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New histamine H3-receptor antagonists were synthesised and tested on rat brain membranes and on electrically stimulated guinea-pig ileum. The new compounds have a central polar group represented by a 2-alkylimidazole or a 2-thioimidazoline nucleus. The effect of the polar group basicity on the optimal length of the alkyl chain, connecting this group to a 4(5)-imidazolyl ring, was investigated. The best affinity values, obtained by displacement of [3H]-RAMHA from rat brain, were obtained for the 2-alkylimidazole derivatives (2a-f) with tetramethylene chain (pKi 8.03-8.97), having an intermediate basicity between that of the previously reported 2-thioimidazoles (1a-i) and that of 2-alkylthioimidazolines (3a-h). In contrast, a general lowering of affinity (pKi 5.90-7.63) was observed for compounds of the last series (3a-h), with a complex dependence on the terminal lipophilic group and chain length.

The present note describes the use of surface pressure measurements (Langmuir monolayer technique) for the analysis of interactions of two different anthracyclines (adriamycin and daunorubicin) with a non-ionic, zwitterionic phospholipid monolayer, at the air-water interface. Because the surface membrane of the cell is the first barrier encountered by the anthracyclines in the treatment of cancer, drug-membrane interactions studied in model (monolayers or bilayers) and natural systems play an important role in the understanding of the bioactivity properties of these molecules. We report here the rate constants of the adsorption process of adriamycin and daunorubicin in the presence of a zwitterionic phospholipid monolayer at the air-water interface. Because interactions with the lipid monolayer strongly depend on the molecular packing of the lipid, we investigated this process at a relatively low surface pressure (7 mN/m), the interactions being favoured by the gaseous and liquid expanded structure of the lipid monolayer. The apparent molecular area of these molecules during the insertion into the lipid film and their interactions with the phospholipid polar head groups was evaluated and the estimated percentage of anthracyclines at the interface after adsorption into the lipid monolayer is briefly discussed. The rate constants for the adsorption and desorption process at the water-monolayer interface have been calculated on the basis of a single-exponential model. The observed difference of these parameters for daunorubicin and adriamycin suggests a different interaction of these anthracyclines during the adsorption to and/or penetration across the phospholipid monolayer.

The interaction of aerosil particles with human erythrocytes was investigated by electron microscopy methods complemented with hemolysis and radio wave dielectric spectroscopy to elucidate the extent of morphological and functional modification induced by aerosil surface. Scanning electron microscopy and freeze-fracturing techniques were used to follow morphological and ultrastructural modifications and hemolysis tests and radio wave dielectric spectroscopy to monitor the membrane damage. All experimental results indicate that there is an effect depending on both silica concentration and incubation time. Our results are in good agreement with an interaction model based on membrane protein denaturation due to the electrostatic attraction between (-SiO-) groups at the silica surface and proteins embedded in the membrane. The process is time-limited and reaches saturation after about 20 min. The extent of the damage is determined mainly by the ratio between cell and aerosil surface, that is, aerosil concentration. Limited damage is observed, especially when little aerosil surface per cell is available. Conversely, strong membrane damage is obtained when aerosil surface is considerable. In any case, due to the high surface/volume of aerosil particles used in our experiments we obtained considerable membrane damage with small weight concentrations., (Copyright 1999 Academic Press.)

We report the synthesis, octanol/water partition coefficient (log P), dissociation constants (pKa), H3-receptor affinity (pKi in rat brain membranes, [3H]-N alpha-methylhistamine), and H3-antagonist potency (pA2 in guinea ileum, (R)-alpha-methylhistamine) of novel H3-receptor antagonists obtained by introducing a para or meta substituent on the phenyl ring of the lead compound 4(5)-phenyl-2-[[2-[4(5)-imidazolyl]ethyl]thio]imidazole (3a). The substituents were chosen to obtain broad and uncorrelated variation in their lipophilic, electronic, and steric properties. The log P values of the neutral species cover almost 3 orders of magnitude (from 1.40 to 4.11). The pKa,2 values (protonation of the 2-thioimidazole fragment) vary from 3.13 to 4.34, indicating that this fragment, which incorporates the so-called polar group common to many H3-receptor antagonists, is neutral at physiological pH. The compounds had pKi values in a range too narrow (from 7.28 to 8.03) to derive QSAR equations. In one case (3g), a biphasic displacement curve was observed (pKi,1 = 8.53; pKi,2 = 6.90). The pA2 values ranged 2 orders of magnitude (from 6.83 to 8.87) and yielded a QSAR model (PLS) indicating that antagonist potency depends parabolically on lipophilicity and is decreased by bulky para substituents. The compounds of this series, therefore, maintain a fair-to-good affinity for rat brain H3-receptor and a fair-to-good H3-antagonist potency on guinea pig ileum, although varying markedly in their lipophilicity. The series thus appears as a good candidate for pharmacokinetic optimization leading to brain-penetrating H3-receptor antagonists.

This paper summarizes the findings obtained for three different series of original compounds designed as potential H3-antagonists starting from thioperamide structure. The compounds were tested in functional and binding assays to estimate their potency, affinity and selectivity for histamine H3 receptors. Among them, many non-thiourea/isothiourea derivatives acted as selective H3 competitive antagonists and, particularly, 4(5)-[2-[4(5)-cyclohexylimidazol-2-ylthio]ethyl] imidazole (dIII) proved to be the most potent H3 blocker vs (R)-alpha-methylhistamine in electrically-stimulated ileum. This imidazole derivative, devoid of thiourea dependent toxic effects, with high affinity displaced biphasically [3H]-N alpha-methylhistamine bound to rat brain H3 sites. Thus, such compound could be proposed as the prototype molecule for the development of new non-thiourea/isothiourea H3-antagonists and as experimental tool to explore the intriguing question of H3 receptor heterogeneity.

