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Biomedical subjects

R N Takahashi

Publications and source records attributed to R N Takahashi.

At least 19 recordsLinked to original sources

Evidence for a female-specific effect of a chromosome 4 locus on anxiety-related behaviors and ethanol drinking in rats.

Previous studies using the inbred rat strains Lewis (LEW) and spontaneously hypertensive rats (SHR) led to the mapping of two quantitative trait loci, named Ofil1 (on chromosome 4 of the rat) and Ofil2 (on chromosome 7), for open-field inner locomotion, a behavioral index of anxiety. Studies using other strains showed that the region next to Ofil1 influences measures of not only anxiety but also ethanol consumption. In view of the high prevalence of psychiatric disorders such as anxiety and alcoholism, as well as the comorbidity between them, the present study was designed to better characterize the contribution of these two loci to complex emotional and consummatory responses. Rats deriving from an F2 intercross between the LEW and the SHR strains were selected according to their genotype at markers flanking the loci Ofil1 and Ofil2 and bred to obtain lines of rats homozygous LEW/LEW or SHR/SHR for each of the two loci, thus generating four genotypic combinations. These selected animals as well as purebred LEW and SHR rats of both sexes were submitted to a battery of tests including measures of locomotor activity, anxiety, sweet and bitter taste reinforcement and ethanol intake. Lewis rats displayed more anxiety-like behavior and less ethanol intake than SHR rats. Ofil1 (on chromosome 4) affected both the activity in the center of the open field and ethanol drinking in females only. These results suggest that Ofil1 contains either linked genes with independent influences on anxiety-related responses and ethanol drinking or a pleiotropic gene with simultaneous effects on both traits.

Alcohol Drinking↗

Antagonistic interaction between adenosine A2A and dopamine D2 receptors modulates the social recognition memory in reserpine-treated rats.

Increasing evidence suggests that antagonistic interactions between specific subtypes of adenosine and dopamine receptors in the basal ganglia are involved in the control of motor activity. However, there are few studies investigating this interaction in other brain regions and its role in additional functions. In the present study, we evaluated whether reserpine-treated rats (1.0 mg/kg, i.p.) exhibit altered social recognition memory abilities. The effects of acute administration of the dopamine receptor agonists 7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3 benzazepine (SKF 38393, dopamine D(1) receptor agonist) and quinpirole (dopamine D(2) receptor agonist), together with the adenosine receptor antagonists caffeine (non-selective), 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, adenosine A(1) receptor antagonist) and 4-(2-[7-amino-2-{2-furyl}{1,2,4}triazolo-{2,3-a}{1,3,5}triazin-5-yl-amino]ethyl)phenol (ZM241385, adenosine A(2A) receptor antagonist), were also investigated. Twenty-four hours after treatment, reserpine-treated rats exhibited a significant disruption in the ability to recognize a juvenile rat after a short period of time. These animals did not show any motor deficit. The social recognition disruption induced by reserpine was reversed by acute treatment with quinpirole (0.05-0.1 mg/kg, i.p.), caffeine (10.0-30.0 mg/kg, i.p.) or ZM241385 (0.5-1.0 mg/kg, i.p.), but not with SKF 38393 (0.5-3.0 mg/kg, i.p.) or DPCPX (0.5-3.0 mg/kg, i.p.). Moreover, a synergistic response was observed following the co-administration of 'non-effective' doses of ZM241385 (0.1 mg/kg, i.p.) and quinpirole (0.01 mg/kg, i.p.). These results reinforce and extend the notion of antagonistic interactions between adenosine and dopamine receptors, and demonstrate, for the first time, that the blockade of adenosine A(2A) receptors and the activation of dopamine D(2) receptors can reverse the social recognition deficits induced by reserpine in rats.

Adenosine A2 Receptor Agonists↗

Comparison of voluntary ethanol intake by two pairs of rat lines used as genetic models of anxiety.

