 He identified it as the blood pressure decreasing contaminant from some "Claviceps purpurea" ergot extracts, by the request of Henry Hallett Dale.Later in 1914, Dale outlined the effects of acetylcholine at various types of peripheral synapses and also noted that it lowered the blood pressure of cats via subcutaneous injections even at doses of one nanogram.The concept neurotransmitters was unknown before 1921, when Otto Loewi noted that the vagus nerve secreted a substance that stimulated the heart muscle whilst working as a professor in the University of Graz.