“Cannabis has been demonstrated to have bronchodilator, anti-inflammatory and anti-tussive activity in the airways, but, information on the active cannabinoids, their receptors and the mechanisms for their effects is limited.

We compared the effects of Δ9-tetrahydrocannabinol, cannabidiol, cannabigerol, cannabichromene, cannabidiolic acid and tetrahydrocannabivarin…

The other cannabinoids did not influence cholinergic transmission and only Δ9-THC demonstrated effects on airway hyperresponsiveness, anti-inflammatory activity and antitussive activity in the airways.”

http://www.ncbi.nlm.nih.gov/pubmed/25655949

http://jpet.aspetjournals.org/content/early/2015/02/05/jpet.114.221283.long