 They are present in CNS where they INDUCE PRESYNAPTIC INHIBITION and behavioural effects. They exhibit vascular effects as well, such as pulmonary vasoconstriction. o Discovery of antimigraine properties of Sumatriptan (non-selective 5-HT1D/1B agonist) increased intrest in this sub type of receptors.  Expression of 5-HT1D receptor is very low as compared to 5-HT1B and their clinical significance still largely unknown.  The function of 5-HT1E receptor is unknown but it is hypothesized that they are involved in regulation of memory.  5-HT1F receptor has possible role in vascular contraction. Distribution in brain appears limited.