Competition and disturbance affect elevational distribution of two congeneric conifers.

Climatic change will affect elevational vegetation distribution because vegetation distribution is related to thermal conditions. However, how elevational species distributions are determined by biotic and abiotic factors is not clear. The long-term plot census along an elevational gradient is indispensable to clarify mechanisms of elevational distribution of tree species. Two congeneric conifers, the less shade-tolerant Abies veitchii and shade-tolerant A. mariesii, dominate at low and high elevations, respectively, in the subalpine zone in Japan. This study investigated the population dynamics of the two species at three elevations (low, middle, high) for 13 years to examine why the two species dominated the different elevations from the viewpoints of competition and disturbance. This study showed that growth and survival rates were not highest at the most dominant elevations for each species. At the high elevation where A. mariesii dominated and small disturbances frequently occurred, the recruitment rate of A. mariesii was highest among the three elevations and that of A. veitchii was largely decreased by tree competition. However, A. veitchii was dominant earlier than A. mariesii at the low elevation after large disturbances by the high growth rate of individual trees. Therefore, A. mariesii was superior to A. veitchii at the high elevation because of its high recruitment rate and large reduction of recruitment of A. veitchii due to competition, while A. veitchii was superior to A. mariesii at the low elevation after large disturbances because of higher growth rate than A. mariesii. It is suggested that the elevational distributions of the two species were determined by elevational changes in population dynamics in relation to competition and disturbance. Long-term observational studies of forest dynamics among various elevations are indispensable to predict the effects of climatic change on vegetation distribution.

Identification and classification of innexin gene transcripts in the central nervous system of the terrestrial slug Limax valentianus.

Intercellular gap junction channels and single-membrane channels have been reported to regulate electrical synapse and the brain function. Innexin is known as a gap junction-related protein in invertebrates and is involved in the formation of intercellular gap junction channels and single-cell membrane channels. Multiple isoforms of innexin protein in each species enable the precise regulation of channel function. In molluscan species, sequence information of innexins is still limited and the sequences of multiple innexin isoforms have not been classified. This study examined the innexin transcripts expressed in the central nervous system of the terrestrial slug Limax valentianus and identified 16 transcripts of 12 innexin isoforms, including the splicing variants. We performed phylogenetic analysis and classified the isoforms with other molluscan innexin sequences. Next, the phosphorylation, N-glycosylation, and S-nitrosylation sites were predicted to characterize the innexin isoforms. Further, we identified 16 circular RNA sequences of nine innexin isoforms in the central nervous system of Limax. The identification and classification of molluscan innexin isoforms provided novel insights for understanding the regulatory mechanism of innexin in this phylum.

FxRIamide regulates the oscillatory activity in the olfactory center of the terrestrial slug Limax.

The terrestrial slug Limax acquires odor-aversion memory. The procerebrum is the secondary olfactory center in the brain of Limax, and functions as the locus of the memory formation and storage. The change in the local field potential oscillation in the procerebrum reflects the information processing of the learned odor. However, it is not fully understood what factors, intrinsic or extrinsic in the procerebrum, alter the oscillatory activity and how it is regulated. In the present study, we found that FxRIamide (Phe-x-Arg-Ile-NH2), which was previously identified as a myomodulatory peptide in the gastropod Fusinus ferrugineus, downregulates the oscillatory frequency of the local field potential oscillation in the procerebrum of Limax. FxRIamide peptides were encoded by two distinct transcripts, which exhibit partially overlapping expression patterns in the brain. Immunohistochemical staining revealed a scattered distribution of FxRIamide-expressing neurons in the cell mass layer of the procerebrum, in addition to the ramified innervation of FxRIamidergic neurons in the neuropile layers. Down-regulation of the oscillatory frequency of the local field potential was explained by the inhibitory effects of FxRIamide on the bursting neurons, which are the kernels of the local field potential oscillation in the procerebrum. Our study revealed the previously unidentified role of FxRIamide peptides in the network of interneurons of Limax, and these peptides may play a role in the mnemonic functions of the procerebrum.