The relationship between anxiety-related behaviors and voluntary ethanol intake was examined in two pairs of rat lines by the oral ethanol self-administration procedure. Floripa high (H) and low (L) rats selectively bred for contrasting anxiety responses in the open-field test, and two inbred strains, spontaneously hypertensive rats (SHR) and Lewis rats which are known to differ significantly when submitted to several behavioral tests of anxiety/emotionality, were used (9-10 animals/line/sex). No differences in the choice of ethanol solutions (2%, days 1-4, and 4%, days 5-8, respectively) in a 2-bottle paradigm were detected between Floripa H and L rats (1.94 +/- 0.37 vs 1.61 +/- 0.37 g/kg for ethanol intake on day 8 by the Floripa H and L rat lines, respectively). Contrary to expectations, the less anxious SHR rats consumed significantly more ethanol than Lewis rats (respective intake of 2.30 +/- 0.45 and 0.72 +/- 0.33 g/kg on day 8) which are known to be both addiction-prone and highly anxious. Regardless of strain, female rats consumed more ethanol than males (approximately 46%). The results showed no relationship between high anxiety and voluntary intake of ethanol for Floripa H and L rats. A negative association between these two variables, however, was found for SHR and Lewis rat strains. Data from the literature regarding the association between anxiety and alcohol intake in animal models are not conclusive, but the present results indicate that factors other than increased inborn anxiety probably lead to the individual differences in ethanol drinking behavior.

Alcohol Drinking↗

Rapid tolerance to Delta(9)-tetrahydrocannabinol and cross-tolerance between ethanol and Delta(9)-tetrahydrocannabinol in mice.

Motor incoordination in the rota-rod test was used to assess the development of rapid tolerance to Delta(9)-tetrahydrocannabinol and rapid cross-tolerance between ethanol and Delta(9)-tetrahydrocannabinol in mice. Further, the influence of the cannabinoid receptor antagonist SR 141716A (N-(piperidin-1-yl)-5-(4-chlorophenyl)-4-methyl-1H-pyrazole-3-carboxyamide) on the motor impairment induced by both drugs was examined. Mice were injected on day 1 with equipotent doses of Delta(9)-tetrahydrocannabinol (28 mg/kg, i.p.) and ethanol (2.25 g/kg, i.p.) and tested at 30, 60 and 90 min after the injections. On day 2, control groups received ethanol or Delta(9)-tetrahydrocannabinol, some groups received the same treatment as the day before, while the remaining groups switched the treatment. All groups were tested to evaluate tolerance. The development of rapid tolerance to Delta(9)-tetrahydrocannabinol was observed and pretreatment with ethanol resulted in rapid cross-tolerance to Delta(9)-tetrahydrocannabinol. SR 141716A (2 mg/kg, i.p.) failed to block the development of rapid tolerance to both drugs, ethanol and Delta(9)-tetrahydrocannabinol. These results suggest that Delta(9)-tetrahydrocannabinol, similarly to ethanol, can induce rapid tolerance to motor incoordination in mice. They also support the use of the 2-day protocol as an effective procedure to reduce the length of drug exposure necessary to induce tolerance.

Animals↗

Memory disruption in rats with nigral lesions induced by MPTP: a model for early Parkinson's disease amnesia.

Intra-nigral administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine (MPTP) caused a lesion in the substantia nigra, compact part (SNc) and a specific loss of dopamine and its metabolites in the striatum of rats. The animals were then tested in the two-way active avoidance task. MPTP-treated animals presented lower learning scores in the training and test sessions, an effect that was not caused by motor impairment or by a decreased sensitivity to footshock since their reaction time to the footshock (unconditioned stimulus - UCS) was not reduced. These lower scores were also not attributable to lower acoustic sensitivity or to a slowing in the association of the sound cue (conditioned stimulus - CS) with the UCS since the reaction time to the CS in the active avoidance response did not differ between MPTP-treated and control groups. Therefore, these results are more properly attributable to an impairment of the memory acquisition and retention processes. In addition, this study is presented as a model of early Parkinson's Disease amnesia and is discussed in terms of the importance of the nigrostriatal pathway to memory acquisition and storage processes.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

Caffeine reverses the memory disruption induced by intra-nigral MPTP-injection in rats.

