Stefania Ruiu

Differential distribution of functional cannabinoid CB1 receptors in the mouse gastroenteric tract.

Recently, the gastrointestinal pharmacology of cannabinoid CB(1) receptors has been extensively explored. We employed western blotting and immunohistochemistry techniques to study the distribution of the cannabinoid CB(1) receptor protein in the mouse gastroenteric tract. The cannabinoid CB(1) receptor peptide was detected by western blotting only in its glycosylated form (63 kDa) with a significant differential distribution. The highest levels of expression were detected in the stomach and in the colon, while the pyloric valve was devoid of any cannabinoid CB(1) receptor protein. The immunohistochemical study showed intense cannabinoid CB(1) receptor immunoreactivity in ganglia subadjacent to the gastric epithelium and in the smooth muscle layers of both the small and large intestine. Only the small intestine showed (-)-3-[2-hydroxyl-4-(1,1-dimethylheptyl)-phenyl]-4-(3-hydroxylpropyl) cyclohexan-1-ol) ([3H]CP 55,940) specific binding (27%). These receptors mediated pharmacologically significant effects since the cannabinoid CB(1) receptor agonist R(-)-7-hydroxy-delta-6-tetra-hydrocannabinol-dimethylheptyl (HU 210) dose dependently inhibited gastrointestinal transit up to 70%, while the cannabinoid CB(1) receptor antagonist N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide (SR 141716A) increased gastrointestinal transit. Moreover, the dose of 0.3 microg/kg of HU 210, devoid per se of any activity on mouse intestinal propulsion, blocked the increased gastroenteric transit induced by the cannabinoid CB(1) antagonist SR 141716A.

Tricyclic Pyrazoles. Part 1: Synthesis and Biological Evaluation of Novel 1,4-Dihydroindeno[1,2-c]pyrazol-based Ligands for CB1and CB2 Cannabinoid Receptors

Cannabinoids receptors, cellular elements of the endocannabinoid system, have been the focus of extensive studies because of their potential functional role in several important physiological and pathological processes. To further evaluate the properties of CB receptors, especially CB(1) and CB(2) subtypes, we have designed, using SR141716A as a benchmark, a new series of rigid 1-aryl-1,4-dihydroindeno[1,2-c]pyrazole-3-carboxamides. Compounds 1 were synthesized from substituted 1-aryl-1,4-dihydroindeno[1,2-c]pyrazole-3-carboxylic acids and requisite amines. The various analogues were assayed for binding both to the brain and peripheral cannabinoid receptors (CB(1) and CB(2)). Seven of the new compounds displayed very high in vitro CB(2) binding affinities, especially 1a, 1b, 1c, 1e, 1g, 1h and 1j which showed K(i) values of 0.34, 0.225, 0.27, 0.23, 0.385, 0.037 and 0.9 nM, respectively. Compounds 1a, 1b, 1c and 1h showed the highest selectivity for CB(2) receptor with K(i)(CB(1)) to K(i)(CB(2)) ratios of 6029, 5635, 5814 and 9810, respectively. Noticeably, 1h exhibited the highest affinity and selectivity for CB(2) receptors.

Sub-chronic treatment with classical but not atypical antipsychotics produces morphological changes in rat nigro-striatal dopaminergic neurons directly related to "early onset" vacuous chewing.

In the present work, we investigated if an impairment of dopaminergic neurons after subchronic haloperidol treatment might be a possible physiopathologic substrate of the ‘early onset’ vacuous chewing movements (VCMs) in rats. For this purpose, different antipsychotics were used to analyse a possible relationship between VCMs development and morphological alterations of tyrosine‐hydroxylase‐immunostained (TH‐IM) neurons.

Evaluation of Tamsulosin and Alfuzosin Activity in the Rat Vas Deferens: Relevance to Ejaculation Delays