Distribution and physiological effect of enterin neuropeptides in the olfactory centers of the terrestrial slug Limax.

In gastropods, the function of neuropeptides has been studied primarily in the peripheral motor systems. Their functional roles in the central nervous system have received less attention. The procerebrum, the secondary olfactory center of the terrestrial slug Limax, consists of several hundred thousand interneurons, and plays a pivotal role in olfactory learning and memory. In the present study, we found that enterin, known as a myoactive peptide functioning in the enteric and vascular system of Aplysia, is expressed in the procerebrum of Limax. These enterin-expressing neurons primarily make projections within the cell mass layer of the procerebrum. The oscillatory frequency of the local field potential in the procerebrum was reduced by an exogenous application of enterin. The local field potential oscillation in the tentacular ganglion, the primary olfactory center, was also modulated by enterin. Whole-cell patch-clamp recordings revealed that the modulatory effect in the procerebrum was due to the inhibitory effect of enterin on the bursting neurons, which function as the kernels determining the oscillatory activity of the procerebrum. Our results revealed the novel role of the myoactive neuropeptide enterin in the higher olfactory function in terrestrial gastropods.

Effects of propofol on IPSCs in CA1 and dentate gyrus cells of rat hippocampus: Propofol effects on hippocampal cells' IPSCs.

Propofol (2, 6-diisopropylphenol) is one of the most popular intravenous anesthetic agents. In this study, we compared the effects of propofol on inhibitory postsynaptic currents (IPSCs) induced by single and paired electrical stimulations in CA1 pyramidal cells (CA1-PCs) and dentate gyrus granule cells (DG-GCs) in rat hippocampal slices using the whole cell patch-clamp technique. In the absence of propofol, the amplitude of evoked IPSC by single stimulation and decay time constants were stable in both CA1-PCs and DG-GCs for 30 min. Propofol (1 µM and 10 µM) increased both IPSC amplitude in CA1-PCs, but not in DG-GCs. Further, using a paired pulse stimulation protocol, the ratio of IPSC amplitudes (the second response: A2/the first response: A1) was increased by propofol in CA1, but not in DG-GCs. These results suggest that propofol selectively affects IPSCs in CA1-PCs, which is similar to previously reported actions of benzodiazepines.

Concept of dual-resolution light field imaging using an organic photoelectric conversion film for high-resolution light field photography.

Light field imaging is an emerging technique that is employed to realize various applications such as multi-viewpoint imaging, focal-point changing, and depth estimation. In this paper, we propose a concept of a dual-resolution light field imaging system to synthesize super-resolved multi-viewpoint images. The key novelty of this study is the use of an organic photoelectric conversion film (OPCF), which is a device that converts spectra information of incoming light within a certain wavelength range into an electrical signal (pixel value), for light field imaging. In our imaging system, we place the OPCF having the green spectral sensitivity onto the micro-lens array of the conventional light field camera. The OPCF allows us to acquire the green spectra information only at the center viewpoint with the full resolution of the image sensor. In contrast, the optical system of the light field camera in our imaging system captures the other spectra information (red and blue) at multiple viewpoints (sub-aperture images) but with low resolution. Thus, our dual-resolution light field imaging system enables us to simultaneously capture information about the target scene at a high spatial resolution as well as the direction information of the incoming light. By exploiting these advantages of our imaging system, our proposed method enables the synthesis of full-resolution multi-viewpoint images. We perform experiments using synthetic images, and the results demonstrate that our method outperforms other previous methods.

Development of a one-run real-time PCR detection system for pathogens associated with bovine respiratory disease complex.

