[The effect of desmethylimipramine and other "anti-tremorine" drugs on the metabolism of tremorine and oxotremorine in rats and mice]

Laboratory of Chemical Pharmacology, National Heart, Lung, and Blood Institute, NIH: a short history

The Laboratory of Chemical Pharmacology (LCP) began in 1950 as the Section of Pharmacology within the National Heart Institute, the National Institutes of Health. Its first chief was Bernard B. Brodie, considered by many to be one of the fathers of modern pharmacology. Since its inception, LCP has made many significant contributions to the fields of pharmacology and toxicology. LCP was among the first to study (a) the effects of drugs on the turnover of serotonin and norepinephrine in brain and other tissues, (b) the absorption of drugs from the gastrointestinal tract and their passage across the blood-brain barrier, (c) the oxidation and reduction of drugs and other foreign compounds by liver microsomal enzymes (later known as the cytochrome P450 enzymes) and inhibitors and inducers of these enzymes, (d) the formation of toxic chemically reactive metabolites of drugs and other foreign compounds, and (e) mechanisms of immunological responses. Approximately 300 scientists worked in LCP during its existence, and they and their collaborators published more than 1,300 papers. This is a short history of the people who worked in it and of their contributions to biomedical sciences.

Changes in body temperature after administration of acetylcholine, histamine, morphine, prostaglandins and related agents

This survey, the second in a series, presents extensive tabulations of literature, primarily since 1965, on thermoregulatory effects of cholinergic agonists and antagonists, histamine and H1- and H2-receptor antagonists, narcotic analgesics and antagonists in both non-tolerant and tolerant subjects and of prostaglandins and related agents. The information listed includes the species used, route of administration and dose of drug, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions, such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary drug.

Genetical differences in sensitivity to tremorine and oxotremorine in mice

Male mice from 14 strains were injected i.p. with tremorine (3.0 mg/kg) or oxotremorine (0.15 or 0.1 mg/kg). Large inter-strain differences in the degree and duration of the subsequent hypothermia were noted. 2 strains, BALB/c and Simpson, were particularly sensitive to the hypothermic effect of oxotremorine. The offspring from a cross between BALB/c and Simpson were less sensitive than the parental strains, suggesting genetic complementation. A set of 7 recombinant inbred (RI) lines derived from strains C57BL and BALB/c were tested with oxotremorine. 5 RI lines resembled strain C57BL in their response and 2 RI lines resembled strain BALB/c. It was concluded that strains C57BL and BALB/c differ at a gene which has a major effect on the response to oxotremorine.

Effect of simultaneous treatment with low doses of perphenazine on plasma and urine concentrations of nortriptyline and 10-hydroxynortriptyline

Plasma levels of nortriptyline and perphenazine were measured in six patients on continuous nortriptyline treatment before, during and after oral administration of perphenazine 4 mg t.i.d. In four patients the plasma levels of the conjugated and unconjugated principal metabolite 10-hydroxynortriptyline were also measured. Urinary excretion of conjugated and unconjugated 10-hydroxynortriptyline and plasma levels of perphenazine were determined in all six patients. During treatment with perphenazine two patients showed a slight increase in the plasma level of nortriptyline. The changes in metabolite excretion rate were inconclusive. Thus, there did not appear to be any important pharmacokinetic interaction between the two drugs at the doses used, which were normal therapeutic doses. The previously reported inhibitory effect of perphenazine on the metabolism of nortriptyline probably depended therefore, either on administration of a higher dose of perphenazine, or on treatment in the reverse sequence--a single dose of nortriptyline was given to patients already receiving perphenazine.

Decreased distribution of oxotremorine to brain after pharmacological blockade of its peripheral acetylcholine-like effects

The distribution of [3H]oxotremorine, after intravenous injection, to brain and tissues of rats and mice has been studied. In rats, oxotremorine (0·3 mg/kg) rapidly reached the brain with a peak concentration of 1200 ng/g at 1 min. Blockade of the peripheral muscarinic effects of oxotremorine with amitriptyline methyl iodide or atropine methyl nitrate (25 mg/kg, s.c.) markedly decreased the brain content of oxotremorine (peak concentration 400 ng/g), probably as a result of its more rapid distribution to peripheral tissues and an increased volume of distribution. The ratio of drug distribution between plasma and brain is unaffected by pretreatment with anticholinoceptive drugs. Also, the total body concentrations of oxotremorine are similar in pretreated rats and controls. A small dose of oxotremorine (10 μg/kg) is distributed similarly in pretreated rats (amitriptyline methyl iodide, 25 mg/kg, s.c.) and in controls. In mice there was a linear relation between dose, up to 180 μg/kg, and brain concentration of oxotremorine. At higher doses, relatively; more drug reached the brain. Oxotremorine induced a marked fall in blood pressure in the unanaesthetized rat that was reduced by amitriptyline methyl iodide and reversed by atropine methyl nitrate. It seems likely that differences in blood flow between pretreated rats and controls are responsible for the differences in the distribution of the drug.

Potentiation of oxotremorine lethality by antihistamines

Antihistamines, representing the major chemical classes, administered intraperitoneally to mice in non-toxic doses potentiated the lethal effects of an LD10 dose (3·5 mg/kg) of oxotremorine in a dose related manner. Atropine and methylatropine were highly effective in blocking oxotremorine lethality alone and when it was potentiated by antihistamines. The antagonism by methylatropine suggests a peripheral site of toxicity. Antihistamines might enhance lethality by interfering with the inactivation of oxotremorine by liver microsomal drugs enzymes in a manner similar to SKF 525A.