[The participation of the endogenous opioid system in regulating the feeding and protective behaviors of the mollusk Lymnaea stagnalis]

Opioids are known to influence feeding behaviour in the land snail. We have found this to be the case in the pond snail Lymnaea stagnalis, i.e. morphine increases while naloxone decreases food consumption. Evidence is presented that the feeding program is influenced by opiates indirectly. The endogenous opioid system seems to control directly a defensive fixed motor action accompanied by an arrest of feeding activity.

Differential trophic effects of ORG 2766, an ACTH(4-9)/MSH(4-9) analogue, on peptidergic neurons and glial cells in the snail Lymnaea stagnalis

Cerebral ganglia of the pond snail Lymnaea stagnalis were incubated in vitro in 10(-6) M ORG 2766 for 10 and 20 h, with or without regular refreshment of the medium. Quantitative ultrastructural study of cross sections of the cerebral commissure showed that the number of microtubules in large axons of all ORG 2766-treated groups had increased after 10 h by approximately 40%. In a separate experiment, central nervous systems were incubated in ORG 2766 for only 15 min and then kept in Ringer's for 9 h and 45 min. Maximal stimulation (40% increase of microtubules) in these specimens was also observed. The results would seem to support the hypothesis that ORG 2766 binds to a receptor and initiates a long-lasting effect. It is argued that ORG 2766 stimulates novel synthesis of tubulin rather than being involved in the assembly of microtubules. Also, glial cells were found to be activated by ORG 2766. This was concluded from the fact that the number of heterochromatin clumps and the size of the clumps in these cells had decreased and the amount of glial tissue surrounding the axons had increased (approximately 50%). In contrast to the activating effects of ORG 2766 on glial tissue, this drug did not affect nucleoli, number, and size of the heterochromatin clumps and the Golgi apparatus in the neuropeptidergic caudodorsal cells. The data indicate that ORG 2766 exerts differential trophic effects.

The ACTH/MSH(4-9) analogue ORG 2766 stimulates microtubule formation in axons of central neurons of the snail Lymnaea stagnalis

Central nervous systems of the pond snail Lymnaea stagnalis were incubated in vitro in different concentrations of ORG 2766 (10(-9)-2.5 x 10(-4) M) for 10 and 20 h. Quantitative ultrastructural study of cross sections of the cerebral commissure showed that the number of microtubules in large axons had increased after 10 h of incubation by approximately 50% (Experiment 1) and 30% (Experiment 2), respectively. No further increase was observed after 20 h of incubation. (The higher concentrations were studied.) Maximal stimulation was already found at a concentration of 10(-8) M. At a concentration of 10(-9) M control levels were observed. It is concluded that ORG 2766 stimulates microtubule formation already at very low concentrations. It is not clear whether the compound stimulates synthesis of tubulin, induces assembly of microtubules, or causes an increase in stability of microtubules. Nevertheless, ultrastructural data on the morphology of the glial cells indicate that these cells are activated by ORG 2766 treatment, which suggest that ORG 2766 has general trophic effects.

Effects of temperature and analyte application technique on neuron-based chemical sensing

Results are presented which enhance the field of neuron-based sensing by providing insight on the effects of operating temperature and analyte application technique (pulse versus back-mixed) on sensing properties. In these studies, serotonin sensing attributes of giant visceral neurons VV1 and VV2 from the pond snail Lymnea stagnalis were measured. Experiments using a rapid fluid-exchange system reveal a concentration-dependent increase in maximum firing frequency similar to that reported earlier for a slow well-mixed application. With a rapid application, however, the maximum firing frequency is reached more quickly, and there is less cell-to-cell variability in both the maximum response and sensitivity. Given an application technique, an increase in temperature causes an increase in sensitivity and maximum firing frequency, as well as a decrease in the time required for the response to return to baseline following removal of the analyte. To provide insights on the kinetics of the serotonin-induced response, the effects of temperature and concentration on the rates of activation, recovery and desensitization were examined in detail. In general, it was found that an increase in temperature increases the rates of activation and desensitization, while the effects on recovery were not apparent. In addition, both the rates of activation and desensitization have a direct dependence on concentration while the rate of recovery has an inverse dependence.