Bovine respiratory disease complex (BRDC) is frequently found in cattle worldwide. The etiology of BRDC is complicated by infections with multiple pathogens, making identification of the causal pathogen difficult. Here, we developed a detection system by applying TaqMan real-time PCR (Dembo respiratory-PCR) to screen a broad range of microbes associated with BRDC in a single run. We selected 16 bovine respiratory pathogens (bovine viral diarrhea virus, bovine coronavirus, bovine parainfluenza virus 3, bovine respiratory syncytial virus, influenza D virus, bovine rhinitis A virus, bovine rhinitis B virus, bovine herpesvirus 1, bovine adenovirus 3, bovine adenovirus 7, Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, Trueperella pyogenes, Mycoplasma bovis and Ureaplasma diversum) as detection targets and designed novel specific primer-probe sets for nine of them. The assay performance was assessed using standard curves from synthesized DNA. In addition, the sensitivity of the assay was evaluated by spiking solutions extracted from nasal swabs that were negative by Dembo respiratory-PCR for nucleic acids of pathogens or synthesized DNA. All primer-probe sets showed high sensitivity. In this study, a total of 40 nasal swab samples from cattle on six farms were tested by Dembo respiratory-PCR. Dembo respiratory-PCR can be applied as a screening system with wide detection targets.

Cacao bean husk: an applicable bedding material in dairy free-stall barns.

OBJECTIVE: The objectives of the study were to assess the effect of cacao bean husk as bedding material in free-stall barn on the behavior, productivity, and udder health of dairy cattle, and on the ammonia concentrations in the barn. METHODS: Four different stall surfaces (no bedding, cacao bean husk, sawdust, and chopped wheat straw) were each continuously tested for a period of 1 week to determine their effects on nine lactating Holstein cows housed in the free-stall barn with rubber matting. The lying time and the milk yield were measured between d 4 and d 7. Blood samples for plasma cortisol concentration and teat swabs for bacterial counts were obtained prior to morning milking on d 7. The time-averaged gas-phase ammonia concentrations in the barn were measured between d 2 and d 7. RESULTS: The cows spent approximately 2 h more per day lying in the stalls when bedding was available than without bedding. The milk yield increased in the experimental periods when cows had access to bedding materials as compared to the period without bedding. The lying time was positively correlated with the milk yield. Bacterial counts on the teat ends recorded for cows housed on cacao bean husk were significantly lower than those recorded for cows housed without bedding. Ammonia concentration under cacao bean husk bedding decreased by 6%, 15%, and 21% as compared to no bedding, sawdust, and chopped wheat straw, respectively. The cortisol concentration was lowest in the period when cacao bean husk bedding was used. We observed a positive correlation between the ammonia concentrations in the barn and the plasma cortisol concentrations. CONCLUSION: Cacao bean husk is a potential alternative of conventional bedding material, such as sawdust or chopped wheat straw, with beneficial effects on udder health and ammonia concentrations in the barns.

Octopaminergic system in the central nervous system of the terrestrial slug Limax.

The terrestrial slug Limax can learn to avoid the odor of some food (e.g., carrot juice) by the simultaneous presentation of an aversive stimulus (e.g., bitterness of quinidine). This type of associative memory critically depends on the higher olfactory center, the procerebrum in the central nervous system. The modulation of the local field potential (LFP) oscillation recorded on the procerebrum has been thought to reflect the information processing of the odor that elicits the behavioral change, such as avoidance of the aversively learned odor or approaching an attractive food's odor. Here we focused on octopamine, an important neuromodulator involved in learning and memory in invertebrates, and considered to be the invertebrate equivalent of noradrenaline. We identified a few octopaminergic neurons in the subesophageal and buccal ganglia, and a larger number near the procerebrum in the cerebral ganglia, using immunohistochmical staining and in situ hybridization of tyramine ß-hydroxylase, an octopamine-synthesizing enzyme. Application of octopamine reduced the frequency of LFP oscillation in a dose-dependent manner, and this effect was inhibited by preincubation with phentolamine. High-performance liquid chromatography analysis revealed the presence of octopamine, noradrenaline, and adrenaline in the central nervous system. Unexpectedly, noradrenaline and adrenaline both accelerated the LFP oscillation, in contrast to octopamine. Our results suggest that octopamine and noradrenaline have distinct functions in olfactory information processing, in spite of their structural similarity. J. Comp. Neurol. 524:3849-3864, 2016. © 2016 Wiley Periodicals, Inc.

Development of a novel detection system for microbes from bovine diarrhea by real-time PCR.

