In-situ X-Ray Absorption Near Edge Structure Spectroscopy of a Solid Catalyst using a Laboratory-Based Set-up

An in-situ laboratory-based X-ray Absorption Near Edge Structure (XANES) Spectroscopy set-up is presented, which allows performing long-term experiments on a solid catalyst at relevant reaction conditions of temperature and pressure. Complementary to research performed at synchrotron radiation facilities the approach is showcased for a Co/TiO2 Fischer-Tropsch Synthesis (FTS) catalyst. Supported cobalt metal nanoparticles next to a (very small) fraction of cobalt(II) titanate, which is an inactive phase for FTS, were detected, with no signs of re-oxidation of the supported cobalt metal nanoparticles during FTS at 523 K, 5 bar and 200 h, indicating that cobalt metal is maintained as the main active phase during FTS.

Potentially hallucinogenic 5‐hydroxytryptamine receptor ligands bufotenine and dimethyltryptamine in blood and tissues

Bufotenine and N,N-dimethyltryptamine (DMT) are hallucinogenic dimethylated indolethylamines (DMIAs) formed from serotonin and tryptamine by the enzyme indolethylamine N-methyltransferase (INMT) ubiquitously present in non-neural tissues. In mammals, endogenous bufotenine and DMT have been identified only in human urine. The DMIAs bind effectively to 5HT receptors and their administration causes a variety of autonomic effects, which may reflect their actual physiological function. Endogenous levels of bufotenine and DMT in blood and a number of animal and human tissues were determined using highly sensitive and specific quantitative mass spectrometric techniques. A new finding was the detection of large amounts of bufotenine in stools, which may be an indication of its role in intestinal function. It is suggested that fecal and urinary bufotenine originate from epithelial cells of the intestine and the kidney, respectively, although the possibility of their synthesis by intestinal bacteria cannot be excluded. Only small amounts of the DMIAs were found in somatic or neural tissues and none in blood. This can be explained by rapid catabolism of the DMIAs by mitochondrial monoamino-oxidase or by the fact that the dimethylated products of serotonin and tryptamine are not formed in significant amounts in most mammalian tissues despite the widespread presence of INMT in tissues.

Reduced aggression in AMPA-type glutamate receptor GluR-A subunit-deficient mice

The importance of AMPA-type glutamate receptors has been demonstrated in neuronal plasticity and in adaptation to drugs of abuse. We studied the involvement of AMPA receptors in social interaction and anxiety and found that in several paradigms of agonistic behavior naïve male mice deficient for the GluR-A subunit- containing AMPA receptors are less aggressive than wild-type littermates. GluR-A deficient mice and wild-type littermates exhibited similar basic behavior and reflexes as monitored by observational Irwin's test, but they tended to be less anxious in elevated plus-maze and light-dark tests. Maternal aggression or male-female encounters were not affected which suggests that male hormones are involved in the expression of suppressed aggressiveness. However, testosterone levels and brain monoamines can be excluded and found to be similar between GluR-A deficient and wild-type littermates. The reduced AMPA receptor levels caused by the lack of the GluR-A subunit, and measured by a 30% reduction in hippocampal [3H]-S-AMPA binding, seem to be the reason for suppressed male aggressiveness. When we analyzed mice with reduced number of functional AMPA receptors mediated by the genomic introduced GluR-A(Q582R) channel mutation, we observed again male-specific suppressed aggression, providing additional evidence for GluR-A subunit-containing AMPA receptor involvement in aggression.

Effects of repeated morphine treatment on metabolism of cerebral dopamine and serotonin in alcohol-preferring AA and alcohol-avoiding ANA rats

