[Inhibitors of neuronal and inducible NO-syntases enhance the effect of short-term adaptation to hypoxia in rats of Krushinsky-Molodkina strain].

We found that selective inhibitors of neuronal and inducible NOS (7-nitroindazole and aminoguanidine) significantly enhance the protective effect of short-term adaptation to hypoxia on the development of stress lesions in rats Krushinsky-Molodkina.

[The influence of inhibitors of neuronal and inducible NO-synthases on experimental hemorrhagic stroke]. / Vliianie ingibitorov neironal'noi i indutsibel'noi NO-sintaz na razvitie gemorragicheskogo insul'ta v éksperimente.

Objectives. To study the effect of inhibitors of neuronal and inducible NO-synthase on the development of hemorrhagic stroke in rats Krushinsky-Molodkina (KM) without adaptation to hypoxia and with short-term adaptation to hypobaric hypoxia. Material and methods. Ninety rats were included in the study. Experiments with short-term adaptation to hypobaric hypoxia were performed on 48 rats. The inhibitor of inducible NO-synthase (aminoguanidine, "Sigma") or the inhibitor of neuronal NO-synthase (7-nitroindasol, "Sigma") were injected in dosage 2.5 mg/100g intraperitoneally. Results. Selective inhibitors of neuronal and inducible NO-synthase had a protective effect on stress injuries in KM rats. The inhibitor of neuronal NO-synthase was more effective than the inhibitor of inducible NO-synthase in the experiments without adaptation to hypoxia. Markedly greater protective effect was achieved by the simultaneous introduction of inhibitors of neuronal and inducible NO-synthase. The greatest protective effect in the development of stress damage in rats of KM was observed in short-term adaptation to hypobaric hypoxia with simultaneous introduction of both inhibitors. Conclusions. It can be assumed that an excessive amount of NO produced by neuronal and inducible NO-synthases during the acoustic exposure in KM rats leads to stress damage. Use of selective inhibitors reduce the excess NO synthesis and the development of audiogenic stress damage caused by hemorrhagic stroke.

[Neurotransmitter mechanisms of context-dependent behavior].

The influence of context on behavioral choice is well known. Context can refer to behavioral state of an animal and to external factors such as season, presence of other individuals or food availability. How external and internal factors influencing decision-making are translated at the cellular level? I review the recent neuroethological data that strongly suggest that context reflects in content of neuroactive substances (neurotransmitters, modulators, hormones) that present in the extraneuronal milieu, while heterochemical neuronal microenvironment in its turn impacts motor program selection.

[Participation of receptors of the NMDA type in regulation by glutamate of alimentary motor program of the freshwater mollusc lymnaea stagnalis].

A possible participation of receptors of the NMDA type in regulation by glutamate of the Lymnaea stagnalis feeding program was studied in electrophysiological experiments. The specific antagonist of receptors of the N-methyl-D-aspartate (NMDA) type MK-801 has been shown to turn off the endogenous generation of the standard three-phase rhythm or the two-phase rhythm. Stimulation of receptors of this type by their specific agonist, NMDA, on the contrary, increased frequency of the alimentary rhythm and transformed it into the two-phase one. All NMDA effects are eliminated by MK-801. Apart from action on generation of central feeding rhythms, ligands of receptors of the NMDA type changes the tonical level of depolarization and activity of the alimentary circuit motoneurons. MK-801 decreased the initial level of the motoneuron B4 activity and inhibited the excitatory effect both of NMDA and of glutamate itself. There are also obtained data in favor of that earlier reported effect of transformation of the inhibitory response of neurons B4 to glutamate into the excitatory one at action of nitric oxide (NO) donors can be mediated by the specific NO effect on the activity of receptors of the NMDA type. The blocker of NMDA receptors MK-801 has been shown to inhibit the effect of transformation of the response to glutamate. The NO donor nitroprusside enhanced essentially the NMDA excitatory action, while the NO acceptor oral PTIO decreased it. The results obtained with use of ODQ, the blocker of NO-sensitive guanylyl cyclase (GC), allow thinking that effect of NO on activity of the NMDA receptors of the pond snail feeding program can be realized through the metabolic pathway GC--cGMP. On the whole, the obtained results show the pond snail receptors of the NMDA type to participate in generation and rearragement of rhythmical alimentary programs in the tonical excitatory effect on the feeding program motoneurons in the NO-dependent transformation of the glutamate response.

[Behavioral functions of serotonin and octopamine: some paradoxes of comparative physiology].

