Proliferating ability,morphological development and acetylcholinesterase activity of the neural tube cells in early chick embryos

Summary Using ³H-thymidine autoradiography and AChE histochemistry at the electron microscopic level on the same sections, the interrelationships between loss of proliferating ability, morphological development and increase of AChE activity during the course of differentiation of the neural tube cells were investigated in early chick embryos. The neural tube wall consisted of spindle-shaped cells with no AChE activity, weakly positive spindle-shaped cells showing AChE activity in the cisternae of the nuclear envelope and in a few short profiles of r-ER, moderately positive spindle-shaped cells showing AChE activity in the nuclear envelope and in a moderate number of r-ER profiles and intensely positive large round cells showing AChE activity in the nuclear envelope and in a large number of r-ER profiles. Nuclei of the AChE-negative, weakly positive and moderately positive cells were located in the ependymal layer (matrix). The AChE-intensely positive cells were in the mantle layer. The AChE-negative and weakly positive cells were capable of proliferation and were regarded as undifferentiated neuroepithelial cells. In contrast, the moderately positive and intensely positive cells were no longer capable of proliferation and were considered to be neurons. These findings indicate that the r-ER increases rapidly in amount and volume in newly formed neurons soon after their final cell division, and that AChE increases in the neurons in parallel to the development of the r-ER.     

Evidence for homologous peptidergic neurons in the buccal ganglia of diverse nudibranch mollusks

The buccal ganglia of seven nudibranches (Aeolidia papillosa, Armina californica, Dirona albolineata, D. picta, Hermissenda crassicornis, Melibe leonina, and Tritonia diomedea) were examined to explore possible homologies between large cells that reacted with antibodies directed against small cardioactive peptide B (SCP_B). The buccal ganglion of each species possessed a pair of large, dorsal–lateral, whitish neurons that contained an SCP_B-like peptide. We refer to these neurons as the SLB (SCP_B-immunoreactive Large Buccal) cells. In all species examined, the SLB cells project out the gastroesophageal nerves and appear to innervate the esophagus. In each species, an apparent rhythmic feeding motor program (FMP) was observed by intracellular recording from both SLB neurons and other neurons in isolated preparations of the buccal ganglia. SLB cells often fire at a high frequency, and usually burst in a specific phase relation to the FMP activity. Stimulation of SLB cells enhances expression of the feeding motor program, either by potentiating existing activity or eliciting the FMP in quiescent preparations. Finally, perfusion of isolated buccal ganglia with SCP_B excites the SLB cells and activates FMPs. Thus, both the immunohistochemical and electrophysiological data suggest that the SLB cells within three suborders of the opistobranchia (Dendronotacea, Arminacea, and Aeolidacea) are homologous. A comparison of our data with previously published studies indicates that SLB cell homologs may exist in other gastropods as well.     

Small cardioactive peptide-like immunoreactivity and its colocalization with FMRFamide-like immunoreactivity in the central nervous system of the leech Hirudo medicinalis

Summary The distributions of small cardioactive peptide (SCP)- and FMRFamide-like immunoreactivities in the central nervous system of the medicinal leech Hirudo medicinalis were studied. A subset of neurons in the segmental ganglia and brains was immunoreactive to an antibody directed against SCP_B. Immunoreactive cell bodies were regionally distributed throughout the nerve cord, and occurred both as bilaterally paired and unpaired neurons. The majority of the unpaired cells displayed a tendency to alternate from side to side in adjacent ganglia. A small number of neurons were immunoreactive only in a minority of nerve cords investigated. Intracellular injections of Lucifer yellow dye and subsequent processing for immunocytochemistry revealed SCP-like immunoreactivity in heart modulatory neurons but not in heart motor neurons. FMRFamide-like immunoreactivity was also detected in cell bodies throughout the central nervous system. A subset of neurons contained both SCP- and FMRFamide-like immunoreactivities; others stained for only one or the other antigen. These data suggest that an antigen distinct from FMRFamide is responsible for at least part of the SCP-like immunoreactivity. This antigen likely bears some homology to the carboxyl terminal of SCP_A and SCP_B.     