The present study was carried out to test the possible effects of caffeine in improving the memory deficits observed in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine (MPTP)-lesioned rats, an animal model of early stage Parkinson's disease. Caffeine at the doses of 0.1-0.3 mg/kg (intraperitoneal) reversed the impairing effect of the administration of MPTP (1 micromol/side) into the substantia nigra, compact part, of rats on the avoidance scores in the training and test sessions of a two-way active avoidance task. This effect was not due to a motor or sensory alteration because the caffeine-induced learning and memory improvement was independent of the locomotor stimulant effect of the drug and there were no differences in the reaction time of the animals to a footshock (unconditioned stimulus) or a sound cue (conditioned stimulus) after caffeine treatment. These results suggest that the reported dopamine/adenosine-receptor interaction can be used to restore defective learning and memory processes in Parkinson's disease and indicate that caffeine and other adenosine receptor antagonists are drugs with the potential for treatment of the cognitive disabilities of Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

L-Dopa restores striatal dopamine level but fails to reverse MPTP-induced memory deficits in rats.

The objective of the present investigation was to test the effects of benserazide/L-dopa treatment in a model of learning and memory deficits associated with early Parkinson's disease. Intra-nigral administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) caused a lesion in the substantia nigra, compact part and a specific loss of dopamine (DA) and its metabolites in the striatum of rats and a memory impairment in the two-way active avoidance task. The administration of benserazide/L-dopa (50 and 200 mg/kg) to the MPTP-lesioned rats restored the striatal level of DA, but did not reverse the MPTP-induced learning and memory impairment. As this treatment caused a large increase of DA levels in extrastriatal brain regions of the MPTP-lesioned animals, this study suggests that benserazide/L-dopa therapy was not effective in improving the observed learning impairment because this treatment appears to tilt the balance between DA levels in the striatum and in the extrastriatal regions, such as frontal cortex and limbic structures, resulting in a cognitive deficit.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

Strain-dependent effects of diazepam and the 5-HT2B/2C receptor antagonist SB 206553 in spontaneously hypertensive and Lewis rats tested in the elevated plus-maze.

The 5-HT2B/2C receptor antagonist SB 206553 exerts anxiolytic effects in rat models of anxiety. However, these effects have been reported for standard rat strains, thus raising the issue of SB 206553 effects in rat strains displaying different levels of anxiety. Herein, the effects of SB 206553 in a 5-min elevated plus-maze test of anxiety were compared to those of the reference anxiolytic, diazepam, in two rat strains respectively displaying high (Lewis rats) and low (spontaneously hypertensive rats, SHR) anxiety. Diazepam (0.37, 0.75, or 1.5 mg/kg; 30 min before testing) increased in a dose-dependent manner the behavioral measures in SHR, but not in Lewis rats. On the other hand, SB 206553 (1.25, 2.5, or 5 mg/kg; 30 min before testing) failed to alter the anxiety parameters in both strains, whereas it increased closed arm entries in Lewis rats, suggesting that it elicited hyperactivity in the latter strain. Accordingly, the hypolocomotor effect of the nonselective 5-HT2B/2C receptor agonist m-chlorophenylpiperazine (1.5 mg/kg ip 20 min before a 15-min exposure to an activity cage) was prevented by the 1.25 and 2.5 mg/kg doses of SB 206553 in Lewis rats and SHR, respectively. Compared with SHR, Lewis rats may display a lower response to benzodiazepine-mediated effects and a more efficient control of locomotor activity by 5-HT2B/2C receptors.

Animals↗

Dexamethasone reverses the ethanol-induced anxiolytic effect in rats.

The effects of intraperitoneal and intrahippocampal administration of the glucocorticoid dexamethasone were assessed regarding ethanol-induced anxiolysis in the elevated plus-maze in rats. Animals pretreated with systemic injections of dexamethasone (0.5, 1. 0, or 2.0 mg/kg, IP) 15 min before ethanol (1.2 g/kg, 14% w/v, IP) administration showed a significant dose-dependent attenuation of the increased percentage of frequency and time spent on open arms of the maze. However, IP dexamethasone treatment 4 h before the test had no effect. Unilateral intrahippocampal injection of dexamethasone (2 and 20 nmol in 0.5 microl) also significantly attenuated the increased exploration of the open arms induced by ethanol. The results are interpreted in terms of the modulation of the anxiolytic effects of ethanol by glucocorticoids and the possible involvement of hippocampus in this response. The rapid blockade of ethanol induced anxiolysis by dexamethasone strengthens the suggestion that a nongenomic mechanism may underlie this response.