Thioperamide is a potent and selective H3-receptor antagonist, whose in vivo effects have been reported after systemic administration. Some questions have arisen about its ability to cross the blood-brain barrier, since different experimental conditions have given different results in rats, namely a low brain/blood ratio at low doses (10 mg/Kg) and a much higher one at higher doses (60 mg/Kg). In this work we demonstrate the dose-dependence of thioperamide pharmacokinetics, measuring its plasma and cerebral levels after i.p. administration of different doses to rats. Both the plasma half-life and brain penetration of thioperamide resulted as being dose-dependent: when administered to 80 g body weight Wistar rats at 10 mg/Kg i.p., the drug has a short half life (120') and a rather poor brain penetration, but increasing the dose (to 20, 40 and 60 mg/Kg) gives rise to a prolongation of its persistence in the blood (up to 600' at highest dose) and a higher brain penetration. Also, the profile of the plasma concentration curve varies from the dose of 10 to that of 20 mg/Kg, passing from a mono-exponential decrease to a more complex one characterized by an apparent distribution phase. The different distribution processes can be interpreted in the light of thioperamide protein binding and affinity for lipophilic tissues: protein binding can prevent brain penetration (but not distribution to other tissues) at lower doses, while at higher doses the free plasma fraction increases and it can allow passive distribution to lipophilic tissues such as brain tissues. A re-distribution from these tissues and plasma is probably responsible for the strong increase in half-life at high doses.

The neuroprotective activity of the novel, selective glycine antagonist GV150526 was assessed in the middle artery occlusion (MCAo) model of focal ischemia. Postischemia administration of GV150526 (3 mg/kg i.v.) up to 6 h post-MCAo resulted in a significant reduction of the infarct volume measured histologically 24 h later. The neuronal protection by GV150526 was accompanied by functionally significant protection determined by somatosensory evoked potential (SEP) responses recorded from the primary somatosensory cortex of rats under urethane anesthesia. Experimental occlusion of the MCA 7 days prior to electrophysiological testing induced a clear reduction in the SEP amplitude. GV150526 (3mg/kg, i.v.) was able to protect SEP responses recorded from the hindpaw cortical field in two groups of animals treated either 1 (n = 9) or 6 h (n = 10) post-MCAo. SEP responses recorded from the forepaw cortical field, an area closer to the core of the ischemic damage, were significantly protected only in the group treated 1 h post-MCAo. Histological evaluation of the rat brain regions showed a correlated decrease in the ischemic area of GV150526-treated groups. The volumes of the ischemic brains of both GV150526 groups were statistically different from the MCAo group (P < 0.05). These findings demonstrate that GV150526 is able to prevent the ischemic damage assessed histologically and affect the functional correlates of the ischemia evaluated by the electrophysiological SEP measurements.

Thioperamide (N-cyclohexyl-4-[4(5)-imidazolyl]piperidine-1-carbothioamide) is a potent H3-receptor antagonist, the low conformational flexibility of which could be a favourable feature in the design of new H3-receptor antagonists using its structure as a template. Minimum-energy conformations of thioperamide were studied with the molecular mechanics approach, integrated by X-ray crystallography on an analogue, N-cyclohexyl-4-methylpiperidine-1-carbothioamide (1). Compound 1 was synthesized, and its structure has been solved by X-ray diffraction in order to verify the conformation of the piperidine-1-carbothioamide fragment, and to compare the crystallographic results with those of molecular mechanics. Conformational analysis on the free-rotating bonds of thioperamide was performed with different search methods in order to find the minimum-energy conformations and to estimate rotational barriers. For steric reasons, the rotation around the bond connecting the cyclohexane ring with the carbothioamide nitrogen is more hampered than that around the bond connecting imidazole with piperidine. The rotation around the first bond presents two symmetrical energy minima separated from a third minimum by an energy barrier of 40 KJ/mol. The spatial disposition of compound 1 in the crystal and the common part of thioperamide in one of its minimum-energy conformations are very similar. The minimum-energy conformations of thioperamide calculated by molecular mechanics are therefore reliable and they can be used for structural comparisons with other H3-receptor antagonists.

An overview of H3-receptor ligands is presented, with particular attention to antagonists. The protein binding of the classical H3-receptor antagonist thioperamide and its effect on in vivo distribution are discussed. A series of H3-receptor antagonists characterised by the presence of an imidazole ring, a spacer (ethylthio-, ethylamino-, propylthio- or propylamino-chain), a second heterocycle nucleus and a lipophilic group is described. Their H3-receptor antagonist potency has been measured on electrically stimulated guinea-pig intestine, and their affinity for central H3-receptor has been determined by competitive inhibition of [3H]N alpha-methylhistamine binding to rat cortex. Biphasic inhibition curves have been observed in some cases. Compounds endowed with interesting activity belong mostly to the class of 2-[[2-[4(5)-imidazolyl]ethyl]thio]imidazole, having a phenyl or a cyclohexyl group.

The electrical properties of the cytoplasmatic membrane of human erythrocyte cells have been evaluated by means of dielectric spectroscopy measurements in the radiowave frequency range, using the so-called "suspension method". Measurements have been carried out at different volume fractions of the corpuscular phase (the cell haematocrit) in order to investigate the influence of the cell-cell interactions on the electrical parameters (the membrane permittivity epsilon and the membrane conductivity sigma) of the cell membrane and a set of new values are proposed. Moreover, the influence of different alkali metal ions (Na+, K+, Cs+, Li+) on the ion permeation properties of the membrane are investigated and the structural alterations in the membrane organized briefly discussed.

