positive symptoms of schizophrenia and had no beneficial effect in the model for negative symptoms. Consequently, it is clear that SB-258741 affects the PPI phenomenon but is not expected to have an antipsychotic effect on its own in clinic.

Induction of tolerance to the suppressant effect of the neurotensin analogue NT69L on amphetamine-induced hyperactivity.

Although several studies have indicated that neurotensin administered acutely has several pharmacological properties common with those of antipsychotic drugs, the effects of repeated exposure to neurotensin receptor agonism have been less well characterised. Here, we investigated the effect of the novel neurotensin-(8-13) analogue NT69L [(N-methyl-Arg), Lys, Pro, L-neo-Trp, tert-Leu, Leu] in animal models sensitive to central neurotensin receptor stimulation as well as in predictive models for antipsychotic activity and motor side-effect liability. Acute injection of NT69L (0.19-6.1 micromol/kg, s.c./i.p.) caused hypothermia (>2.5 degrees C) and reduction in spontaneous locomotor activity but failed to induce catalepsy. Furthermore, NT69L (0.10 micromol/kg, s.c.) counteracted the hyperlocomotion elicited by amphetamine (0.5 mg/kg, s.c.). However, repeated injections of NT69L (0.19 micromol/kg, s.c. for 6 days, twice daily) significantly reduced its effect on spontaneous locomotor activity and completely abolished its effect on amphetamine-elicited hyperactivity. Our data obtained after single injections of NT69L indicate that this drug stimulates central neurotensin receptors after peripheral administration and collectively support the notion that neurotensin receptor agonism is associated with an attractive pre-clinical profile as regards both antipsychotic activity and motor side-effect liability. However, the present results also indicate that repeated neurotensin receptor stimulation may cause a desensitisation of neurotensin receptor mediated effects.

In-vivo assessment of 5-HT2A and 5-HT2C antagonistic properties of newer antipsychotics.

The effects of serotonin (5-HT) receptor ligands on the MK 212 (6-chloro-2[1-piperazinyl]pyrazine) discriminative stimulus and quipazine-induced head twitches were studied in rats. 5-HT1A (8-OH-DPAT) and preferential 5-HT2A (DOI) receptor agonists did not generalize to the discriminative stimulus. The 5-HT2B/2C-receptor antagonist, SB 206553 (5-methyl-1-(3-pyridylcarbamoyl)-1,2,3,5-tetrahydropyrrolo[2 ,3-f]indole), and the 5-HT2A/2C-receptor antagonist, ritanserin, acted as potent antagonists, whereas the 5-HT2A-receptor antagonist, MDL 100.151 ([(+/-)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4- piperidine-methanol), produced minor and inconsistent inhibition. SB 206553 was a weak antagonist against quipazine-induced head twitches, whereas MDL 100.151 and ritanserin were potent antagonists. This suggests that the MK 212 discriminative stimulus is mediated by 5-HT2C receptors, while quipazine-induced head twitches are mediated primarily by 5-HT2A receptors. The effects on quipazine-induced head twitches were comparable to previously published effects on the DOI discriminative stimulus. 5-HT2A- and 5-HT2C-receptor antagonistic potencies of clozapine, olanzapine, risperidone, sertindole and ziprasidone were compared in the same models. Clozapine showed similar potencies in both models, while sertindole, olanzapine and risperidone inhibited quipazine-induced effects more potently than the MK 212 discriminative stimulus. Ziprasidone exerted a minor preference for 5-HT2A- compared to 5-HT2C-receptor-mediated effects. The ratio between in vivo inhibitory potencies at 5-HT2A and 5-HT2C receptors did not correlate with corresponding ratios from in-vitro affinity and ex-vivo occupancy studies in the literature.

Intracranial self-stimulation and sucrose intake differ as hedonic measures following chronic mild stress: interstrain and interindividual differences.

The present study was designed to assess the utility of sucrose intake and intracranial self-stimulation (ICSS) as hedonic measures for chronic mild stress (CMS) induced behavioural deficits. Wistar and PVG hooded rats were exposed to a variety of mild stressors, e.g. periods of food and/or water deprivation, soiled cage, light/dark reversal, confinement to small cages and pairing, during 6-9 weeks. The intake of 1% sucrose solution was significantly reduced in stressed PVG hooded rats compared to control animals. The sucrose intake in stressed Wistar rats remained unaltered, indicating that CMS-induced decreases in sucrose intake are strain dependent. However, sucrose intake has in our experience been shown to be unreliable as the observed decreases following CMS were inconsistent over time. ICSS behaviour was evaluated from rate/frequency functions by determining the frequency that supported 50% of maximal response rate. Neither the Wistar nor the PVG hooded rats showed an overall decrease in ICSS behaviour following CMS. However, the ICSS measures revealed interindividual differences in both rat strains. In the stress groups a subgroup (14 +/- 2.4%) of rats progressively exhibited an attenuated ICSS behaviour. These findings may reflect the interindividual variability observed in humans as stress does not invariably lead to depression. The model may in its present form be used to study the pathophysiology of depressive disorders. However, the utility of the CMS model to study antidepressant drug actions has to be questioned. Our results show there is a need for rat strains in which there is a greater sensitivity for detecting stress effects. It emphasises the fact that replication of CMS-induced decreases in ICSS behaviour can be as problematic as inducing decreases in sucrose intake.