Regeneration of acetylcholinesterase in clonal neuroblastoma-glioma hybrid NG108-15 cells after soman inhibition: effect of glycyl-l-glutamine

Acetylcholinesterase (AChE) in the clonal NG108-15 cell line has been previously characterized. This cell line represents an in vitro system to study AChE regulation and effects of chemical compounds that may alter AChE activity. Recently, glycyl-L-glutamine (GLG) was demonstrated to function as a neurotrophic factor for maintenance of AChE content in cat denervated superior cervical ganglion cells. In the present study, regeneration of AChE activity in cultures of undifferentiated NG108-15 cells after soman inhibition was investigated in the presence and absence of GLG. Cells were treated with soman (5.5 × 10^–6 M) for 15 min and then washed to remove excess soman. Culture medium containing either GLG (10^–6, 10^–5, or 10^–4M) or glycyl-L-glutamic acid (10^–6 M) was added to cultures after soman treatment and remained in the medium until cell harvest. Cells were physically detached at various times after soman treatment and specific AChE activity was determined. After soman, AChE activity dramatically decreased to less than 1% of untreated cellular activity at 1 hr. AChE activity gradully increased after 5 hr, while untreated cell AChE activity was regained 20 hr after soman. The t_1/2 for AChE regeneration was approximately 10 hr. GLG did not increase the rate of AChE regeneration after soman inhibition. These results indicate that GLG is not a directly acting neurotrophic factor for AChE synthesis in NG108-15 cells after chemical AChE inactivation.Abbreviations AChE acetylcholinesterase - NG108-15 cell neuroblastoma-glioma 108-15 cell - DMEM Dulbecco's modified Eagles minimal essential medium - FBS fetal bovine serum - GLGA glycyl-L-glutamic acid - L-GA L-glutamic acid - GLG glycyl-L-glutamine - GD soman The opinions or assertions contained herein are the private views of the authors and are not to be construed as reflecting the view of the Department of the Army or the Department of the Army or the Department of Defense.     

Effect of pyruvate on rat heart thiol status during ischemia and hypoxia followed by reperfusion

The effect of the neurotoxicant, 1-methyl-4-phenylpyridinium ion (MPP⁺) on acetylcholinesterase (AchE) activity was investigated. The MPP⁺ was found to inactivate the enzyme in a dose dependent manner. The kinetic parameter, K_m for the substrate (acetylthiocholine), was found to be 0.216 mM and K_i for MPP⁺ for the inactivation of AChE was found to be 0.197 mM. It was found that MPP⁺ is neither a substrate of AChE nor the time-dependent inactivator. The studies of reaction kinetics indicate inactivation of AChE to be a linear mixed-type inhibition. The inactivation of AChE by MPP⁺ was partially recovered by either dilution or gel exclusion chromatography. These data suggest that once MPP⁺ enters the basal ganglia of the brain, it can inactivate the AChE and thereby increase the acetylcholine level in the basal ganglia, leading to potential cell dysfunction. It appears likely that the nigrostriatal toxicity by MPP⁺ leading to Parkinson's disease-like syndrome may, in part, be mediated via the AChE inactivation.     

Immunization of syngeneic mice against malignant melanoma with subcellular membrane fractions of a bromodeoxyuridine-grown variant