The alcohol-preferring AA (Alko Alcohol) rats are more rapidly sensitized to the locomotor activity-stimulating effects of small doses of morphine than the alcohol-avoiding ANA (Alko Non-Alcohol) rats. To study the involvement of dopaminergic and serotonergic transmission in this behaviour, the effects of acute morphine (1 mg/kg) challenge on the concentrations of dopamine (DA), 5-hydroxytryptamine (5-HT, serotonin) and their metabolites were estimated in three dopaminergic areas in AA and ANA rats on the fourth day after a 3-day morphine or saline treatment. Acute administration of morphine enhanced DA metabolism in the caudate-putamen in the AA, but not in the ANA, rats; in the nucleus accumbens and in the olfactory tubercle the acute effect of morphine was similar in rats of both lines. Morphine pretreatment did not significantly enhance acute morphine's effects on DA metabolites in any of the brain areas studied in rats of either line. Acute administration of morphine enhanced brain 5-HT metabolism in the AA rats but not in the ANA rats, but after repeated treatment it induced no enhancement of 5-HT metabolism. With the methods used, no significant differences were found between the AA and ANA rats in the effects of repeated morphine on cerebral dopaminergic or serotonergic mechanisms which could account for the different behavioural sensitization found previously in rats of these lines. However, both monoamines studied might be involved in the acute locomotor stimulatory effects of morphine.

Morphine-induced dependence and sensitization are altered in mice deficient in AMPA-type glutamate receptor-A subunits

AMPA-type glutamate receptors have been suggested to be involved in the neurobiological mechanisms of drug addiction. We have made use of two mouse lines, which both have modulated AMPA receptor responses. The first line is entirely deficient in glutamate receptor-A (GluR-A) subunits (A-/- knock-out line) and, in the second one, the Q582 residue of GluR-A subunits is replaced by an arginine residue (R/R mutants), which reduces the calcium permeability and channel conductance of the receptors containing this mutated subunit. Mice of both lines are healthy, but they show slightly increased locomotor activity. Acute morphine administration enhanced locomotor activity of the GluR-A-/- and GluR-A(R/R) mice, at least as much as that of their wild-type littermates. Only in the GluR-A-/- mice did we observe reduced tolerance development in tail-flick antinociception and less severe naloxone-precipitated withdrawal symptoms after treatment with increasing morphine doses, without differences in plasma and brain morphine levels when compared with wild type. Repeated daily morphine administration sensitized the locomotor activity responses in the GluR-A-/- and GluR-A(R/R) mice only when given in the measuring cages, whereas the wild-type mice showed slightly increased responses also when the repeated treatment was given in their home cages. Normal or even enhanced context-dependent sensitization was observed also with repeated amphetamine administration in the GluR-A subunit-deficient mice. The results indicate that AMPA receptors are involved in the acute and chronic effects of morphine, including context-independent sensitization, and that the GluR-A subunit itself is important for morphine tolerance and dependence.

Effects of repeated cocaine treatment on striatal dopamine release in alcohol-preferring AA and alcohol-avoiding ANA rats

Modulation of striatal dopamine (DA) release by acute or repeated cocaine treatment was studied in the nucleus accumbens and caudate-putamen of alcohol-preferring (AA, Alko Alcohol) and alcohol-avoiding (ANA, Alko Non-Alcohol) rats. Cocaine (5-10 mg/kg i.p.) was administered daily for 4 days and the concentrations of extracellular DA measured by in vivo microdialysis on days 1 and 4 in the freely moving rats. The first administration of cocaine increased DA concentration similarly in rats of both lines in both the nucleus accumbens and caudate-putamen. On the 4th day, the effect of cocaine was significantly larger in the nucleus accumbens of AA than in that of ANA rats, whereas no such enhanced effect of cocaine was found in the caudate-putamen of either line. The results suggest that mesolimbic DA release in response to cocaine is sensitized more readily in AA than in ANA rats, which would not only render the former more susceptible to alcohol, but to other drugs of abuse, and might explain our previous findings that AA rats are more susceptible to psychomotor sensitization than ANA rats.

Effects of repeated morphine on cerebral dopamine release and metabolism in AA and ANA rats

Cerebral dopaminergic mechanisms were studied in the nucleus accumbens and caudate-putamen of alcohol-preferring AA (Alko Alcohol) and alcohol-avoiding ANA (Alko Non-Alcohol) rats after 4-day repeated morphine treatment. This treatment has been shown to enhance the locomotor activity stimulating effect of morphine in the AA but not in the ANA rats. Morphine (1 or 3 mg/kg) or saline was administered subcutaneously once daily and the extracellular concentrations of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured, in freely moving rats by in vivo microdialysis on days 1 and 4. Morphine increased accumbal DA, DOPAC and HVA similarly in rats of both lines, and no sensitization of DA release or metabolism was seen in rats of either line given morphine repeatedly. In the caudate-putamen, morphine increased DA, DOPAC and HVA significantly only in the AA rats. During repeated treatment, the morphine-induced elevation of DA metabolites, but not that of DA, was enhanced similarly in rats of both lines. These results suggest that the effects of acute morphine administration on nigrostriatal dopaminergic mechanisms are stronger in the AA than in the ANA rats, whereas the effects of morphine on mesolimbic dopaminergic systems do not differ. Furthermore, in rats of both lines, repeated morphine treatment enhanced the responses of the nigrostriatal dopaminergic systems similarly, but no enhancement occurred in the mesolimbic systems of rats of either line. These findings do not support the critical role of accumbal dopaminergic systems in morphine-induced behavioural sensitization.