The effect of two α-adrenergic receptor antagonists widely employed in the therapy of benign prostatic hyperplasia, tamsulosin [(-)-(R)-5-[2-[[2-(0-ethoxyphenoxy) ethyl]amino]propyl]-2-methoxybenzenesulfonamide] and alfuzosin [(±)-N-[3-[(4-amino-6,7-dimethoxy-2-quinazolinyl) methylamino]propyl] tetrahydro-2-furancarboxamide], was investigated in the rat vas deferens. Because several clinical studies have shown that tamsulosin causes ejaculatory disorders, this study also evaluated the possible mechanisms implicated in these disorders by comparing the effect of tamsulosin with that of alfuzosin. Tamsulosin competitively antagonized the contractions induced by noradrenaline in vitro in the epididymal portion of the vas deferens with a potency pA2 value of 9.2 ± 0.8. In the prostatic portion, tamsulosin increased the amplitude of intermittent spikes induced by exogenous noradrenaline (100–1000 μM). In both portions of the vas deferens, alfuzosin behaved as an α-adrenergic antagonist blocking the contractions induced by exogenous noradrenaline without altering spikes. The administration of tamsulosin (3 μg/kg i.v.) significantly reduced the contractions evoked by electrical pulses in the epididymal portion, whereas it increased those produced in the prostatic portion. Intravenous tamsulosin antagonized the contraction produced by exogenous noradrenaline, whereas alfuzosin administration (10 μg/kg i.v.) did not change the electrically induced contractions in both portions of the rat vas deferens and did not antagonize the contractions produced by exogenous noradrenaline. The fact that tamsulosin unusually enhances noradrenaline-induced intermittent spike contractions and nerve stimulation-induced twitches in the prostatic portions might be linked to its greater propensity to cause sexual dysfunctions.

Haloperidol, but not clozapine, produces dramatic catalepsy in Δ9‐THC‐treated rats: possible clinical implications

The effect on rat catalepsy induced by Δ9‐tetrahydrocannabinol (Δ9‐THC) in association with haloperidol (HP) or clozapine (CLOZ) administration was investigated. Δ9‐THC dose‐dependently increased HP (0.05–1 mg kg−1, s.c.)‐induced rat catalepsy, while no catalepsy was observed after CLOZ (1–20 mg kg−1, s.c.) or Δ9‐THC+CLOZ administration. The CB1 antagonist SR141716A (0.5–5 mg kg−1, i.p.) reversed the increase mediated by Δ9‐THC on HP‐induced catalepsy. The D2 agonist quinpirole completely reversed the catalepsy induced by both HP and HP+Δ9‐THC; however, higher doses of quinpirole were needed in the presence of Δ9‐THC. The M1 antagonist scopolamine and α2 antagonist yohimbine were able to reduce the catalepsy induced by HP and HP+Δ9‐THC in a similar manner. CLOZ and the 5‐HT2A/2C antagonists ritanserin, RS102221 and SB242084 were more effective in antagonizing HP than HP+Δ9‐THC‐induced catalepsy. HP and CLOZ failed to inhibit in vitro [3H]CP‐55,940 binding, while Δ9‐THC and SR141716A did not show an appreciable affinity for the D2 receptor. It was suggested that the different effects on rat catalepsy induced by Δ9‐THC following HP or CLOZ administration may depend on the receptor‐binding profiles of the two antipsychotics. The preferential use of CLOZ rather than HP in the treatment of psychotic symptoms in cannabis abusers was discussed.

Novel pyrazole derivatives as neutral CB1 antagonists with significant activity towards food intake

In spite of rimonabants withdrawal from the European market due to its adverse effects, interest in the development of drugs based on CB1 antagonists is revamping on the basis of the peculiar properties of this class of compounds. In particular, new strategies have been proposed for the treatment of obesity and/or related risk factors through CB1 antagonists, i.e. by the development of selectively peripherally acting agents or by the identification of neutral CB1 antagonists. New compounds based on the lead CB1 antagonist/inverse agonist rimonabant have been synthesized with focus on obtaining neutral CB1 antagonists. Amongst the new derivatives described in this paper, the mixture of the two enantiomers (±)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-3-(2-cyclohexyl-1-hydroxyethyl)-4-methyl-1H-pyrazole ((±)-5), and compound 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-3-[(Z)-2-cyclohexyl-1-fluorovinyl]-4-methyl-1H-pyrazole ((Z)-6), showed interesting pharmacological profiles. According to the preliminary pharmacological evaluation, these novel pyrazole derivatives showed in fact both neutral CB1 antagonism behaviour and significant in vivo activity towards food intake.