Summary Syngeneic C57BL/6 mice immunized with non-tumorigenic B16 melanoma cells and crude membrane fractions are able to reject challenge with the tumorigenic B₅59 parent clone. The immunogenic C₃471 variant was derived from the malignant B₅59 clone by continuous growth in the presence of 1 g 5-bromodeoxyuridine (BrdUrd)/ml. Fifty-one percent (35 of 69) of mice immunized by three inoculations of 10⁶ cell equivalents of C₃471 crude membranes (CM) isolated by nitrogen cavitation remained tumor-free for at least 50 days after challenge with a tumorigenic dose of B₅59 cells. This compares favorably with the virtually 100% protection evoked by 10⁶ viable C₃471 cells. For those CM-immunized mice failing to reject B₅59 challenge, the mean latent period for tumor formation was significantly increased (P0.001) over controls. In addition, mice immunized with cultured C₃471 cells were able to reject, with equal efficiency, challenge with either cultured or tumor-derived B₅59 cells, indicating that the immunogen(s) present on C₃471 cells and CMs was (were) not a tissue culture artifact. Freshly prepared syngeneic fascia cells and membranes as well as CM prepared from cultured malignant B₅59 cells had no tumor rejection activity. In vivo tumor rejection activity in plasma membrane vesicles prepared from C₃471 cells by formaldehyde treatment also demonstrated tumor rejection activity. The host response to CMs, as to C₃471 cells, could be transferred by lymphoid cells from mice immunized with C₃471 CMs or cells. Co-injection of leucocytes from CM-immunized mice together with a tumorigenic dose of B₅59 cells into immunocompetent syngeneic mice resulted in abrogation of B₅59 tumorigenicity. The tumor rejection antigen(s) induced or increased by growth in BrdUrd has not yet been characterized biochemically, but is likely to involve a cell surface component common to both cell types and is retained by crude membrane fractions. The use of subcellular fractions from a spontaneous melanoma grown with BrdUrd, which elicits immunity against the malignant tumor, represents a model with immunoprophylactic potential for human neoplasia. Abbreviations used in this paper are: B16, melanoma of C57BL/6 mouse of spontaneous origin; B₅59, tumorigenic B16 clonal derivative; BrdUrd, 5-bromodeoxyuridine; C₃471, nontumorigenic BrdUrd-grown B16 clonal derivative; ceq, cell equivalents; CM, crude membrane; FBS, fetal bovine serum; MEM, minimal essential medium; MEMF, MEM containing 25 mM formaldehyde; MLP, mean latent period for tumor formation; MTV, mean tumor volume; pc, post challenge; PC, peritoneal cells; PMV, plasma membrane vesicles; TRA, tumor rejection antigen     

Changes in P2X<Subscript>3</Subscript> purinoceptors in sensory ganglia of the mouse during embryonic and postnatal development

The expression of the P2X₃ nucleotide receptor in embryonic day 14–18, postnatal day 1–14 and adult mouse sensory ganglia was examined using immunohistochemistry. Nearly all sensory neurons in dorsal root ganglia, trigeminal ganglia and nodose ganglia in embryos at embryonic day 14 expressed P2X₃ receptors, but after birth there was a gradual decline to about 50% of neurons showing positive immunostaining for P2X₃. In embryos there were only small neurons, while from postnatal day 7 both large and small neurons were present. Isolectin B₄ (IB₄)-positive neurons in dorsal, trigeminal and nodose ganglia did not appear until birth, but the numbers increased to about 50% by postnatal day 14 when a high proportion of IB₄-positive neurons were also positively labelled for the P2X₃ receptor. About 10% of neurons in dorsal, trigeminal and nodose ganglia were positive for calcitonin gene-related peptide in embryos, nearly all of which stained for P2X₃ receptors. This increased postnatally to about 35–40% in adults, although only a few colocalised with P2X₃ receptors. Neurofilament 200 was expressed in about 50% of neurons in trigeminal ganglia in the embryo, and this level persisted postnatally. All neurofilament 200-positive neurons stained for P2X₃ in embryonic dorsal root ganglia, trigeminal ganglia and nodose ganglia, but by adulthood this was significantly reduced. The neurons that were positive for calbindin in embryonic dorsal, trigeminal and nodose ganglia showed colocalisation with P2X₃ receptors, but few showed colocalisation postnatally.     

Acetylcholinesterase activity in neural crest cells of the early chick embryo

The appearance and distribution of AChE activity in the neural crest cells of the chick embryo were histochemically investigated. Prior to closure of the neural tube, neural crests were not demonstrated and most of the cells constituting the neural plate and the more lateral ectoderm were AChE-negative. With the closure of the neural tube, the neural crests assumed the form of a cell mass in its mid-dorsal portion and AChE activity was demonstrated in some elements of both tube and crests. The neural crest cells beginning to migrate ventrally or laterally were AChE-positive, and some showed intense enzymatic activity. Electron microscopically, the neural crest cells and the cells migrating from the neural crest displayed AChE activity in the cisternae of the nuclear envelope and in a few r-ER profiles, but were morphologically undifferentiated. As assessed by 3H-thymidine autoradiography, these cells possessed the potential to proliferate. These findings indicate that with the formation of the neural tube and neural crest, cells constituting these structures begin to differentiate with respect to AChE activity and that the enzyme appears in the neural crest cells before the onset of neuronal differentiation.     