Enhanced locomotor stimulation by NMDA receptor antagonists in alcohol-sensitive ANT rats

The ability of the antagonists for the N-methyl-D-aspartate (NMDA) type of glutamate receptor to modulate locomotor activity were compared in alcohol-sensitive (or alcohol-nontolerant, ANT) and alcohol-insensitive (or alcohol-tolerant, AT) rat lines. Both rat lines showed altered locomotor activity after acute injections of a competitive antagonist (LY235959), a glycine-site antagonist (L-701,324), or noncompetitive antagonists [MK-801, phencyclidine (PCP), and ketamine] of the NMDA receptor. MK-801 at 0.5 mg/kg caused a strong increase in horizontal activity in both rat lines, the effect being significantly greater in the ANT rats. There was a subpopulation among AT rats that was almost completely unresponsive to MK-801. This insensitivity to MK-801 correlated with the lack of c-fos induction in the retrosplenial and cingulate cortices. Fos immunoreactive cells in these brain regions after MK-801 treatment were more numerous in ANT than AT rats, although c-fos induction in the inferior olivary nucleus was similar in all animals after MK-801. The ANT rats showed greater locomotor stimulation also after ketamine and LY235959, while stimulation induced by PCP and depression induced by L-701,324 did not differ between the rat lines. The data suggest that altered NMDA receptor-mediated processes may correlate with differences in innate alcohol sensitivity in the ANT/AT rat model.

Cerebellar GABA(A) receptors and anxiolytic action of diazepam

Alcohol-sensitive ANT rats have a point mutation in the cerebellum-enriched GABA(A) receptor alpha6 subunit, which makes this subunit and the ANT rats in vivo highly sensitive to benzodiazepine agonists. In the elevated plus maze test of anxiety, diazepam produced a greater anxiolytic response in the ANT rats than in the control, alcohol-insensitive AT rats. The ANT rats were less sensitive to the sedative effect of diazepam in the staircase test of exploration. The results thus suggest that the mutant cerebellar granule cell layer receptors can participate in GABA(A) receptor-activation-induced anxiolysis.

Involvement of opioid mu1-receptors in opioid-induced acceleration of striatal and limbic dopaminergic transmission

The role of mu1-opioid receptors in the acceleration of cerebral dopaminergic transmission induced by morphine and the putative mu1-opioid agonist, etonitazene, was studied in rats by measuring the tissue levels of dopamine (DA) and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the dorsal striatum and nucleus accumbens. The striatal extracellular concentrations of DA and its metabolites in freely moving rats were estimated as well. Morphine (3 mg/kg) and etonitazene (2.5 microg/kg) increased the striatal and accumbal dopamine metabolism as measured by the tissue ratios of DOPAC/DA and HVA/DA. The mu1-opioid receptor antagonist, naloxonazine (15 mg/kg), significantly antagonized these elevations except the morphine-induced elevation of striatal HVA/DA ratio. Both morphine (3 mg/kg) and etonitazene (1, 2.5, and 5 microg/kg) elevated the striatal extracellular DA, DOPAC, and HVA. Naloxonazine antagonized the effects of morphine and etonitazene on striatal extracellular DA concentration as well as etonitazene's effects on DOPAC and HVA, but not morphine's effects on DOPAC and HVA. As we previously showed concerning morphine, the conditioned place preference induced by etonitazene was inhibited by naloxonazine. These findings emphasize the role of mu1-opioid receptors in opioid reward, in which the mesolimbic dopaminergic system is considered to be importantly involved. Our results clearly show that in addition to the mesolimbic dopaminergic system the mu1-opioid receptors are also involved in the control of nigrostriatal DA release and metabolism. However, the effects of etonitazene on the striatal DA differ from those of morphine, suggesting that the opioid mechanisms regulating these two DA systems differ.

