Ontogeny of phenylalanine (endogenous cholecystokinin) induced modulation of food intake in normal and undernourished rats

Emerging roles of the extracellular calcium-sensing receptor in nutrient sensing: control of taste modulation and intestinal hormone secretion

The extracellular Ca-sensing receptor (CaSR) is a sensor for a number of key nutrients within the body, including Ca ions (Ca²⁺) and L-amino acids. The CaSR is expressed in a number of specialised cells within the gastrointestinal (GI) tract, and much work has been done to examine CaSR's role as a nutrient sensor in this system. This review article examines two emerging roles for the CaSR within the GI tract--as a mediator of kokumi taste modulation in taste cells and as a regulator of dietary hormone release in response to L-amino acids in the intestine.

Food, mood and health: a neurobiologic outlook

Hippocrates was the first to suggest the healing power of food; however, it was not until the medieval ages that food was considered a tool to modify temperament and mood, although scientific methods as we know them today were not in use at the time. Modern scientific methods in neuroscience began to emerge much later, leading investigators to examine the role of diet in health, including mental wellbeing, with greater precision. This review shows how short- and long-term forced dietary interventions bring about changes in brain structure, chemistry, and physiology, leading to altered animal behavior. Examples will be presented to show how diets alter brain chemistry, behavior, and the action of neuroactive drugs. Most humans and most animal species examined in a controlled setting exhibit a fairly reproducible pattern of what and how they eat. Recent data suggest that these patterns may be under the neurochemical and hormonal control of the organisms themselves. Other data show that in many instances food may be used unconsciously to regulate mood by seemingly normal subjects as well as those undergoing drug withdrawal or experiencing seasonal affective disorders and obesity-related social withdrawal. We will discuss specific examples that illustrate that manipulation of dietary preference is actually an attempt to correct neurochemical make-up.

Effects of CCK-8 on ingestive behaviors of suckling and weanling rats

The present series of experiments was designed to determine the dose-response characteristics of the cholecystokinin suppression effect on rat pups ingesting through suckling and adult modes. Pups at 10-22 days of age were deprived of their dam and food for 6 hr. At test time, the subjects received intraperitoneal injections or intravenous infusions of CCK-8 at 2, 4, 8, or 16 micrograms/kg in saline, or the saline vehicle alone. The pups were permitted to ingest for 30 min immediately after the injection or during the infusion. Ingestion included taking milk from the dam by suckling or feeding from the substrate. Regardless of the route of administration, CCK-8 elicited a low level of suppression across all doses and all ages when pups ingested within the natural suckling situation. In marked contrast, pups ingesting from the substrate in the adult mode suppressed their intake of bovine light cream or chow pellets in a dose-related manner following injections of the peptide. The blockade of the CCK dose-related suppression effect during suckling indicates that a different set of mechanisms governs intake of milk from the mother. The results may be related to the level of arousal required to sustain motivated behaviors while pups engage in the different modes of ingestion.