Pharmacological differentiation of classical and novel antipsychotics.

The symptoms of schizophrenia are treated through the blockade of mesolimbic and mesocortical dopamine activity. However, if dopamine activity in the nigrostriatal region is also blocked, extrapyramidal syndromes (EPS) are induced, and EPS are a major cause of noncompliance. It is therefore important for antipsychotic drugs with selective pharmacological profiles to be developed. Animal models for limbic selectivity and dose-response separation between behavioural and pharmacological parameters, which are analogous to EPS and antipsychotic effects, can now be used to differentiate between novel antipsychotics with few or no EPS and classical antipsychotics. Schizophrenic patients also often experience cognitive dysfunction, and it is important that antipsychotic drugs are developed that do not exacerbate this. Again, animal models can be used to give an indication of whether a compound has any effect on cognition. Both behavioural and electrophysiological rat models indicate that novel antipsychotic drugs, such as sertindole, but not classical antipsychotic drugs, such as haloperidol, demonstrate marked limbic selectivity. Nonhuman primate models of EPS show that the novel antipsychotics have a much greater separation between dose-response curves for antipsychotic effect and the development of EPS. The Morris water maze confirmed that sertindole does not adversely affect spatial learning or memory in rats. This paper reports on the differentiation between classical and novel antipsychotics using animal models.

In vivo muscarinic cholinergic mediated effects of Lu 25-109, a M1 agonist and M2/M3 antagonist in vitro.

Lu 25-109 [5-(2-ethyl-2H-tetrazol-5-yl)-1,2,3,6-tetrahydro-1-methylpyridine] , has M agonistic and M2/M3 antagonistic effects at muscarinic receptors in vitro; a pharmacological profile that may be beneficial in treatment of Alzheimer's disease. In the present study, we compare functional in vivo effects of Lu 25-109 and reference compounds in animal models of muscarinic cholinergic function. Lu 25-109 substituted completely for the discriminative stimulus effects of (-)-7-methyl-3-(2-propynyloxy)-4,5,6,7-tetrahydroisothiazolo -[4, 5-c]pyridine (Lu 26-046), a partial M1/M2 agonist, but only weakly for the effects of the non-selective M1/M2/M3 agonist 3-methoxy-4,5,6,7-tetrahydro-isoxazolo[4, 5-c] pyridine (O-Me-THPO). Lu 25-109 did not reverse O-Me-THPO-induced discriminative stimulus. Tacrine did not substitute for any of the training drugs. Lu 25-109 did not substitute in (-)-nicotine trained rats. Lu 25-109 did not antagonize oxotremorine-induced hypothermia, tremor and salivation in mice and antagonized physostigmine-induced lethality with low potency. Unlike non-selective muscarinic agonists and acetylcholinesterase inhibitors, Lu 25-109 did not induce hypothermia, tremor or salivation in mice. Spontaneous locomotor activity and motor co-ordination were inhibited only at high doses. Lu 25-109 had no effect on mean blood pressure in anaesthetized rats. Lu 25-109 and O-Me-THPO produced a significant increase in heart rate. The maximum increase was 37%. In anaesthetized cats, increasing i.v. doses of Lu 25-109 were without effect on the mean blood pressure, except for a short lasting (<2 min) depressor effect following the IV injection. Furthermore, Lu 25-109 did not attenuate the reflex mechanisms restoring blood pressure following orthostasis in cats. In conclusion, the drug discrimination studies suggest a unique activity profile of Lu 25-109, and the in vivo profile suggests none or a very low frequency of unwanted cholinergic mediated effects.

Do novel antipsychotics have similar pharmacological characteristics? A review of the evidence.

The pharmacological properties of the novel antipsychotic drugs (APDs) risperidone, sertindole, olanzapine, quetiapine, ziprasidone, remoxipride, and amperozide are reviewed and compared with haloperidol and clozapine. Focus is made on their receptor profiles, their effects in animal models used for evaluation of antipsychotic activity, and extrapyramidal side effects (EPS). In addition, the contrasting actions of these compounds on animal models of cognition, anxiety, and depression are briefly reviewed. The available evidence indicates that novel APDs and clozapine can be differentiated from haloperidol, particularly in models of EPS and cognitive side effects. However, among the group of novel APDs there are many individual differences in models reflecting limbic versus striatal inhibition of dopamine function: clozapine and sertindole show the largest limbic selectivity, followed by quetiapine, ziprasidone, olanzapine and remoxipride, whereas risperidone in many respects has a profile that resembles haloperidol. To date, the results of clinical studies have confirmed the predictions of lower incidence or absence of EPS after administration of novel APDs in doses which demonstrate antipsychotic efficacy.

Differentiation of classical and novel antipsychotics using animal models.

The criteria that have been used to differentiate classical and atypical antipsychotics include measures of neurological and cognitive side effects and therapeutic effects. Novel antipsychotic compounds with few or no extrapyramidal syndromes (EPS) can be differentiated from classical neuroleptics by a number of animal models for limbic selectivity and dose-response separation between behavioral and pharmacological parameters analogous to EPS and antipsychotic effects. The results obtained using these models seem to be concordant with clinical findings. Moreover, animal models expand our understanding of the pharmacological mechanisms responsible for EPS and for the therapeutic effects of antipsychotics, and they allow an examination of the possible effects of new compounds on cognition. Here we review a number of key reports on the differentiation of classical and novel antipsychotics using animal models.