Tachykinin involvement in parasympathetic nerve-evoked salivation of the ferret

1. The tachykinin antagonist (D-Arg1, D-Cl2Phe5, Asn6, D-Trp7.9, Nle11)-substance P, injected intravenously, blocked salivary secretion from the ferret parotid and submandibular glands in response to subsequent i.v. injections of the tachykinins, substance P and neurokinin A. 2. The tachykinin antagonist reduced the parasympathetic nerve-evoked secretion of parotid and submandibular saliva by 15-20% and 35-40%, respectively. Atropine abolished the remaining secretory response. 3. The 'atropine-resistant' parasympathetic nerve-evoked secretion of saliva from the parotid and submandibular glands (about 5 and 30%, respectively, of that before administration of atropine) was abolished by the tachykinin antagonist. 4. The tachykinin antagonist was without effect on the protein concentration of parotid and submandibular saliva secreted in response to parasympathetic nerve stimulation. Parotid and submandibular saliva lacked amylase. 5. Atropine reduced the protein concentration of the submandibular saliva secreted in response to parasympathetic nerve stimulation by 50%; this was the protein concentration of substance P-evoked saliva. 6. The secretory response to methacholine and to stimulation of preganglionic sympathetic nerve fibres, tested in rats, was unaffected by the tachykinin antagonist, contra-indicating an unspecific action of the antagonist. 7. The results suggest that the neuronal release of tachykinins is probably important in the nerve-evoked secretory response of the parotid and submandibular glands.