Effects of Ethanol on EEG and Blood Pressure in the Rabbit

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Abstract
The effects of different blood ethanol levels on the spontaneous electroencephalogram (eeg) and blood pressure responses evoked by noxious and nonnociceptive stimuli were investigated in 27 rabbits: 6 were injected intravenously with 0.8 g of a 20% solution per kg of body weight, 6 intramuscularly with 6.01 g per kg of a 45% solution, 11 intramuscularly with 4.41 g per kg of a 33% solution; 4 additional animals were given intravenously 10 [mu]g of epinephrine per kg before and after 4.41 g per kg of ethanol. The average blood ethanol level 75 min. after the 4.41 g injection was 214 mg per 100 cc; after 6.01 g, 469 mg; and 15 min. after the 0.8 g injection, 145 mg. Ethanol at a dose of 4.41 g per kg intramuscularly blocked the blood pressure rise following nociceptive stimulation 15-30 min. after administration, but the eeg response not until 30-50 min. At a higher dose of 6.01 g per kg the blood pressure rise was blocked in 5-15 min. and the eeg response 10-15 min. later. When 0.8 g per kg was intravenously injected the blood pressure rise was prevented immediately and the eeg arousal response within 5 min. Alterations in the eeg consisted of the suppression of spindling and the introduction and augmentation of delta activity. The changes occurred progressively but at different rates and at different levels of blood ethanol which varied with the dose and route of administration. In response to a noxious stimulus (pressing the skin against the paw bone, or touching the nasal mucous membrane or cornea) the blood pressure rise failed but eeg arousal was elicited; and blood pressure fell while the eeg arousal reaction was still maintained. After the pressor centers were obtunded and hypotension occurred, some animals died in shock. Thus it would seem that the vasopressor mechanism failed while the depressor one remained functional. As the administration of epinephrine both before and after ethanol produced comparable increases in blood pressure, the possibility that the suppression of blood pressure rises is effected through a peripheral blocking action of ethanol upon the sympathetic nervous system seems unlikely.