Diarrhea in cattle is one of the most economically costly disorders, decreasing milk production and weight gain. In the present study, we established a novel simultaneous detection system using TaqMan real-time PCR designed as a system for detection of microbes from bovine diarrhea using real-time PCR (referred to as Dembo-PCR). Dembo-PCR simultaneously detects a total of 19 diarrhea-causing pathogens, including viruses, bacteria and protozoa. Specific primer-probe sets were newly designed for 7 pathogens and were synthesized on the basis of previous reports for 12 pathogens. Assays were optimized to react under the same reaction conditions. The PCR efficiency and correlation coefficient (R(2)) of standard curves for each assay were more than 80% and 0.9766, respectively. Furthermore, the sensitivity of Dembo-PCR in fecal sample analysis was measured with feces spiked with target pathogens or synthesized DNA that included specific nucleotide target regions. The resulting limits of detection (LOD) for virus-spiked samples, bacteria and DNA fragments were 0.16-1.6 TCID50 (PFU/reaction), 1.3-13 CFU/reaction and 10-100 copies/reaction, respectively. All reactions showed high sensitivity in pathogen detection. A total of 8 fecal samples, collected from 6 diarrheic cattle, 1 diarrheic calf and 1 healthy cow, were tested using Dembo-PCR to validate the assay's clinical performance. The results revealed that bovine coronavirus had infected all diarrheic adult cattle and that bovine torovirus had infected the diarrheic calf. These results suggest that Dembo-PCR may be a powerful tool for diagnosing infectious agents in cattle diarrhea.

Distribution of histaminergic neurons and their modulatory effects on oscillatory activity in the olfactory center of the terrestrial slug Limax.

Terrestrial mollusks can form an odor aversion memory following the simultaneous presentation of a food odor and an aversive stimulus. The local field potential oscillation recorded on the surface of the procerebrum (PC; the higher olfactory center) exhibits a frequency change in response to the detection of a learned odor; such a change is thus considered to reflect the internal state of the brain during memory recall. Thus far, dopamine and serotonin have been demonstrated to change the oscillatory frequency. Other monoamines, however, have not yet been studied. In the present study, we investigated the possible involvement of histamine (HA). Immunohistochemical staining of HA and in situ hybridization against histidine decarboxylase revealed the location of the cell bodies of HAergic neurons in all ganglia of the brain. The majority of them were located at the medial aspect of the pedal ganglia, and the cerebral ganglia also contained numerous HAergic neurons in their posterior regions. The neuropil layers of the PC received HAergic innervation from the neurons in the cerebral ganglion, as well as from a few neurons located in the dorsomedial part of the cell mass layer of the PC. The HAergic fibers, however, innervated spatially limited regions of the PC, and seemed to affect a small fraction of the PC neurons. HA exerted accelerating effects on the LFP oscillation in a dose-dependent manner, and this effect was suppressed by an H2 blocker, cimetidine. Our results support the involvement of HA in the functioning of the PC.

Nitric Oxide-Mediated Modulation of Central Network Dynamics during Olfactory Perception.

Nitric oxide (NO) modulates the dynamics of central olfactory networks and has been implicated in olfactory processing including learning. Land mollusks have a specialized olfactory lobe in the brain called the procerebral (PC) lobe. The PC lobe produces ongoing local field potential (LFP) oscillation, which is modulated by olfactory stimulation. We hypothesized that NO should be released in the PC lobe in response to olfactory stimulation, and to prove this, we applied an NO electrode to the PC lobe of the land slug Limax in an isolated tentacle-brain preparation. Olfactory stimulation applied to the olfactory epithelium transiently increased the NO concentration in the PC lobe, and this was blocked by the NO synthase inhibitor L-NAME at 3.7 mM. L-NAME at this concentration did not block the ongoing LFP oscillation, but did block the frequency increase during olfactory stimulation. Olfactory stimulation also enhanced spatial synchronicity of activity, and this response was also blocked by L-NAME. Single electrical stimulation of the superior tentacle nerve (STN) mimicked the effects of olfactory stimulation on LFP frequency and synchronicity, and both of these effects were blocked by L-NAME. L-NAME did not block synaptic transmission from the STN to the nonbursting (NB)-type PC lobe neurons, which presumably produce NO in an activity-dependent manner. Previous behavioral experiments have revealed impairment of olfactory discrimination after L-NAME injection. The recording conditions in the present work likely reproduce the in vivo brain state in those behavioral experiments. We speculate that the dynamical effects of NO released during olfactory perception underlie precise odor representation and memory formation in the brain, presumably through regulation of NB neuron activity.

