David Hirst is one of the most original and productive scientists working in the fields of the innervation of smooth muscle and the physiological mechanisms that control its contractility. He has made major contributions to understanding the mechanisms underlying transmission at the junctions formed by autonomic nerves with smooth muscle and cardiac muscle. The unifying concept from Hirst's research is that receptors activated by neurally released transmitters act differently on target tissue compared with receptors activated by the same substances but not located subsynaptically. This has changed the traditional concept that autonomic nerves supply transmitter non-specifically to smooth muscle membrane.