Characterisation of an octopamine-sensitive adenylate cyclase in haemocyte membrane fragments of the American cockroach Periplaneta americana L.

Pharmacology of octopamine‐, dopamine‐, and 5‐hydroxytryptamine‐stimulated cyclic amp accumulation in the corpus cardiacum of the american cockroach, Periplaneta americana L

“…In general, the data presented in Table 3 confirm earlier studies on insect octopamine receptors in that the a-adrenergic antagonist phentolamine and the 5-hydroxytryptaminelhistamine inhibitor cyproheptadine are effective antagonists of the octopamine-stimulated cyclic AMP increase, whereas /3-adrenergic blockers, such as propranolol, are ineffective [1,[20][21][22]28,29]. In addition, gramine, a 5-hydroxytryptamine antagonist, which is a potent inhibitor of octopamine-sensitive receptors in locust CC 1291, was also effective in cockroach CC (Table 3).…”

“…In this classification, the antagonists chlorpromazine and metochlopramide are used to distinguish between octopamine-1 and octopamine-2 receptors. However, in cockroach hemocytes, metochlopramide and chlorpromazine are equally poor antagonists [22]; therefore, although the agonist profile approximates that of locust octopamine-2 receptors, the antagonist profile is not supportive. The classification proposed by Evans [28] is based on physiological responses …”

“…The other phenylethylamine derivatives tested are typically poor agonists of insect adenylate cyclase (K, values greater than 10-fold those of octopamine), since substitution at either the /3-hydroxyl or p-hydroxyl group on the octopamine molecule substantially reduces potency [21,22].…”

Calcium involvement in mediating the action of octopamine and hypertrehalosemic peptides on insect haemocytes

“…IP3 causes release of calcium from intracellular pools [16] and, either directly or indirectly, elicits the opening of 'calcium gates' in the plasma membrane [17]. It is possible that the octopamine-receptor, which is involved in the increased cytosolic calcium concentrations observed in the present study, may also be coupled to phospholipase C. Mianserin, which is an inhibitor of 5-hydroxytryptamine-and histamine-receptors in vertebrate systems, is a potent inhibitor of octopaminemediated activation of adenylate cyclase in insects [2,18]. Mianserin also blocks the octopamineinduced elevation of cytosolic calcium levels in cultured haemocytes (figs 2 and 3) but does not affect the actions of HT-I, HT-II or A23187 in this regard.…”

Pharmacological characterization of a 5‐hydroxytryptamine‐sensitive receptor/adenylate cyclase complex in the mandibular closer muscles of the cricket, Gryllus domestica

“…2c). Lineweaver-Burk plots of the 5-HT response in the presence and absence of these antagonists do not intercept at the Y-axis as would be expected if competitive inhibition was the predominant mechanism [14]. The Lineweaver-Burk plots for the effect of these antagonists is, however, more consistent with "uncompetitive" inhibition, where the inhibitor binds to the agonist-receptor complex, but not to the vacant receptor [15].…”