To clarify the role of serotonin (5-HT) in the regulatory mechanism of L-tryptophan (TRP)--induced growth hormone (GH) secretion in cattle, changes in 5-HT concentrations in the cerebrospinal fluid (CSF) in the third ventricle (3V) and GH in plasma before and after the peripheral infusion of TRP were determined simultaneously. The direct effect of TRP on GH release from the dispersed anterior pituitary cells was also assessed. A chronic cannula was placed in 3V by stereotaxic surgery, then CSF and blood were withdrawn under physiological conditions. TRP (38.5 mg/kg BW) was infused through an intravenous catheter from 12.00 to 14.00 hours and CSF and blood sampling were performed from 11.00 to 18.00 hours at 1-h intervals. The concentration of 5-HT in CSF was determined by high-performance liquid chromatography with electrochemical detection. GH, melatonin (MEL), and cortisol (CORT) concentrations were measured by radio-immunoassay and enzyme-immunoassay. Concentrations of 5-HT were increased by TRP infusion. The TRP infusion significantly increased GH release. On the other hand, TRP did not stimulate GH release from the bovine pituitary cells. MEL and CORT concentrations were not altered by TRP infusion. These results suggest that TRP induced GH release via the activation of serotonergic neurons in cattle.

No abstract

The γ-aminobutyric acid (GABA) is the amino acid which is known to have an antihypertensive effect and to have a stress reduction effect. It is known to be able to produce GABA high component food by using a lactic acid bacterium accumulating GABA, however, in many cases, sodium glutamate was added to substrate. We tried the production of GABA-enriched food or feed material without adding sodium glutamate by choosing a cultivar kind of the rice and the kind of the lactic acid bacterium. First, we selected the plant origin lactic acid bacterium Lactococcus lactis RO50 which GABA accumulate in large quantities to rice. Next, we considered whether a cultivar kind and a fertilization condition of the rice influenced GABA accumulation. The additional nitrogen fertilization to rice did not have a big influence on GABA accumulation by the lactic fermentation, but the GABA accumulation greatly varied according to a cultivar kind of the rice. We succeeded in producing the GABA-enriched food or feed material rice flour which accumulated GABA 120-150 mg/100 g (per dry weight) by high-yielding rice Momiroman cultivated a lot of nitrogen basal fertilizer and using lactic acid bacterium RO50.