N-alkanoic, N-arylalkanoic and N-aryloxyalkanoic acids of 1,2-benzisothiazolin-3-one, esters and amides of N-arylalkanoic and N-aryloxyalkanoic acids and 1,1-dioxide derivatives of N-arylalkanoic acids and esters were investigated in vitro antimicrobial activity. N-arylalkanoic and N-aryloxyalkanoic acids (compounds 4-12) and their esters and amides (compounds 13-26) exhibited a good antimicrobial activity against Gram positive bacteria, with several compounds showing potencies 10-20 times higher than 1,2-benzisothiazolin-3-one. None of the chemicals tested inhibited the growth of E. coli. Yeasts and moulds possess a considerable susceptibility to compounds 12-23. The logP (octanol-water) of esters and amides of N-arylalkanoic and N-aryloxyalkanoic acids were measured by the shake-flask technique and the potencies against Gram positive bacteria of the compounds tested was related to their lipophilicity. QSAR analysis showed a bilinear relation, with a logD0 around 3 for the activity on B. subtilis. The phenoxyacetic and phenoxybutyric acid derivatives are positive outliers, showing a potency higher than that predicted from their lipohilicity. The most active compounds were further tested against different Gram positive bacteria and moulds, including Bacilli, Sarcina lutea, Staphylococcus epidermidis, Candida spp. and dermatophytes. The antibacterial and antifungal activity was specific for 1,2-benzisothiazolin-3-ones, the corresponding 1,1-dioxide derivatives being inactive. The genotoxic properties of the compounds studied were evaluated by the Bacillus subtilis rec-assay and Salmonella-microsome test. None of the compounds showed DNA-damaging or mutagenic activity.

The dielectric properties of poly(alpha-glutamic acid) and poly(gamma-glutamic acid) aqueous solutions in the fully ionized state have been investigated in the frequency range from 1 MHz to 1 GHz by means of frequency-domain dielectric spectroscopy measurements. In this frequency range, micro-Brownian dynamics and internal motion of side-chain polar groups give rise to nonexponential relaxation processes resulting in an intermediate dielectric relaxation between that due to the counterion atmosphere polarization and that due to the orientational polarization of the water molecules. In this work, we study the influence of the polymer concentration in the dilute--semidilute regime on the dielectric parameters, i.e., the dielectric increment delta epsilon and the relaxation time tau, and discuss their relevance in the light of some scaling pictures recently proposed by Dobrynin, Colby, and Rubinstein to describe the unentangled regime of flexible polyelectrolyte solutions.

Metabotropic glutamate receptor 1 (mGluR1) is a member of a large family of G-protein-coupled glutamate receptors, the physiological functions of which are largely unknown. Mice deficient in mGluR1 have severe motor coordination and spatial learning deficits. They have no gross anatomical or basic electrophysiological abnormalities in either the cerebellum or hippocampus, but they show impaired cerebellar long-term depression and hippocampal mossy fibre long-term potentiation. mGluR1-deficient mice should therefore be valuable models for studying synaptic plasticity.

Starting from the structure of thioperamide, a known H3-antagonist, a new series of compounds with a benzothiazole nucleus instead of the cyclohexylcarbothioamide moiety was synthesized. Various substituents, selected by experimental design, were introduced in position 6 of the benzothiazole nucleus, in order to change its physico-chemical characteristics. The lipophilicity of the synthesized compounds was measured by means of RP-HPLC, and their H3-receptor affinity was evaluated by competitive binding assays on rat cortex synaptosomes, with the labelled ligand N alpha-[3H]methylhistamine. A QSAR analysis was performed on the experimental data, using also substituent constants taken from the literature. The newly synthesized compounds showed lower H3-affinities than thioperamide; quantitative structure-activity relationships, described by models obtained with PLS and MRA techniques, were observed among benzothiazole derivatives. According to these relationships, any attempt to improve the potency of these compounds should involve the substitution of the benzothiazole moiety with less bulky and/or more flexible structures, which should also be less lipophilic and allow better electronic interactions with the binding site. 1-(Benzothiazol-2-yl)-4-[(1H)-imidazol-4-yl]piperidine represents a limit structure for H3-activity, since it seems impossible to improve its affinity by means of substitution in the studied position of the benzothiazole nucleus, as shown by predictions performed by a PLS model.

The purpose of this study was to further our understanding of the contribution of auditory thalamoamygdala projections to conditioned emotional memories formed when auditory and noxious somatosensory stimuli are associated. Single unit activity was recorded in the acoustic thalamus of chloral hydrate-anesthetized rats in response to auditory (white noise, clicks, tones) and somatosensory (foot-shock) stimulation. The thalamic areas focused on were the medial division of the medial geniculate body (MGm), the suprageniculate nucleus (SG), and the posterior intralaminar nucleus (PIN), thalamic areas that receive inputs from both the inferior colliculus and the spinal cord and that project to the lateral nucleus of the amygdala (AL). For comparison, recordings were also made from the specific thalamocortical relay nucleus, the ventral division of the medial geniculate body (MGv), which receives projections from the inferior colliculus but not from the spinal cord. Auditory but not somatosensory responses were recorded from MGv, while both auditory and somatosensory responses were frequently found in MGm, PIN, and SG. In these areas, convergent auditory and somatosensory responses were more frequently found rostrally than caudally. Within a thalamic subregion, the acoustic response properties of the convergence cells were not different from the response properties of unimodal auditory cells. Some cells that responded to somatosensory but not auditory stimuli showed a potentiated response when tested with simultaneous presentation of auditory and somatosensory stimuli. In some studies, thalamic cells that project to the amygdala were antidromically activated by stimulation of the AL. Consistent with anatomical tracing results, antidromically activated cells were found in MGm, PIN, and SG, but not in MGv. Antidromically activated cells were more likely to respond to auditory stimuli than to somatosensory stimuli, but unimodal somatosensory and convergence cells were also found. These findings, which provide the first characterization of acoustic response properties of multimodal cells in the auditory thalamus and of cells in the auditory thalamus that project to amygdala, suggest insights into the emotional functions of the thalamoamygdala pathway.

