It is generally accepted that all living organisms present on earth derive from one single primordial cell born several billion years ago. One important step in the evolution occurred some 1. 5 billion years ago with the transition from small procaryote cells with relatively simple internal structures such as bacteria to larger and more compleX: eucaryotic cells such as those found in higher animals and plants. Large membrane proteins which enable the cells to communicate appeared early in evolution, and it is believed that the nerve membrane receptors and ionic channels which are observed today in both invertebrate and vertebrate species derive from a common ancestor. Basically, the three identified superfamilies, 1) ionotropic receptors (i. e. receptors containing an integral ionic channel), 2) metabotropic receptors (receptors coupled to G proteins) and 3) voltage-dependent ionic channels (Na+, K + and Ca2+ channels) were already well differentiated when vertebrates separated from invertebrate species. The large number of subtypes which are observed in each superfamily may be of more recent evolutionary origin. To understand how this happened, the best approach was to compare the sequences and the properties of the receptors and ionic channels in species sufficiently distant in the evolutionary tree. In the present volume, many of the best specialists in the field of comparative molecular neurobiology, several of them working on vertebrate and invertebrate species, have accepted to report their most recent findings.

Inhalt
Old concepts and new approaches.- The major lines of metazoan evolution: Summary of traditional evidence and lessons from ribosomal RNA sequence analysis.- Heterologous expression of the membrane proteins that control cellular excitability.- Ligand-gated ion channels.- Molluscan ligand-gated ion-channel receptors.- Acetylcholine receptor molecules of the nematode Caenorhabditis elegans.- Acetylcholine receptor/channel molecules of insects.- Muscarinic acetylcholine receptors in invertebrates: Comparisons with homologous receptors from vertebrates.- Pharmacology of the GABA receptor of insect central neurones in culture: A patch-clamp study.- GABA Receptor molecules of insects.- Cloning of a putative GABAA receptor from cyclodiene-resistant Drosophila: A case study in the use of insecticide-resistant mutants to isolate neuroreceptors.- Molecular biology of excitatory amino acid receptors: Subtypes and subunits.- Molecular analysis of Drosophila glutamate receptors.- Channels formed by M2 peptides of a putative glutamate receptor subunit of locust.- Single channel properties at the synaptic site.- Second messenger-linked receptors.- Structural and functional conservation of serotonin receptors throughout evolution.- The wide range of actions of the FMRFamide-related peptides and the biological importance of peptidergic messengers.- Molecular studies on insect octopamine receptors.- Bioamine receptors: Evolutionary and functional variations of a structural leitmotiv.- Voltage-gated ion channels.- Molecular basis of K+ channel inactivation gating.- Potassium conductance and potassium channels in a primitive insect: The cockroach Periplaneta americana.- Ionic channels in cultured Drosophila neurons.- Receptor diversity and integrative properties of the neurons.- The electrophysiological pharmacology of neurotransmitter receptors on locust neuronal somata.- Modulation of insect neurone properties.