Rapid Absorption of Dietary 1,8-Cineole Results in Critical Blood Concentration of Cineole and Immediate Cessation of Eating in the Common Brushtail Possum (Trichosurus vulpecula)

Abstract

The blood concentration of 1,8-cineole and its metabolites was measured in six male brushtail possums while they voluntarily fed on diets laced with varying concentrations of cineole for 3 d. On the third day, blood samples were collected during and after each bout of feeding for 3 hr. Blood cineole was measured by using headspace solid-phase microextraction (SPME), while cineole metabolites were measured by liquid-liquid extraction followed by gas chromatography-mass spectroscopy. Feeding patterns were measured by continual recording of residual food weight and time. Cineole absorption was rapid, resulting in a peak blood concentration at the end of each feeding bout. The blood concentration of cineole did not exceed a critical value (51.8 +/- 14.1 micromol/l) regardless of the concentration in the diet. Food and, therefore, cineole intake was regulated. The amount of food ingested in the first feeding bout decreased from 236 +/- 52 g on the control diet to 36 +/- 20 g on the 4% cineole diet. The amount of cineole ingested in the first bout (1.18 +/- 1.10 g) was the same regardless of the dietary concentration and was controlled by the size of the meal. Total food eaten during the 7-hr feeding session decreased by 64% from 368 +/- 94 g (control diet) to 131 +/- 52 g (4% diet). Total cineole intake increased from 2.47 +/- 0.60 g (1% diet) to 5.05 +/- 2.41 g (4% diet). Cineole metabolites accumulated throughout the sampling period and were generally still rising at the end of blood sampling period. Blood levels of metabolites were at least 10-fold higher than cineole levels. The immediate control of feeding seems to be regulated by blood levels of cineole, whereas metabolites are likely to be more important in regulating the chronic ingestion of cineole.

Integrating the costs of plant toxins and predation risk in foraging decisions of a mammalian herbivore

“…With increasing dietary cineole concentration, possums eat less, and have both smaller feeding bouts and a lower rate of intake (Wiggins et al 2003). Similar changes in feeding patterns have also been shown in other species (Marsh et al 2007;Sorensen et al 2005;Wiggins et al 2006a) and can be explained by feedback associated with toxin blood concentrations (Boyle et al 2005). These results indicate that toxins impose not only metabolic costs (C) affecting fitness (Schmidt 2000), but also influence fitness through harvest rates and, therefore, energy uptake (H).…”

“…Cineole is absorbed quickly and its effect on intake and foraging behaviour is played out within minutes of it being consumed (Boyle et al 2005) and is maintained as long as there are physiological constraints on the rate at which it can be detoxified. This means that possums cannot habituate to cineole over time, in contrast to their capacity to habituate to a perceived risk of predation (discussed below).…”

Any Sense in Classroom Scents? Aroma of Rosemary Essential Oil Significantly Improves Cognition in Young School Children

“…In terms of the overall pattern of impact on cognition, we contend that there is the potential for a synergistic effect derived from the presence of all three of these compounds in blood serum as previously reported elsewhere [52]. Given their small size and lipid soluble chemical nature passage across the blood brain barrier would be facilitated [53], permitting direct action at the neuronal receptor site, or indirectly at the enzymatic level. The differential in impact across tasks being a consequence of the involvement of specific neurotransmitter systems that underpin their performance.…”

A Pharm-Ecological Perspective of Terrestrial and Aquatic Plant-Herbivore Interactions

“…The mechanisms of absorption of PSMs and the resultant kinetics (i.e. time course) of secondary metabolites are known in some vertebrate (Boyle et al, 2005;Dziba et al, 2006;Mclean et al, 2007) and invertebrate herbivores (Zangerl et al 2012). However, detailed pharmacokinetic studies where the concentration-time profile is linked to a specific mechanisms (e.g.…”

“…Several mammalian herbivores appear to use the strategy of altering meal size as a function of PSM concentration (Boyle et al, 2005;Marsh et al, 2007;Sorensen et al, 2005a;Torregrossa et al, 2011;Torregrossa et al, 2012;Wiggins et al, 2006a;Wiggins et al, 2006b;Wiggins et al, 2003). Of the five species studied to date (three woodrats of the genus Neotoma and two marsupials: the koala and brushtail possum), only one exhibited a change in intermeal interval when fed increasing concentration of dietary PSMs (Sorensen et al, 2005a;Torregrossa and Dearing, 2009).…”