A genome-wide association study identifies two novel susceptibility loci and trans population polygenicity associated with bipolar disorder.

Genome-wide association studies (GWASs) have identified several susceptibility loci for bipolar disorder (BD) and shown that the genetic architecture of BD can be explained by polygenicity, with numerous variants contributing to BD. In the present GWAS (Phase I/II), which included 2964 BD and 61 887 control subjects from the Japanese population, we detected a novel susceptibility locus at 11q12.2 (rs28456, P=6.4 × 10-9), a region known to contain regulatory genes for plasma lipid levels (FADS1/2/3). A subsequent meta-analysis of Phase I/II and the Psychiatric GWAS Consortium for BD (PGC-BD) identified another novel BD gene, NFIX (Pbest=5.8 × 10-10), and supported three regions previously implicated in BD susceptibility: MAD1L1 (Pbest=1.9 × 10-9), TRANK1 (Pbest=2.1 × 10-9) and ODZ4 (Pbest=3.3 × 10-9). Polygenicity of BD within Japanese and trans-European-Japanese populations was assessed with risk profile score analysis. We detected higher scores in BD cases both within (Phase I/II) and across populations (Phase I/II and PGC-BD). These were defined by (1) Phase II as discovery and Phase I as target, or vice versa (for 'within Japanese comparisons', Pbest~10-29, R2~2%), and (2) European PGC-BD as discovery and Japanese BD (Phase I/II) as target (for 'trans-European-Japanese comparison,' Pbest~10-13, R2~0.27%). This 'trans population' effect was supported by estimation of the genetic correlation using the effect size based on each population (liability estimates~0.7). These results indicate that (1) two novel and three previously implicated loci are significantly associated with BD and that (2) BD 'risk' effect are shared between Japanese and European populations.

A novel Alzheimer disease locus located near the gene encoding tau protein.

APOE ɛ4, the most significant genetic risk factor for Alzheimer disease (AD), may mask effects of other loci. We re-analyzed genome-wide association study (GWAS) data from the International Genomics of Alzheimer's Project (IGAP) Consortium in APOE ɛ4+ (10 352 cases and 9207 controls) and APOE ɛ4- (7184 cases and 26 968 controls) subgroups as well as in the total sample testing for interaction between a single-nucleotide polymorphism (SNP) and APOE ɛ4 status. Suggestive associations (P<1 × 10(-4)) in stage 1 were evaluated in an independent sample (stage 2) containing 4203 subjects (APOE ɛ4+: 1250 cases and 536 controls; APOE ɛ4-: 718 cases and 1699 controls). Among APOE ɛ4- subjects, novel genome-wide significant (GWS) association was observed with 17 SNPs (all between KANSL1 and LRRC37A on chromosome 17 near MAPT) in a meta-analysis of the stage 1 and stage 2 data sets (best SNP, rs2732703, P=5·8 × 10(-9)). Conditional analysis revealed that rs2732703 accounted for association signals in the entire 100-kilobase region that includes MAPT. Except for previously identified AD loci showing stronger association in APOE ɛ4+ subjects (CR1 and CLU) or APOE ɛ4- subjects (MS4A6A/MS4A4A/MS4A6E), no other SNPs were significantly associated with AD in a specific APOE genotype subgroup. In addition, the finding in the stage 1 sample that AD risk is significantly influenced by the interaction of APOE with rs1595014 in TMEM106B (P=1·6 × 10(-7)) is noteworthy, because TMEM106B variants have previously been associated with risk of frontotemporal dementia. Expression quantitative trait locus analysis revealed that rs113986870, one of the GWS SNPs near rs2732703, is significantly associated with four KANSL1 probes that target transcription of the first translated exon and an untranslated exon in hippocampus (P ⩽ 1.3 × 10(-8)), frontal cortex (P ⩽ 1.3 × 10(-9)) and temporal cortex (P⩽1.2 × 10(-11)). Rs113986870 is also strongly associated with a MAPT probe that targets transcription of alternatively spliced exon 3 in frontal cortex (P=9.2 × 10(-6)) and temporal cortex (P=2.6 × 10(-6)). Our APOE-stratified GWAS is the first to show GWS association for AD with SNPs in the chromosome 17q21.31 region. Replication of this finding in independent samples is needed to verify that SNPs in this region have significantly stronger effects on AD risk in persons lacking APOE ɛ4 compared with persons carrying this allele, and if this is found to hold, further examination of this region and studies aimed at deciphering the mechanism(s) are warranted.

