Thiamine deficiency: selective impairment of the cerebellar serotonergic system.

To explore the role of thiamine deficiency in synaptic transmission, the high-affinity uptake and release systems for putative neurotransmitters were studied in synaptosomal preparations isolated from the telencephalon, hypothalamus, and cerebellum of rats made thiamine deficient by diet or pyrithiamine. There was significant decrease in the uptake of serotonin by the synaptosomal preparations of the cerebellum. Although thiamine and its phosphorylated forms added in vitro did not restore the decreased serotonin uptake, the administration of the vitamin in vivo resulted in a significant reversibility of the inhibition of serotonin uptake, coinciding with dramatic clinical improvement. The study supports the possibility of an important serotonergic innervation of the cerebellum and suggests a selective involvement of this system in the pathogenesis of some of the neurologic manifestations of thiamine deficiency.