Analysis of Variance↗

Involvement of dopamine receptors on locomotor stimulation and sensitization elicited by the interaction of ethanol and mazindol in mice.

We have previously observed that the combination of ethanol (EtOH) and the anorectic drug mazindol (MZ) produces more marked effects on behavior than either substance alone. In the present study we examined whether the repeated administration of the drug combination could induce sensitization to its motor activating effects in mice and, if so, whether this response could be affected by dopamine (DA) receptors antagonists. Male Swiss albino mice were treated daily for 7 days with combined EtOH+MZ (1.2 g/kg, 5.0 mg/kg IP), EtOH (1.2 g/kg IP), MZ (5.0 mg/kg IP), or control solution coadministered with the D1 dopamine antagonist SCH-23390 (0.025 or 0.05 mg/kg IP), the mixed dopamine antagonist haloperidol (0.05 or 0.075 mg/kg IP), or vehicle. After the injections on days 1, 7, and 10, mice were assessed in activity cages at different time intervals. Repeated administration of MZ resulted in an enhancement of its locomotor activating effects, behavioral sensitization. Further, the combined EtOH+MZ treatment also resulted in sensitization to its locomotor effects. Moreover, the development of MZ and EtOH+MZ sensitization was attenuated by both SCH-23390 and haloperidol. These data demonstrate that following repeated MZ or EtOH+MZ exposure mice show locomotor sensitization through DA receptor stimulation. Also, these findings suggest that a major determinant of combined anorectic-alcohol misuse may be the increased stimulating effects produced by such combination.

Animals↗

Experimental anxiety and the reinforcing effects of ethanol in rats.

In order to examine the relationship between anxiety and reinforcing effects of alcohol, drug-naive male Wistar rats weighing 250-300 g were classified as "anxious" and "non-anxious" in the elevated plusmaze test. A conditioned place preference test was then used to investigate the reinforcing effects of ethanol (EtOH) on these animals. On 2 alternate days, groups of "anxious", "non-anxious" and "normal" rats received intraperitoneal (i.p.) injections of EtOH (0.5, 1.0 or 1.5 g/kg) immediately before a 15-min confinement to the white compartment. On the 2 intervening days the same rats received i.p. injections of saline before confinement to the opposite compartment. On day 5, a 15-min free-choice test was carried out with no injections. Rats classified as "anxious" showed a significant, though not dose-dependent preference for all doses of ethanol compared to saline-treated animals. These data demonstrate that rats regarded as "anxious" are more sensitive to the reinforcing effects of EtOH than "non-anxious" and "normal" Wistar rats and emphasize the relevance of the basal levels of anxiety of rats when trying to detect the reinforcing effects of EtOH.

Animals↗

Combined effects of diethylpropion and alcohol on locomotor activity of mice: participation of the dopaminergic and opioid systems.