Increased expression of BIN1 mediates Alzheimer genetic risk by modulating tau pathology.

Genome-wide association studies (GWAS) have identified a region upstream the BIN1 gene as the most important genetic susceptibility locus in Alzheimer's disease (AD) after APOE. We report that BIN1 transcript levels were increased in AD brains and identified a novel 3 bp insertion allele ∼28 kb upstream of BIN1, which increased (i) transcriptional activity in vitro, (ii) BIN1 expression levels in human brain and (iii) AD risk in three independent case-control cohorts (Meta-analysed Odds ratio of 1.20 (1.14-1.26) (P=3.8 × 10(-11))). Interestingly, decreased expression of the Drosophila BIN1 ortholog Amph suppressed Tau-mediated neurotoxicity in three different assays. Accordingly, Tau and BIN1 colocalized and interacted in human neuroblastoma cells and in mouse brain. Finally, the 3 bp insertion was associated with Tau but not Amyloid loads in AD brains. We propose that BIN1 mediates AD risk by modulating Tau pathology.

Genome-wide haplotype association study identifies the FRMD4A gene as a risk locus for Alzheimer's disease.

Recently, several genome-wide association studies (GWASs) have led to the discovery of nine new loci of genetic susceptibility in Alzheimer's disease (AD). However, the landscape of the AD genetic susceptibility is far away to be complete and in addition to single-SNP (single-nucleotide polymorphism) analyses as performed in conventional GWAS, complementary strategies need to be applied to overcome limitations inherent to this type of approaches. We performed a genome-wide haplotype association (GWHA) study in the EADI1 study (n=2025 AD cases and 5328 controls) by applying a sliding-windows approach. After exclusion of loci already known to be involved in AD (APOE, BIN1 and CR1), 91 regions with suggestive haplotype effects were identified. In a second step, we attempted to replicate the best suggestive haplotype associations in the GERAD1 consortium (2820 AD cases and 6356 controls) and observed that 9 of them showed nominal association. In a third step, we tested relevant haplotype associations in a combined analysis of five additional case-control studies (5093 AD cases and 4061 controls). We consistently replicated the association of a haplotype within FRMD4A on Chr.10p13 in all the data set analyzed (OR: 1.68; 95% CI: (1.43-1.96); P=1.1 × 10(-10)). We finally searched for association between SNPs within the FRMD4A locus and Aß plasma concentrations in three independent non-demented populations (n=2579). We reported that polymorphisms were associated with plasma Aß42/Aß40 ratio (best signal, P=5.4 × 10(-7)). In conclusion, combining both GWHA study and a conservative three-stage replication approach, we characterised FRMD4A as a new genetic risk factor of AD.

Common variant in 6q26-q27 is associated with distal colon cancer in an Asian population.

BACKGROUND AND AIM: Colorectal cancer (CRC) is a multifactorial disease with both environmental and genetic factors contributing to its development. The incidence of CRC is increasing year by year in Japan. Patients with CRC in advanced stages have a poor prognosis, but detection of CRC at earlier stages can improve clinical outcome. Therefore, identification of epidemiologial factors that influence development of CRC would facilitate the prevention or early detection of disease. METHODS: To identify loci associated with CRC risk, we performed a genome-wide association study (GWAS) for CRC and sub-analyses by tumour location using 1583 Japanese CRC cases and 1898 controls. Subsequently, we conducted replication analyses using a total of 4809 CRC cases and 2973 controls including 225 Korean subjects with distal colon cancer and 377 controls. RESULTS: We identified a novel locus on 6q26-q27 region (rs7758229 in SLC22A3, p = 7.92 × 10⁻9, OR of 1.28) that was significantly associated with distal colon cancer. We also replicated the association between CRC and SNPs on 8q24 (rs6983267 and rs7837328, p = 1.51 × 10⁻8 and 7.44 × 10⁻8, ORs of 1.18 and 1.17, respectively). Moreover, we found cumulative effects of three genetic factors (rs7758229, rs6983267, and rs4939827 in SMAD7) and one environmental factor (alcohol drinking) which appear to increase CRC risk approximately twofold. CONCLUSIONS: We found a novel susceptible locus in SLC22A3 that contributes to the risk of distal colon cancer in an Asian population. These findings would further extend our understanding of the role of common genetic variants in the aetiology of CRC.

