We report the discovery and initial characterization of the T-superfamily of conotoxins. Eight different T-superfamily peptides from five Conus species were identified; they share a consensus signal sequence, and a conserved arrangement of cysteine residues (--CC--CC-). T-superfamily peptides were found expressed in venom ducts of all major feeding types of Conus; the results suggest that the T-superfamily will be a large and diverse group of peptides, widely distributed in the 500 different Conus species. These peptides are likely to be functionally diverse; although the peptides are small (11-17 amino acids), their sequences are strikingly divergent, with different peptides of the superfamily exhibiting varying extents of post-translational modification. Of the three peptides tested for in vivo biological activity, only one was active on mice but all three had effects on fish. The peptides that have been extensively characterized are as follows: p5a, GCCP-KQMRCCTL*; tx5a, ␥CC␥DGW ؉ CCT § AAO; and au5a, FC-CPFIRYCCW (where ␥ ‫؍‬ ␥-carboxyglutamate, W ؉ ‫؍‬ bromotryptophan, O ‫؍‬ hydroxyproline, T § ‫؍‬ glycosylated threonine, and * ‫؍‬ COOH-terminal amidation). We also demonstrate that the precursor of tx5a contains a functional ␥-carboxylation recognition signal in the ؊1 to ؊20 propeptide region, consistent with the presence of ␥-carboxyglutamate residues in this peptide.Cone snails (genus Conus) are perhaps the most successful genus of marine invertebrates, with over 500 species, all of which are venomous (1, 2). These predatory marine snails have evolved a highly sophisticated neuropharmacological strategy based on small peptides (10 -35 amino acids) in their venoms (3, 4). Most Conus peptides potently affect ion channel function; these are widely used pharmacological reagents in neuroscience, and several are being directly developed as diagnostic and therapeutic agents. Most Conus peptides are highly disulfide-rich; generically, Conus peptides with multiple disulfide cross-links have been referred to as conotoxins. It has become apparent in recent years that there are tens of thousands of different conotoxins in Conus venoms. Because of the remarkably rapid interspecific divergence of peptide sequences, each Conus species has its own distinct repertoire of between 50 and 200 different venom peptides (5).A major simplification in understanding this complex array of Conus venom peptides is that most of the ϳ50,000 different molecular forms can be grouped into just a few superfamilies. Peptides in the same superfamily share both a conserved pattern of disulfide connectivity and a highly conserved signal sequence (when prepropeptide precursor sequences of the peptides are compared) (5, 6). Three large superfamilies of conotoxins are well characterized: the O-superfamily, comprising several distinct pharmacological families including the -, -, ␦-, and O-conotoxins (7); the A-superfamily, to which the ␣-conotoxins belong (8); and the M-superfamily, to which the -conotoxins belong. In this paper, we describe the ...

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A comparison was made of the actions of phencyclidine receptor agonists and N-methyl-D-aspartate (NMDA) receptor antagonists in two well-defined neurochemical test systems. These included (i) [3H]acetylcholine release from striatal cholinergic interneurons in vitro, a system known to be positively modulated by corticostriatal excitatory amino acid inputs in vivo; and (ii) cerebellar cGMP levels in vivo, an indicator of cerebellar Purkinje cell activity, which is also modulated by excitatory amino acid inputs. Using these neuronal systems, we report that phencyclidine receptor agonists demonstrated a noncompetitive antagonism of NMDA receptor agonist actions.

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Arachidonic acid is converted to (8R)-hydroperoxyeicosa-5,9,11,14-tetraenoic acid (8-HPETE) during incubations with homogenates of the central nervous system of the marine mollusc, Aplysia californica. 8-HPETE can be reduced to the corresponding hydroxy acid or be enzymatically converted to a newly identified metabolite, 8-ketoeicosa-5,9,11,14-tetraenoic acid (8-KETE). These metabolites were identified by high performance liquid chromatography, UV absorbance, and gas chromatography/mass spectrometry. Stereochemical analysis of the products demonstrate that the neuronal enzyme is an (8R We previously found that the 12-lipoxygenase pathway is activated by histamine and FMRF-amide, 1 two neurotransmitters in identified Aplysia neurons (1-3). Activation occurs through receptor-mediated release of arachidonic acid by a phospholipase and is blocked by pertussis toxin (4, 5), indicating that arachidonate metabolism is regulated by a G protein.In electrophysiological studies, application of (12S)-lipoxygenase metabolites, including (12S)-hydroperoxyeicosatetraenoic acid ((12S)-HPETE), mimics the action of histamine (2, 6) and modulates the action of FMRF-amide (7-9), suggesting that these lipids function as second messengers. There is evidence that lipoxygenase metabolites also act as second messengers in