Projections from the auditory thalamus to the amygdala have been implicated in the processing of the emotional significance of auditory stimuli. In order to further our understanding of the contribution of thalamoamygdala projections to auditory emotional processing, acoustic response properties of single neurons were examined in the auditory thalamus of chloral hydrate-anesthetized rats. The emphasis was on the medial division of the medial geniculate body (MGm), the suprageniculate nucleus (SG), and the posterior intralaminar nucleus (PIN), thalamic areas that receive inputs from the inferior colliculus and project to the lateral nucleus of the amygdala (AL). For comparison, recordings were also made from the specific thalamocortical relay nucleus, the ventral division of the medial geniculate body (MGv). Responses latencies were not statistically different in MGv, MGm, PIN, and SG, but were longer in the posterior thalamic region (PO). Overall, frequency tuning functions were narrower in MGv than in the other areas but many cells in MGm were as narrowly tuned as cells in MGv. There was some organization of MGv, with low frequencies represented dorsally and high frequencies ventrally. A similar but considerably weaker organization was observed in MGm. While the full range of frequencies tested (1-30 kHz) was represented in MGv, cells in MGm, PIN, and SG tended to respond best to higher frequencies (16-30 kHz). Thresholds were higher in PIN than in MGv (other areas did not differ from MGv). Nevertheless, across the various areas, the breadth of tuning was inversely related to threshold, such that more narrowly tuned cells tended to have lower thresholds. Many of the response properties observed in MGm, PIN, and SG correspond with properties found in AL neurons and thus add support to the notion that auditory responses in AL reflect thalamoamygdala transmission.

Acoustic responses of single units were examined in awake, freely behaving rats in the lateral nucleus of the amygdala (AL). Recordings were made from a movable bundle of 9 microwires. Most cells had very low rates of spontaneous activity (about 3 spikes/s average). Firing rates increased during sleep states. Short-latency auditory responses (12-25 ms) were found in the dorsal subnucleus (ALd) of the AL. Cells in the ALd most typically responded in a sustained fashion. Some of the cells in the ALd showed preferences for high frequencies, tone bursts, or frequency-modulated stimuli with center frequencies above 12 kHz. Response latencies were considerably longer in other areas of the amygdala. Our results corroborate the main findings of a previous study (F. Bordi & J. LeDoux, 1992) that examined the acoustic response properties of single cells in the AL in anesthetized rats. Together the findings from awake and anesthetized rats provide the most precise information about sensory processing in amygdala neurons available to date.

Previous studies have shown that the lateral nucleus of the amygdala (AL) is essential in auditory fear conditioning and that neurons in the AL respond to auditory stimuli. The goals of the present study were to determine whether neurons in the AL are also responsive to somatosensory stimuli and, if so, whether single neurons in the AL respond to both auditory and somatosensory stimulation. Single-unit activity was recorded in the AL in anesthetized rats during the presentation of acoustic (clicks) and somatosensory (footshock) stimuli. Neurons in the dorsal subdivision of the AL responded to both somatosensory and auditory stimuli, whereas neurons in the ventrolateral AL responded only to somatosensory stimuli and neurons in the ventromedial AL did not respond to either stimuli. These findings indicate that the dorsal AL is a site of auditory and somatosensory convergence and may therefore be a locus of convergence of conditioned and unconditioned stimuli in auditory fear conditioning.

The recent availability of potent and selective ligands, namely R-(alpha)-methylhistamine and thioperamide, led to conclusive progresses as regards histamine H3-receptor knowledge. The aim of this work is to investigate by in vitro tests the pharmacological properties of new amino and methyl derivatives of the H3-antagonist thioperamide. Such original compounds, developed by the modulation of the thioperamide imidazolyl moiety, were assayed at guinea-pig ileal contractile H1-, atrial chronotropic H2- and enteric neuronal H3-receptors. None of the drugs exhibited interaction with H1 or H2 sites. On electrically stimulated ileum, two of the thioperamide methyl derivatives competitively antagonized the inhibitory effect of the H3-agonist R-(alpha)-methylhistamine. On the basis of the Schild analysis, the more active isomer (compound IV) displayed an affinity at H3-receptors only five times lower than thioperamide. These results could contribute to elucidate further the structural features required to develop potent and selective H3-antagonists. On the other hand, to prove the hypothesized apparent heterogeneity between peripheral and central H3-sites, as emerged by pharmacological and binding studies, autoradiographic investigations are in progress.

