(3S)-3-(2,3-difluorophenyl)-3-methoxypyrrolidine (IRL752) -a Novel Cortical-Preferring Catecholamine Transmission- and Cognition-Promoting Agent.

Here we describe for the first time the distinctive pharmacological profile for (3S)-3-(2,3-difluorophenyl)-3-methoxypyrrolidine (IRL752), a new phenyl-pyrrolidine derivative with regioselective central nervous system transmission-enhancing properties. IRL752 (3.7-150 µmol/kg, s.c.) was characterized through extensive in vivo studies using behavioral, tissue neurochemical, and gene expression as well as microdialysis methods. Behaviorally, the compound normalized tetrabenazine-induced hypoactivity, whereas it was unable to stimulate basal locomotion in normal animals or either accentuate or reverse hyperactivity induced by amphetamine or MK-801. IRL752 induced but minor changes in monoaminergic tissue neurochemistry across noradrenaline (NA)- and dopamine (DA)-dominated brain regions. The expression of neuronal activity-, plasticity-, and cognition-related immediate early genes (IEGs), however, increased by 1.5-fold to 2-fold. Furthermore, IRL752 dose-dependently enhanced cortical catecholamine dialysate output to 600%-750% above baseline, whereas striatal DA remained unaltered, and NA rose to ∼250%; cortical and hippocampal dialysate acetylcholine (ACh) increased to ∼250% and 190% above corresponding baseline, respectively. In line with this cortically preferential transmission-promoting action, the drug was also procognitive in the novel object recognition and reversal learning tests. In vitro neurotarget affinity and functional data coupled to drug exposure support the hypothesis that 5-hydroxytryptamine 7 receptor and α2(C)-adrenoceptor antagonism are key contributors to the in vivo efficacy and original profile of IRL752. The cortical-preferring facilitatory impact on catecholamine (and ACh) neurotransmission, along with effects on IEG expression and cognition-enhancing features, are in line with the potential clinical usefulness of IRL752 in conditions wherein these aspects may be dysregulated, such as in axial motor and cognitive deficits in Parkinson disease. SIGNIFICANCE STATEMENT: This report describes the distinctive preclinical profile of (3S)-3-(2,3-difluorophenyl)-3-methoxypyrrolidine (IRL752). Its in vivo neurochemical, behavioral, microdialysis, and gene expression properties are consistent with a cortically regioselective facilitatory impact on catecholaminergic and cholinergic neurotransmission accompanied by cognitive impairment-reversing features. The pharmacological characteristics of IRL752 are in line with the clinical usefulness of IRL752 in conditions wherein these aspects may be dysregulated, such as in axial motor and cognitive deficits in Parkinson disease.

Synthesis and pharmacological evaluation of 4-phenoxy-1,2,3,4-tetrahydroisoquinolines and 4,5,6,6a-tetrahydrochromeno[2,3,4-de]isoquinolines.

The novel 4-phenoxy-1,2,3,4-tetrahydroisoquinolines 6a-c and their rigid congeners 4,5,6,6a-tetrahydro-chromeno[2,3,4-de]isoquinolines 7a,b were synthesized in order to obtain dopamine D2-like receptor ligands. The new compounds were evaluated for their in vitro binding affinities, in vivo behavioral activities on rats, and for their effects on rat brain neurochemistry. Compounds 6b (toward both D2 and D3 dopamine receptors) and 7a,b (toward D3 only dopamine receptors) showed the most significant affinities. However none of the new compounds was able to stimulate behavioral activity in non pre-treated rats, nor to influence brain neurochemistry.

Proteome analysis after co-administration of clozapine or haloperidol to MK-801-treated rats.

MK-801, a glutamergic, N-methyl-D-aspartate (NMDA)-receptor antagonist that mediates neurotransmission and has psychotomimetic properties, giving schizophrenia-like symptom. The objective of this study was to investigate the effects on the thalamic and cortical proteome of one typical (haloperidol) and one atypical (clozapine) antipsychotic drug in interaction with MK-801 in rats. Rats received subcutaneous injections of MK-801 or vehicle (controls) or MK-801 together with concurrent administration of haloperdol or clozapine for eight days. Protein samples from thalamus and cortex were analyzed with two-dimensional gel electrophoresis in combination with mass spectrometry. MK-801 induced alterations in the levels of three proteins in both cortex and thalamus. Clozapine reversed all the protein changes. Haloperidol reversed two. Both antipsychotics induced new protein changes in both cortex and thalamus not seen after MK-801-treatment by alone. In conclusion, the MK-801 animal model shows potential for investigation of different antipsychotic drugs and biochemical treatment effects in schizophrenia.

