THE ROLE OF CYCLIC NUCLEOTIDES AND RELATED COMPOUNDS IN NERVE‐MEDIATED VASODILATATION IN THE CAT SUBMANDIBULAR GLAND

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Abstract
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.