Acetylcholinesterase activity in the myotome of the early chick embryo

Summary The myotome of early chick embryos was investigated histochemically by means of the acetylcholinesterase (AChE) reaction.Light-microscopically, at the cervical level, the myotome was first recognized and AChE activity demonstrated at stage 13 (2 day-old embryo). Subsequently, the myotome elongated ventro-laterally along the inner surface of the dermomyotome and reached the ventro-lateral end of the dermomyotome at stage 17 to 18 (3 day-old embryo). AChE activity in the myotome showed subsequent increase in intensity during the course of development. The myotome consisted mainly of AChE-positive cells displaying enzymatic activity along the nuclear membrane and within the cytoplasm. In contrast, almost all cells of the dermomyotome and the interstitial cells were AChE-negative.Electron-microscopically, the myotome cells of the 2 day-old embryo and the cells in the dorso-medial portion of the myotome of the 3 day-old embryo were morphologically undifferentiated; AChE activity was detected in the nuclear envelope and in single short profiles of the endoplasmic reticulum (ER). On the other hand, in the 3 day-old embryo the cells in the ventro-lateral portion of the myotome showed AChE activity in the nuclear envelope, numerous profiles of the ER and some Golgi complexes. These AChE-positive cells were regarded as developing myogenic cells based on their morphological characteristics.The present findings indicate (i) that the appearance of AChE activity in the cytoplasm is the first sign of the differentiation of myogenic cells, and (ii) that in these myogenic cells the increase in AChE activity is based on the development of the ER.     

Two-Site Immunoradiometric Assay of Chicken Acetylcholinesterase: Active and Inactive Molecular Forms in Brain and Muscle

Abstract: Several monoclonal antibodies were raised against chicken acetylcholinesterase (AChE; EC 3.1.1.7). Some of these antibodies react with quail AChE but not with AChEs from nonavian vertebrates or invertebrates and not with butyrylcholinesterase. They may be classified in several mutually compatible groups, i.e., that can bind simultaneously to the monomeric form of AChE. Most antibodies recognize a peptidic domain that does not exist in mammalian AChE and that may be digested by trypsin without loss of activity or dissociation of quaternary structure. The only exception is the antibody C-131, which is conformation dependent and preferentially recognizes active AChE. We have set up two-site immunoradiometric assays, using an immobilized capture antibody, C-6 or C-131, and a radiolabeled antibody, ¹²⁵I-C-54. The C-6/C-54 assay quantifies the totality of inactive and active AChE subunits: It detects 10^?3 Ellman unit (～40 pg of protein) and yields a linear response up to at least 25 10^?3 Ellman units. An analysis of gradient fractions, using C-6/C-54 and C-131/C-54 assays as well as activity determination, shows that the A₁₂ and G₄ forms are exclusively composed of active subunits, whereas inactive molecules cosediment with the active G₂ and G₁ forms. Both active and inactive G₂ and G₁ forms are amphiphilic, as indicated by the influence of detergents on their sedimentation coefficients and Stokes radii. In brain, the proportion of inactive forms decreases from 40% at embryonic day 11 (E11) to 20% at birth [day 1 (D1)]. In muscle, we observed no inactive AChE at E11 and a small proportion of inactive G₁ at D1. The proportion of inactive forms was much higher in cultured myotubes, obtained from E11 myoblasts. These results show that the proportion of inactive AChE depends on the tissue and varies during development. Thus, the cells seem to control actively the acquisition of AChE activity, as well as the formation of the various oligomeric forms.     

Inactivation of acetylcholinesterase by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride

The neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been shown to reversibly inhibit the activity of acetylcholinesterase. The inactivation of the enzyme was detected by monitoring the accumulation of yellow color produced from the reaction between thiocholine and dithiobisnitrobenzoate ion. The kinetic parameter, K _m for the substrate (acetylthiocholine), was found to be 0.216 mM and K _i for MPTP inactivation of acetylcholinesterase was found to be 2.14 mM. The inactivation of enzyme by MPTP was found to be dose-dependent. It was found that MPTP is neither a substrate of AChE nor the time-dependent inactivator. The studies of reaction kinetics indicate the inactivation of AChE to be a linear mixed-type inhibition. The dilution assays indicate that MPTP is a reversible inhibitor for AChE. These data suggest that once MPTP enters the basal ganglia of the brain, it can inactivate the acetylcholinesterase enzyme and thereby increase the acetylcholine level in the basal ganglia of brain, leading to potential cell dysfunction. It appears that the nigrostriatal toxicity by MPTP leading to Parkinson's disease-like syndrome may, in part, be mediated via the acetylcholinesterase inactivation.     