[3H]ethylketocyclazocine binding to brain opioid receptor subtypes in alcohol-preferring AA and alcohol-avoiding ANA rats

We measured brain regional patterns of [3H]ethylketocyclazocine binding to brain opioid receptors in ethanol-naive alcohol-preferring Alko, Alcohol (AA) and alcohol-avoiding Alko, Non-Alcohol (ANA) rats, by using quantitative autoradiography. This agonist ligand labels all opioid receptor subtypes. The proportions of mu- and delta-opioid receptor binding were evaluated by displacing the mu- and delta-opioid receptor components by the peptides Tyr-D-Ala-Gly-N(Me)Phe-Gly-ol (DAMGO, 100 nM) and Tyr-D-Pen-Gly-Phe-D-Pen (DPDPE, 100nM), respectively, the K-component being the naltrexone-sensitive binding left after removal of the above two components. The labeling patterns in the brains of the AA and ANA rats were consistent with the well-known distributions of the opioid receptor subtypes in nonselected rat strains and there was no major difference between the lines. The mu-opioid receptor binding was greater in the AA than ANA rats in several brain regions, most interestingly in the substantia nigra pars reticulata and striatal clusters with elevated shell/core ratios in the nucleus accumbens. The delta-opioid receptor binding did not differ between the lines, whereas the AA rats had more K-opioid receptors than the ANA rats in several brain regions, including limbic areas and basal ganglia. The observed results might indicate altered action of the opioidergic system on dopaminergic pathways in rats with differential alcohol preference.

Effects of morphine on metabolism of dopamine and serotonin in brains of alcohol-preferring AA and alcohol-avoiding ANA rats

Morphine induces a larger locomotor stimulation in the alcohol-preferring AA rats than in the alcohol-avoiding ANA rats. We have now studied the acute effects of morphine (1 and 3 mg/kg) on metabolism of dopamine and serotonin (5-HT) in the dorsal and ventral striatum of the AA and ANA rats. The basal level of dopamine release, as reflected by the concentration of dopamine metabolite 3-methoxytyramine (3-MT), was lower in the caudate-putamen and nucleus accumbens of the AA rats than in the ANA rats. In the caudate-putamen, morphine increased dopamine metabolism and release more in the AA than in the ANA rats. In the nucleus accumbens and olfactory tubercle, the effects of morphine on dopamine metabolism and release did not differ between the rat lines. Morphine elevated the metabolism of 5-HT in the caudate-putamen and nucleus accumbens of the AA but not in those of the ANA rats. The results suggest that the larger morphine-induced psychomotor stimulation of the AA rats in comparison with the ANA rats is associated with the larger effect of morphine on dopamine metabolism in the caudate-putamen and 5-HT metabolism in the caudate-putamen and nucleus accumbens. Furthermore, low basal dopamine release may play a role in the high alcohol-preference of AA rats.

Enhanced morphine- and cocaine-induced behavioral sensitization in alcohol-preferring AA rats

Locomotor stimulation and behavioral sensitization induced by acute and repeated treatment with alcohol, cocaine or morphine were studied in the alcohol-preferring AA (Alko, Alcohol), alcohol-avoiding ANA (Alko, Non-Alcohol) rats and non-selected Wistar rats. Daily treatment with alcohol (ethanol, 0.4 or 1.0 g/kg, IP) for 6 days had no effect on locomotor activity either in the AA or ANA rats. Acute cocaine (5, 10 or 20 mg/kg, IP) produced a locomotor stimulation in the animals of all lines studied, and there was no difference in this effect between the AA and ANA rats. During a 4-day repeated cocaine treatment, the AA rats became sensitized with the 10 mg/kg dose, while the ANA rats did not show any sensitization with this dose. With the 20 mg/kg cocaine dose, in addition to locomotor stimulation, the rats of all lines studied showed stereotyped behavior, which response was enhanced during repeated treatment. Morphine-induced locomotor stimulation was larger in the AA rats than in the ANA or Wistar rats both with 1.0 and 3.0 mg/kg doses and only the AA rats were sensitized during 4-day treatment with the 1 mg/kg dose. With the 3.0 mg/kg morphine dose, only the AA rats showed a weak sensitization evident only during the initial 30 min after morphine injection. As the drug-induced behavioral sensitization is an important factor in the development of drug addiction, it is possible that mechanisms underlying the enhanced susceptibility of the AA rats to morphine- and cocaine-induced sensitization contribute to the high intake of alcohol and other abused drugs by these animals.

