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Biomedical subjects

F P Bymaster

Publications and source records attributed to F P Bymaster.

101 records · Page 6Linked to original sources
PubMed1976

The comparison of fluoxetine and nisoxetine with tricyclic antidepressants in blocking the neurotoxicity of p-chloroamphetamine and 6-hydroxydopamine in the rat brain.

Fluoxetine prevents the loss of 5-hydroxytryptamine (5HT) uptake in synaptosomes of cerebral cortex after intraperitoneally administered p-chloroamphetamine (p-CA) with an ED50 of 3.8 mg/kg i.p. in rats. However, at 50 mg/kg, it does not prevent the loss of norepinephrine (NE) uptake in synaptosomes of hypothalamus after intraventricularly administered 6-hydroxydopamine (6-OHDA). Nisoxetine, on the other hand, centrally protects NE uptake from the neurotoxic effect of 6-OHDA with an ED50 value of 5 mg/kg i.p. At 50 mg/kg, it gives only 35% protection of 5HT uptake from the neurotoxic effect of p-CA. In comparison with the ED50 values of tricyclic antidepressants, both fluoxetine and nisoxetine are more potent and selective blockers of neurotoxicity resulting from the central actions of p-CA and 6-OHDA, respectively, in vivo.

Amphetamines↗
PubMed1975

A new selective inhibitor for uptake of serotonin into synaptosomes of rat brain: 3-(p-trifluoromethylphenoxy). N-methyl-3-phenylpropylamine.

3-(p-Trifluoromethylphenoxy)-N-methyl-3-phenylpropylamine (Lilly 110140) competitively inhibited the uptake of serotonin (5-HT), norepinephrine (NE) and dopamine into synaptosomes of rat brain with Ki values of 5.5 x 10-minus8, 9.5 x 10-minus6 and 1.3 x 10-minus5 M, respectively. Aiming for a more effective inhibitor of 5-HT uptake, we found the trifluoromethyl group in the phenoxy ring was most favorable at the para-position and was better than other substituting groups including fluoro, chloro, methyl and methoxy groups. The N-demethylated (primary amine) and the N.N-diemthylated (tertiary amine) derivatives inhibited the uptake of monoamines with the same effectiveness as Lilly 110140 (a secondary amine). The uptake of 5-HT into synaptosomes was significantly inhibited 15 minutes after an intraperitoneal administration of Lilly 110140. The inhibition persisted for a 24-hour period. NE uptake in vitro maintained a normal rate during the entire time course. Lilly 110140 likewise had no effect on the in vitro and in vivo accumulation of 3-H-tryptophan in the brain. The effect of Lilly 110140 and the tricyclic drug, chlorimipramine, was compared. Although chlorimipramine inhibited the uptake of 5-HT into synaptosomes with same effectiveness as Lilly 110140 in vitro, it reduced the uptake of both 5-HT and NE in vivo. Chlorimipramine exerted its greatest inhibition on the two uptake processes in the 1st hour and none by the 4th hour. Unlike the tricyclic drugs, imipramine, chlorimipramine, desipramine and chlordesipramine, Lilly 110140 and its primary amine derivative did not block the in vivo uptake of NE into rat heart. The present study suggests that Lilly 110140 is a potent and selective inhibitor for uptake of 5-HT into synaptosomes of rat brain.

Animals↗
PubMedDate not supplied

PET study of the M1-agonists [11C]xanomeline and [11C]butylthio-TZTP in monkey and man.

Xanomeline, a substituted TZTP, is a new M1 selective muscarinic agonist in clinical trials for Alzheimer's disease. The brain uptake of [11C]xanomeline and the analog [11C]butylthio-TZTP was examined by positron emission tomography (PET). Radioactivity accumulated most markedly in the neocortex and the striatum. Pharmacological characterization in vitro and in cynomolgus monkeys in vivo by PET indicated specific [11C]butylthio-TZTP binding to muscarinic receptors and to sigma-1 recognition sites. More than 5% of the radioactivity was in the human brain 5 min after i.v. injection of [11C]xamomeline or [11C]butylthio-TZTP. This high brain uptake may be clinically advantageous in the sense that substituted TZTP may induce central muscarinic agonist effects at a dose level for which there is a low risk of peripheral side-effects.

Adult↗