Differential responses of two identified neurons of the pond snail Lymnaea stagnalis to the convulsant drug pentylenetetrazol

The convulsant drug pentylenetetrazol (PTZ) induces tonic depolarization in the identified B1 neuron of Lymnaea stagnalis. Another identified neuron, right parietal dorsal 1 (RPD1), gives the opposite response: tonic hyperpolarization and cessation of spontaneous firing. These effects are mimicked by intracellular injection of calcium ions and reversed following injection of ethylene glycol-bis(beta-aminoethyl ether) N,N,N,'N'-tetraacetic acid (EGTA). Responses to PTZ are retained in the presence of extracellular cobalt ions to block calcium influx. Under voltage clamp, PTZ or injection of calcium ions induces a slow inward current in B1, which is abolished in zero sodium saline. In RPD1 the current response to PTZ or intracellular calcium ions is outward, and is blocked by potassium channel blockers. Thus, differential responses of the two neurons to PTZ appear to be mediated via increased intracellular calcium ions, leading to activation of specific ion currents in each cell type.

[The effect of taurine on the electrically controlled ion channels of the somatic membrane of pond snail neurons]

Isolated and internally dialysed neurons from the molluscs Lymnaea stagnalis were investigated under voltage-clamp conditions. The increasing of taurin concentration (from 1.10(-8) to 1.10(-2) mol/l) reduced the calcium inward--and delayed potassium outward currents, and exerted no effect on the fast potassium outward current. Sodium inward current was increased by taurin concentrations 1.10(-8)-1.10(-4) mol/l, and reduced by 1.10(-3)-1.10(-2) mol/l. Membrane leakage currents were reduced by small taurin concentrations and increased by large concentrations.

[The effect of different concentrations of surface-active substances on the size of the circadian rations and on the duration of food passage in Lymnaea stagnalis infected with Echinostoma revolutum parthenitae]

In solutions of the detergent "Kristall" (0.9 and 90 mg.l.-1) there were established statistically reliable differences in the values of day rations and duration of food passing both in infected and free from infection molluscs. In noninfected individuals day rations increase 1.5 to 5 times and the duration of food passing 5 to 7 times. In infected animals the value of day rations decrease and the duration of food passing increases less intensively.

[Comparative analysis of quinolinic acid and L-kynurenine action on the electrically controlled membrane ion channels of mollusk neurons]

Extrasynaptic effects of kynurenines (chynoline acid and L-kynurenin) on the membrane electrosensitive ionic channels were studied in experiments using isolated somata from the c. n. s. of mollusc Lymnaea stagnalis. The kynurenines either blocked or induced biphasic dose-dependent effect on amplitudes of the membrane ionic currents.

[Effect of the endogenous peptide factor and vasopressin on the neurons of mollusks of different ages]

Electric reactions of the identified neurons in adult (10-12 months) and old (22-24 months) molluscs Lymnaea stagnalis to endogenous peptide isolated from the water soluble fraction of the Helix Pomatia brain homogenate as well as to vasopressin are studied. The endogenous peptide causes a significant activation of the burst both in adult and old neurons of the molluscs. No significant age-related differences in the pronouncement of the above shifts of the molluscan neurons are found. There is an increased sensitivity to the identified peptide, vasopressin, in the old individuals. A non-uniform change in the sensitivity of mollusk neurons to various neuropeptides may affect the synaptic conduction in old age.

[Comparative characteristics of the membrane mechanisms of the action of fenamine and its derivatives on the ion channels of isolated mollusk neurons]

Phenamine (10(-12)-10(-5) M/l) increased by 20-60 per cent the input (sodium and calcium) currents (Iin), the output slow potassium (Ikm) and fast potassium (Ikb) ones, and decreased the currents in higher concentrations. The volt-ampere characteristics of the membrane (VAC) and the curves of stationary inactivation (CSI) shifted along the potentials axis. The phenamine analogue IEM 1365 only decreased the currents leaving the VAC and CSI unaltered. Another analogue IEM 1370 only decreased the Iin whereas VAC and CSI also shifted along the potentials axis. The ion channels seem to be blocked in a decrease of the currents and the membrane surface potential induced with fixed charges seems to change.

Characterization of pre- and postsynaptic dopamine receptors in Lymnaea

1. The effects of dopamine and several synthetic agonists and antagonists were studied using two identified neurons of the snail Lymnaea stagnalis. 2. In both the buccal-2 (B-2) neurons and the pedal giant (RPeD1) neuron dopamine elicited a hyperpolarizing response at least partly due to potassium efflux. RPeD1 is itself dopaminergic, implicating autoreceptors in its response to dopamine. 3. The following agents were tested: agonists--LY171555, pergolide, SKF38393, (-)-3-PPP, R(-)NPA and dopamine; antagonists--SCH23390, sulpiride, and metaclopramide. Dibutyryl cAMP was applied to determine whether the response is cAMP-mediated. 4. Results indicate that the pharmacological profiles of dopamine receptors on these neurons are inconsistent with those of either D-1, D-2 or autoreceptors in mammals.