Conditioned place preference induced by a combination of L-dopa and a COMT inhibitor, entacapone, in rats

The interaction of dopamine (DA) precursor L-dopa and catechol-O-methyltransferase (COMT) inhibitor, entacapone, was examined in rats using conditioned place preference (CPP) paradigm to assess reinforcement, and by measuring DA metabolism in the striatum and the limbic forebrain. Neither L-dopa (100 mg/kg i.p.) nor entacapone (30 mg/kg i.p.) alone induced CPP, but in combination they induced significant CPP. Entacapone alone had no effect on limbic or striatal DA concentrations, while it reduced the concentrations of the COMT products 3-methoxytyramine (3-MT), a metabolite reflecting DA release, and homovanillic acid (HVA) in both brain areas. L-dopa elevated limbic but not striatal 3-MT. L-dopa also slightly elevated limbic DA but had no effect on striatal DA concentration. L-Dopa-induced increase of 3-MT was attenuated by entacapone. Our results show for the first time that L-dopa is able to produce CPP in intact animals. This effect may be related to the findings that L-dopa increases synaptic DA concentrations in the limbic areas, and entacapone may enhance this elevation as it prevents the synaptic metabolism of DA.

Brain opioid receptor binding of [3H]CTOP and [3H]naltrindole in alcohol-preferring AA and alcohol-avoiding ANA rats

We compared mu- and delta-opioid receptor distributions between the brains of alcohol-preferring Alko, Alcohol (AA) and alcohol-avoiding Alko, Non-Alcohol (ANA) rat lines, using autoradiography on brain sections with mu- and delta-opioid receptor antagonist ligands [3H]CTOP and [3H]naltrindole, respectively. The labeling patterns of the ligands were consistent with the known opioid receptor distributions in both rat lines and no major genetic differences were found between the lines. However, the binding density of mu- and delta-opioid receptors differed slightly in several brain areas: in the AA brain sections, limbic areas, such as hippocampus and amygdala, showed decreased mu- and delta-opioid receptor binding, whereas the striatal patches were larger and the substantia nigra showed higher binding density of the mu-receptors compared to the ANA sections. The small differences observed between the rat lines could be due to adaptations to altered endogenous opioid peptide levels or neural circuits, and associated with the differences in alcohol drinking or other behaviors.

Voluntary alcohol drinking selectively accelerates dopamine release in the ventral striatum as reflected by 3-methoxytyramine levels

Alcohol-preferring Alko, Alcohol (AA) rats with free access to food and water were taught to voluntarily consume 10% alcohol solution during 20-min sessions. After the drinking session, rats had elevated dopamine release (as reflected by 3-methoxytyramine concentrations) in the nucleus accumbens, olfactory tubercle, and caudate-putamen. When alcohol solution was replaced by plain water, dopamine release was increased only in the caudate-putamen, indicating selective activation of the mesolimbic dopaminergic pathway by alcohol.

Behavioral sensitivity and ethanol potentiation of the N-methyl-D-aspartate receptor antagonist MK-801 in a rat line selected for high ethanol sensitivity

The role of the N-methyl-D-aspartate (NMDA) receptors in differential ethanol sensitivity of the alcohol-insensitive [alcohol-tolerant (AT)] and alcohol-sensitive [alcohol-nontolerant (ANT)] rat lines selected for low and high sensitivity to ethanol-induced (2 g/kg) motor impairment was studied in behavioral and neurochemical experiments. A noncompetitive antagonist of the NMDA receptor, dizocilpine maleate (MK-801; 0.2 mg/kg), impaired motor function in ANT rats, but not in AT rats, in a tilting plane test. The impairment was further potentiated by a dose (0.75 g/kg) of ethanol, which alone was inactive. This effect was apparently not associated with the locomotor stimulation produced by MK-801 (0.1 and 0.2 mg/kg), because stimulation did not differ between the rat lines. Locomotor stimulation was potentiated by the low ethanol dose in both rat lines. Ethanol treatment decreased the cerebellar and hippocampal cGMP concentrations both with and without MK-801 pretreatment in both rat lines. In situ hybridization using oligonucleotide probes specific for NMDA receptor subunit mRNAs NR1 and NR2A, B, C, and D revealed no clear differences in brain regional expression between ANT and AT rates. These results indicate that the alcohol-sensitive ANT rats are very sensitive to a low dose of ethanol in the presence of NMDA receptor antagonism, consistent with the hypothesis that this receptor system is involved in acute ethanol intoxication.