The preparation of a representative group of derivatives of the known H3-antagonist thioperamide is described. Binding affinity for histamine H3-receptors of thioperamide and its derivatives, which were obtained by substitution on the imidazole ring, was measured on rat brain cortex synaptosomes. Competitive binding assays were performed with two different labelled ligands, the physiological agonist [3H]histamine ([3H]HA) and the potent H3-agonist N alpha-[3H]methyl-histamine ([3]NAMHA). We observed a remarkable difference in Ki values obtained versus the two labelled ligands, both for thioperamide and its derivatives. In particular, 5-methylthioperamide showed a considerable selectivity for the system recognized by [3H]NAMHA, being about 100 times more potent versus this system than versus the system recognized by [3H]HA. On the basis of these observations, we suggest that it is necessary to consider this difference in evaluating the affinity of new compounds for the H3-receptors.

Among muscarinic agonists, the compound McN-A-343, originally proposed as selective stimulant of M1 cholinergic site, was subsequently questioned as a useful pharmacological tool in the classification of muscarinic receptors. In this work, evidence is presented for a dual response of McN-A-343 on longitudinal muscle-myenteric plexus preparation. On electrically-stimulated preparation, this agonist exhibited a pirenzepine-sensitive inhibition of the twitch contractions due to the involvement of neural M1-muscarinic receptor. On the other hand, a direct myogenic contractile action on the unstimulated tissue was observed using McN-A-343 in the same range of concentrations. This latter response, on the basis of the effects of muscarinic and non-muscarinic antagonists tested, seems to involve effectorial muscarinic sites with an unusual mechanism.

Thioperamide is a potent and selective antagonist on histamine H3 receptors. A method for its isolation and quantitation by HPLC from rat plasma and brain samples has been developed. Using this technique, thioperamide concentrations in rat plasma and brain were measured after systemic administration, in order to evaluate its persistence in blood and its ability to cross the blood-brain barrier. We observed that, at a dose of 60 mg/Kg, thioperamide undergoes a slow elimination from plasma, with a half-life of 10 hours, and can readily cross the blood-brain barrier.

Continuing their studies on benzisothiazolyl derivatives, Authors refer to the preparation and pharmacological properties of 4-(1,2-benzisothiazol-3-yl) alkanoic and phenylalkanoic acids. All substances were tested for anti-inflammatory, analgesic and antipyretic properties. As reference compounds, 1,2-benzisothiazolin-3-one and 4-(3-oxo-1,2-benzisothiazolin-3-yl) phenylacetic acid, as prototypes of benzisothiazolinonic derivation. Ibuprofen, as a prototype of substituted arylalkanoic acids, and Phenylbutazone were used. Analysis of the data leaded to the following conclusions. Introduction of the aryl moiety, passing from benzisothiazolylalkanoic to benzisothiazolyl-phenylalkanoic structures, produced a remarkable increase of activity. 2-[4-(1,2-benzisothiazol-3-yl)phenyl] propionic and 2-[4-(1,2-benzisothiazol-3-yl)phenyl]butyiric acids showed anti-inflammatory, analgesic and antipyretic properties comparable to those of Ibuprofen. Substantial differences in variations in activities were observed comparing the properties of benzisothiazolylphenylalcanoic acids with those of the benzisothiazolinonic series, object of preceding studies.

Two experiments explored the functional character of 2 schedule-induced interim behaviors (pacing and retreat) and 1 terminal behavior (keypecking) that developed on fixed-time (FT) schedules of food delivery with a keylight that increased in brightness throughout the interstimulus interval. In Experiment 1, this ramp procedure was compared with a less discriminable ramp, and FT and Random Time (RT) procedures without a signal. Decreased discriminability expanded keypecking in the trial. The FT schedule eliminated only keypecking and the RT procedure eliminated keypecking and retreat while pacing remained. In Experiment 2, predictive and unpredictive ramps were added to the RT procedure. The data suggest that schedule-induced stereotypy can be divided into kinesic stereotypy (pacing), which arises from repeated reinforcer presentations, and taxic stereotypy, which is tied to an increase (keypecking) or decrease (retreat) in the momentary probability of reinforcement.

Pigeons were trained on a variant of the autoshaping procedure devised by Matthews and Lerer (1987) in which a keylight stimulus ramp of increasing brightness signaled the passing of a 30-s interfood interval. This procedure generates two distinct behavioral components: key pecking and locomotor activity. The effects of three psychoactive drugs on these behavior classes were measured. d-Amphetamine had negligible effects on both types of behavior, whereas diazepam and pentobartital increased key pecking and decreased activity in a dose-dependent fashion. In Experiment 2, the possibility that drug effects were suppressed by excessively strong stimulus control exerted in Experiment 1 was tested by decreasing the discriminability of the stimulus ramp. The direction of the effects of diazepam and pentobarbital was the same as in Experiment 1 but the magnitude of the effects tended to be larger. The effects of d-amphetamine, however, remained quite small, suggesting that, under these conditions, locomotor activity and key pecking are less sensitive to d-amphetamine. In Experiments 3 and 4, key pecking was eliminated by removing the keylight. Reinforcers were presented at fixed intervals in Experiment 3 and at variable intervals in Experiment 4. The drug effects on activity observed in Experiments 1 and 2 disappeared in both Experiments 3 and 4. The results suggest that diazepam and pentobarbital affect activity indirectly by increasing key-pecking behavior, which, in turn, competitively decreases activity.

