Immobilization Decreases Amino Acid Concentrations in Plasma but Maintains or Increases Them in Brain

Abstract

Immobilization for 2 h significantly decreased plasma concentrations of 13 of 16 amino acids assayed, including the transmitter amine precursors tyrosine and total tryptophan. The level of plasma free tryptophan, however, was increased. Despite the reduced plasma levels, corresponding brain concentrations of many large neutral amino acids (LNAAs) were increased (tryptophan, phenylalanine, valine, leucine, and isoleucine). Brain concentrations of tyrosine and the other amino acids measured were unaltered. The results for the LNAAs were not explained by calculated brain influx rates. Therefore, altered influx kinetics or perhaps altered brain protein metabolism or efflux may be responsible. Comparison of calculated brain influxes and brain concentrations of LNAAs suggests that the rise in level of plasma free tryptophan during immobilization is not responsible for the increase in level of brain tryptophan and that the mechanism responsible for the maintenance of or increase in brain concentrations of the other LNAAs is probably involved. Maintenance of brain concentrations of basic amino acids is explicable by reduced competition for brain uptake.

Effects of sex and deletion of neuropeptide Y2 receptors from GABAergic neurons on affective and alcohol drinking behaviors in mice

“…While many rodent studies reveal similar results, particularly in mice on a C57BL/6J background (Kennett et al, 1986; Johnston and File, 1991; Middaugh et al, 1999; Frye et al, 2000; Adamec et al, 2006; Dalla and Shors, 2009; Stack et al, 2010; ter Horst et al, 2012b; Melon et al, 2013), a number of studies report that male rodents exhibit greater anxiety-related behavior, depending on the strain and behavioral assay used (Johnston and File, 1991; Rodgers and Cole, 1993; Zimmerberg and Farley, 1993; Leret et al, 1994; Voikar et al, 2001; Adamec et al, 2006; ter Horst et al, 2012a). Therefore, we used both male and female mice to investigate potential sex differences in these behaviors and the role of GABAergic Y2R.…”

Semistarvation-induced hyperactivity compensates for decreased norepinephrine and dopamine turnover in the mediobasal hypothalamus of the rat

“…One possible interpretation is that activity stress might alter the transport kinetics at the blood-brain barrier, increasing precursor influx into the brain. Kennett et al (1986) stressed rats by immobilization for two hours and detected an overproportional rise in brain LNAA (including tyrosine and tryptophan), that is, brain concentrations were higher than would be expected from plasma concentrations using the formula of Pardridge and Oldendorff (1975). Kennett (1986) discusses a breakdown of the blood brain barrier, since other investigators had reported (Belova and Jonsson, 1982) that albumin penetrated into the brain during immobilization.…”

“…Kennett et al (1986) stressed rats by immobilization for two hours and detected an overproportional rise in brain LNAA (including tyrosine and tryptophan), that is, brain concentrations were higher than would be expected from plasma concentrations using the formula of Pardridge and Oldendorff (1975). Kennett (1986) discusses a breakdown of the blood brain barrier, since other investigators had reported (Belova and Jonsson, 1982) that albumin penetrated into the brain during immobilization. The enhancement of brain uptake of LNAA's by isoprenaline (Hudson et al, 122 A. Broocks et al 1980) suggests that increased catecholamine secretion could be involved under certain circumstances.…”

The Chronic Ingestion of Diets Containing Different Proteins Produces Marked Variations in Brain Tryptophan Levels and Serotonin Synthesis in the Rat

“…Further, it is unlikely that non-specific effects, such as stress, were responsible for the observed TRP and 5HT effects of zein. For example, stress (immobilization; fasting) raises brain TRP and 5HT concentrations [38,39], it does not lower them. The fact that such stress effects are opposite to those observed here in zein rats suggests that the effects are unrelated to stress.…”