The cholinergic system in the olfactory center of the terrestrial slug Limax.

Acetylcholine plays various important roles in the central nervous system of invertebrates as well as vertebrates. In the olfactory center of the terrestrial slug Limax, the local field potential (LFP) oscillates, and the change in its oscillatory frequency is thought to correlate with the detection of odor that potentially changes an ongoing behavior of the animal. Acetylcholine is known to upregulate the frequency of the LFP oscillation, and is one of the candidates for the neurotransmitters that are involved in such higher cognitive functions. However, there have been no histological data on the cholinergic system in gastropods, nor are there data on the receptors that are responsible for the upregulation of the oscillatory frequency of LFP due to the lack of analytical tools (such as antibodies or cDNA sequence information on cholinergic system-related genes). Here we cloned the cDNAs of choline acetyltransferase (ChAT), acetylcholinesterase, vesicular acetylcholine transporter, and several nicotinic acetylcholine receptors (nAChRs), and investigated their localization in the brain of Limax. We also generated a polyclonal antibody against ChAT to examine its localization, and investigated pharmacologically the involvement of nAChRs in the LFP oscillation. Our data showed: 1) dense distribution of the neurons expressing mRNAs of ChAT and vesicular acetylcholine transporter in the olfactory center; 2) spatially unique expression patterns of different nAChRs in the olfactory center; 3) involvement of nAChRs in the upregulation of the oscillation; 4) localization of ChAT protein in nerve fibers and/or terminals; and 5) the presence of cholinergic nerves in the tentacles.

Involvement of insulin-like peptide in long-term synaptic plasticity and long-term memory of the pond snail Lymnaea stagnalis.

The pond snail Lymnaea stagnalis is capable of learning taste aversion and consolidating this learning into long-term memory (LTM) that is called conditioned taste aversion (CTA). Previous studies showed that some molluscan insulin-related peptides (MIPs) were upregulated in snails exhibiting CTA. We thus hypothesized that MIPs play an important role in neurons underlying the CTA-LTM consolidation process. To examine this hypothesis, we first observed the distribution of MIP II, a major peptide of MIPs, and MIP receptor and determined the amounts of their mRNAs in the CNS. MIP II was only observed in the light green cells in the cerebral ganglia, but the MIP receptor was distributed throughout the entire CNS, including the buccal ganglia. Next, when we applied exogenous mammalian insulin, secretions from MIP-containing cells or partially purified MIPs, to the isolated CNS, we observed a long-term change in synaptic efficacy (i.e., enhancement) of the synaptic connection between the cerebral giant cell (a key interneuron for CTA) and the B1 motor neuron (a buccal motor neuron). This synaptic enhancement was blocked by application of an insulin receptor antibody to the isolated CNS. Finally, injection of the insulin receptor antibody into the snail before CTA training, while not blocking the acquisition of taste aversion learning, blocked the memory consolidation process; thus, LTM was not observed. These data suggest that MIPs trigger changes in synaptic connectivity that may be correlated with the consolidation of taste aversion learning into CTA-LTM in the Lymnaea CNS.

Organization of the procerebrum in terrestrial pulmonates (Helix, Limax) reconsidered: cell mass layer synaptology and its serotonergic input system.

