Biomedical subjects

H Haikala

Publications and source records attributed to H Haikala.

21 records · Page 2Linked to original sources

PubMed1987

Use of a novel type of rotating disc electrode and a flow cell with laminar flow pattern for the electrochemical detection of biogenic monoamines and their metabolites after Sephadex gel chromatographic purification and high-performance liquid chromatographic isolation from rat brain.

A novel type of rotating disc electrode and a flow cell with laminar flow pattern were developed and applied to the electrochemical detection of dopamine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, 3-methoxytyramine (3-MT), noradrenaline, 3-methoxy-4-hydroxyphenylethyleneglycol (MOPEG), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid after HPLC of these compounds. The active surface of the rotating disc working electrode was made from solid paraffin (40% wt/wt) and graphite powder (60% wt/wt). The sensitivity of the detector was proportional to the square root of the angular velocity and was practically independent of the flow rate of the mobile phase. The surface of the working electrode was very large (radius = 12 mm), and so the percentage of oxidation was 24-67% (flow rate = 1.0 ml/min), depending on the compound. Electrical noise between 20 and 40 pA and background current of 20-60 nA were observed. In practice, the sensitivity for the detection of the compounds examined here was 8-16 nA/ng, and so a detection limit of 5 pg/injection could be achieved, when the detector was combined with reversed-phase HPLC. Supernatants obtained from the extracts of the tissue samples (nine brain parts of rat brain were studied) were purified by using Sephadex G-10 gel chromatography. Before this procedure, the proteins of the tissue extracts were precipitated by 0.2 M HClO4, and the excess of HClO4 was precipitated by KOH/HCOOH buffer. Simultaneously, the pH of the extracts was set to 2.4 by the above buffer.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗

PubMed1986

The nicotine-induced changes in striatal dopamine metabolism of mice depend on body temperature.

The effects of single and 4 times repeated doses of nicotine on the striatal concentrations of dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were studied in mice in relation to the nicotine-induced decrease of the body temperature. The single doses of nicotine (0.3, 1, 3 or 10 mg/kg s.c.) increased the DOPAC and HVA concentrations in mouse striatum depending on the dose and the rectal temperature of the mice. The elevations lasted longer and were induced by smaller doses when the decrease of the rectal temperature was prevented by increasing the ambient temperature. At a high ambient temperature (32-34 degrees C) the repeated nicotine doses (4 X 1, 3 or 10 mg/kg s.c.) elevated the striatal DOPAC and HVA concentration. When, however, the hypothermia was not prevented, the repeated doses decreased the striatal HVA concentration and induced less elevation of the striatal DOPAC concentration. It is suggested that nicotine acts on the cholinoceptive receptors regulating striatal dopamine release as it acts on the nicotinic receptors in the autonomic ganglia or in the end-plate regions of the skeletal muscle. Initial activation of the receptors could be followed by a block, which is enhanced by hypothermia.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1986

Different changes in striatal dopamine metabolism induced by nicotine in mice kept at different ambient temperatures. Evidence for partly separate metabolic routes of dopamine derived from separate compartmentations.

Further information about the nicotine-induced changes in striatal dopamine metabolism in hypothermic mice was searched by measuring the contents of dopamine and its metabolites (3,4-dihydroxyphenylacetic acid, DOPAC; 3-methoxytyramine, 3-MT; and homovanillic acid, HVA) after blocking the synthesis of dopamine by alpha-methyl-p-tyrosine (alpha-MT). This method gave a possibility to study the effect of nicotine on the metabolism of dopamine in two pools (the cytoplasmic "newly-synthesized" dopamine and the granular dopamine). 3 mg/kg of (-)nicotine was given s.c. four times, at 110, 80, 50 and 20 min, and alpha-MT (250 mg/kg i.p.) at 60 min before sacrifice. To prevent the peripheral effects of nicotine all mice were given hexamethonium (10 mg/kg i.p.) at 140 min before sacrifice. Hexamethonium did not alter striatal dopamine metabolism. Experiments were performed at 20-22 degrees C at which temperature nicotine induced hypothermia or at 32-34 degrees C. The alpha-MT-induced proportional decrease of 3-MT content was clearly less than that of dopamine content. On the contrary the alpha-MT treatment decreased the DOPAC content proportionally more than the dopamine content. Thus DOPAC could not be solely formed from the same dopamine pool as 3-MT. These results indicate that 3-MT reflects best the metabolism of the granular dopamine and DOPAC that of the "newly-synthesized" dopamine. In hypothermic mice nicotine administration reduced the alpha-MT-induced depletion of the dopamine content.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