CENTRAL CARDIOVASCULAR EFFECTS OF TAURINE - COMPARISON WITH HOMOTAURINE AND MUSCIMOL

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Abstract
The central cardiovascular effects of taurine were compared with those of homotaurine and muscimol. The drugs were injected i.c.v. [intracerebral ventricle] in cumulative doses into pentobarbital-anesthetized cats. Muscimol (0.1-30 .mu.g/kg) produced dose-dependent hypotension and bradycardia, with a maximum effect of 70 .+-. 5 mm Hg and 75 .+-. 5 beats/min, respectively. Homotaurine led to a dose-related fall in blood pressure and heart rate; maximum effects were obtained with 300 .mu.g/kg and averaged 55 .+-. 3 mm Hg and 73 .+-. 3 beats/min. For both drugs, the dose-response curves were shifted to the right by pretreatment with 10 .mu.g/kg of bicuculline i.c.v. This antagonism confirms that the central cardiovascular effects of muscimol and homotaurine are mediated by a stimulation of GABA receptors. Tuarine produced dose-related hypotension and bradycardia. The depressive effects of taurine started at a dose of 10 .mu.g/kg; at a dose of 1000 .mu.g/kg, the maximum effects observed were a 55 .+-. 7 mm Hg hypotension and a 53 .+-. 8 beats/min bradycardia. These effects were not affected by bicuculline pretreatment, but strychnine (i.c.v.) prevented the effects of taurine. Glycine-type receptors may be involved in the taurine effects rather than GABA type receptors. These results do not exclude the involvement of taurine-type receptors for which the specific antagonist is not yet available.

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