Antagonism of cocaine's pharmacological effects by the stimulant dopaminergic antagonists, (+)-AJ76 and (+)-UH232.

The aminotetralins (+)-AJ76 and (+)-UH232 are stimulant dopaminergic antagonists, which may preferentially antagonize autoreceptors of dopamine nerve terminals. Both agents antagonized cocaine's depressant effects on firing rates of ventral tegmental dopaminergic neurons, but (+)-UH232 was much more potent. When injected simultaneously with cocaine, (+)-UH232 inhibited and (+)-AJ76 enhanced the locomotor stimulation observed during the first 30 min following s.c. cocaine administration. However, (+)-AJ76 antagonized cocaine-induced stereotypies as well as the later more intense cocaine locomotor stimulation. It is suggested that preferential dopamine autoreceptor antagonists may provide a novel approach to a pharmacotherapy for treating cocaine abuse.

Effects of the dopamine D3-and autoreceptor preferring antagonist (-)-DS121 on locomotor activity, conditioned place preference and intracranial self-stimulation in the rat.

The phenylpiperidine (-)-DS121 (S-(-)-3-(-3-cyanophenyl)-N-n-propyl piperidine) represents a new class of weak stimulants acting as preferential dopamine autoreceptor antagonists. (-)-DS121 dose-dependently increases locomotor activity over a wide dose range in rats after systemic administration. (-)-DS121 also exhibits a weak preference for the D3 receptor in in vitro binding studies. The relevance of this D3 preference is not clear and it is not known whether the D3 receptor site influences reward mechanisms. The present results showed that (-)-DS121 induced place conditioning in the dose range 3.3-13.3mg/kg s.c. as did d-amphetamine (0.25-4.0mg/kg, s.c.). However, in contrast to d-amphetamine, (-)-DS121 failed to facilitate infracranial self-stimulation in the dose range that produced place conditioning. Local bilateral infusion of (-)-DS121 (0.05-53.0µg/side) into the nucleus accumbens or ventral tegmental area did not produce locomotor stimulation. A weak but significant increase in locomotor activity was detected after bilateral infusion of (-)-DS121 (66.3µg/side) into the lateral ventricles. This study suggests that the behavioural stimulant (-)-DS121 does not possess strong reward-facilitating properties and that local application in either the terminal or somatodendritic regions of the mesolimbic pathway does not produce the same degree of locomotor activity as seen after systemic administration.

The preferential dopamine autoreceptor antagonist (+)-UH232 antagonizes the positive reinforcing effects of cocaine and d-amphetamine in the ICSS paradigm.

The dopamine autoreceptor and D3 preferring antagonist [cis-(+)-5-methoxy-1-methyl-2-(di-n-propylamino)tetralin] (+)-UH232, exerts weak stimulatory effects when tested in locomotor activity experiments using habituated animals. (+)-UH232 also blocks d-amphetamine-, cocaine-, and apomorphine-induced hyperactivity, but fails to induce catalepsy. Thus, the behavioral effects of (+)-UH232 appear to be dependent upon the baseline activity of the animal. The antagonistic properties of (+)-UH232 were studied in the intracranial self-stimulation (ICSS) technique in the rat. (+)-UH232 and haloperidol produced inhibitory effects over a wide dose range. Cocaine, GBR12909 and d-amphetamine clearly lowered ICSS thresholds, indicating stimulatory effects. (+)-UH232 antagonized the stimulatory effects of cocaine, GBR12909, and d-amphetamine, whereas haloperidol, at a dose producing an inhibition similar to (+)-UH232, was significantly weaker in antagonizing cocaine- or d-amphetamine-induced stimulation. This difference between (+)-UH232 and haloperidol with respect to stimulant-blocking ability, support the concept that the effects of (+)-UH232 are not representative of either classical DA agonists or DA antagonists.

Effects on locomotor activity after local application of (+)-UH232 in discrete areas of the rat brain.

