ISSN:
1432-1912
Keywords:
Hypercarbia
;
Acidosis
;
Monoamine metabolism
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary White male albino rats were exposed to artificial atmosphere containing 20% of O2 and 5, 10 and 15% of CO2, for periods of time ranging from 30 min to 2 h. Monoamine synthesis in different dissected brain areas was measured by estimating Dopa and 5-hydroxytryptophan (5-HTP) accumulation after inhibition of their decarboxylation with the L-aromatic aminoacid decarboxylase inhibitor NSD 1015 (3-hydroxybenzylhydrazine). Endogenous levels of noradrenaline (NA), dopamine (DA), serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), and NA and DA levels after inhibition of catecholamine synthesis with α-methyltyrosine (α-MT) were measured in dissected areas and whole brain. The synthesis of all three monoamines was found to be increased in all the cerebral regions. Endogenous dopamine levels with or without α-MT treatment were increased while NA levels decreased. 5-HT decreased in at least one area and 5-HIAA increased in several brain areas. These observations indicate that the utilization of NA and 5-HT is increased and that of DA is diminished in acidosis, presumably as a consequence of a corresponding change in nerve impulse flow. The similarity between the monoamine changes induced by hypercarbia and by GABA are pointed out. It is suggested that GABA-ergic activity is elevated in acidosis and that GABA may be involved in the pH dependence of seizure thresholds, as well as in the increased tendency to respiratory depression induced by central nervous system depressant drugs in patients with chronic respiratory failure.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00501258
