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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of an identified cerebrobuccal neuron containing the neuropeptide APGWamide (Ala-Pro-Gly-Trp-NH2) in the snailLymnaea stagnalis (1997)
    Springer
    Invertebrate neuroscience 2 (1997), S. 273-282 
    Details
    ISSN: 1439-1104
    Keywords: Lymnaea stagnalis ; feeding motor output ; molluscan nervous system ; neuropeptide ; APGWamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A bilaterally symmetrical pair of cerebrobuccal neurons inLymnaea stagnalis shows immunoreactivity for the molluscan neuropeptide APGWamide. The neuron somata are whitish in colour and located on the ventral surface of each cetebral ganglion between the roots of the labial nerves. A single axon travels via the ipsilateral cerebrobuccal connective into the buccal ganglia, where it gives rise to fine neuritic branching. Based upon these characteristics, the neuron has been named the cerebrobuccal white cell (CBWC). In isolated CNS preparations, in the absence of feeding motor output, the CBWC is silent and receives few, low amplitude, synaptic inputs. During generation of fictive feeding, the CBWC bursts in phase with cycles of feeding motor output. Tonic or phasic stimulation of CBWC leads to initiation of rhythmic feeding motor output. However, evoked bursts of activity in CBWC, which mimic its normal burst pattern, cannot entrain the buccal rhythm, suggesting that CBWC is not itself a major component of the feeding central pattern generator (CPG). Strong stimulation of CBWC during ongoing feeding motor output leads to a reduction in frequency and/or intensity of the buccal rhythm. Bath application of synthetic APGWamide (10−2 M −10−4 m) to the isolated CNS can activate feeding motor output in quiescent preparations after a delay, but disrupts ongoing buccal rhythms. This study represents the first description of a peptidergic cerebrobuccal neuron in the well described gastropod feeding system and also provides new information about the role of a novel molluscan neuropeptide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02211940
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  • 2
    Electronic Resource
    Electronic Resource
    Motor program switching inPleurobranchaea (1981)
    Springer
    Journal of comparative physiology 145 (1981), S. 277-287 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The gastropod molluskPleurobranchaea performs at least two distinct cyclic behaviours using its buccal musculature, namely ingestion of food and egestion of unpalatable objects. The movements and motor programs underlying each of these behaviours have been characterized by cinematography and electromyography in intact specimens. A third buccal movement of unknown behavioural significance, is also described. 2. Both ingestion and egestion entail cyclic protraction and retraction of the radula within the buccal mass at slightly different cycle frequencies (Table 1). Cinematography has revealed three principal differences in the respective movements (Figs. 1, 2): 1) during egestion, the radula protraction phase of the movement cycle (the functional power stroke) is proportionately longer in duration than protraction during ingestion (the functional return stroke); 2) during the retraction phase of ingestion the radula is medially folded and rolls inward, while during the retraction phase of egestion the radula is flattened and does not roll inward; 3) during ingestion the jaws close near the end of retraction, while during egestion the jaws close near the beginning of retraction. 3. The functional morphology of the buccal musculature was studied anatomically (Fig. 3) and physiologically (Table 2). Attention was focussed on seven muscles, two radula retractors, two protractors, a buccal constrictor, jaw closer and lip retractor. 4. Electromyograms (EMG's) from five of these muscles were made during ingestion, egestion and the third, undefined rhythm. Ingestion and egestion are characterized by reliable differences in EMG activity which are consistent with observed differences in the movements (Figs. 4–6, Tables 3 and 4). The EMG differences during egestion include: 1) a relative increase in protractor muscle discharge (duration and intensity); 2) reduction or elimination of discharge in the buccal constrictor, a muscle which contributes to radular folding; 3) increase in the activity of lip retractor and jaw closer muscles; 4) a phase advance of the jaw closer muscle in the retraction phase of the cycle. The respective motor programs for the different behaviours are summarized in bar diagrams (Fig. 7). 5. The results are consistent with the hypothesis that ingestion and egestion employ the same basic central nervous oscillator and motor neurons, with distinctions between these behaviours caused by shifts in the balance of activity in different motor pools.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00605040
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  • 3
    Electronic Resource
    Electronic Resource
    Plasticity of olfactory orientation to foods in the snailAchatina fulica (1980)
    Springer