Evaluation of recent data on monoaminergic control of invertebrate behavior suggests that behavioral functions of serotonin in molluscs and octopamine in insects are remarkably similar. Specifically, in the respective taxa, these monoamines are responsible for activation of food searching and intense locomotion, increase in food consumption and general activity, enhancement of cardial and respiratory rhythms, facilitation of learning, sensitization of sensory circuits. At the same time, in insects, behavioral effects of serotonin are opposite to those of octopamine. It seems thus that two monoamines have exchanged their behavioral roles in the two major invertebrate taxa. Possible reasons of this paradoxical inversion touches inevitably upon basic questions of signal molecular evolution.

[Function of glutamate in pattern-gene-rating network is modified by nitric oxide NO].

In previous study on the terrestrial snail Helix pomatia, it has been shown that responsiveness of certain neurons to glutamate is controlled by NO; specifically, the donors of NO produced transformation of inhibitory responses to excitatory ones. Here, we extend this study to buccal neurons related to feeding behavior of the pond snail L. stagnalis. Glutamate is known to operate in the standard three-phase feeding pattern as a phase transmitter which mediates the effects of the second phase interneuron N2v. In isolated CNS, we recorded motor neuron B4 that was inhibited during firing of glutamatergic N2v, but expressed excitatory glutamate receptors as well. In some preparations (n = 17), bath application of 0.1 mM glutamate resulted in profound hyperpolarization of, and cessation of synaptic inputs to, the B4. Following treatment for 10-15 min with the NO donor sodium nitroprusside (n = 9), glutamate effect on B4 became excitatory, and a peculiar, sustained two-phase rhythmic activity of the pattern-generating network appeared. In other non-treated preparations (n = 12), 0.1 mM glutamate produced depolarization and excitation of B4, supplemented, in 8 cases, with emergence of the above mentioned two-phase rhythmic activity. Pretreatment for 10-20 min with the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (n = 7) abolished these effects of glutamate. Our results suggest that 1) glutamate role in buccal rhythm generation depends on NO level, and 2) this mechanism is involved in modification of the feeding behavior in Lymnaea.

[NO-synthase inhibitor prevents flight-induced activation of agressiveness and courtship in male].

Previous experience of flying enhances the aggressiveness (Hofmann and Stevenson, 2000, Nature, 403: 613) and accelerates the courtship behaviour (Dyakonova and Krushinski, 2003, DAN, 390: 709-712) of crickets Gryllus bimacultus. We present evidence that these effects may be mediated by activation of nitric oxide synthesis. The effects of flying on fighting and courtship were largely abolished in crickets who received haemocoel injections of a nonspecific NO-synthase inhibitor LNNA. Unlike this, LNNA exerted no significant effects on aggressive and courtship behaviour of nonflown males.

[The endogenous opioid system tonically activates the locomotor neurons in the mollusk Lymnaea stagnalis]. / Endogennaia opioidnaia sistema tonicheski aktiviruet lokomotornye motoneirony molliuska Lymnaea stagnalis.

Keeping specimens of the pond snail Lymnaea stagnalis in the aqueous solution of the opiate antagonist naloxone (0.1 mM) or naltrexone (0.1 mM) resulted in a suppression of motor activity, and, particularly, in a decrease in the rate of ciliary locomotion. The activity of ciliomotor serotonergic neurons of the Pedal A cluster was intracellularly recorded in preparations of isolated ganglia. Naloxone (0.1 mM) suppressed, whereas the opiate agonists morphine (0.1 mM) and DAGO (0.05 mM) accelerated the synaptically driven firing of the Pedal A neurons both in preparations of the entire CNS and isolated pedal ganglia. The obtained results testify to the occurrence of tonic activatory influence of the endogenous opioids on the ciliomotor pedal neurons of snails and suggest that this influence is, at least partially, mediated by their synaptic input.

[The neurotransmitter basis of mollusk behavior: the control of the choice between exploratory and defensive responses to the presentation of an unknown object]. / Neirotransmitternaia osnova povedeniia molliuska: upravlenie vyborom mezhdu orientirovochnym i oboronitel'nym otvetom na pred''iavlenie neznakomogo ob''ekta.

The role of serotonin and opioid peptides in decision making was studied in the pond snail Lymnaea stagnalis. It was shown that 5-HTP increased the number of searching responses to a sudden presentation of a novel object. Opiate antagonist naloxone decreased the number of searching responses and increased the number of defensive and escape reactions. The effect of 5-HTP and naloxone on decision making appear to be coordinated with their effects on their behavioural state.

[The participation of the endogenous opioid system in regulating the feeding and protective behaviors of the mollusk Lymnaea stagnalis]. / Uchastie éndogennoi opioidnoi sistemy v reguliatsii pishchevogo i zashchitnogo povedeniia molliuska 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.