The pharmacodynamical action of chloralose

The terms 'autacoid', 'hormone' and 'chalone' and how they have shifted with time

The increase of knowledge in a particular field (endocrinology) can be understood if one follows how certain key concepts were constructed and transformed over time. To explore such construction and transformation (shifts in meaning), we studied the use of the concepts 'autacoid' and 'chalone' in a period of one century (1916-2016), since the introduction of these concepts by the British professor of physiology Sir Sharpey-Schäfer. We could identify that the use of 'autacoid' shifted from a very broad category encompassing both stimulating and inhibiting hormones, in the period 1916-1960, to a much more specific use of the term for locally produced bioactive molecules, from the 1960s onwards. Histamine was the first compound seen as an 'autacoid', followed by prostaglandins, ATP, ADP and bradykinin, and from 1993 onwards, compounds such as 'palmitoylethanolamide' were also classified as 'autacoids'. For 'chalone', a comparable shift was noticed around the 1960s, when the concept suddenly changed from the category of inhibiting hormones into a substance that is produced within a tissue, inhibiting mitosis of the cells of that tissue. For both concept shifts, we could not find any argument. Around 1980, authors started to relate autacoids to various promising indications in the field of inflammation and immune modulation. The Nobel laureate Rita Levi-Montalcini gave an extra dimension to the concept autacoid in 1993, and introduced a new class of compounds modulating mast cells, the ALIAmides (from Autacoid Local Inflammation Antagonist), of which palmitoylethanolamide was the prototype. Our exploration demonstrates that biomedical concepts can be constructed and defined differently as time goes by, while concept transformations seem to emerge without arguments.

Responses of the three-toed sloth, Bradypus tridactylus, to some commonly used pharmacologic agents. II. Chloralose and reserpine

1. Chloralose, 50 mg/kg i.v., is a safe effective anesthetic for sloths and reduces incidence of cardiac arrhythmias. 2. However, chloralose blocks baroreflexes and may reduce the sensitivity of beta 1 cardiac receptors. 3. Reserpine, 0.70 mg/kg given i.v. in divided doses, blocks the hypertensive effect of 100 micrograms/kg of tyramine in sloths. 4. Reserpine in this dosage materially reduces arterial pressure and heart rate; these effects last at least 7 days. 5. Reserpine potentiates the hypertensive effects of epinephrine and norepinephrine materially. 6. In sloths reserpine increases cardiac irritability but does not block baroreflexes. 7. As is true with most other drugs sloths are more sensitive to chloralose and reserpine than most common laboratory animals.

Tyrosine's vasoactive effect in the dog shock model depends on the animal's starting blood pressure

We examined the effect of tyrosine (10-200 mg/kg given intravenously) or placebo on blood pressure (BP) in dogs made hypotensive (systolic BP = 50 mm Hg) by bleeding one hour previously. Animals which, prior to induction of hypotension, had been normotensive (mean arterial pressures, [MAP] less than or equal to 145 mm Hg) subsequently exhibited a dose-related increase in BP after tyrosine administration. In contrast, dogs which had been hypertensive prior to bleeding exhibited a fall in BP after tyrosine. These observations indicated that prior cardiovascular status may be an important factor influencing responses to exogenous tyrosine, and to endogenous catecholamines produced from the tyrosine.

Circulatory effects of chloralose-urethane and sodium pentobarbitone anaesthesis in the rabbit

1. The effects of chloralose-urethane and sodium pentobarbitone anaesthesia on heart rate, blood pressure and cardiac output were studied in normal rabbits, in animals given atropine and in animals without functioning autonomic effectors. The findings under anaesthesia were compared during spontaneous and artificial intermittent positive pressure respiration.2. The circulatory effects of chloralose-urethane and sodium pentobarbitone anaesthesia differed significantly for the first hour after induction of anaesthesia. During the subsequent 3 hr of maintained anaesthesia differences in the circulatory effects of the two anaesthetics were small.3. The direct local effects of these anaesthetics were assessed during the maintenance phase from the responses of animals without functioning autonomic effectors. With both anaesthetics there was peripheral vasodilatation and minimal effects on heart rate.4. The autonomic activity in the normal animal was assessed by comparing the changes in normal, atropinized and ;de-efferented' rabbits without functioning autonomic effectors. During chloralose-urethane anaesthesia there was reduction in cardiac vagal efferent activity and no change in cardiac sympatho-adrenal activity. With both anaesthetics there was an increase in peripheral sympatho-adrenal constrictor activity, tending to minimize the local vasodilator effects.