Engineering topics

During, Matthew J.

Publications and source records attributed to During, Matthew J..

3 records

NASA NTRS1989

Dopamine release in rat striatum - Physiological coupling to tyrosine supply

Intracerebral microdialysis was used to monitor dopamine release in rat striatal extracellular fluid following the intraperitoneal administration of dopamine's precursor amino acid, L-tyrosine. Dopamine concentrations in dialysates increased transiently after tyrosine (50-100 mg/kg) administration. Pretreatment with haloperidol or the partial lesioning of nigrostriatal neurons enhanced the effect of tyrosine on dopamine release, and haloperidol also prolonged this effect. These data suggest that nigrostriatal dopaminergic neurons are responsive to changes in precursor availability under basal conditions, but that receptor-mediated feedback mechanisms limit the magnitude and duration of this effect.

During, Matthew J.↗

NASA NTRS1988

Effects of systemic L-tyrosine on dopamine release from rat corpus striatum and nucleus accumbens

Intracerebral dialysis was used to monitor extracellular fluid from rat striatum and nucleus accumbens following the intraperitoneal administration of tyrosine. Dopamine concentrations in dialysates from both the striatum and the nucleus accumbens increased significantly in response to the tyrosine. The magnitude of the tyrosine effect was greater in the nucleus accumbens than in the striatum. Hence, mesolimbic dopaminergic neurons may be especially responsive to precursor availability.

During, Matthew J.↗

NASA NTRS1988

Tyrosine - Effects on catecholamine release

Tyrosine administration elevates striatal levels of dopamine metabolites in animals given treatments that accelerate nigrostriatal firing, but not in untreated rats. We examined the possibility that the amino acid might actually enhance dopamine release in untreated animals, but that the technique of measuring striatal dopamine metabolism was too insensitive to demonstrate such an effect. Dopamine release was assessed directly, using brain microdialysis of striatal extracellular fluid. Tyrosine administration (50-200 mg/kg IP) did indeed cause a dose related increase in extracellular fluid dopamine levels with minor elevations in levels of DOPAC and HVA, its major metabolites, which were not dose-related. The rise in dopamine was short-lived, suggesting that receptor-mediated feedback mechanisms responded to the increased dopamine release by diminishing neuronal firing or sensitivity to tyrosine. These observations indicate that measurement of changes in striatal DOPAC and HVA, if negative, need not rule out increases in nigrostriatal dopamine release.

Acworth, Ian N.↗