Effect of the amisulpride isomers on rat catalepsy

The substituted benzamide amisulpride is currently administered in its racemic form. In the present study, the biochemical and cataleptogenic profiles of the two enantiomers (R+ and S-) were compared with those of the racemic mixture. Displacement binding studies showed that the (S-)-isomer possesses an higher affinity for dopamine D2-like receptor (K(i) 5.2+/-0.4 nM) compared to (R+)-amisulpride (K(i) 244+/-12 nM) and to (RS)-amisulpride (K(i) 9.8+/-0.8 nM). In contrast, (S-)-amisulpride binds the alpha(2)-receptor with an affinity (K(i) 1528+/-45 nM) lower than that of the (R+)-isomer (K(i) 375+/-34 nM) and of (RS)-amisulpride (K(i) 783+/-27 nM). The bar test was used to evaluate the catalepsy induced by each drug. (RS)-amisulpride induced catalepsy only at very high doses (>100 mg/kg, s.c.) whereas, (S-)-amisulpride produced a catalepsy at a lower dose (30 mg/kg, s.c.) and (R+)-amisulpride did not produce any catalepsy up to the dose of 75 mg/kg. Interestingly, (R+)-amisulpride reduced the catalepsy induced by (S-)-amisulpride (50 mg/kg, s.c.) or haloperidol (0.3 mg/kg, s.c.), at the doses of 50 or 30 mg/kg, respectively. These results indicate that the weak cataleptic properties of (RS)-amisulpride might partially rely on its (R+)-isomer and provide a further explanation for the atypical properties of amisulpride as an antipsychotic.

Tricyclic pyrazoles. Part 6. Benzofuro[3,2-c]pyrazole: a versatile architecture for CB2 selective ligands.

A new series of 1H-benzofuro[3,2-c]pyrazole-3-carboxamides was synthesized. The novel compounds (15-24) were evaluated for their affinity to CB2 and CB1 cannabinoid receptors. The synthesis of the title compounds takes advantage of the acid-catalysed thermal cyclization of bicyclic hydrazone ethyl 2-(2-(2,4-dichlorophenyl)hydrazono)-2-(6-methyl-3-oxo-2,3-dihydrobenzofuran-2-yl)acetate to tricyclic ethyl 1-(2,4-dichlorophenyl)-6-methyl-1H-benzofuro[3,2-c]pyrazol-3-carboxylate. All the obtained derivatives showed high affinity to CB2 receptors. Moreover, significant selectivity for CB2 over CB1 receptors was highlighted for lead derivatives amongst the novel series. The best binding profiles were determined for homologues bearing monocyclic and bicyclic monoterpenic substituents at the carbamoyl group at 3 position of the pyrazole ring (KiCB2 < 4 nM). In particular, the isopinocampheyl-substituted derivative 22 exhibited the highest selectivity for CB2 receptors with Ki values of 3.7 and 2398 nM for CB2 and CB1 receptors, respectively. Preliminary functional assays evidenced CB2 agonism behaviour for all the assayed novel derivatives.

Tricyclic Pyrazoles. Part 5. Novel 1,4-Dihydroindeno[1,2-c]pyrazole CB2 Ligands Using Molecular Hybridization Based on Scaffold Hopping.

In search of new selective CB2 ligands, the synthesis and preliminary biological evaluation of novel 1,4-dihydroindeno[1,2-c]pyrazole hybrids of the highly potent prototypicals 5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-N-fenchyl-1H-pyrazole-3-carboxamide 1 and 1-(2,4-dichlorophenyl)-6-methyl-N-(piperidin-1-yl)-1,4-dihydroindeno[1,2-c]pyrazole-3-carboxamide 2 are detailed. We postulated that the introduction of those pharmacophoric elements essential for activity of 1 in the tricyclic core of 2 might provide CB2 ligands with further improved receptor selectivity and biological activity. Among the compounds, 6-chloro-7-methyl-1-(2,4-dichlorophenyl)-N-fenchyl-1,4-dihydroindeno[1,2-c]pyrazole-3-carboxamide (22) exhibited low two digit nanomolar affinity for the cannabinoid CB2R and maintained a high level of CB2-selectivity.

N-3(9)-Arylpropenyl-N-9(3)-propionyl-3,9-diazabicyclo[3.3.1]nonanes as μ-Opioid receptor agonists. Effects on μ-Affinity of arylalkenyl chain modifications

Two series of N-3-arylpropenyl-N-9-propionyl-3,9-diazabicyclo[3.3.1]nonanes (1b-j) and of the reverted N-3-propionyl-N-9-arylpropenyl isomers (2b-j) as analogues of the previously reported analgesic N-3(9)-cinnamyl-N-9(3)-propionyl-3,9-diazabicyclo[3.3.1]nonanes (DBN) (1a, 2a) were synthesised and their affinity and selectivity towards opioid mu-, delta- and kappa-receptors were evaluated. Several compounds (1e,i,j-2d,e,f,g,j) exhibited a mu-affinity in the low nanomolar range with moderate or negligible affinity towards delta- and kappa-receptors. The representative term N-9-(3,3-diphenylprop-2-enyl)-N-3-propionyl-DBN (2d) displayed in vivo (mouse) a potent analgesic effect (ED(50) 3.88 mg/kg ip) which favourably compared with that of morphine (ED(50) 5 mg/kg ip). In addition, 2d produced in mice tolerance after a period twice as long with morphine.