Genomewide Association Studies in Pharmacogenomics: Meeting Report of the NIH Pharmacogenomics Research Network-RIKEN (PGRN-RIKEN) Collaboration.

Genomewide association studies (GWAS) have resulted in the identification of many heritable genetic factors that underlie risk for human disease or variation in physiologic traits. In contrast, there are fewer GWAS of drug response phenotypes, despite extensive unexplained interindividual variability. To address this urgent need, the NIH Pharmacogenomics Research Network (PGRN) and the Center for Integrative Medical Sciences (IMS) at RIKEN support a collaboration, PGRN-RIKEN, with the goal of accelerating GWAS of drug response phenotypes.

Trypsin inhibitors from bottle gourd (Lagenaria leucantha Rusby var. Depressa Makino) seeds. Purification and amino acid sequences.

Two almost identical trypsin isoinhibitors, LLDTI-I and LLDTI-II, from bottle gourd (Lagenaria leucantha Rusby var. Depressa Makino) seeds were purified by acetone precipitation, gel filtration and reversed phase chromatography. LLDTI-I and LLDTI-II consist of 30 and 29 amino acid residues, respectively, and have identical sequences, except that LLDTI-I has one additional pyroglutamic acid residue at N-terminus. Both proteins are strong inhibitors of bovine trypsin, with Ki values of 2.4.10(-10) M (LLDTI-I) and 9.6.10(-11) M (LLDTI-II). Amino acid sequences are as follows: [sequence: see text]

Molecular conformation of achatin-I, an endogenous neuropeptide containing D-amino acid residue. X-ray crystal structure of its neutral form.

The molecular conformation of achatin-I neutral form (H-Gly-D-Phe-Ala-Asp-OH), an endogenous neuropeptide, was elucidated by X-ray crystal analysis. The molecule has a type II' beta-turn structure with the D-Phe-Ala residues at the corner of the bend, which is further stabilized by two NH(Gly)...C gamma = O sigma(Asp) and NH(Asp)...C gamma = O sigma(Asp) intramolecular hydrogen bonds. This turn conformation may be an important feature of achatin-I related to its neuroexcitatory activity.

Effect of the D-Phe2 residue on molecular conformation of an endogenous neuropeptide achatin-I. Comparison of X-ray crystal structures of achatin-I (H-Gly-D-Phe-Ala-Asp-OH) and achatin-II (H-Gly-Phe-Ala-Asp-OH).

The molecular conformation of achatin-II neutral form (H-Gly-Phe-Ala-Asp-OH), an endogenous peptide from the Achatina fulica ganglia, was elucidated by X-ray crystal analysis. The molecule takes an extended beta-pleated structure stabilized by 5 intermolecular hydrogen bonds with the antiparallely arranged molecules. This is in contrast with the turn conformation of a neuroactive achatin-I (H-Gly-D-Phe-Ala-Asp-OH) [(1992) FEBS Lett. 276,95-97]. The conformational comparison of both of the molecules makes clear the structural role which D-Phe residue of achatin-I plays in forming a definite active form.

Molluscan neuropeptides.

Achatin-I, fulicin, fulyal, Mytilus-FFRFamide and Helix CCAP-RP-III are D-amino acid-containing neuropeptides from molluscs. Achatin-I, fulicin and fulyal from Achatina showed excitatory and/or modulatory actions on the penis retractor, radula retractor or ventricular muscles and neurons, though their L isomers were devoid of activity. On the other hand, both Mytilus-FFRFamide and its L isomer showed excitatory effects on the anterior byssus retractor muscle. Moreover, in contrast to Achatina neuropeptides, Helix CCAP-RP-III exhibited no remarkable activities on any of the muscles tested; instead, its L isomer possessed various excitatory effects. The molecular structures of these short peptides would be affected by the L-->D conversion and could influence activity. Molecular biological studies on the fulicin precursor suggest that fulicin, fulyal and related peptides are produced in Achatina ganglia and heart by processing of the ribosomally made precursor, and that L-isomeric fulicin and fulyal further undergo epimerization to yield the D-isomers.

A novel D-amino acid-containing peptide, fulyal, coexists with fulicin gene-related peptides in Achatina atria.