[Poisoning by copper sulfate of Lymnaea stagnalis infected with trematode parthenitae]

The effect of different concentrations of copper sulphate on the content level of carotinoid pigments in the haemolymph of Lymnaea stagnalis infected with parthenitae of trematodes was studied. The content level of carotinoid pigments in haemolymph of molluscs steadily decreases with an increasing concentration of the toxicant. The mortality of experimental animals under such conditions rises considerably, the mortality of infected animals being much higher than that of non-infected ones.

The impairment of mobility and development in freshwater snails (Physa fontinalis and Lymnaea stagnalis) caused by herbicides

1. The pulmonate freshwater snails Physa and Lymnaea and the earthworms Eisenia and Lumbricus can take up and concentrate a carbamate herbicide (chlorpropham). 2. The mobility of freshwater snails was diminished in the presence of the herbicides chlorpropham (carbamate), cycloate (thiocarbamate), pentanochlor (amide) and chloroxurone (urea derivate). 3. The egg-assemblies of Lymnaea stagnalis turned out to be suitable objects for testing the influences of herbicides upon embryonic development. 4. In the presence of chlorpropham, chloroxurone, cycloate, propanil, simazine and terbutryne, all applied in concentrations lower than in practical use, the period of egg-maturing was delayed and the total number of dead embryos increased. 5. Developing snail eggs were very sensitive towards triazine herbicides (simazine, terbutryne) reflecting in an ED50-value lower than 10(-7) M. 6. Similar herbicidal-induced effects suggested that the developing stages of snail embryos may be suitable models for the ecologically more important but experimentally less accessible earthworms.

Fever in snails, reflection on a negative result

1. Groups of aquatic snails (Limnaea auricularia) were placed in a temperature gradient and their thermopreferendum measured. 2. Injected with various amounts of killed Escherichia coli, bacterial endotoxin, human interleukin, and prostaglandin E1, E2 and F2 alpha, they did not develop a fever. 3. High doses of prostaglandins were toxic. 4. These results suggest that fever appeared in the course of evolution after the emergence of molluscs and before that of arthropods.

[Effect of prostaglandin E2 and its derivatives on the reaction of isolated mollusk neurons to acetylcholine]

A study was made of the effect of PGE2, ethyl ether and a carbohydrate derivative of PGE2 on the sensitivity to acetylcholine (ACh) of identified neurons of the mollusk pond snail. The response recorded in the mode of membrane potential fixation diminished in the presence of PGE2 and its derivatives. The rate of the decrease and the degree of the response blockade depended on the substance concentration. Washing of PGE2 made the neuronal sensitivity to ACh return to normal. With the use of PGE2 derivatives the sensitivity recovery was incomplete. The radioimmunochemical technique has demonstrated PGE2 to raise the cAMP level in the pond snail brain.

Direct effects of the hyperglycemic factor of the freshwater snail Lymnaea stagnalis on isolated glycogen cells

In the freshwater pulmonate snail Lymnaea stagnalis special cells, the glycogen cells (GC) are present for the storage of glycogen reserves. These cells occur in large numbers in the anterior mantle region. In a previous paper in vitro experiments with intact anterior mantle tissue indicated that a hyperglycemic factor is released from the central nervous system (CNS) which stimulates glycogen mobilization in mantle tissue (M. A. Hemminga, J. J. Maaskant, W. Koomen, and J. Joosse (1985). Neuroendocrine control of glycogen mobilization in the freshwater snail Lymnaea stagnalis. Gen. Comp. Endocrinol. 57, 117-123). In the present study the question of whether this factor affects glycogen metabolism of GC isolated from mantle tissue was investigated. It is reported that in high-K+ Ringers the CNS is stimulated to release a factor which, in a dose-dependent way, inhibits glycogen synthesis in isolated GC (measured as a decreased incorporation of [14C]glucose into glycogen). Simultaneous with this glycogen synthesis-inhibiting effect, stimulation of glycogen degradation is found (measured as a decreased retention of prelabeled glycogen). It is concluded that (1) the factor released by the CNS having these effects on isolated GC is the same as the hyperglycemic factor which was reported to stimulate glycogen mobilization in intact mantle tissue, and (2) GC after isolation from mantle tissue have retained their ability to respond to this factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Alteration in biogenic amine levels in the snail Lymnaea acuminata by the latex of Euphorbia royleana

The latex of Euphorbia royleana which has high molluscicidal and anti-cholinesterase activity against Lymnaea acuminata reduced the levels of 5-hydroxytryptamine (5HT) and dopamine (DA) in the nervous tissue of L. acuminata. There was, however, no significant change in the level of 5-hydroxyindole acetic acid (5HIAA). The changes were found to be dependent on concentration of the latex extract. Similar changes were produced by both water and organic solvent extracts of the latex. The latex of E. royleana thus affects all the known neurotransmission mechanisms in the snail either separately or through a complex interaction between the different neurotransmitters. This may account for its high toxicity to snails.

