APPARENT OPPOSING EFFECTS OF CYCLIC-AMP AND DIBUTYRYL-CYCLIC GMP ON NEURONAL FIRING OF BLOWFLY CHEMORECEPTORS

Cyclic [c] AMP and its dibutyryl derivative inhibit neuronal firing of the labellar sugar sensitive receptor of the blowfly [Phormia regina] when applied in conjunction with the stimulant sucrose. Simultaneous application of aminophylline (phosphodiesterase inhibitor) and sucrose or in combination with cAMP caused a similar depression of the sugar receptors response. In contrast, dibutyryl cGMP elicited an increase in sugar receptor firing when applied with sucrose to the sugar receptor. Either 5''-AMP or 5''-GMP in combination with sucrose had no discernable effect on the sugar receptors response. Different ratio combinations of cAMP and dibutyryl cGMP showed the striking inhibitory effect of cAMP upon the dibutyryl cGMP elicited increases in receptor firing frequency. These 2 nucleotides may be mediating different but complimentary aspects of sugar receptor function in a push-pull manner.