The effect of paper dust collected at two different locations in a paper recycling plant (PD1 and PD2) on isolated nonsensitized guinea pig tracheal smooth muscle was studied in vitro. Dust extracts were prepared as a 1:10 w/v aqueous solution. Dose-related contractions of guinea pig tracheal rings were elicited with both PD1 and PD2. Pharmacologic studies were performed with atropine (10(-6) M), indometacin (10(-6) M), pyrilamine (10(-6) M), LY171883 (10(-5) M), nordihydroguaiaretic acid (10(-5) M), and TMB8 (10(-5) M). The possible role of endogenous neuropeptides in this constrictor process was studied by depleting neural mediators with capsaicin (5 x 10(-6) M) before challenge with dust extracts. Constrictor effects were partially inhibited by a wide variety of the mediator blocking agents. The effects of both extracts were almost totally inhibited by the anticholinergic agent atropine, suggesting that a principal pathway mediating this response may involve the parasympathetic nervous system. The intracellular calcium-blocking agent TMB8 also induced a reduction of the contractile responses to PD1 and PD2 consistent with the well established role of intracellular calcium in smooth muscle constriction. Pretreatment with capsaicin significantly increased the contractile activity of paper dust extracts but only at the higher doses of these extracts. This suggests that the effect of paper dust is not initiated by the release of mediators stored in sensory nerves but that the prerelease of these mediators may enhance the constrictor effects of these dusts. We suggest that paper dust extracts cause dose-related airway smooth muscle constriction possibly associated with the release of cholinergic as well as other mediators. The constrictor effect does not require tissue presensitization or the release of neuropeptides from sensory nerves.