As a part of a study on H2-agonists, the preparations and properties are reported for a representative group of 2-aminothiazolethylamine derivatives which contain the gastric secretion stimulating S-aminoalkylisothiourea moiety. The test compounds were obtained by known methods or from 2-(2-amino-5-thiazolyl)ethyl chloride and were tested for their possible histamine-like activities on different biological substrates. From the biological results it appears that the behaviour of the substances is rather complex, but the following general observations can be pointed out: the contracturant properties, sometimes quite marked, do not derive from direct H1-specific activities; the effects, particularly evident in stimulating in vitro or in vivo gastric secretion, in relaxing gall-bladder smooth muscle, on auriculae and/or on blood pressure, are not competitively antagonized by cimetidine; none of the tested compounds proved to be an antagonist of histamine H2-receptors, while one of them is found to inhibit competitively the H1-receptors. On the basis of structure-activity relationships it can be excluded that the iuxta-nuclear NH2 group of 2-aminothiazolethylamines reacts, in some way, with the H2-receptors, since, in this case, the 2-aminothiazole group is not a pharmacophore like the 2-aminoimidazole or isothiurea group. Consequently the hypotheses, that the flexibility of the molecule is a fundamental requirement for the H2-stimulating properties of S-(3-dimethylaminopropyl)isothiurea and that the different activities of 2-aminohistamine, in comparison with those of 2-methylhistamine, are due to the existence of a hydrophilic area suitable for the allocation of the iuxta-nuclear NH2 group in the H2-receptor, are strengthened.

2-Amino- and 2-guanidinothiazole derivatives having in position 5 a methylthioalkyl side-chain with urea-equivalent moieties were prepared for comparison with H2-antagonists of cimetidine and tiotidine series. Examination of the pharmacological results obtained from experiments on guinea pig atria and in cat gastric fistula, suggests some general observations about the structure-activity relationship of the compounds synthesized. The activity trend of these products is different from that of H2-imidazole antagonists while it is similar to that of the tiotidine series. Unlike the tiotidine similar compounds, the 2-guanidino-5-thiazolyl derivatives are less potent than the corresponding 2-amino-5-thiazolyl products. The activity of the latter ones is reduced in comparison to that of tiotidine or cimetidine.

Dose-response curves of histamine were studied on the mesenteric circulation of the anaesthetized rat. The vasodilation produced by small doses of histamine was prevailingly H2-receptor-dependent, as shown by its inhibition by cimetidine but not by mepyramine, and by its reproducibility by some H2-receptor agonists, but not by specific H1-receptor agonists. The vasodilation produced by high doses of histamine was mainly due to stimulation of H1-receptors, as shown by its 70% inhibition by mepyramine. Mepyramine and cimetidine given simultaneously nearly completely inhibited the vasodilating action of high doses of histamine. Certain H2-receptor agonists, administered at high doses, induced a paradoxical vasoconstriction. It is suggested that a small number of H2-receptors is present in rat mesenteric arterioles, and that these receptors may play a physiological role in the control of mesenteric circulation.

Synthesis of some 5-methylhistamines alkylated on the amino group (form. I) together with a new method (C) of obtaining them via 5-methylhistaminol, are described. Both the agonistic and antagonistic pharmacological activities of these methylhistamines were studied in vivo on gastric secretion of different animal species (conscious dogs and cats and anaesthetized rats). The potency of the compounds, as far as the H2-receptor stimulant effect is concerned, was very remarkable in the first members of the series and decreased by increasing the degree of substitution. Independently from their "potency" some members of the series showed an "efficacy" which was actually greater than that of histamine. All the compounds tested were completely devoid of any antagonistic activity against gastric hypersecretion induced by histamine.

Injection of the dopamine (DA) agonist R-(-)-N-n-propylnorapomorphine (NPA; 5-40 micrograms) into anterior ventral striatal sites (either lateral (VL) or medial (VM) elicited dose-dependent oral and sniffing stereotypies of rapid onset, long duration and high intensity. In contrast, injection into anterior dorsolateral (DL) or posterior ventral (lateral (PL) or medial (PM] sites produced little oral and moderate sniffing behavior of slower onset, shorter duration and low intensity. Injection into the dorsomedial (DM) striatum produced intermediate effects. Intra-accumbens NPA elicited weak oral activity and moderate sniffing which was similar in onset, duration and intensity to the least sensitive striatal sites (DL, PM and PL). In other experiments, DA receptors were inactivated with the irreversible blocking agent N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ; 6 mg/kg) and behavioral recovery was monitored by challenge with 20 micrograms NPA into the VL or the nucleus accumbens (NA) at various times after EEDQ. Sniffing behavior recovered rapidly (normal by day 4 in both regions), whereas oral activity required 8 (NA) and 12 days (VL) to return to control levels. The results are discussed in terms of a possible topographic distribution of behavior in the striatum. Alternatively, heterogeneity of DA receptor density may account for these findings.

Carrying on the study of the effects induced by substitution at position 2- of histamine imidazole ring, this article briefly reports the synthesis of 2-(2-oxo-4-imidazolin-4-yl)ethylamine. The pharmacological properties of this compound and its sulphurated analogue 2-(2-thiono-4-imidazolin-4-yl)ethylamine, showed that the marked structural modification of the critical moieties involved in the binding at the H1- and H2-receptors resulted in a loss of histamine-like activity.

The synthesis and chemical and pharmacological properties of 3-benzyl-1,2-benzisothiazoleaminoalkyl derivatives are reported. These compounds were studied because 4-dimethyl-2-phenyl-2-(1,2-benzisotiazol-3-yl)-butyramide and N,N-dimethyl-3-phenyl-3-(1,2-benzisothiazol-3-yl)propylamine were recently found to have antispasmodic properties. Most of the compounds studied aspecifically inhibited the contracturant effects of acetylcholine, histamine and BaCl2. Three of them showed mixed antagonism (competitive and non-competitive) versus acetylcholine and histamine, showing both antimuscarinic and antihistaminic properties. However the antimuscarinic action prevailed over the others, as shown by pA2 and pD'2 calculated values. On the basis of the results obtained, the structure-activity relationships is discussed.

