Abstract
Grown in liquid culture in the presence of a variety of structurally unrelated drugs, mycelia of wild-type Neurospora assume a colonial or semicolonial growth habit similar to that of known morphological mutants. Drugs that produce these morphological changes include atropine, theophylline, histamine, and several of the quinoline-containing antimalarials. Each of these drugs decrease the endogenous adenosine 3',5'-cyclic monophosphate (cAMP) concentration of mycelia as a result of their effect on the activity of adenyl cyclase, the cAMP-dependent phosphodiesterase, or both. The evidence indicates a relationship between the degree of morphological abnormality, the degree to which intracellular cAMP is reduced, and the action of the drugs on the adenyl cyclase and phosphodiesterase.