Proctolin and octopamine actions on the contractile systems of insect leg muscles |
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Institution: | 1. Laboratory of Drosophila Neural Development, Centre for DNA Fingerprinting and Diagnostics (CDFD), 4-1-714, Tuljaguda Complex, Nampally, Hyderabad-500001, India;2. Graduate Studies, Manipal University, Manipal 576104, India |
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Abstract: | 1. The pentapeptide proctolin produced contractions of the coxal depressor muscle of the cockroach, Periplaneta americana.2. The contraction was dependent upon extracellular calcium and the contraction was completely blocked by a Ca-free EGTA saline.3. Caffeine elicited transient contractions which were unaffected by manganese treatment.4. When the muscle was pre-treated with the conditioning solution with different K+ concentrations (1–100 mM), the amplitude of proctolin-induced contractions was reduced in the low K+ saline as well as in the high K+ saline.5. The results suggest that voltage sensitive calcium channels account for the proctolin-induced contractions.6. Octopamine (OA) reduced the contractions resulting from brief applications of elevated K+ concentration and of caffeine.7. The effect of OA on the response to elevated K+ concentrations was blocked by the α-adrenergic blocker, phentolamine. |
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