Alcohol drinking is reduced by a mu 1- but not by a delta-opioid receptor antagonist in alcohol-preferring rats

To assess the roles of opioid receptor subtypes in voluntary alcohol drinking, alcohol-preferring AA (Alko, Alcohol) rats, non-deprived of food or water, were used in a paradigm where access to 10% alcohol solution was limited to 1-4-h sessions on every 2nd working day. The delta-opioid receptor antagonist naltrindole (1-5 mg/kg i.p. 15 min before the session) had no effect on alcohol drinking, while it attenuated the delta-opioid receptor agonist [D-Pen2, D-Pen5]enkephalin-induced locomotor stimulation. The mu1-opioid receptor antagonist naloxonazine (1-15 mg/kg i.p. 20 h before the session), at the largest dose, decreased alcohol drinking. It also decreased food intake. When naltrindole (1 mg/kg) and naloxonazine (15 mg/kg) were given prior to 3 consecutive sessions, the former had no effects at any session. Naloxonazine decreased alcohol consumption only in the 1st session, although the reduction of daily water intake became stronger during repeated administration. 4 days after the last drug administration, naloxonazine-treated animals consumed alcohol nearly twice as much as in the control session before any drug treatment. These data suggest that delta-opioid receptors are not involved in the regulation of alcohol drinking in AA rats. mu1-Opioid receptors may be involved in alcohol drinking, although the data suggest that even their prolonged blockade alone is insufficient to induce a sustained decrease in alcohol drinking.

Defective habituation to nociceptive stimulation in alcohol-avoiding ANA rats

Brain opioidergic mechanisms participate in the regulation of motivational and ingestive behaviours. Since alcohol is believed to activate endogenous opioid systems and to produce opioid-mediated antinociception, the present experiments were performed to find out if alcohol-induced antinociception differs between the alcohol-preferring AA and alcohol-avoiding ANA rat lines. Alcohol doses relevant to the voluntary alcohol intake by the AA rats (0.5-1.0 g/kg, intraperitoneally) failed to alter tail-flick (TF) latency in a 55 degrees C water bath by either rat line. However, repeated measurement of TF latency, even without any alcohol treatment, prolonged tail-flick latencies in AA but not in ANA rats. Prolongation of TF latency was also seen in non-selected Wistar rats, indicating that the ANA rats respond abnormally in this test. The antinociceptive effects of swimming-induced stress (3 min at 15 degrees C) and those of cumulative morphine administration (0.5-16.0 mg/kg, subcutaneously) were similar in both rat lines. Using higher, motor-impairing alcohol doses with repeated baseline TF determinations, it was observed that a dose of 1.5 g/kg induced slight antinociception only in the AA rats, while 2.0 g/kg produced similar effects in both rat lines. It is thus concluded that the alcohol-preferring AA rats do not show any enhanced alcohol-induced antinociception at relevant alcohol doses. However, the alcohol-avoiding ANA rats appear to have a defective ability to habituate to repeated sensory stimuli, which could contribute to their alcohol avoidance by preventing the development of tolerance to aversive effects of alcohol.

Effect of sex and age on brain monoamines and spatial learning in rats

The concentrations of noradrenaline (NA), dopamine (DA), serotonin (5-HT), and their metabolites were measured in the prefrontal cortex, caudate-putamen, and hippocampus in young (3 months) and aged (27-31 months) Wistar rats of both sexes. Age-related changes were found in prefrontal NA and HVA/DA ratio, striatal DA and DOPAC/DA ratio, and striatal and hippocampal 5-HT and 5-HIAA/5-HT ratio. Age and sex dependent changes were found in striatal DA and DOPAC/DA ratio, and hippocampal MHPG-SO4/NA ratio. The aged rats were tested in spatial discrimination and reversal tasks in a T maze. The effects of alpha 2-agonist medetomidine (3 micrograms/kg) on the task performance were assessed in relation to individual variation in monoamine metabolism. Medetomidine impaired spatial discrimination learning of the aged rats by interacting with the hippocampal 5-HT turnover. Medetomidine improved reversal learning through an interaction with the striatal DA turnover and reduced the number of perseverative errors after reversal, mainly due to its interaction with the prefrontal NA turnover. It is concluded that the memory enhancing effect of drugs acting through the brain monoamine systems is highly dependent on the stage of degeneration of these systems that show considerable individual variation in aged animals.