Design,synthesis and biological evaluation of coumarin derivatives as novel acetylcholinesterase inhibitors that attenuate H2O2-induced apoptosis in SH-SY5Y cells

A novel series of coumarin derivatives were designed, synthesized and investigated for inhibition of cholinesterase, including acetyl cholinesterase (AChE) and butyrylcholinesterase (BuChE). This biological study showed that these compounds containing piperazine ring had significant inhibition activities on AChE rather than BuChE. Further study suggested that 9x, as one of this kind of structure derivative, showed the strongest inhibition activity on AChE with an IC₅₀ value of 34 nM. Moreover, molecular docking, flow cytometry (FCM), and western blot assay suggested that 9x could induce cytoprotective autophagy to attenuate H₂O₂-induced cell death in human neuroblastoma SH-SY5Y cells. These findings highlight a new approach for the development of a novel potential neuroprotective compound targeting AChE with autophagy-inducing activity in future Alzheimer’s disease (AD) therapy.     

Cellular expression patterns of acetylcholinesterase activity during grasshopper development

We examined the expression of acetylcholinesterase (AChE) in the nervous system and epidermal body structures during embryonic and larval development of two grasshopper species: Locusta migratoria and Schistocerca americana. Histochemical labelling was blocked by the enzyme inhibitors eserine and BW284c51, but not by iso-OMPA, showing that the staining reflected true AChE activity. The majority of staining was localized on the cell surface but granular intracellular staining was also visible in many cell bodies. In both species, the cellular expression of AChE followed a similar but complex spatiotemporal staining pattern. Initially, mainly epidermal tissue structures were stained in the various body appendages (stages 25%–30%). Labelling subsequently appeared in outgrowing neurons of the central nervous system (CNS) and in the nerves innervating the limbs and dorsal body wall (stages 30%–40%). The latter staining originated in motoneurons of the ventral nerve cord. In a third phase (after 45%), the somata of certain identified mechanosensory neurons started to express AChE activity, presumably reflecting cholinergic differentiation. Staining was also found in repo-positive glial cells of the CNS, longitudinal glia of connectives, glia of the stomatogastric nervous system and glial cells ensheathing peripheral nerves. Glial cells remained AChE-positive during larval to adult development, whereas motoneurons lost their AChE expression. The expression pattern in non-neuronal cells and glutamatergic motoneurons and the developmental appearance of AChE prior to synaptogenesis in the CNS suggest non-cholinergic functions of AChE during grasshopper embryogenesis. Financial support was provided by the Deutsche Forschungsgemeinschaft (Bi 262/7-1 and 262/11-1)     

Differential effects of denervation on acetylcholinesterase activity in parasympathetic and sympathetic ganglia of the frog, Rana pipiens

The transsynaptic regulation of acetylcholinesterase (AChE) was studied by recording the changes in enzymatic activity following denervation in two types of autonomic ganglia in the frog, Rana pipiens. Opposite effects on AChE were found in the parasympathetic cardiac ganglion and in the sympathetic lumbar ganglion; denervation produced a significant increase in AChE activity in cardiac ganglia but a significant decrease in lumbar ganglia. The relative effects of denervation on intracellular and total AChE were examined by selectively inhibiting extracellular AChE with echothiophate, a poorly lipid-soluble cholinesterase inhibitor. Denervation resulted in a significant increase in intracellular AChE in cholinergic cardiac ganglia but had no effect on intracellular AChE activity in adrenergic lumbar ganglia. Histochemical studies revealed little change in extracellular AChE staining upon denervation in the cardiac ganglion, whereas in the lumbar ganglia there was a loss of AChE-specific reaction product. These results raise the possibility that the transsynaptic control of AChE activity by innervation in the frog is influenced by the transmitter synthetic properties of the postsynaptic ganglion cells.     

Histo- and immunocytochemical characterization of the neurons of the mucosal plexus in the rat colon.

