Hypothalamic and serum catecholamines in ethanol and acetaldehyde treated guinea-pigs. Relation to moderate...

Adult guinea-pigs were treated with ethanol (2.5 g/kg, IP) or acetaldehyde (100 mg/kg, IP) and exposed to moderate cold (+4 degrees C) for 50 minutes. Controls were given 0.9% NaCl solution. The hypothalamic catecholamines norepinephrine (NE) and dopamine (DA) and also norepinephrine and epinephrine (E) in the serum were analyzed by high-performance liquid chromatography with an electrochemical detector. Blood glucose, free fatty acids and glycogen in the liver and skeletal muscle were also measured. Acetaldehyde caused a similar drop in colon temperature as did ethanol, but neither could prevent cold-induced vasoconstriction in the ear lobe. Ethanol significantly reduced the concentration of NE in the hypothalamus compared to the controls. Acetaldehyde had a tendency to lower hypothalamic NE. There was no significant difference between drug-treated groups in NE concentration. Neither ethanol nor acetaldehyde had any effect on hypothalamic DA. In the ethanol group serum E and glucose were significantly elevated compared to the acetaldehyde group. Serum glucose was also higher compared to the controls, and the difference in serum E concentration near the level of significance. No significant differences were found between the groups in serum NE, FFA or skeletal muscle and liver glycogen concentration. The results point to a possible central effect of ethanol during a short-term moderate cold exposure. The effects of acetaldehyde on neuronal tissue remain speculative, but a possible effect on noradrenergic neurons cannot be ruled out. Although the hypothermic effect of acetaldehyde corresponded that of ethanol, further experiments are required to elucidate the role of acetaldehyde in ethanol-induced hypothermia.