The role of cyclic nucleotides and related compounds in nerve-mediated vasodilatation in the cat submandibular gland.

1 Intra-arterial administration of a number of purine compounds to the cat submandibular salivary gland led to an increased blood flow. The threshold concentration of the most potent vasodilators, adenosine 5'-triphosphate (ATP) and adenosine 5'-diphosphate (ADP) was about 2 mumol/l. Adenosine and guanosine 5'-triphosphate (GTP) required about 25 mumol/l, adenosine 3',5'-cyclic monophosphate (cyclic AMP) 40 mumol/l, guanosine 5'-diphosphate (GDP) 125 mumol/l and dibutyryl guanosine 3',5' cyclic monophosphate (db cyclic GMP) 400 mumol/l. Dibutyryl cyclic AMP and cyclic GMP were ineffective. 2 The cyclic nucleotide phosphodiesterase inhibitors, theophylline, papaverine, quinine and 3-isobutyl-1-methylxanthine (IBMX), all acted as vasodilators. 3 When intra-arterial infusion of theophylline or IBMX was combined with sympathetic nerve stimulation, the vasodilatation observed after the stimulus ceased was significantly potentiated. 4 Theophylline and IBMX also potentiated the vasodilatation accompanying parasympathetic nerve stimulation and this response persisted after atropine. 5 These results are discussed in relation to the possible mediators of sympathetic and parasympathetic vasodilatation in the gland.