Page "Neurotransmitter" Paragraph 1

Until the early 20th century, scientists assumed that the majority of synaptic communication in the brain was electrical.

However, through the careful histological examinations of Ramón y Cajal ( 1852 – 1934 ), a 20 to 40 nm gap between neurons, known today as the synaptic cleft, was discovered.

The presence of such a gap suggested communication via chemical messengers traversing the synaptic cleft, and in 1921 German pharmacologist Otto Loewi ( 1873 – 1961 ) confirmed that neurons can communicate by releasing chemicals.

Through a series of experiments involving the vagus nerves of frogs, Loewi was able to manually slow the heart rate of frogs by controlling the amount of saline solution present around the vagus nerve.

Upon completion of this experiment, Loewi asserted that sympathetic regulation of cardiac function can be mediated through changes in chemical concentrations.

Furthermore, Otto Loewi is accredited with discovering acetylcholine ( ACh )— the first known neurotransmitter.

Some neurons do, however, communicate via electrical synapses through the use of gap junctions, which allow specific ions to pass directly from one cell to another.