    Journal of comparative physiology 136 (1980), S. 267-277 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Snails were tested in an olfactometer for their orientation to food odours. Measures of odour choice, latency to make a choice and percentage of upwind orientations were obtained after experimental manipulations of dietary experience and hunger motivation. Juvenile snails, given an exclusive diet of a certain food for 12 h or less, oriented preferentially toward the odour of that food when subsequently presented with a choice between it and a novel food odour (Fig. 2). A 48 h period of exposure to a food resulted in a 21 day retention of the odour preference (Fig. 3). There was no evidence for an especially sensitive period for conditioning during the first 50 days of age (Fig. 4); however, adult snails (minimum 1 year old) required longer periods of dietary exposure to establish equivalent food odour memories (Fig. 5). Measures of latency and percentage of upwind orientations confirmed the choice data in demonstrating an effect of dietary experiences on olfactory orientation. Hunger motivation increased the selection for familiar food odours, and reduced the latency (Fig. 6 and Tables 3 and 4). Sensory adaptation appears inadequate to explain the conditioning phenomenon since formation of the preferences was contingent upon ingestion of the foods; exposure to the food odours alone was insufficient (Table 2). The data suggest that orientation preferences derive from a learned association between the odour of a food and its nutritional value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657543
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  • 4
    Electronic Resource
    Electronic Resource
    Tentacular function in snail olfactory orientation (1981)
    Springer
    Journal of comparative physiology 143 (1981), S. 357-362 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The olfactory orienting behavior of the terrestrial snailAchatina fulica was studied in intact animals, in animals with bilateral lesions of either the anterior tentacles or the posterior tentacles, and in animals with unilateral lesions of the posterior tentacles. Tentacular function was evaluated under three different conditions. 2. One assay required the snails to locomote upwind in a two-armed olfactometer and enter the side in which the airstream contained a food odor. The performance of intact controls was statistically indistinguishable from that of snails with bilateral anterior tentacle lesions or snails with unilateral lesions of the posterior tentacles. Snails lacking both posterior tentacles performed at chance levels (Table 1). 3. The second assay consisted of trail following on a mucus slime trail. Bilateral posterior tentacle amputations were without effect, but bilateral amputations of the anterior tentacles led to a significant deficit compared to intact controls (Table 2). 4. The third assay measured the accuracy of locomotion to a distant odor source in still air. A circular arena was employed. Intact snails and snails with bilateral lesions of the anterior tentacles consistently oriented with a high degree of accuracy. Animals with unilateral or bilateral lesions of the posterior tentacles failed to orient. The unilateral amputations produced a turning bias towards the intact side (Fig. 2). 5. The results demonstrate thatAchatina can orient to olfactory stimuli by at least three different means, namely, anemotaxis, movement up a concentration gradient and trail following. The anterior and posterior tentacles are involved differentially in these behaviors. Also, anemotaxis requires only a single tentacle (klinotaxis), whereas orientation to concentration gradients utilizes simultaneous bilateral comparisons (tropotaxis) (Table 3).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00611173
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  • 5
    Electronic Resource
    Electronic Resource
    Motor program switching inPleurobranchaea (1982)
    Springer
    Journal of comparative physiology 147 (1982), S. 143-154 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Three distinct motor programs, namely ingestion, egestion and a third slower rhythm, have been identified in the buccal musculature of intact specimens of the gastropod molluscPleurobranchaea (Croll and Davis 1981). In the present study we have elicited each of these motor programs and characterized them in greater detail utilizing the technically more amenable reduced preparation, consisting of mouth, buccal mass, esophagus and attached central nervous system. 2. The ingestion motor program, rigorously identified by inward movement of objects placed in the buccal mass, is characterized by alternate bursts of activity in protractor and retractor muscles. The duration of the retraction phase of the cycle is longer than the duration of the protraction phase. The buccal constrictor muscle fires in phase with retractors. Salivary duct activity is in phase with protraction. In accordance with these muscle activities, the activity of buccal nerve root 3 is of longer duration and more intense than that of buccal root 1 during ingestion, and the salivary nerve is active in bursts during ingestion. The stomatogastric nerve fires cyclically in phase with retraction. 