Fulicin (Phe-D-Asn-Glu-Phe-Val-NH2) is a neuropeptide from ganglia of the African giant snail (Achatina fulica). Previously, the sequences of nine fulicin gene-related peptides (FGRP-1 to -9) have been predicted from the cDNA encoding the ganglia fulicin precursor and the transcripts have been detectable in the heart. We synthesized twenty peptides related to fulicin and FGRPs containing either an L- or a D-amino acid at position 2 and used them to identify FGRPs in atrial extracts. We identified ten alpha-amidated peptides, including fulicin and confirmed their structures as follows: Tyr-Ala-Glu-Phe-Leu-NH2 (FGRP-9), [D-Ala2]FGRP-9 (fulyal), [L-Asn2]fulicin, fulicin, Ser-Tyr-Asp-Phe-Val-NH2 (FGRP-2), Thr-Tyr-Asp-Phe-Leu-NH2 (FGRP-3), Tyr-Asp-Phe-Ile-NH2 (FGRP-5), Ser-Pro-Tyr-Asp-Phe-Ile-NH2 (FGRP-6), Asn-Tyr-Asp-Phe-Val-NH2 (FGRP-7) and Ser-Pro-Tyr-Asp-Phe-Val-NH2 (FGRP-8). We analyzed the biological activities of synthetic FGRPs using the snail penis retractor muscle. The results revealed that fulyal remarkably potentiated the tetanic contraction at concentrations as low as 10(-12) M. FGRP-9 was about 10,000-fold less potent. Fulyal, like fulicin, seems to undergo preferential maturation to participate in the penis retractor muscle contraction as a neuropeptide containing a D-amino acid.

Slow inward current induced by achatin-I, an endogenous peptide with a D-Phe residue.

Following a preliminary report on the isolation of a neuroactive tetrapeptide, achatin-I (Gly-D-Phe-L-Ala-L-Asp) that has a D-phenylalanine residue, from the Achatina fulica ganglia, the pharmacological features of this peptide on Achatina giant neurones were now worked out in detail. Of the eight possible stereoisomers, only achatin-I markedly, and [D-Ala3]achatin-I slightly, induced a slow inward current (Iin) with an increase in membrane conductance (g) of the identifiable neurones, tonically autoactive neurone (TAN), dorsal-right cerebral distinct neurone (d-RCDN) and periodically oscillating neurone (PON) which had been tested previously. Of 23 types of neurones tested, 10 types including the three mentioned were excited by achatin-I, whereas no neurone was inhibited. The ED50 of achatin-I for the neurones tested were 0.2-2.7 x 10(-5) M, and that for PON was the lowest. The Hill coefficients of achatin-1. 0.62-0.80, derived from 1.0 Emax values of achatin-I for producing Iin, 4.2-6.3 nA, were significantly greater than those of [D-Ala3]achatin-I, 1.8-3.4 nA. Iin of TAN and d-RCDN induced by achatin-I was blocked in the Na(+)-free state, but unaffected in the Ca2(+)-free (replaced with Co2+), Cl(-)-free or K(+)-enriched (3.0X) state, indicating that the current was produced by the g increase in response to Na+. However, the Iin was partially blocked by tetrodotoxin 10(-4) M. We propose that achatin-I is an excitatory neurotransmitter on Achatina neurones.

Structure-activity relationship studies on the endogenous neuroactive tetrapeptide achatin-I on giant neurons of Achatina fulica Ferussac.

The structure-activity relationships of achatin-I, a neuroactive peptide containing a D-phenylalanine residue, for producing excitatory effects on three different types of Achatina neurons, PON, TAN and d-RCDN, were studied under the voltage clamp method. Of the peptides examined, only Gly-Gly-D-Phe-L-Ala-L-Asp (IV). D-Phe-L-Ala-L-Asp (V) and Gly-D-Phe-L-Ala-L-Asn (XVI) produced an inward current with increased membrane conductance similar to achatin-1 (I). The structure-activity relationship was essentially the same for the three Achatina neuron types. The equiactive molar ratios (EMRs) of the active peptides vs. achatin-I (I) were calculated from their dose-response curves: 8 - 60 for Gly-Gly-DPhe-L-Ala-L-Asp (IV), 200 - greater than 250 for D-Phe-L-Ala-L-Asp (V) and greater than 200 for Gly-D-Phe-L-Ala-L-Asn (XVI). These values indicate that the achatin-I receptor in the Achatina neurons is highly structure-specific.

Destructive calcium pyrophosphate dihydrate temporo-mandibular arthropathy (pseudogout).