The sites of action of praziquantel in a smooth muscle of Lymnaea stagnalis

Praziquantel (1.6 X 10(-6) M), a new anthelmintic drug, was shown to produce a sustained contracture in the penis retractor muscle of the freshwater snail Lymnaea stagnalis. Calcium-free saline greatly reduced the magnitude and duration of the praziquantel contractures if the preparation had been previously exposed to praziquantel. The praziquantel contracture in zero-calcium saline was abolished if the preparation was pretreated with successive applications of 2 X 10(-2) M caffeine. Lanthanum (1.0 mM) in zero-calcium saline prevented the contractures normally produced by 30 mM potassium saline, but did not prevent the praziquantel contracture. In normal saline, however, 1.0 mM lanthanum greatly reduced the magnitude of a praziquantel-induced contracture. We conclude that praziquantel increases sarcolemmal calcium permeability and releases calcium from intracellular stores in Lymnaea stagnalis smooth muscle.

Influence of biologically active substances isolated from Galleria mellonella on neurons of Lymnaea stagnalis in culture

A procedure for isolating biologically active substances from Galleria mellonella using a culture of isolated giant neurons of mollusc Lymnaea stagnalis as a test-system is described. Fractions capable of activating neurites and inhibiting aggregation of neuronal cells within a range of concentrations from 1 to 30 micrograms/ml were isolated. The fractions obtained have in their chemical composition about 10.5% N, also contain P and S. They have a carbohydrate component.

Chronic intoxication by an herbicide, 2,4,5-trichlorophenoxyacetic acid, in the pond snail, Lymnaea stagnalis L

Experiments of chronic intoxication with three concentrations (10, 20, and 40 ppm) of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were conducted in the freshwater mollusc Lymnaea stagnalis. Snail survival was concentration dependent. In all cases the growth can be described by the von Bertalanffy pattern (ht = h (1 - e-k(t-to)) and the variations of the k values showed that growth was significantly altered in all the groups treated. The overall fecundity (F) was always reduced; the decrease was due both to a lower number of eggs per egg mass (-7.8 to -12%) and to an earlier death of the intoxicated snails. Fecundity studied in terms of size, according to the law F = ahz, points out the loss of equilibrium between growth and fecundity: in all groups treated the values of the exponent z were increased. The importance of these perturbations can be quantified by the calculation of a "Snail Yield" which is reduced by 72.6% in the 40 ppm group. Egg fertility was also reduced. It can be concluded that 2,4,5-T disturbs the physiological equilibrium of Lymnaea stagnalis leading even to earlier death of the snails.

Heavy metal ion toxicity in the freshwater gastropod snail host, Lymnaea luteola

Copper sulphate is in use as the molluscicide since six decades. However, the cidal mechanism involved is not understood. Therefore, the effect of copper sulphate added to the ambient medium at a concentration duration strength of 2 ppm X 6 hr, on the particulate fractions of the digestive gland of the pulmonate gastropod snail. Lymnaea luteola has been elucidated. Parameters such as oxidizing capacity, phosphorylating capacity and respiratory control have been studied. P:O and R.C. ratios dropped phenomenally and no uncoupling effect was seen in the presence of PCP in treated snails. These results show that some of the important properties of the particulate preparations have been affected by copperations.

Changes in carbohydrate metabolism in various organs of the snail, Lymnaea acuminata following exposure to trichlorfon

Several aspects of carbohydrate metabolism following 24 hr and 48 hr treatment with 10 and 20 mg/l of trichlorfon, were studied in hepatopancreas, mantle, intestine and foot of the snail. Lymnaea acuminata. Following treatment with the pesticide, the rate of oxygen consumption and concentration of glycogen were reduced, while the levels of lactic acid and reducing sugars were enhanced. Withdrawal of pesticide for 7 days following trichlorfon treatment (10 mg/l for 48 hrs) could not reverse these changes.