3. The egestion motor program, rigorously identified by outward movement of objects, is also characterized by alternate bursts of activity in protractor and retractor muscles. The egestion motor program differs from ingestion, however, in several specific respects. First, the duration of the protraction phase of the cycle is longer than the duration of the retraction phase. Second, the buccal constrictor muscle is silent during egestion. Third, the salivary duct is typically also silent during egestion. Fourth, the amplitude of recorded potentials from retractor muscles (m.1 and m.3) is significantly suppressed during egestion. Fifth, as would be expected, the activity of buccal nerve root 1 is longer and more intense than that of buccal root 3. Sixth, the salivary nerve is silent. Seventh, the stomatogastric nerve fires tonically rather than cyclically during egestion. 4. The ‘neutral’ or third buccal rhythm is generally significantly slower than ingestion or egestion, but is qualitatively similar in most respects to ingestion and dissimilar from egestion. 5. Stretching the esophagus induces the egestion motor program. This reflex is interpreted as a ‘clearance’ reflex which ensures egestion of objects too large to swallow. 6. Low-intensity stimulation of the stomatogastric nerve elicits a motor rhythm similar to ingestion but different from egestion. High-intensity stomatogastric nerve stimulation elicits the ingestion motor program, interrupted by stereotypic episodes of egestion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609839
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  • 6
    Electronic Resource
    Electronic Resource
    Histochemical localization of FMRFamide, serotonin and catecholamines in embryonic Crepidula fornicata (Gastropoda, Prosobranchia) (1999)
    Springer
    Zoomorphology 119 (1999), S. 49-62 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Recent reports indicate that neuronal elements develop in early larval stages of some Gastropoda from the Pulmonata and Opisthobranchia prior to the appearance of any ganglia of the future adult central nervous system (CNS). The present study describes similar early neuronal elements in Crepidula fornicata. A posterior FMRFamide-like immunoreactive (LIR) cell with anteriorly projected fibers was observed in the trochophore stage. Additional FMRFamide-LIR and serotonin-LIR cells and fibers were found in the apical organ in the trochophore and early veliger stages. FMRFamide-LIR and serotonin-LIR projections to the velum and foot were also detected at this time. As the veliger developed, peripheral FMRFamide-LIR and later catecholaminergic cells were located in the foot region. Also during this stage, catecholaminergic cells and processes were observed near the mouth. In addition, this study tentatively identified the first serotonin- and FMRFamide-LIR cells and fibers within the developing ganglia of the adult CNS, which appeared in close proximity to the earlier developing elements. These observations are consistent with the hypothesis that, in addition to its presumed role in the control of larval behaviors, the larval nervous system guides the development of the adult CNS. Larvae from the class Bivalvia and other invertebrate phyla also have neuronal elements marked by the presence of FMRFamide, serotonin, and catecholamines, and, therefore, this study may provide additional insights into phylogenetic relationships of the Gastropoda with other representatives of the Mollusca and different invertebrate phyla.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004350050080
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  • 7
    Electronic Resource
    Electronic Resource
    Tyrosine hydroxylase-negative, dopaminergic neurons are targets for transmitter-depleting action of haloperidol in the snail brain (1996)
    Springer
    Cellular and molecular neurobiology 16 (1996), S. 451-461 
    Details
    ISSN: 1573-6830
    Keywords: antipsychotic ; neuroleptic ; gastropod ; monoamine ; catecholamine ; serotonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. The effects of long term administration of micromolar concentrations of the D2 antagonist haloperidol upon monoaminergic neurons in the snailLymnaea stagnalis was investigated. 2. Treatment by bath application with 0.5–2.0 micromolar haloperidol, caused a significant, continuous depletion of dopamine levels in the nervous system as revealed by high performance liquid chromatography. 3. A transient depletion of serotonin was also observed, but DOPA and norepinephrine levels were unaffected. Similar depletion of dopamine was observed after the land snail,Achatina fulica, was injected with haloperidol on each of 4 consecutive days. 4. The depletion of dopamine as revealed with glyoxylate-induced fluorescence inLymnaea appears to be restricted to a subpopulation of catecholaminergic neurons which are immuno-negative for tyrosine hydroxylase, the synthetic enzyme responsible for the conversion of tyrosine to DOPA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02150226
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  • 8
    Electronic Resource
    Electronic Resource
    Introduction (1996)
    Springer
    Cellular and molecular neurobiology 16 (1996), S. 529-531 
    Details
    ISSN: 1573-6830
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02152055
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  • 9