The preferential dopamine autoreceptor, and slightly D3 preferring, antagonist (+)-UH232 (cis-(+)-(1S,2R)-5-methoxy-1-methyl-2-(n-dipropylamino) tetralin) increases locomotor activity and synaptic dopamine release in the nucleus accumbens and striatum after systemic administration to the rat. As shown in this study, (+)-UH232, was unable to produce an increase in locomotor activity measured for 60 minutes after local administration into the terminal or somato-dendritic regions of the mesolimbic dopamine pathways or into the lateral ventricle. Instead, a dose dependent decrease of spontaneous locomotor activity after local application (0.05-50.0 nmol/side) of (+)-UH232 into the nucleus accumbens, was seen. A similar reduction in locomotor activity was produced by the classical dopamine antagonist raclopride. Analysis of the dose*time interactions on locomotor activity did, however, indicate that there is a significant dose*time interaction after local application of (+)-UH232 into the lateral ventricle and VTA. Raclopride, on the other hand, produced only a weak time dependent effect in the VTA. The potential problem of Leao's spreading depression in micro-injection experiments were considered, however, spreading depression does not seem to influence the effects of (+)-UH232 locally applied into the nucleus accumbens. In conclusion, both (+)-UH232 and raclopride produced a dose dependent decrease in spontaneous locomotor activity when examined as the total activity count over 60 minutes after local application into the N Acc.

Effects of dopamine D3 preferring compounds on conditioned place preference and intracranial self-stimulation in the rat.

Compounds showing an in vitro binding preference for the dopamine D3 receptor were tested in two models designed to assess positive reinforcement in the rat: intracranial self-stimulation (ICSS) and conditioned place preference (CPP). R-(+)-7-OH-DPAT, a D3 preferring agonist, inhibited ICSS behaviour over a wide dose range. At higher doses, a facilitation of ICSS was seen. In the CPP model, 7-OH-DPAT was inactive except at the highest dose where a significant change in preference was seen. A dose of R-(+)-7-OH-DPAT, that significantly inhibited ICSS behaviour, was combined with a dose of d-amphetamine, that significantly facilitated ICSS behaviour. Surprisingly, this resulted in a significant synergistic facilitation of the amphetamine response. The putative D3 antagonist, U99194A was inactive in the ICSS model but induced significant place preference. The present results suggest that the dopamine D3 receptor, in contrast to the D2 receptor, has an inhibitory influence on reward mechanisms.

Effects on locomotor activity after local application of D3 preferring compounds in discrete areas of the rat brain.

Compounds showing an in vitro binding preference for the dopamine D3 vs. D2 receptors were tested for effects on locomotor activity after local application in the nucleus accumbens (N Acc) and the ventral tegmental area (VTA) of the rat brain. R-(+)-7-OH-DPAT, a dopamine D3 preferring agonist, inhibited spontaneous locomotor activity over a wide dose range after injection into the N Acc. A decrease in activity over a wide dose range was also seen after local application into the VTA of both R-(+)-7-OH-DPAT and the dopamine D2 preferring agonist (+)-3-PPP. Furthermore, (+)-3-PPP produced a dose dependent increase in activity after local application into the N Acc. The putative D3 antagonist, U99194A, with a 30 fold preference for the dopamine D3 vs. D2 receptor, produced an increase in activity when injected into the N Acc. A similar pattern were seen after infusion into the lateral ventricle. Local application into the VTA did, however, not produce any significant effects. The present results support the hypothesis that dopamine D3 receptors (in contrast to the D2 receptors) are mainly postsynaptically located where they display an inhibitory action on locomotor activity.

Anabolic steroids and violent crime--an epidemiological study at a jail in Stockholm, Sweden.

Violent crime has been associated with the abuse of anabolic-androgenic steroids (AAS) in several reports. Speculations concerning such associations have been raised with regard to several recent crimes committed in Sweden. To test this hypothetical relationship, individuals in a Stockholm jail who had been arrested for violent crimes were screened for AAS in the urine. No AAS were detected in the urine samples of 50 prisoners who had volunteered for the study. However, 16 prisoners refused to participate. AAS abuse was admitted by two of the participating subjects. Although there is a great need for epidemiological studies to objectively confirm the association of AAS abuse and violence, it seems that such studies will be impossible to conduct as long as they, for legal reasons, depend on voluntary participation.