The widespread consumption of anorectics and combined anorectic + alcohol misuse are problems in Brazil. In order to better understand the interactive effects of ethanol (EtOH) and diethylpropion (DEP) we examined the locomotion-activating effects of these drugs given alone or in combination in mice. We also determined whether this response was affected by dopamine (DA) or opioid receptor antagonists. A total of 160 male Swiss mice weighing approximately 30 g were divided into groups of 8 animals per group. The animals were treated daily for 7 consecutive days with combined EtOH + DEP (1.2 g/kg and 5.0 mg/kg, ip), EtOH (1.2 g/kg, ip), DEP (5.0 mg/kg, ip) or the control solution coadministered with the DA antagonist haloperidol (HAL, 0.075 mg/kg, ip), the opioid antagonist naloxone (NAL, 1.0 mg/kg, ip), or vehicle. On days 1, 7 and 10 after the injections, mice were assessed in activity cages at different times (15, 30, 45 and 60 min) for 5 min. The acute combination of EtOH plus DEP induced a significantly higher increase in locomotor activity (day 1: 369.5 +/- 34.41) when compared to either drug alone (day 1: EtOH = 232.5 +/- 23.79 and DEP = 276.0 +/- 12.85) and to control solution (day 1: 153.12 +/- 7.64). However, the repeated administration of EtOH (day 7: 314.63 +/- 26.79 and day 10: 257.62 +/- 29.91) or DEP (day 7: 309.5 +/- 31.65 and day 10: 321.12 +/- 39. 24) alone or in combination (day 7: 459.75 +/- 41.28 and day 10: 427. 87 +/- 33.0) failed to induce a progressive increase in the locomotor response. These data demonstrate greater locomotion-activating effects of the EtOH + DEP combination, probably involving DA and/or opioid receptor stimulation, since the daily pretreatment with HAL (day 1: EtOH + DEP = 395.62 +/- 11.92 and EtOH + DEP + HAL = 371.5 +/- 6.76; day 7: EtOH + DEP = 502.5 +/- 42.27 and EtOH + DEP + HAL = 281.12 +/- 16.08; day 10: EtOH + DEP = 445.75 +/- 16.64 and EtOH + DEP + HAL = 376.75 +/- 16.4) and NAL (day 1: EtOH + DEP = 553.62 +/- 38.15 and EtOH + DEP + NAL = 445.12 +/- 55.67; day 7: EtOH + DEP = 617.5 +/- 38.89 and EtOH + DEP + NAL = 418.25 +/- 61.18; day 10: EtOH + DEP = 541.37 +/- 32.86 and EtOH + DEP + NAL = 427.12 +/- 51.6) reduced the locomotor response induced by combined administration of EtOH + DEP. These findings also suggest that a major determinant of combined anorectic-alcohol misuse may be the increased stimulating effects produced by the combination.

Animals↗

Memory-impairing effects of local anesthetics in an elevated plus-maze test in mice.

Post-training intracerebroventricular administration of procaine (20 micrograms/microliter) and dimethocaine (10 or 20 micrograms/microliter), local anesthetics of the ester class, prolonged the latency (s) in the retention test of male and female 3-month-old Swiss albino mice (25-35 g body weight; N = 140) in the elevated plus-maze (mean +/- SEM for 10 male mice: control = 41.2 +/- 8.1; procaine = 78.5 +/- 10.3; 10 micrograms/microliter dimethocaine = 58.7 +/- 12.3; 20 micrograms/microliter dimethocaine = 109.6 +/- 5.73; for 10 female mice: control = 34.8 +/- 5.8; procaine = 55.3 +/- 13.4; 10 micrograms/microliter dimethocaine = 59.9 +/- 12.3 and 20 micrograms/microliter dimethocaine = 61.3 +/- 11.1). However, lidocaine (10 or 20 micrograms/microliter), an amide class type of local anesthetic, failed to influence this parameter. Local anesthetics at the dose range used did not affect the motor coordination of mice exposed to the rota-rod test. These results suggest that procaine and dimethocaine impair some memory process(es) in the plus-maze test. These findings are interpreted in terms of non-anesthetic mechanisms of action of these drugs on memory impairment and also confirm the validity of the elevated plus-maze for the evaluation of drugs affecting learning and memory in mice.

Analysis of Variance↗

Mazindol and lidocaine are antinociceptives in the mouse formalin model: involvement of dopamine receptor.

The antinociceptive potential of mazindol, an anorectic drug, and lidocaine, an amide-type local anesthetic, were investigated in the mouse formalin test with concurrent motor function assessment. In addition, the role of dopamine and opioid receptors in mediation of the antinociceptive action of these drugs was examined. The i.p. injection of mazindol (1.25-10 mg/kg) and lidocaine (10-30 mg/kg) induced significant antinociceptive responses in both phases of the test. Cocaine (20 mg/kg, i.p.), used as positive control, also inhibited the pain responses caused by formalin. Haloperidol (0.2 mg/kg, i.p.), and sulpiride (5 mg/kg, i.p.), a dopamine D2 receptor antagonist, reduced the antinociceptive actions of mazindol and cocaine, while SCH 23390, R(+)-7-chloro 8-hydroxy-3methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3 benzazepine (0.03 mg/kg, i.p.), a dopamine D1 receptor antagonist, did not affect these responses. Only the antinociception associated with mazindol was reversed by naloxone (2 mg/kg, i.p.). The same pretreatments failed to modify lidocaine-induced antinociception. The drug conditions used in this study did not reveal any motor impairment in the rotarod test. These observations suggest an involvement of dopaminergic mechanisms, mainly via dopamine D2 receptors, in the antinociceptive action of mazindol in the formalin test, but the nature of mechanisms involved in the lidocaine responses remains unsolved.

