Role of taurine in thermoregulation and motor control. Behavioural and cellular studies

The effect of supplemental dietary taurine on tinnitus and auditory discrimination in an animal model

Loss of central inhibition has been hypothesized to underpin tinnitus and impact auditory acuity. Taurine, a partial agonist at inhibitory glycine and γ-amino butyric acid receptors, was added to the daily diet of rats to examine its effects on chronic tinnitus and normal auditory discrimination. Eight rats were unilaterally exposed once to a loud sound to induce tinnitus. The rats were trained and tested in an operant task shown to be sensitive to tinnitus. An equivalent unexposed control group was run in parallel. Months after exposure, 6 of the exposed rats showed significant evidence of chronic tinnitus. Two concentrations of taurine in drinking water were given over several weeks (attaining average daily doses of 67 mg/kg and 294 mg/kg). Water consumption was unaffected. Three main effects were obtained: (1) The high taurine dose significantly attenuated tinnitus, which returned to near pre-treatment levels following washout. (2) Auditory discrimination was significantly improved in unexposed control rats at both doses. (3) As indicated by lever pressing, taurine at both doses had a significant group-equivalent stimulant effect. These results are consistent with the hypothesis that taurine attenuates tinnitus and improves auditory discrimination by increasing inhibitory tone and decreasing noise in the auditory pathway.

Comparison of the effects of taurine with those of related sulfur-containing compounds on pyridoxal-induced adrenomedullary catecholamine release and glycogenolysis in the rat

Taurine (2-aminoethanesulfonic acid) is known to attenuate the release of adrenomedullary catecholamines and ensuing hepatic glycogenolysis and hyperglycemia induced by pyridoxal in the rat. Using this animal model, the present study was undertaken to assess the impact that simple structural modifications of the taurine molecule might have on its antagonistic actions against PL. Removal of the amino group (ethanesulfonic acid) or shortening the carbon chain by one methylene (2-aminomethanesulfonic acid) raised the protective actions of taurine. While N-alkylation (N-methyltaurine) or replacement of the amino group by hydroxyl (isethionic acid) had a lowering effect, substituting a sulfhydryl group (2-mercaptoethanesulfonic acid) for the 2-amino group abolished all antagonistic properties associated with taurine. The sulfinic acid analog (hypotaurine) was equipotent with taurine, but the carboxylate isostere (beta-alanine) was inactive. Propranolol, a nonspecific beta-adrenoceptor antagonist, enhanced the antiglycogenolytic effect of taurine and of all structurally related compounds capable of attenuating the outflow of adrenal catecholamines elicited by pyridoxal.

Effects of taurine and some structurally related analogues on the central mechanism of thermoregulation: a structure-activity relationship study

There is large body of evidences on the role of taurine in the central mechanisms of thermoregulation in mammals, but it is not clear, whether the hypothermic effect of taurine depends on its interaction with GABA receptors or with a specific receptor. In order to answer this question, we have performed a structure-activity relationship study by using both in vitro and in vivo preparations. MicroM amounts of taurine or each of 20 analogues were injected intracerebroventricularly in conscious, restrained rabbits while rectal temperature was recorded. Receptor-binding studies, with synaptic membrane preparations from rabbit brain were used to determine the affinities of these compounds for GABA(A) and GABA(B) receptors. Furthermore, the interaction with presynaptic GABA and taurine uptake systems was studied using crude synaptosomal preparations from rabbit brain. Among the compounds tested, (+/-)-cis-2-aminocyclohexanesulfonic acid, induced hypothermia, but did not interact with GABA(A) and GABA(B) receptors neither did it affect GABA and taurine uptake, thus suggesting that its effect on body temperature is not mediated by the central GABAergic system. Interestingly, the trans-isomer was devoid of effects either in vivo or in vitro. In order to explain (+/-)-cis-2-aminocyclohexanesulfonic acid-induced hypothermia, a stereoscopic model was produced showing its possible interactions with a putative taurine brain receptor.