The synaptology of the cell body layer of the olfactory center, procerebrum, was investigated in two prominent terrestrial pulmonate gastropod species, Helix pomatia and Limax valentianus. In addition, the analysis of the 5-HT-immunoreactive innervation, including ultrastructural level, was performed at high resolution in H. pomatia. A highly complex system of synaptic and non-synaptic connections was found in the procerebrum of both species connected to local neuropil areas of different size. The procerebral (globuli) cell perikarya were richly innervated by varicosities meanwhile the axon profiles also established contacts with each other. Synaptic configurations including convergence, divergence and presynaptic modulation were also revealed. The frequent occurrence of unspecialized but close axo-somatic and axo-axonic membrane contacts referring to the modulatory forms of transmitter release were also accompanied by membrane configurations indicative of active exocytosis. In H. pomatia, the cell mass layer was shown to receive a rich 5-HT-immunoreactive innervation, forming a dense network around the cell bodies. At ultrastructural level, 5-HT-immunoreactive varicosities contacted both cell bodies and different unlabeled axon profiles. Our results suggest that the local neuropil regions in the cell body layer are site of local circuits, which may play a decisive role in olfactory integrative processes bound to the procerebrum. The pattern and form of the 5-HT-immunoreactive innervation of extrinsic origin suggest an overall modulatory role in the cell body layer. The results may serve a basis for considering the role of local intercellular events, connected to microcircuits, within the procerebrum cell body layer involved in oscillation activities.

Memory trace in feeding neural circuitry underlying conditioned taste aversion in Lymnaea.

BACKGROUND: The pond snail Lymnaea stagnalis can maintain a conditioned taste aversion (CTA) as a long-term memory. Previous studies have shown that the inhibitory postsynaptic potential (IPSP) evoked in the neuron 1 medial (N1M) cell by activation of the cerebral giant cell (CGC) in taste aversion-trained snails was larger and lasted longer than that in control snails. The N1M cell is one of the interneurons in the feeding central pattern generator (CPG), and the CGC is a key regulatory neuron for the feeding CPG. METHODOLOGY/PRINCIPLE FINDINGS: Previous studies have suggested that the neural circuit between the CGC and the N1M cell consists of two synaptic connections: (1) the excitatory connection from the CGC to the neuron 3 tonic (N3t) cell and (2) the inhibitory connection from the N3t cell to the N1M cell. However, because the N3t cell is too small to access consistently by electrophysiological methods, in the present study the synaptic inputs from the CGC to the N3t cell and those from the N3t cell to the N1M cell were monitored as the monosynaptic excitatory postsynaptic potential (EPSP) recorded in the large B1 and B3 motor neurons, respectively. The evoked monosynaptic EPSPs of the B1 motor neurons in the brains isolated from the taste aversion-trained snails were identical to those in the control snails, whereas the spontaneous monosynaptic EPSPs of the B3 motor neurons were significantly enlarged. CONCLUSION/SIGNIFICANCE: These results suggest that, after taste aversion training, the monosynaptic inputs from the N3t cell to the following neurons including the N1M cell are specifically facilitated. That is, one of the memory traces for taste aversion remains as an increase in neurotransmitter released from the N3t cell. We thus conclude that the N3t cell suppresses the N1M cell in the feeding CPG, in response to the conditioned stimulus in Lymnaea CTA.

Excitatory effects of GABA on procerebrum neurons in a slug.

Classical neurotransmitters, such as glutamate and γ-aminobutyric acid (GABA), often have different actions on invertebrate neurons from those reported for vertebrate neurons. In the terrestrial mollusk Limax, glutamate was found to function as an inhibitory transmitter in the procerebrum (PC), but it has not yet been clarified how GABA acts in the PC. We thus examined what effects GABA exerts on PC neurons in the present study. For this purpose, we first applied GABA to isolated PC preparations and recorded postsynaptic currents and potentials in PC neurons. The GABA application reduced the amplitude of inhibitory postsynaptic currents and depolarization-induced outward currents recorded in nonbursting neurons and increased the number of spontaneous spikes of nonbursting neurons. However, direct GABA-induced currents were not observed in either bursting or nonbursting neurons. These results suggest a potential direct effect of GABA on outward currents resulting in enhanced excitability of PC neurons. Next, we measured the change in [Ca(2+)](i) in cultured PC neurons by application of GABA. The GABA application increased spontaneous Ca(2+) events in cultured neurons. These Ca(2+) events were ascribable to the influx of extracellular Ca(2+). We then confirmed the presence of GABA and GABA receptors in the PC. The GABA-like immunoreactivity was observed in the neuropil layers of the PC, and the mRNAs for both GABA(A) and GABA(B) receptors were expressed in the PC. In particular, GABA(B) receptor mRNA, rather than GABA(A), was found to be more abundantly expressed in the PC. These results suggest that GABA functions as an excitatory modulator for PC neurons via mainly GABA(B) receptors.