Anesthetics, Local↗

Stimulant activities of dimethocaine in mice: reinforcing and anxiogenic effects.

The present study evaluated the effects of dimethocaine and procaine, esteratic local anesthetics, on locomotor activity, conditioned place preference and on the elevated plus-maze test of anxiety in mice, behavioral tests believed to be sensitive to cocaine action. Acute administration of dimethocaine (10-40 mg/kg, IP) significantly increased locomotor activity and time spent on the drug-paired side and reduced the relative number of entries and time spent on the open arms of the plus-maze in mice. Procaine (20-50 mg/kg, IP) failed to affect these responses. These data demonstrate the locomotor stimulant, reinforcing and anxiogenic actions of dimethocaine similar to those reported for cocaine in animals. In addition, these findings support a role for dopaminergic activity, rather than local anesthetic action, in the behavioral effects caused by dimethocaine.

Aminobenzoates↗

The effects of systemic procaine, lidocaine and dimethocaine on nociception in mice.

1. Different local anesthetics were tested for analgesic activity in three antinociceptive models, the acetic acid-induced abdominal constriction, tail-flick and hot plate tests in the mouse. 2. In the abdominal constriction test, subcutaneous, SC, injection of lidocaine (10, 20 or 30 mg/kg) and dimethocaine (5, 10 or 20 mg/kg) induced dose-dependent antinociceptive responses. Procaine (20, 30 or 50 mg/kg) was also able to reduce the response to noxious chemical stimuli. 3. The IP injection of lidocaine and dimethocaine significantly inhibited the tail-flick and paw-licking hot plate responses; procaine was weak or inactive in these tests, in which heat was the noxious stimulus. 4. Taken together, these results suggest that antinociception produced by systemically administered lidocaine and dimethocaine at nontoxic doses in mice is due, at least in part, to their central effects.

Acetic Acid↗

Interaction of mazindol with alcohol in mice.

Combined anorectic-alcohol misuse is a prevalent problem in Brazil. In order to understand better the interactive effects of ethanol (EtOH) and mazindol (MZ), we examined the effects of EtOH (1.2 g/kg) and MZ (5.0 mg/kg) given alone or in combination, on mouse behaviour. The results indicate that EtOH plus MZ induces a significantly greater increase in locomotor activity of mice than either constituent alone. However, no such interactive effect was detected in the place preference and in the plus-maze test of anxiety. MZ given alone was found to increase the locomotor activity and to possess rewarding effects as measured in the place preference conditioning. At the dose selected, EtOH alone showed anxiolytic and rewarding effects. These results provide some evidence of increased behavioural effects in mice due to combinations of EtOH and MZ. These findings suggest that a major determinant of combined anorectic-alcohol misuse may be the increased stimulating effects produced by such combination.

Journal Article↗

Effects of carbaryl on some dopaminergic behaviors in rats.

1. The effects of acute oral administration of carbaryl (10-80 mg/kg), a carbamate insecticide, on some experimental models for detecting dopaminergic activity were examined in rats. Also, serum biochemical variables following carbaryl treatments were determined. 2. Carbaryl (20 and 40 mg/kg) significantly increased the number of apomorphine-induced yawns and at dose of 80 mg/kg it prolonged the duration time of haloperidol-induced catalepsy. Pretreatment with carbaryl failed to affect apomorphine-induced stereotypes. 3. Carbaryl significantly reduced blood cholinesterase activity and elevated blood glucose levels and SGOT and SGPT activities. 4. These results indicate that low oral doses of carbaryl can cause behavioral and toxicological effects in rats.

Administration, Oral↗