fmrfamide and pyroglutamyl-aspartyl-prolyl-phenylalanyl-leucyl-arginyl-phenylalaninamide

The endogenous neuropeptides FMRFamide and FLRFamide (tetrapeptides) reversibly reduced a voltage-activated calcium current in the C1 neuron of Helix aspersa by an average of 20%. Two structurally related heptapeptides, pQDPFLRFamide and pQDPFLRIamide, both derived from another precursor protein in this species, did not reduce the current at all.

Topics: Animals; Calcium Channels; Enkephalin, Methionine; Evoked Potentials; FMRFamide; Helix, Snails; Neurons; Neuropeptides; Oligopeptides; Pyrrolidonecarboxylic Acid

The FMRFamide-related peptides (FaRPs) of Helix fall into two groups with often different pharmacological effects: the tetrapeptides FMRFamide and FLRFamide (tetraFaRPs) and the heptapeptides, which have the general structure XDP(F or Y)LRFamide (heptaFaRPs). Previously, we have shown that each group of FaRPs is encoded within a separate type of cDNA clone, a situation which corresponds to two distinct mRNA species existing in the CNS of Helix. Here, we report on the expression patterns of the two FaRP mRNAs both through embryo-genesis and in the fully differentiated regions of the adult nervous system. The levels and locations of FaRP mRNAs were studied by molecular and in situ hybridization using antisense riboprobes. The onset of expression of FaRP mRNAs occurs in Helix embryos about half-way between egg laying and hatching. First detection of the FaRPs themselves occurs about 2 days later. In embryos, as in the adult CNS, the heptaFaRP mRNA is at least five times more abundant than the tetraFaRP mRNA. In adults, the tetraFaRP mRNA is located primarily in the cerebral ganglia, most obviously in the C3 neuron, but also in a crescent-shaped cluster of small neurons lying anterior to C3. Occasional neurons expressing the tetraFaRP mRNA are detected in the parietal ganglia, but these have not yet been mapped. In contrast, the heptaFaRP mRNA is expressed almost exclusively in the parietal ganglia: in large clusters of about 100 neurons lying near to the anterior surface. The most interesting aspect of FaRP mRNAs is that their expression is not only exclusive to a relatively small number of specified neurons, but that expression appears to be mutually exclusive, that is, a particular neuron expresses only the mRNA for tetra-FaRPs or heptaFaRPs, never both. These results are discussed in relation to what we now know about the structure of the individual mRNA molecules.

Topics: Age Factors; Amino Acid Sequence; Animals; Central Nervous System; FMRFamide; Ganglia, Invertebrate; Helix, Snails; Molecular Sequence Data; Neurons; Neuropeptides; Oligopeptides; Pyrrolidonecarboxylic Acid; RNA, Messenger

The C3 neurone, which acts as a motoneurone for the tentacle retractor muscle in Helix aspersa, contains both Phe-Met-Arg-Phe-NH2 (FMRFamide) and acetylcholine (ACh). Each of these transmitter substances evokes contraction of the isolated muscle. FMRFamide induces a delayed rise in tension followed by phasic contractions. Unlike the response to ACh, this response is not associated with a depolarization of the muscle cells. Here we show that FMRFamide stimulates the inositol phosphate second messenger system in the muscle and causes a significant increase in total inositol trisphosphate (InsP3) levels. The isomer which releases intracellular Ca2+ stores, inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), is increased in a similar proportion to the total InsP3. The production of Ins(1,4,5)P3 is therefore likely to be involved in the response of the muscle to FMRFamide and may account for the oscillatory nature of the mechanical response. The N-terminally extended heptapeptide pGlu-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (pQDPFLRFamide), which relaxes the muscle, had no acute effect on InsP3 levels. Indirect evidence also indicates that intracellular Ca2+ stores are required for the generation of the FMRFamide response.

Topics: Amino Acid Sequence; Animals; Calcium; FMRFamide; Helix, Snails; Inositol 1,4,5-Trisphosphate; Molecular Sequence Data; Muscle Contraction; Muscles; Neuropeptides; Pyrrolidonecarboxylic Acid; Second Messenger Systems

1. The molluscan neuropeptides FMRFamide, pQDPFLRFamide, and SCPB were tested on the isolated crop and penis of the terrestraial slug, Limax maximus. FMRFamide and pQDPFLRFamide stimulated the penis and inhibited contractions of the crop. In contrast, SCPB either stimulated or relaxed the penis and increased the tone of the crop. 2. Fibers and varicosities containing immunoreactive (ir-) FMRFamide and ir-SCPB were located in the penis and crop. 3. Extracts of penes, crops, ganglia, and whole animals all contained FMRFamide, FLRFamide, SDPFLRFamide, NDPFLRFamide, and pQDPFLRFamide. 4. These results suggest that the FMRFamide-related peptides and SCPB are involved in the regulation of the reproductive and digestive activities of Limax.

Topics: Animals; Chromatography, High Pressure Liquid; Digestive System; FMRFamide; Immunohistochemistry; In Vitro Techniques; Male; Mass Spectrometry; Mollusca; Muscles; Neuropeptides; Penis; Pyrrolidonecarboxylic Acid; Radioimmunoassay

Phe-Met-Arg-Phe-NH2 (FMRFamide) and pyroGlu-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (pQDPFLRFamide) occur in the ganglia and tissues of the snail, Helix aspersa. This report describes the effects of these two neuropeptides on five visceral organs or somatic muscles isolated from the snail (Table 1). The epiphallus, as well as the rest of the male reproductive tract, was contracted by both FMRFamide and pQDPFLRFamide, and the threshold was usually below 5 X 10(-9) mol l-1 (Fig. 1). Both peptides also reduced the resting tone of the crop and decreased the force and frequency of its rhythmic activity; FMRFamide is about 10 times more potent (Fig. 4). In contrast, pQDPFLRFamide was about 100 times more potent than FMRFamide as a cardioexcitatory agent (Fig. 5). The actions of the peptides on the pharyngeal and tentacle retractor muscles were markedly different: FMRFamide primarily contracted these muscles; and pQDPFLRFamide usually had no effect alone, but relaxed or diminished contractions induced by FMRFamide and acetylcholine (ACh) (Figs 6, 8, 9). Other analogues of FMRFamide were tested, but none was as effective a relaxing agent as pQDPFLRFamide. The effects of FMRFamide and pQDPFLRFamide on all of the preparations could be distinguished from those produced by ACh and 5-hydroxytryptamine (5-HT); thus the actions of the neuropeptides were not mediated by cholinergic or serotonergic neurones. The stimulation of the musculature in the male reproductive tract and the inhibition of motility of the digestive system by FMRFamide and pQDPFLRFamide implicate these peptides in the control of reproductive behaviour. The effectiveness of pQDPFLRFamide in relaxing the retractor muscles and as a cardioexcitatory agent led to the hypothesis that this heptapeptide and FMRFamide, acting at distinct receptors, cooperate to regulate the excitability and contractility of the snail's musculature between the extremes of aestivation and active locomotion.

Topics: Acetylcholine; Animals; Digestive System; Digestive System Physiological Phenomena; FMRFamide; Helix, Snails; In Vitro Techniques; Muscle Contraction; Muscle, Smooth; Muscles; Neuropeptides; Organ Specificity; Pyrrolidonecarboxylic Acid; Serotonin