The mucosal plexus of the rat colon descendens is constituted of a network of nerves that, in contrast to most other segments of the digestive tract, contains also ganglia. The ganglia, consisting of neurons and glial cells, are located in the basal part of the lamina propria at distances between 100 and 1,200 microns. They are not vascularized. The neurons in these ganglia were characterized by means of: (1) the histochemical demonstration of acetylcholinesterase (AChE) activity, (2) the immunocytochemical identification of neurofilament proteins (NFP; 200 kD) and (3) their ultrastructure. The glial cells, which were AChE negative, could be distinguished from the neurons by differences in size and chromatin pattern. All neurons of the mucosal plexus reveal AChE activity in the perikaryon, but only parts of the axons are AChE positive. NFP-like immunoreactivity was detected in the perikarya but only in a minor part of the axons. These findings confirm previous light-microscopical observations and add new evidence for the existence of neurons (ganglia) in the mucosal plexus of the rat colon.     

Lectin-induced apoptosis of tumour cells

The mechanisms of cytotoxic activity of Griffonia simplicifolia1-B₄ (GS1B₄) and wheat germ agglutinin (WGA) lectins againstvarious murine tumour cell lines were studied. Tumour cellsthat lack lectin-binding carbohydrates were resistant to lysisby these lectins. However, YAC-1 cells that expressed GS1B⁴lectin-binding sites showed low sensitivity to lysis. To furtheranalyse the relative importance of cell surface carbohydratesin lectin cytotoxicity, BL6–8 melanoma cells, which donot express the     

Neuropathological effect of carbamate molluscicides on the land snail, <Emphasis Type="Italic">Eobania vermiculata</Emphasis>

The present study was designed to investigate the neuropathological effect of the two carbamate pesticides: methomyl and methiocarb on the neurons of the buccal ganglia in the land snail Eobania vermiculata using topical application and baiting technique. Their in vivo effects on acetylcholinesterase (AChE, EC 3.1.1.7) activity were also investigated. Sublethal dose and concentration (1/4 LD₅₀ and 1/4 LC₅₀) of both pesticides were used, and the experiment lasted for 14 days. Histopathological and ultrastuctural alterations in the buccal ganglia were more obvious after the baiting technique treatment than after the topical application method, and methomyl was found to be more toxic than methiocarb. These alterations included shrinkage of the perikarya of neurons, increased cytoplasmic basophilia, and extreme indentation of the plasma membrane. In addition, the nuclei appeared karyolitic, eccentric, and highly shrunken with an irregular nuclear envelope. The most outstanding symptom observed after topical application of methiocarb was a highly vacuolated cytoplasm with a peripheral increase in electron density associated with dense accumulations of free ribosomes. On the other hand, an increased number of lysosomes and autophagosomes were observed after topical application of methomyl. Mitochondrial damage, increased number of lipid droplets, and myelin figures were frequently observed in ganglia treated with either methomyl or methiocarb. Moreover, it was noticed that both compounds induced reductions in AChE activity. However, methomyl exhibited more potency in reducing AChE activity than methiocarb.     

Effect of synthetic bag cell and atrial gland peptides on identified nerve cells in Aplysia

We have examined the effects of peptides on the neuroendocrine bag cells, the R2 neuron and the left upper quadrant (LUQ) neurons of the abdominal ganglion of Aplysia californica. Peptides include those extracted from the atrial gland, a reproductive organ; those released by an afterdischarge of the bag cells; and 2 synthetic peptides: the amidated 9-amino acid C-terminal portion of atrial gland peptides A/B/ERH (B_26–34), and the 8-amino acid alpha-bag cell peptide (α-BCP_1–8). Peptides were applied by superfusion, arterial perfusion, pressure ejection from micropipettes, or by inducing a bag cell afterdischarge. Both α-BCP_1–8 and B_26–34 are able to produce a bag cell afterdischarge when applied to the abdominal ganglion but are not as effectively able to trigger the bag cells when applied selectively to the ganglia of the head ring. Peptides released by the bag cells inhibit R2 and LUQ neurons; whereas atrial gland extract mildly excites LUQ neurons and powerfully excites R2. The inhibitory effect of the LUQ cells and R2 following an afterdischarge of the bag cells in mimicked by α-BCP_1–8. The excitatory effect of the atrial gland extract cannot be duplicated with B_26–34. Rather, instead of having an excitatory effect on R2 and LUQ cells, B_26–34 seems to mimick α-BCP_1–8 and inhibit these neurons. Both peptides produce a membrane conductance increase in R2 and LUQ cells.