Morphine-stimulated metabolism of striatal and limbic dopamine is dissimilarly sensitized in rats upon withdrawal from chronic morphine treatment

The effects of acute morphine on the release of dopamine (DA) in the striatum and limbic forebrain of rats upon 48 h withdrawal from 20-day morphine treatment were studied using 3-methoxytyramine (3-MT) in tissue as an index of DA release. Homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were also measured. The chronic morphine treatment did not alter the concentrations of DA metabolites. Acute morphine (10 mg/kg) elevated all three DA metabolites in both brain areas. Morphine withdrawal potentiated the elevation of striatal and limbic 3-MT as well as that of striatal but not limbic HVA. These findings show that both striatal and limbic DA mechanisms are sensitized to morphine upon withdrawal but that sensitization of DA metabolism in these two brain areas occurs differently.

Benzodiazepine receptor ligands modulate ethanol drinking in alcohol-preferring rats

The effects of benzodiazepine receptor ligands with different intrinsic activity profiles were studied on voluntary ethanol consumption in the selectively bred alcohol-preferring AA (Alko, Alcohol) rat line, and compared to those of an opiate antagonist, naloxone, and a serotonin uptake inhibitor, citalopram. The rats were first allowed to develop a strong preference for 10% (v/v) ethanol solution in tap water over plain water until their ethanol consumption stabilized. Thereafter, the period when ethanol solution was available for the rats was gradually reduced to 4 h, 3 times a week, every second working day. The acute effects of positive allosteric modulators (agonists) of the gamma-aminobutyric acid type A (GABAA)/benzodiazepine receptor [midazolam, abecarnil, ethyl 5-benzyloxy-4-methoxymethyl-beta-carboline-3-carboxylate (ZK 91296), bretazenil, and 2,5-dihydro-2-(4-methylphenyl)-3H-pyrazolo[4,3-C]quinolin-3(5H)-on e (CGS 9895)] and of negative allosteric modulators [inverse agonists, ethyl 8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5- a][1,4]benzodiazepine-3-carboxylate (Ro 15-4513) and t-butyl 5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-a]thieno[2,3- f][1,4]diazepine-3-carboxylate (Ro 19-4603)] were tested after i.p. injections of three different drug doses using saline injections as a control treatment. The benzodiazepine agonists had rather modest effects on ethanol intake, measured 1 and 4 h after the injections, whereas the inverse agonists and naloxone strongly decreased ethanol consumption. Acute citalopram had no clear effect on ethanol drinking, but it slightly decreased the consumption of novel food during the 4-h session, as did all other benzodiazepine agonists except bretazenil. Neither the inverse agonists nor naloxone had any significant effect on food intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenotypic characterization of second generation offspring of alcohol-sensitive ANT and alcohol-insensitive AT rat lines

The alcohol-sensitive ANT and the alcohol-insensitive AT rat lines developed by selective breeding for differential sensitivity to motor impairment on the tilting plane by a moderate ethanol dose (2 g/kg, IP), were cross-bred to produce second generation (F2) offspring to study phenotypic correlations between various behavioral and biochemical properties and the degree of initial alcohol sensitivity in the tilting plane test. The F2 population (n = 75) was subjected to alcohol sensitivity tests using a tilting plane test and a sleep time test, and to the elevated plus-maze test of sober activity and anxiety. Finally, the animals were sacrificed and the concentrations of dopamine and its acidic metabolites were analyzed in their striatal tissues. Serum corticosterone was determined to obtain information about the stress responses of the animals after the tilting plane test. The behaviors studied had no significant correlations with each other, suggesting that the various genetic and environmental factors affecting these behavioral phenotypes are different for each behavior. The biochemical measures yielded some correlations with the tilting plane test results that were contrary to the differences between the parent rat lines (dopaminergic indices) or that were confounded by the correlations with the body weight of the animals (corticosterone). Body-weight independent correlational tendency between the alcohol-induced impairment in motor performance and serum corticosterone concentration, however, fitted the differences between the parent lines, suggesting that stress mechanisms cannot be fully excluded as factors contributing to the differential alcohol sensitivity between the ANT and AT rat lines.