    Electronic Resource
    Electronic Resource
    Modulation ofin vivo neuronal sprouting by serotonin in the adult CNS of the snail (1996)
    Springer
    Cellular and molecular neurobiology 16 (1996), S. 561-576 
    Details
    ISSN: 1573-6830
    Keywords: buccal ganglia ; neurite outgrowth ; supernumerary fibres ; cyproheptadine ; molluscs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Duringin situ recovery from a lesion to the cerebrobuccal connective (CBC) in the snailAchatina fulica, neurons of the buccal ganglia undergo extensive regeneration and sprouting as assessed by axonal dye-fillings of the CBC. 2. These changes are preceded by the distal degeneration of severed fibres from the serotonergic metacerebral giant neuron (MCG), which results in the depletion of serotonin (5-HT) in the ipsilateral buccal ganglion. We have investigated the potential role of this depletion in causing some of the ensuing neuroplastic events. 3. Pharmacological depletion of 5-HT using either 5,7-dihydroxtryptamine or p-chlorophenylalanine in normal, unlesioned animals was found to produce supernumerary neuronal labelling similar to that seen following a lesion. 4. Systemic daily injections of 5-HT were found to partly suppress the sprouting response following the CBC lesion. For example, the contralateral uninjured MCG which is normally induced by the lesion to sprout novel projections into the denervated ganglion, is suppressed from doing so by the 5-HT treatment. 5. These growth inhibiting effects of 5-HT upon the contralateral MCG could be antagonized by the prior administration of the 5-HT receptor blocker cyproheptadine, suggesting a specific receptor mediated action. 6. We suggest that 5-HT may play a role in governing the state of neuronal outgrowthin vivo in the CNS of the adult snail, as has been suggested by early developmental and neuronal cultural studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02152057
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  • 10
    Electronic Resource
    Electronic Resource
    Distribution of catecholamines, indoleamines, and their precursors and metabolites in the scallop,Placopecten magellanicus (Bivalvia, Pectinidae) (1995)
    Springer
    Cellular and molecular neurobiology 15 (1995), S. 371-386 
    Details
    ISSN: 1573-6830
    Keywords: mollusk ; monoamines ; catabolites ; γ-glutamyl amine ; HPLC/ED
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Although monoamines are well-known to play important roles in molluscan physiology, we are far from fully understanding the synthetic and degradative pathways of these substances, particularly in commercially important bivalve species. In the present study endogenous catecholamines, indoleamines, and their possible precursors and metabolites were detected in the scallop,Placopecten magellanicus, by high-performance liquid chromatography coupled to electrochemical detection. 2. Chromatographic analysis of CNS (cerebral, pedal, and parietovisceral combined), gill, gonad, kidney, mantle, liver, heart, fast adductor muscle, and foot disclosed the presence of the catecholamines 3,4-dihydroxyphenylalanine, dopamine, norepinephrine, and epinephrine and their metabolites normetanephrine, metanephrine, 3,4-dihydroxyphenylacetic acid, and homovanillic acid. 3. Dopamine was detected most frequently and most consistently among all catecholamines. The concentrations of dopamine (1400 pg/mg wet weight) and its major metabolite 3,4-dihydroxyphenylacetic acid (300 pg/mg wet weight) were highest in the CNS. Following the CNS, dopamine was also abundant in other tissues such as heart, foot, and gill. The concentration of norepinephrine (1000 pg/mg wet weight) was highest in the CNS followed by the heart (700 pg/mg wet weight) and gill (600 pg/mg wet weight). 4. The indoleamine, 5-hydroxytryptamine, was present in considerable amounts in all tissues, but its content was highest in the foot (2700 pg/mg wet weight) followed by the CNS (1150 pg/mg wet weight) and gonad (1000 pg/mg wet weight). The precursor 5-hydroxytryptophan was also abundant in the foot followed by the gonad, CNS, and heart. 5. The oxidative metabolite 5-hydroxy-3-indole acetic acid was detected in the largest amount in CNS (200 pg/mg wet weight), whereasN-acetyl-5-hydroxytryptamine was detected in trace amounts in CNS, gonad and foot. This study also presents evidence for γ-glutamyl dopamine and γ-glutamyl 5-hydroxytryptamine as the possible alternate catabolic products of dopamine and 5-hydroxytryptamine, respectively, as previously described in gastropods. 6. Thus, the detection of monoamines and their precursors and metabolites in scallop strongly suggests the presence of mammalian-type enzymic action of hydroxylation, oxidation, and methylation pathways leading to synthesis and degradation of detected compounds. Furthermore, this is the first study to disclose the evidence of nonconventional metabolic pathways for dopamine (γ-glutamyl dopamine ⇐ dopamine ⇒ dihydroxyphenylacetic acid ⇒ homovanillic acid) and 5-hydroxytryptamine (γ-glutamyl 5-hydroxytryptamine ⇐ 5-hydroxytryptamine ⇒ 5-hydroxy-3-indoleacetic acid) inactivation in a bivalve species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02089947
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