Effect of an intraduodenal injection of fat on the activities of the adrenal efferent sympathetic nerve and the gastric efferent parasympathetic nerve in urethane-anesthetized rats.

Nutrient information from the gastrointestinal tract to the brain plays a critical role in the regulation of appetite and energy homeostasis. The autonomic nervous system controls the functions of several tissues to regulate the energy homeostasis of the whole body. Autonomic nerve activity is influenced by environmental or exogenous changes in even a single tissue. In the present study, we investigated the effect of an intraduodenal injection of fat on the activities of the autonomic nerves innervating the adrenal gland and stomach in urethane-anesthetized rats. An intraduodenal injection of corn oil suppressed adrenal efferent sympathetic nerve activity (ASNA) and stimulated gastric efferent vagal nerve activity (GVNA). A lipase inhibitor, epsilon-polylysine, coinjected with corn oil completely suppressed the corn oil-induced changes in ASNA and GVNA. Further, an intraduodenal injection of fatty acid (linoleic acid) moderately suppressed ASNA and significantly stimulated GVNA; these results indicate that fat may affect autonomic nerve activity partly through the chemoreception of free fatty acids (FFAs), which are produced during the hydrolysis of fat (corn oil) by a pancreatic lipase, in the intestinal lumen. Furthermore, an intraduodenal injection of an intravenous fat emulsion with the same pH and osmotic pressure as the body fluid affected ASNA and GVNA in a similar manner as corn oil. These results suggest that intraduodenal fat suppresses ASNA and stimulates GVNA partly via the chemoreception of FFAs-the degradation products of fats-in the intestinal lumen.

Colocalization of GPR120 with phospholipase-Cbeta2 and alpha-gustducin in the taste bud cells in mice.

A recent study has demonstrated that the G-protein coupled receptor GPR120 is expressed in the taste bud cells in rats. In this study, we have identified the types of taste cell that express GPR120 in C57/BL6 mice. Double immunostaining for GPR120 and the markers of type II taste cells (phospholipase-Cbeta2 and alpha-gustducin) revealed that the majority of the GPR120-positive taste cells are type II taste cells. In contrast, it was observed that GPR120 was rarely colocalized with the marker of type III cells (neuronal cell adhesion molecule). These results suggested that GPR120 is mainly expressed in the type II taste cells and might function as a sensor for dietary fat.

Specific acupuncture sensation correlates with EEGs and autonomic changes in human subjects.

Sympathetic overactivation is suggested to be associated with chronic pain syndrome, and acupuncture is frequently applied in therapy for this syndrome. Furthermore, the forebrain including the various cerebral cortices has been implicated in inhibitory and facilitatory control of pain as well as autonomic functions. We investigated relationships among specific sensations induced by acupuncture manipulation, effects on sympathetic and parasympathetic autonomic functions, and EEG changes. An acupuncture needle was inserted into the right trapezius muscle of the subjects, and acupuncture manipulation was repeated to induce specific acupuncture sensation repeatedly while the needle was left in the muscle. Acupuncture manipulation significantly decreased heart rate (HR), and increased systolic blood pressure (SBP). Spectral analysis indicated that acupuncture manipulation significantly decreased low frequency components (LF) of both HR variability (HRV) and SBP variability (SBPV), and significantly reduced ratio of LF to high frequency component (HF) of HRV (LF/HF, index of sympathetic activity). Furthermore, there was a significant negative correlation between changes in LF/HF ratio of HRV and the number of specific acupuncture sensations reported, and a significant positive correlation between HF of HRV and the number of acupuncture sensations. Analyses of EEG data indicated that acupuncture manipulation non-specifically increased power of all spectral bands except the gamma band. Furthermore, changes in HF (index of parasympathetic activity) and total power (overall activity of the autonomic nervous system) of HRV were positively correlated with changes in theta, alpha, and gamma power, while changes in LF of SBPV and LF/HF of HRV were negatively correlated with changes in power of all spectral bands. These results are consistent with the suggestion that autonomic changes induced by manipulation inducing specific acupuncture sensations might be mediated through the central nervous system, especially through the forebrain as shown in EEG changes, and are beneficial to relieve chronic pain by inhibiting sympathetic nervous activity.

Active behavior and 1/f noise in shell-changing behavior of the hermit crabs.

Hermit crabs are known to carry a gastropod shell to prevent abdomen from injuring by predators and cannibalism. One can regard the shell as a boundary between inside and outside worlds for hermit crabs. We conducted an experiment in which hermit crabs without shells deal with artificial tubes. The situation without a shell requires a part of experimental setup to be regarded as inside by each hermit crab. We accept the distance of locomotion as the indication of the estimation process performed by an individual on parts of the experimental setup. As a result, behavioral hierarchy was found with respect to the way of constituting the boundary. At each level of hierarchy, active behavior produced 1/f noise in comparison with the passive one. It suggests that finding 1/f noise at each level of hierarchy may lead to a lower level of hierarchy in another situation.