Compound 2-(5-methyl-4-imidazolyl)-1-methylethylamine was tested on different preparations for its histamine-like activity. It was found to markedly affect H2 receptors and at the same time to be practically devoid of any activity on H1 receptors. This high selectivity of action indicates that this compound may represent a useful tool for characterizing the distribution of H2 and H1 receptor sites.

Five components of behavior elicited by dopamine (DA) agonists (locomotor hyperactivity, sniffing, oral activity, grooming and paw nibbling) were evaluated after bilateral infusion of the selective D1 agonist fenoldopam (SKF 82526; 2.5-10 micrograms), the selective D2 agonist quinpirole (LY 171555; 5-40 micrograms) and the muscarinic cholinergic antagonist scopolamine (5-20 micrograms) into the ventral striatum of awake, unrestrained rats. Simultaneous bilateral infusion of various dose combinations of fenoldopam (2.5-10 micrograms) and quinpirole (5-20 micrograms) elicited dramatic increases in stereotyped behaviors relative to the effects produced by corresponding doses of each drug alone. Stereotyped sniffing and paw nibbling (self-directed oral activity) were markedly enhanced, whereas conventional oral behaviors (licking, chewing and/or biting) were either slightly or not at all increased. These potentiated responses were reduced or blocked by concomitant infusion of either the selective D1 antagonist SCH 23390 (1 and 5 micrograms) or the selective D2 antagonist sulpiride (0.15 microgram). Scopolamine (10 micrograms) only slightly increased the effects of quinpirole (5 micrograms) on both sniffing and oral behaviors, whereas it dramatically potentiated the effects of fenoldopam (2.5 micrograms) on oral activity; sniffing was only slightly increased. The effects of both drug combinations were almost completely antagonized by infusion of either SCH 23390 (1 microgram) or sulpiride (0.1 microgram). The results demonstrate that the synergistic effects of co-activation of D1 and D2 receptors observed after systemic administration are mediated at least in part by an interaction at the level of the striatum. Differences and similarities between the behaviors expressed after various treatments are discussed.

The synthesis of a new series of 4-(3-oxo-1,2-benzisothiazolin-2-yl)phenylalkanoic compounds and some of their functional derivatives is described. The compounds, on the basis of data obtained from 1,2-benzisothiazolin-3-one derivatives, were biologically examined mainly for their antiphlogistic and analgesic actions. Results obtained, in analyzing the relationship between structure and pharmacological actions, suggest that both 4-(3-oxo-1,2-benzisothiazolin-2-yl)-phenyalkanoic acids and o-sulphobenzimido alkanoic esters are endowed with pain-killing effects comparable in potency and efficacy with phenylbutazone.

In the present paper the authors describe the effects of Dimaprit analogs on guinea pig gastric mucosa "in vitro". This preparation, widely described by Holton and Spencer, is useful for studying the actions of stimulants and inhibitors which act directly on the oxyntic cells. Such compounds are weakly active as stimulants of H2-receptors and studied as antagonists fail in inhibiting acid secretion evoked by Dimaprit, the most specific H2-receptors agonist. In particular, the compound marked Ros 5 clarifies that the isothiourea group of Dimaprit simulates the amidine system only chemically but not pharmacologically. The different mechanism of Dimaprit and Histamine on H2-receptors has been discussed.

Dose-effect curves were obtained for five specific components of stereotyped behavior (locomotor hyperactivity, rearing, sniffing, grooming and oral activity) elicited by the nonselective dopamine agonists N-propylnorapomorphine (NPA; 0.001-4.5 mg/kg) and apomorphine (APO; 0.3-10.0 mg/kg), the selective D2 agonists LY 171555 (0.1-18.0 mg/kg) and RU 24213 (0.7-20.0 mg/kg) and the selective D1 agonist SKF 38393 (0.6-40.0 mg/kg) in male Sprague-Dawley rats. All the agonists except SKF 38393 elicited dose-dependent sniffing. Both NPA and APO produced robust oral activity at high doses, with concomitant reductions in other behaviors. Neither RU 24213 nor SKF 38393 elicited dose-dependent oral behavior, whereas LY 171555 induced a maximal level of oral activity which was much less intense than that produced by NPA or APO. SKF 38393 alone induced only dose-dependent grooming. Co-treatment of Sprague-Dawley rats with SKF 38393 (5-40 mg/kg) and either LY 171555 (0.1-1.6 mg/kg) or RU 24213 (6.7 mg/kg) produced significant enhancement of sniffing but not of oral activity. Significant enhancement of both behavioral components was observed in male Wistar rats. Differences in specific components of behavioral response on treatment with combinations of D1 and D2 agonists may reflect use of animal strains with different ratios of D1/D2 innervation and/or different behavioral criteria.

The results of 2-aminohistamine (compound I) and 2-amino-5-methylhistamine (compound II) on cat acid secretion and on guinea pig gall-bladder motility are described and compared with those of Histamine or Dimaprit. The compound (I) showed a greater H2- than H1-receptor stimulating activity, while compound (II), inactive on H1, was effective on H2-receptors, being endowed with a less "potency" and "efficacy" than compound (I). The pharmacological activities of both compounds, related to their chemical structure, are discussed.

