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 μmol/l. Adenosine and guanosine 5′‐triphosphate (GTP)required about 25 μmol/l, adenosine 3′,5′‐cyclic monophosphate (cyclic AMP) 40 μmol/l, guanosine 5′‐diphosphate (GDP) 125 μmol/l and dibutyryl guanosine 3′,5′ cyclic monophosphate (db cyclic GMP) 400 μmol/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.