fmrfamide and phenylalanyl-leucyl-arginyl-phenylalanine

The potency (muscle force-generated) of a number of long-chain RFamide neuropeptides was examined in mechanical experiments with the radular-retractor and radular-sac muscles of gastropods Buccinum undatum and Neptunea antiqua. Many of the heptapeptides, octapeptides and the decapeptide LMS were found to induce greater contraction than FMRFamide in both smooth muscles and in both species. RFamide neuropeptides interacted with the neurotransmitter acetylcholine in an additive way and RFamide-induced contractions were inhibited by the neuromodulator serotonin. Pre-treatment with a calcium-free saline completely abolished acetylcholine-induced responses but only partially inhibited RFamide responses in the muscles, suggesting that acetylcholine acts to cause influx of extracellular calcium for contraction. In contrast, RFamide neuropeptides may mobilise intracellular calcium to maintain sustained tonic force in calcium-free conditions. This suggests that an additional involvement of a fast calcium channel may be present in the RFamide responses, since loss of the usual superimposed twitch activity is observed. Force regulation in these muscles appears to result from a complex interaction of RFamide neuropeptides with the primary transmitter acetylcholine and the neuromodulator serotonin.

Topics: Acetylcholine; Animal Structures; Animals; Calcium; FMRFamide; Muscle Contraction; Muscle, Smooth; Neuropeptides; Oligopeptides; Serotonin; Snails; Sodium Chloride; United Kingdom

The distribution of Phe-Leu-Arg-Phe (FLRF)-like immunoreactivity is described in the brain and in the ganglia of the ventral nerve cord of the locust Schistocerca gregaria. A single homologous pair of immunoreactive cell bodies occurs ventrally and medially in the suboesophageal ganglion. Each cell sends a process dorsally which bifurcates into anteriorly and posteriorly running neurites. The single anterior neurite passes along the circumoesophageal connectives to the brain where it ascends in a posterior running tract, giving off branches to innervate the tritocerebral neuropile and ending in an extensive network of highly varicose immunoreactive processes in the protocerebral neuropile. No processes are seen in the optic lobes or associated with the structured neuropiles of the muschroom bodies. The single posterior neurite from each cell passes into the suboesophageal-prothoracic connectives. It runs in the lateral dorsal tract of each ganglion in the ventral nerve cord as a highly varicose process and in each ganglion gives rise to an ipsilateral network of varicose processes in the dorsal and lateral neuropiles. In the seventh and terminal abdominal ganglia the innervation pattern exhibits sexual dimorphism. Vasopressin-like immunoreactivity is co-localized in the same pair of suboesophageal neurones and their processes. A similar pair of ventral median neurones stains with both antibodies in the suboesophageal ganglion of another species of locust, Locusta migratoria. Although the basic distribution pattern of immunoreactive processes is similar in both species there are also marked species differences in the pattern.

Topics: Amino Acid Sequence; Animals; Female; FMRFamide; Grasshoppers; Immunohistochemistry; Invertebrate Hormones; Male; Molecular Sequence Data; Nervous System; Nervous System Physiological Phenomena; Neuropeptides; Oligopeptides; Sex Characteristics; Vasopressins