A case of a 57-year-old man with destructive calcium pyrophosphate dihydrate (CPPD) arthropathy (pseudogout) together with pseudotumor formation in the temporomandibular joint (TMJ).

Achatin-I, an excitatory neurotransmitter having a D-phenylalanine residue of Achatina giant neurones.

The neuroexcitatory peptide isolated from Achatina ganglia was identical to the synthetic Gly-D-Phe-L-Ala-L-Asp with respect to either the bioassay experiments using the Achatina neurones or the instrumental analysis (1H-NMR, SIMS, CD and HPLC). We termed it achatin-I (yield: 50 micrograms from 30,000 animals). Its stereoisomer, Gly-L-Phe-L-Ala-L-Asp, termed achatin-II, was also isolated from the ganglia (yield: 17 micrograms), but this was ineffective on the Achatina neurones. Of the eight possible stereoisomers, only achatin-I markedly showed excitatory effects on the two Achatina neurones, PON and TAN, and [D-Ala3] achatin-I (Gly-D-Phe-D-Ala-L-Asp) had the slight effects. Among the fourteen neurones tested, seven, including the two mentioned above, were excited by achatin-I, whereas no neurone was inhibited. Achatin-I produced an inward current (Iin) with an increase in the membrane conductance (g) under voltage clamp. ED50 of achatin-I for exciting the neurones were 0.20-1.47 x 10(-5) M, and its Emax were 6.33-5.02 nA. Of the achatin-I analogues examined, only the three, Gly-Gly-D-Phe-L-Ala-L-Asp, D-Phe-L-Ala-L-Asp and Gly-D-Phe-L-Ala-L-Asn, produced Iin, but much smaller than that of achatin-I. The equiactive molar ratios (EMRs) of the four effective related peptides (three analogues and a stereoisomer) vs. achatin-I were: 8-60 for Gly-Gly-D-Phe-L-Ala-L-Asp, 200 - > 250 for D-Phe-L-Ala-L-Asp and > 200 for Gly-D-Phe-L-Ala-L-Asn and Gly-D-Phe-D-Ala-L-Asp. The Iin induced by achatin-I was blocked under the /Na+/0-free state, but unaffected under the [Ca2+]-free (replaced with Co2+), [Cl-]0-free or [K+]-enriched (3.0 x) medium, indicating that the Iin is produced by the gNa increase of neuromembrane. We propose that achatin-I having a D-phenylalanine residue is an excitatory neurotransmitter of the Achatina neurones.

Meta-analysis of 74,046 individuals identifies 11 new susceptibility loci for Alzheimer's disease.

Eleven susceptibility loci for late-onset Alzheimer's disease (LOAD) were identified by previous studies; however, a large portion of the genetic risk for this disease remains unexplained. We conducted a large, two-stage meta-analysis of genome-wide association studies (GWAS) in individuals of European ancestry. In stage 1, we used genotyped and imputed data (7,055,881 SNPs) to perform meta-analysis on 4 previously published GWAS data sets consisting of 17,008 Alzheimer's disease cases and 37,154 controls. In stage 2, 11,632 SNPs were genotyped and tested for association in an independent set of 8,572 Alzheimer's disease cases and 11,312 controls. In addition to the APOE locus (encoding apolipoprotein E), 19 loci reached genome-wide significance (P < 5 × 10(-8)) in the combined stage 1 and stage 2 analysis, of which 11 are newly associated with Alzheimer's disease.

Genome-wide association study on bipolar disorder in the Bulgarian population.

Bipolar disorder is a severe psychiatric disorder influenced by environmental and genetic factors. Genetic studies have implicated many variants in the disease's etiology but only few have been successfully replicated. We conducted a genome-wide association study (GWAS) on bipolar disorder in the Bulgarian population followed by a replication study of the top 100 single nucleotide polymorphisms (SNPs) showing the smallest P values. The GWAS was performed on 188 bipolar disorder patients and 376 control subjects genotyped on the Illumina 550 platform. The replication study was conducted on 122 patients and 328 controls. Although our study did not show any association P value that achieved genome-wide significance, and none of the top 100 SNPs reached the Bonferroni-corrected P value in the replication study, the plausible involvement of some variants cannot be entirely discarded. Three polymorphisms, rs8099939 [P = 2.12 × 10(-6), odds ratio (OR) = 1.95, 95% confidence interval (CI) = 1.43-2.67] in GRIK5, rs6122972 (P = 3.11 × 10(-6), OR = 2.02, 95% CI = 1.46-2.80) in PARD6B and rs2289700 (P = 9.14 × 10(-6), OR = 2.13, 95% CI = 1.53-2.95) in CTSH remained associated at a similar level after Mantel-Haenszel test for combining the results from the genome-wide and replication studies. A modest association was also detected for SNP rs1012053 (GWAS P = 4.50 × 10(-2)) in DGKH, which has already been reported as the most significant variant in a previous genome-wide scan on bipolar disorder. However, further studies using larger datasets are needed to identify variants with smaller effects that contribute to the risk of bipolar disorder.