Multiple subtypes of serotonin receptors in the feeding circuit of a pond snail.

In the central nervous system of the pond snail Lymnaea stagnalis, serotonergic transmission plays an important role in controlling feeding behavior. Recent electrophysiological studies have claimed that only metabotropic serotonin (5-HT(2)) receptors, and not ionotropic (5-HT(3)) receptors, are used in synapses between serotonergic neurons (the cerebral giant cells, CGCs) and the follower buccal motoneurons (the B1 cells). However, these data are inconsistent with previous results. In the present study, we therefore reexamined the serotonin receptors to identify the receptor subtypes functioning in the synapses between the CGCs and the B1 cells by recording the compound excitatory postsynaptic potential (EPSP) of the B1 cells evoked by a train of stimulation to the CGC in the presence of antagonists: cinanserin for 5-HT(2) and/or MDL72222 for 5-HT(3). The compound EPSP amplitude was partially suppressed by the application of these antagonists. The rise time of the compound EPSP was longer in the presence of MDL72222 than in that of cinanserin. These results suggest that these two subtypes of serotonin receptors are involved in the CGC-B1 synapses, and that these receptors contribute to compound EPSP. That is, the fast component of compound EPSP is mediated by 5-HT(3)-like receptors, and the slow component is generated via 5-HT(2)-like receptors.

Expression of Asn-d-Trp-Phe-NH2 in the brain of the terrestrial slug Limax valentianus.

The tripeptide Asn-d-Trp-Phe-NH(2) (NdWFamide) is a D-amino acid-containing cardioexcitatory peptide initially isolated from Aplysia. Previously we detected NdWFamide immunoreactivity in the visceral giant cells, the largest neurons in the brain of the terrestrial slug Limax located at the dorsal surface of the visceral ganglia. In the present study, we further analyzed the morphological features of these neurons by an intracellular injection of Lucifer yellow, and found that these neurons extend neurites out of the brain through at least 5 nerve bundles. We then isolated a gene and a cDNA clone potentially encoding a NdWFamide precursor, and investigated expression at the levels of mRNA and protein in Limax. The NdWFamide gene consists of 5 exons spanning at least 17 kb of the genome, and its open reading frame extends over 3 exons. The spatial expression pattern of NdWFamide mRNA was almost identical to that of the NdWFamide peptide, with some minor discrepancies in between. Although the most remarkable expression was evident in the visceral giant cells, we also found the expression of NdWFamide mRNA and peptide in the cerebral and pedal ganglia. These results suggest the involvement of NdWFamide in the regulation of a broad area of the slug's body.

Two pairs of tentacles and a pair of procerebra: optimized functions and redundant structures in the sensory and central organs involved in olfactory learning of terrestrial pulmonates.

Terrestrial pulmonates can learn olfactory-aversion tasks and retain them in their long-term memory. To elucidate the cellular mechanisms underlying learning and memory, researchers have focused on both the peripheral and central components of olfaction: two pairs of tentacles (the superior and inferior tentacles) and a pair of procerebra, respectively. Data from tentacle-amputation experiments showed that either pair of tentacles is sufficient for olfactory learning. Results of procerebrum lesion experiments showed that the procerebra are necessary for olfactory learning but that either one of the two procerebra, rather than both, is used for each olfactory learning event. Together, these data suggest that there is a redundancy in the structures of terrestrial pulmonates necessary for olfactory learning. In our commentary we exemplify and discuss functional optimization and structural redundancy in the sensory and central organs involved in olfactory learning and memory in terrestrial pulmonates.