sdpflrfamide and phenylalanyl-leucyl-arginyl-phenylalaninamide

Topics: Analysis of Variance; Animals; Brugia pahangi; Dirofilaria immitis; Kinetics; Luminescent Measurements; Neuropeptides; Nitric Oxide; Oligopeptides

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 stellate ganglion of the squid Loligo pealli contains the neuropeptides Phe-Met-Arg-Phe-NH2 (FMRFamide), Phe-Leu-Arg-Phe-NH2 (FLRFamide) and at least one N-terminally extended FMRFamide-related peptide that is yet to be fully characterized. Both local application and arterial perfusion of FLRFamide potentiate transmission at the giant synapse. The N-terminally related peptide Ser-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (SDPFLRFamide) produced a similar effect. The threshold for both the tetra- and the hepta-peptides was less than 10 microM. Potentiation could be detected as an increase in rate of rise of the EPSPs, as an increase in amplitude of the EPSP in the absence of spikes, or under voltage clamp as an increase in the EPSC. The effect was most pronounced when the synapse was fatigued by high frequency stimulation. Another molluscan peptide, eledoisin and also leucine enkephalin were without effect. In the absence of any detectable effects of FLRFamide on the resting membrane potential of either pre- or postsynaptic terminals or on the presynaptic spike, it is suggested that the peptide influences transmitter mobilization. However, the peptide could also exert small changes in preterminal calcium currents, which so far we have been unable to detect.

Topics: Animals; Arteries; FMRFamide; Microinjections; Neuropeptides; Neurotransmitter Agents; Oligopeptides; Perfusion; Stellate Ganglion; Synapses; Synaptic Transmission