Pharmacological responses of thiamine-deficient rat tissues

Rats were rendered deficient in thiamine by feeding a synthetic diet free of the vitamin. Responses of the isolated heart to acetylcholine, adrenaline, noradrenaline and isoprenaline, and of the phrenic nerve-diaphragm preparation to tubocurarine, gallamine and eserine, were compared with responses of tissues obtained from littermate rats pair-fed an identical diet with the addition of 25 mug of thiamine hydrochloride per day. In thiamine-deficient tissues eserine failed to produce sustained potentiation of the twitch response of the phrenic nerve-diaphragm preparation to single supramaximal nerve stimuli. The perfused thiamine-deficient heart was more sensitive to acetylcholine, adrenaline, noradrenaline and isoprenaline, which produced greater negative or lesser positive chronotropic and inotropic effects. There was no significant difference in the response of the phrenic nerve-diaphragm preparation to tubocurarine and gallamine, or to eserine with faradic stimulation.