activity of VMAT1 in these cells has a seemingly inhibitory effect on the processing of gastrin. Essentially, this means that certain compounds in the gut can be taken into these G cells and either amplify or inhibit the function of VMAT1, which will impact gastrin processing (conversion from G34 to G17). Additionally, VMAT1 is known to play a role in the uptake and secretion of serotonin in the gut. Enterochromaffin cells in the intestines will secrete serotonin in response to the activation of certain mechanosensors. The regulation of serotonin in the gut is critically important, as it modulates appetite and controls intestinal contraction. Protection against hypothermia Presence of VMAT1 in cells has been shown to protect them from the damaging effects of cooling and rewarming associated with hypothermia. Experiments were carried out on aortic and kidney cells and tissues. Evidence was found that an accumulation of serotonin using VMAT1 and TPH1 allowed for the subsequent release of serotonin when exposed to cold temperatures. This allows cystathionine beta synthase (CBS) mediated generation of H2S. The protection against the damage caused by hypothermia is due to a reduction in the generation of reactive oxygen species (ROS), which can induce apoptosis, due to the presence of H2S. Mental disorders VMAT1 (SLC18A1) maps to a shared bipolar disorder(BPD)/schizophrenia locus, which is located on chromosome 8p21. It is thought that disruption in transport of monoamine neurotransmitters due to variation in the VMAT1 gene may be relevant to the etiology of these mental disorders. One study looked at a population of European descent, examining the genotypes of a bipolar group and a control group. The study confirmed expression of VMAT1 in the brain at a protein and mRNA level, and found a significant difference between the two groups, suggesting that, at least for people of European descent, variation in the VMAT1 gene may confer susceptibility. A second study examined a population of Japanese individuals, one group healthy and the other schizophrenic. This study resulted in mostly inconclusive findings, but some indications that variation in the VMAT1 gene would confer susceptibility to schizophrenia in Japanese women. While these studies provide some promising insight into the cause of some of the most prevalent mental disorders, it is clear that additional research will be necessary in order to gain a full understanding. References External links Amphetamine Biogenic amines Molecular neuroscience Neurotransmitter transporters Receptors Signal transduction Solute carrier family