The synthesis of 2-(4-imidazolyl)ethylamines with hydrocarbon substituents on the heterocyclic ring or on the side-chain, from 2-acylbutyrrolactones (V) or from similar ester-type open structures (VII) is described in this paper. In particular, the results already obtained, show that the scheme given for the preparation of 2-(5-methyl-4-imidazolyl)ethylamines can be rendered general, by suitable variations correlated more with side-chain branching, than with the nature of the heterocyclic ring substituents. Synthetized imidazolyethylamines have been preliminarily tested for their properties towards H2 receptors and, secondly, towards H1 receptors.

The syntheses of 2-(2-amino-4-imidazolyl)ethylamine (2-aminohistamine) dihydrochloride and of the corresponding 5-methyl derivative are described. The histamine-like properties of the two salts are tested in vitro on isolated ileum and gastric fundus of guinea-pig. The results are discussed and compared with those of other H2-agonists.

Based on previous observations, the preparation, some physicochemical (partition coefficient, pKa) and pharmacological properties of 4-(3-oxo-1,2-benzisothiazolin-2-yl)alkanoic, benzoic, phenyl, phenoxyalkanoic acids and of some of their functional derivatives are reported. All new compounds were biologically examined for their antiphlogistic, analgesic and antipiretic actions, in comparison with those of 1,2-benzisothiazolin-2-one and with those of ibuprofen as the antiphlogistic, analgesic, antipyretic arylalkanoic prototype. Structure-activity relationships showed that the 1,2-benzisothiazolin-2-one and its new alkanoic and arylalkanoic derivatives have strong actions which are however specific for some of the tested pharmacological properties. From this point of view, the synthesized substances have a narrow spectrum of activity, if compared with ibuprofen which is at the same time an antiphlogistic, analgesic and antipiretic substance. The antiphlogistic and antipyretic activities of 4-(3-oxo-1,2-benzisothiazolin-2-yl)benzoic, phenylacetic and phenylmethylacetic acids and the antipyretic and analgesic actions of 3-oxo-1,2-benzisothiazolin-2-ylacetic acid, which are comparable or higher in "potency" than those of ibuprofen, are noteworthy.

This paper describes the synthesis of 3-benzyl-1,2-benzisothiazole derivatives, structurally related to benzylisoquinolines, and their analgesic activity studied using writhing technique in the mouse. The presence of lipophilic substituents in position 3, 4 of the benzyl group give substances with analgesic activity, although their "potency" is lower than that shown by papaverine.

In the present paper pharmacological properties studied on the gastrointestinal tract of two new alkylaminoalkylphenylbenzisothiazole derivatives, 4-dimethylamino-2-phenyl-2-(1,2-benzisothiazole-3-yl)butyramide (PM2) and N,N-dimethyl-3-phenyl-3-(1,2-benzisothiazole-3-yl)propylamine (PM3) have been reported. Both drugs showed antispasmodic effects on gastroduodenal junction of the anaesthetized rat stimulated by Caerulein, according to previous results obtained on guinea-pig isolated ileum. On this substrate they were different in the potency being PM3 more active than PM2. On the contrary, the hypersecretion induced by Histamine or Gastrin-17 in rat perfused stomach was potentiated by PM2 and inhibited by PM3. Similar effects were observed on guinea-pig "in vitro" stomach preparation where PM2 and Papaverine were ineffective in modifying Histamine dose-response curves and PM3 reduced significantly maximal peak effects of Histamine, behaving as a non-competitive antagonist. The significant differences observed on gastric secretion but not on other substrates, from compounds structural analysis, appear scarcely justified and seem to us important to be further investigated.

The pharmacological properties of 2-aminohistamine and 2-amino-5-methylhistamine were studied and compared with those of histamine, 5-methylhistamine and dimaprit. The introduction of an amino group in position 2 of the histamine imidazole ring caused a reduction of histamine potency, mostly with respect to H1 receptors. Such disactivation was much more evident in its corresponding 5-methyl derivative. The pharmacological activity related to the chemical structure will be discussed in the paper.

Irreversible inactivation of both D-1 and D-2 dopamine (DA) receptors by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) resulted in complete loss of stereotypy response to R-(-)-N-propylnorapomorphine (NPA; 0.1-1.0 mg/kg, s.c.) 24 hr later. Stereotyped sniffing recovered much more rapidly than oral behaviors. The D-2 antagonist sulpiride (200 mg/kg) and the putatively nonselective antagonist cis-flupenthixol (2 mg/kg), administered prior to EEDQ, prevented the loss of NPA-induced sniffing but only partially protected against loss of oral behaviors 24 hr later. Complete protection of both behaviors was seen after pretreatment with a combination of sulpiride and the selective D-1 antagonist SCH 23390 (1 mg/kg); pretreatment with the selective D-1 antagonist SCH 23390 alone, however, did not modify the rate of recovery of either behavioral response. The results suggest that either different populations of DA receptors mediate expression of these behaviors or stimulation of a small fraction of the total DA receptor pool may be sufficient to elicit sniffing but not oral responses. Furthermore, maintaining a normal complement of D-2 rather than D-1 receptors appears to be a critical determinant for the elicitation of these behaviors.

Two series of experiments were performed on rat chronic ulcer in order to assess the possible curative and mucosal protective properties of 2 week treatments, or the preventive properties of 4 week treatments with antisecretory agents, acting with different mechanisms of action. At the end of the treatments the gastric secretory and motor responsiveness to a gastrin-like stimulus was simultaneously evaluated. The results support the view that antimuscarinic agents as well as H2-blockers cannot be defined as protective and that after a 4 week treatment they can induce modifications of gastric functions.