Octopamine and tyramine effectively antagonize AKDNFIRFamide (RhoprFIRFa)-induced contraction of the oviducts of R. prolixus. (A) Octopamine (10⁻⁴ mol l⁻¹) significantly reduces the amplitude of the RhoprFIRFa (10⁻⁶ mol l⁻¹)-induced contraction. (B) Tyramine (10⁻⁴ mol l⁻¹) significantly reduces the RhoprFIRFa (10⁻⁶ mol l⁻¹)-induced contraction. The black bar indicates the period of application of the neurochemical and the white bar indicates the wash period. (C) Inhibition of RhoprFIRFa-induced contraction by octopamine and tyramine is dose dependent (one-way ANOVA followed by Tukey multiple comparisons test; *P<0.05, **P<0.01, ***P<0.001). Concentrations are given as mol l⁻¹; control group refers to the amplitude of 10⁻⁶ mol l⁻¹ RhoprFIRFa-induced contraction. Means±s.e.m. of n samples noted at the bottom of each bar.

Octopamine and tyramine abolish the rhythmic contractions of the bursa in R. prolixus. (A–D) Application of 10⁻⁶ mol l⁻¹ octopamine (A) or tyramine (B) abolishes contractions of the bursa. Note that contractions are unchanged at 10⁻⁷ mol l⁻¹ octopamine (C) and tyramine (D). The black bar indicates the period of application of the neurochemical and the white bar indicates the wash period. (E) Dose–response curve showing the sudden abolishment of rhythmic contractions at concentrations greater than 5×10⁻⁷ mol l⁻¹ neurochemical (n=5–9). (F) Octopamine and tyramine both significantly decrease the burst frequency relative to the saline control. (G) Dibutyryl cAMP reduces the frequency of contractions significantly at 10⁻² mol l⁻¹ relative to the saline control. (F and G: one-way ANOVA followed by Dunnett's multiple comparison test; *P<0.05, **P<0.01.) Means±s.e.m. of n samples noted at the bottom of each bar in F and G.

Phentolamine blocks the inhibitory effect of octopamine on rhythmic contractions of the oviducts. (A) Octopamine (10⁻⁴ mol l⁻¹) reduces the amplitude of spontaneous contraction. (B) The effect of octopamine (10⁻⁴ mol l⁻¹) is inhibited by application of phentolamine (10⁻⁷ mol l⁻¹, Phen). The black bar indicates the period of application of the neurochemical and the white bar indicates the wash period. (C) Phentolamine alone does not affect the amplitude of contraction. Phentolamine is capable of reversing the inhibition of oviduct contraction by octopamine. (D) Phentolamine attenuates the octopamine-induced rise in cAMP levels in the oviducts. Concentrations in C and D are mol l⁻¹. (C and D: one-way ANOVA followed by Tukey multiple comparisons test; *P<0.05.) Means±s.e.m. of n samples noted at the bottom of each bar in C and D; for 10⁻⁶ mol l⁻¹ OA+10⁻⁴ mol l⁻¹ Phen in D, n=4.

Phentolamine blocks abolishment of rhythmic contractions in the bursa by octopamine. (A) Octopamine abolishes bursal contractions at 10⁻⁵ mol l⁻¹. (B) Phentolamine (10⁻⁵ mol l⁻¹) blocks the inhibition induced by octopamine (10⁻⁵ mol l⁻¹) on bursal contraction. The black bar indicates the period of application of the neurochemical and the white bar indicates the wash period. (C) Phentolamine at 10⁻⁵ mol l⁻¹ does not significantly increase the amplitude of bursal contractions when compared with saline. Phentolamine significantly blocks the inhibitory effect of octopamine on bursal contractions (concentrations are mol l⁻¹; one-way ANOVA followed by Tukey multiple comparisons test; ***P<0.001). Means±s.e.m. of n samples noted at the bottom of each bar.