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Biomedical subjects

Katsumasa Miyasato

Publications and source records attributed to Katsumasa Miyasato.

9 recordsLinked to original sources
PubMed2005

Nicotine normalizes increased prefrontal cortical dopamine D1 receptor binding and decreased working memory performance produced by repeated pretreatment with MK-801: a PET study in conscious monkeys.

The effects of acute nicotine were determined on dopamine (DA) D(1) (D(1)R) and D(2) (D(2)R) receptor binding in the neocortex of conscious monkeys under control conditions as well as after chronic pretreatment with MK-801 (dizocilpine), a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist. Extrastriatal neocortical D(1)R and D(2)R binding was evaluated with [(11)C]NNC112 and [(11)C]FLB457 with high-specific radioactivity using positron emission tomography (PET). Acute administration of nicotine bitartrate, given as an intravenous (i.v.) bolus plus infusion for 30 min at doses of 32 microg/kg+0.8 microg/kg/min or 100 microg/kg+2.53 microg/kg/min as base, induced slight but significant dose-dependent increases of DA in the extracellular fluid of prefrontal cortex (PFC) as determined by microdialysis. However, acute nicotine did not affect either [(11)C]NNC112 or [(11)C]FLB457 binding to D(1)R or D(2)R, respectively, in any cortical region. Chronic MK-801 (0.03 mg/kg, intramuscularly (i.m.), twice daily for 13 days) increased [(11)C]NNC112 binding to D(1)R in PFC. No significant changes were detected in [(11)C]FLB457 binding to PFC D(2)R. Although chronic MK-801 lowered baseline DA and glutamate levels in PFC, acute nicotine normalized reduced DA to control levels. Acute nicotine dose-dependently normalized the increased binding of [(11)C]NNC112 to D(1)R produced by chronic MK-801 but [(11)C]FLB457 binding to PFC D(2)R did not change. Working memory performance, impaired after chronic MK-801, was partially improved by acute nicotine. These results demonstrate that acute nicotine normalizes MK-801-induced PFC abnormality of D(1)R in PFC.

Animals↗
PubMed2004

Clinical features of nicotine dependence compared with those of alcohol, methamphetamine, and inhalant dependence.

A new clinical evaluation form was developed to compare the clinical features of nicotine dependence with those associated with other abused drugs. A new scoring system for clinical evaluation was developed. The form consisted of five scoring items: subjective effects, liking (of drug), withdrawal syndrome, acute psychic and physical disorders, and social disturbance. A preliminary clinical investigation was performed to test the validity of the evaluation form. Study subjects were those showing dependence on nicotine (cigarette smoking, n = 40), alcohol (n = 39), methamphetamine (n = 31), and inhalants (n = 30), who fulfilled the DSM-IV-TR criteria for drug dependence disregarding the state of "a maladaptive pattern of substance use, leading to clinically significant impairment or distress," and gave written informed consent for participation in the study. Nicotine caused a mild or the least degree of subjective effects, liking, and psychic and physical withdrawal symptoms, without any significant social disturbance or acute disorders. With alcohol, liking, withdrawal syndrome, and acute physical disorders were prominent. Methamphetamine produced the most serious acute psychic disorders, with intensive acute physical disorders and psychic withdrawal symptoms. Inhalants were characterized by an intensive degree of acute psychic disorders. As for social disturbance, alcohol, methamphetamine, and inhalants showed more significant influence than nicotine. Our study findings revealed that the clinical features of drug dependence could be evaluated by using the new clinical evaluation form. Further study is required to clarify the clinical features of nicotine dependence compared with those of other drugs of dependence.

Administration, Inhalation↗
PubMed2004

[Studies on clinical characteristics of nicotine dependence using a two compartment model of drug dependence].

The purpose of the present study was to develop a new clinical evaluation form to compare the clinical characteristics of nicotine dependence with those associated with other drugs of abuse, using a two-compartment model consisting of "drug dependence" and "dependence syndrome". The evaluation form consisted of five scoring items: subjective effects, drug liking, withdrawal syndrome, acute psychic and acute physical disorders, and social disturbance. "Drug dependence" was defined by positive scores on the "drug liking" item. "Dependence syndrome" was defined by positive scores on drug-induced pathological symptoms (withdrawal syndrome, and acute psychic and physical disorders) and social disturbance. The subjects were dependent on nicotine (cigarette smoking) (n = 114), alcohol (n = 101), methamphetamine (n = 90), inhalants (n = 63), and benzodiazepines (n = 39). All subjects met the DSM-IV-TR criteria for drug dependence. Nicotine produced a mild or the least degree of drug liking and withdrawal syndrome, without any significant social disturbance, or acute disorders. The other four drugs produced more intensive degrees of withdrawal syndrome and acute psychic and physical symptoms, with more significant social disturbance than nicotine. The present study indicated that nicotine dependence differed from other forms of drug dependence in that nicotine was not associated with "dependence syndrome".

Adult↗
PubMed2002

Comparative effects of methamphetamine and nicotine on the striatal [(11)C]raclopride binding in unanesthetized monkeys.

Although a very large literature exists on the in vitro, ex vivo, and in vivo effects of nicotine on dopamine release in rodents, similar data in primates are scant. This study was initiated to compare methamphetamine to nicotine given i.v. to normal unanesthetized monkeys using positron emission tomography (PET) techniques. Release of dopamine in the striatum using [(11)C]raclopride was determined indirectly in four nicotine-naïve adult Macaca mulatta monkeys under conscious and isoflurane-anesthetized conditions using high-resolution PET. [(11)C]Raclopride was given i.v. as a bolus injection followed by continuous infusion with steady state over 30-45 min. Nicotine bitartrate was then given as a bolus plus infusion for 30 min in doses of 32 microg/kg + 0.8 microg/kg/min or 100 microg/kg + 2.53 microg/kg/min as base. The larger doses of nicotine caused significant cardiovascular effects; these doses did not displace [(11)C]raclopride binding in either dorsal or ventral striatum under the anesthetized conscious condition. In contrast, isoflurane-anesthesia induced a slight but significant dose-dependent reduction of [(11)C]raclopride binding by nicotine even at the same doses used in the anesthetized condition. Methamphetamine in bolus doses of 0.1, 0.3, and 1.0 mg/kg i.v. under conscious condition caused a significant displacement of [(11)C]raclopride and isoflurane-anesthesia facilitated the displacement induced by nicotine. These results indicate that nicotine, in high tobacco-smoking-related doses, does not release sufficient brain dopamine to displace [(11)C]raclopride in the striatum in the awake and fully conscious state, in contrast to small doses of methamphetamine.

Anesthesia↗