Alterations in dopamine metabolism by intraperitoneal ethanol in rats selected for high and low ethanol preference: a 3-methoxytyramine study

Effects of an ethanol dose (1 g/kg, IP) on the metabolism of dopamine (DA) in the nucleus accumbens, striatum and hypothalamus of ethanol-naive alcohol-preferring (AA) and alcohol-avoiding (ANA) rats were studied. Rats were sacrificed by focused-beam microwave irradiation of the brain 20 minutes after ethanol administration, and the concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), assumed to reflect DA metabolism, and of 3-methoxytyramine (3-MT), assumed to reflect DA release, were measured using gas chromatography-mass spectrometry. Basal striatal DOPAC and HVA concentrations were higher in the AA rats in comparison with ANA rats. Ethanol increased HVA, but not DOPAC, concentration in the nucleus accumbens and striatum, but not in the hypothalamus. There was a significant rat line x ethanol treatment interaction with respect to HVA concentration in the nucleus accumbens. The increase in HVA was higher in the AA than ANA rats. Basal 3-MT concentration was not changed by ethanol, except in the nucleus accumbens, where a significant rat line x ethanol treatment interaction was found. A decrease in 3-MT concentration was only detected in the ANA rats. After inhibition of monoamine oxidase with pargyline hydrochloride (75 mg/kg, IP, 10 min before sacrifice), 3-MT accumulation was decreased by ethanol, especially in the nucleus accumbens of both AA and ANA rat lines as well as in that of nonselected Wistar rats.(ABSTRACT TRUNCATED AT 250 WORDS)

The Dental Fear Survey Schedule: a study with Finnish children

The reliability and validity of the Dental Fear Survey Schedule for Children (DFSS-C) was examined in a sample of 828 school children in Finland. The DFSS-C mean was 22.1. Choking, injections and drilling were the most common fears. Internal consistency indicated a high level of reliability. Factor analysis (principal components, varimax rotation) found three factors accounting for 54% of the scale variance. Factors were defined as (1) fear of highly invasive procedures, such as injections and drilling; (2) fear of potential victimization, including fear of strangers, choking and hospitals; and (3) fear of less invasive procedures, such as opening the mouth and being examined by the dentist. The factor pattern was similar to results obtained with a sample of children in the United States. There were significant differences in fear score for children whose parents reported them fearful and/or reported them to have had a previous bad experience at the dentist. Boys (but not girls) who had a DMFT score of at least 1 had a significantly higher mean DFSS-C score (21.1) than those who were caries free (20.0). These data suggest the DFSS-C operates in Finland as it does in the United States, but that culture-specific minimal scores for determining high dental fear are needed.

Binding of serotonergic ligands to brain membranes of alcohol-preferring AA and alcohol-avoiding ANA rats

The alcohol-preferring AA rats have higher concentration of 5-hydroxytryptamine (5-HT) in the brain than the alcohol-avoiding ANA rats. In the present study, the 5-HT1, 5-HT2, and 5-HT3 receptors were studied with [3H]5-HT, [3H]ketanserin, and [3H]LY278584, respectively, in membrane homogenates from different brain regions of both rat lines using in vitro binding assays. No differences in the 5-HT1 and 5-HT2 receptor binding in the brainstem, hippocampus, frontal cortex, and hypothalamus or in the 5-HT3 receptor binding in the nucleus accumbens, amygdala, hippocampus, and frontal cortex were observed between the ethanol-naive animals of the rat lines. In rats given the opportunity to voluntarily consume alcohol, there was a tendency to increase 5-HT1 binding in the ANA rats, which tendency was, however, also found in their ethanol-naive controls subjected to the same handling and behavioral tests as the ethanol-experienced animals. The results do not, however, indicate that any genetic modifications of the 5-HT receptor-binding sites have occurred in the process of the selective breeding of AA and ANA rats for alcohol preference and avoidance, respectively.