Cyclic Amp as a Possible Mediator of Dopamine Stimulation of Cockroach Gland Cells

Abstract

Isolated salivary glands of the cockroach Nauphoeta cinerea Olivier secrete fluid in response to nerve stimulation or application of dopamine, the acinar cells undergoing a hyperpolarization during secretion. The aim of the present work was to examine whether cyclic AMP acts as a second messenger in the acinar cells to cause the secretory and electrical responses to the transmitter dopamine. Cyclic AMP (10-500 microM) in the bathing solution of isolated glands caused a dose-dependent secretory response but no change in the membrane potential of acinar cells. The time courses and magnitudes of the secretory responses to cyclic AMP resembled those features of responses to dopamine. Forskolin, an adenylate cyclase activator, caused fluid secretion but the responses were small and irregular. The phosphodiesterase inhibitor, 3-isobutyl-l-methylxanthine (IBMX)(1-1000 microM) produced fluid secretion in a dose-dependent manner, the maximal response being equal to that of dopamine. Maintained responses to cyclic AMP or IBMX required the presence of extracellular calcium ions. An inhibitor (MDL 12,330A) of adenylate cyclase suppressed the secretory responses to dopamine, cyclic AMP, IBMX, the ionophore A23817 or the readmission of calcium ions to the bathing solution; this inhibitor did not block the acinar hyperpolarization caused by nerve stimulation. Cyclic AMP stimulation of glands, bathed in chloride-free solution to prevent fluid secretion, produced a change in the gland cells which outlasted the period of exogenous cyclic AMP stimulation and expressed itself as a transient secretion upon return of the normal bathing solution. It was concluded that stimulus-secretion coupling in this gland involves a calcium-dependent second messenger system and that cyclic AMP is probably the second messenger. The evidence did not support the idea that cyclic AMP is also a second messenger for the acinar cell hyperpolarization evoked by nerve stimulation.

Cyclic nucleotide–gated channels, calmodulin, adenylyl cyclase, and calcium/calmodulin-dependent protein kinase II are required for late, but not early, long-term memory formation in the honeybee

“…We verified this conclusion by performing a further experiment with two additional AC antagonists, SQ 22536 (Heinrich et al 2001) and MDL 12330A (Gray et al 1984), already assayed in other insect preparations. We injected bees with saline (n ¼ 45) or with SQ 22536 (n ¼ 58) or with MDL 12330A (n ¼ 57) 20 min before acquisition.…”

The aminergic control of cockroach salivary glands

“…From these data, Evans and Green concluded that only one class of receptor with pharmacological properties similar to those of mammalian D1 receptors mediate the effects of DA in Nauphoeta salivary glands. This is in good agreement with the findings that DA increases [cAMP] i in the salivary glands of Nauphoeta (Grewe and Kebabian, 1982) and that cAMP in the bathing solution causes a dose-dependent secretory response (Gray et al, 1984). Interestingly, cAMP fails to hyperpolarize the acinar cell membrane potential as DA does (Gray et al, 1984).…”

“…This is in good agreement with the findings that DA increases [cAMP] i in the salivary glands of Nauphoeta (Grewe and Kebabian, 1982) and that cAMP in the bathing solution causes a dose-dependent secretory response (Gray et al, 1984). Interestingly, cAMP fails to hyperpolarize the acinar cell membrane potential as DA does (Gray et al, 1984). An explanation could be that the D1-like receptors in the Nauphoeta salivary gland are coupled to phospholipase C (PLC) in addition to adenylyl cyclase .…”

Two-photon microscopy and fluorescence lifetime imaging reveal stimulus-induced intracellular Na+ and Cl− changes in cockroach salivary acinar cells

“…The investigation of the pharmacological properties of the dopamine receptor(s) in these glands could not clearly define which dopamine receptor subtypes are present (51). Furthermore, there are diverse reports on the effect of possible second messengers on saliva secretion in the cockroach N. cinerea, suggesting the involvement of cAMP and/or [Ca 2ϩ ] i (22,23). In the present study, a bumetanide-sensitive [Na ϩ ] i rise could be induced by ionomycin in cockroach salivary acinar peripheral cells.…”