Identification of orcokinin gene-related peptides in the brain of the crayfish Procambarus clarkii by the combination of MALDI-TOF and on-line capillary HPLC/Q-Tof mass spectrometries and molecular cloning.

We developed a strategy for the exploration of brain peptides in the red swamp crayfish, Procambarus clarkii, utilizing the combined techniques of matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry (MALDI-TOF MS), molecular cloning, and on-line capillary reversed-phase HPLC/quadrupole orthogonal acceleration time-of-flight (Q-Tof)-MS. We initially performed direct MALDI-TOF MS analysis with slices of the brain. The MS spectra from a slice of the olfactory lobe indicated that an orcokinin (NFDEIDRSGFGFN) occurs in this species. Subsequently, its occurrence was confirmed by molecular cloning of the cDNAs encoding the precursor protein of orcokinin. The deduced amino acid sequences indicated that there are two different types of preproorcokinins. Preproorcokinin A (251 residues long) contains not only seven copies of orcokinin but also two copies of NFDEIDRSGFGFV and one copy each of NFDEIDRSGFGFA, NFDEIDRTGFGFH, and FDAFTTGFGHS. The former three peptides were previously isolated from another crayfish, Orconectes limosus, and/or the shore crab, Carcinus maenas, and the latter two were novel. Preproorcokinin B (266) harbors one additional orcokinin. All sequences of the peptides are flanked by dibasic sequences which are the consensus signal for processing. Moreover, brain extract was subjected to Sephadex G-25 and, subsequently, to on-line capillary reversed-phase HPLC/Q-Tof MS analysis. From the LC-MS analysis, the molecular weights of orcokinin, NFDEIDRSGFGFV, NFDEIDRSGFGFA, NFDEIDRTGFGFH, and FDAFTTGFGHS were identified as the doubly charged ions at m/z 759.37, 751.92, 737.86, 777.90, and 593. 78, respectively. In addition, the sequences were assigned by the collision-induced dissociation spectra using the doubly charged ions in the LC-MS/MS analysis. These data suggest that orcokinin and its related peptides are especially abundant in the olfactory lobe and are synthesized and processed from the two types of preproorcokinins in the crayfish brain.

Isolation of achatin-I, a neuroactive tetrapeptide having a D-phenylalanine residue, from Achatina ganglia, and its effects on Achatina giant neurones.

1. We have isolated a neuroexcitatory tetrapeptide having a D-phenylalanine (Gly-D-Phe-L-Ala-L-Asp) from the ganglia of Achatina fulica Férussac. This peptide was termed achatin-I (Kamatani et al., 1989). In the present report, we shall present highlights from the original paper concerning the process of peptide isolation and the examination of its effects. 2. From the ganglia of about 30,000 animals, we obtained 50 micrograms of achatin-I and 17 micrograms of its stereoisomer consisting of only L-amino acid residues (Gly-L-Phe-L-Ala-L-Asp) which was termed achatin-II. The data of instrumental analyses (1H-NMR, SIMS, CD and HPLC) of isolated achatin-I and achatin-II were identical to those of synthetic ones. 3. Achatin-I showed marked excitatory effects on the three Achatina giant neurones, PON (periodically oscillating neurone), TAN (tonically autoactive neurone) and v-RCDN (ventral-right cerebral distinct neurone), whereas achatin-II had no effect. Among their stereoisomers, [D-Ala3]-achatin-I (Gly-D-Phe-D-Ala-L-Asp) had slight excitatory effects on the Achatina neurones tested. Amide derivatives of achatin-I and achatin-II were ineffective. 4. Dose-response curves of achatin-I and [D-Ala3]-achatin-I for producing the inward current of PON were measured under voltage clamp at a holding membrane voltage (Vh) of -50 mV.(ABSTRACT TRUNCATED AT 250 WORDS)