It is known that sensory information about relatively constant environmental factors plays important role in formation of relatively constant functional states of human and mammalian nervous system. Therefore strong decrease of total volume of sensory information (sensory deprivation) causes disintegration of normal human and rodents’ behavior.

In order to investigate possible influence of total volume of sensory information on the functional state of C. elegans nervous system young adults, grown in Petri dishes with NGM and E. coli OP50 (Brenner, 1974) at 18°C, were incubated individually in 1 ml of liquid medium (NGM without agar, peptone and cholesterol) during 0.5, 1, 2 or 3 hours. In these conditions sensory deprivation of worms is determined by cessation of sensory inputs from conspecific individuals, food and agar plate. Our experiments show that sensory deprivation rapidly (30 min at 18°C) diminished spontaneous swimming rate and then completely stopped worms’ swimming (after 90 min incubation). This effect of sensory deprivation is prevented by sensory inputs from conspecific worms, since about 85% of worms maintain spontaneous swimming after 3 hours incubation of 100-200 worms in 3 ml of liquid medium. Temperature increase from 18 to 25°C strongly stabilized worms swimming in conditions of sensory deprivation.

It is known that worms’ pretreatment by serotonin (4 or 12 hours) causes adaptation of C. elegans serotonin receptors (Schafer and Kenyon, 1995). This adaptation reveals in the absence of behavior response to exogenous serotonin in fresh medium (Schafer and Kenyon, 1995). In our experiments such C. elegans adaptation to serotonin (12 hours on agar plates containing E. coli OP50 and serotonin 3 mg/ml) diminished effect of sensory deprivation at 18°C, but not at 25°C.

Since exogenous serotonin inhibits C. elegans movement, influence of C. elegans adaptation to serotonin on effect of sensory deprivation displays possible role of endogenous serotonin in this effect.

In whole our data indicate that sensory deprivation can be used for investigation of C. elegans nervous system regulation by continuous and relatively constant sensory inputs, such as social signals and stimulation of inadaptable or partly adaptable thermosensory neurons by constant environmental temperature.

Thermotolerance evolution of poikilothermic organisms consists in adaptation to temperature conditions of habitats of such physiological features as the lower and upper limits of temperature for reproduction, development and behavior and organism’s resistance to short-term temperature extremes.

Previous researches of Caenorhabditis revealed both interspecific and intraspecific significant differences for the upper limits of temperature for reproduction and development. These differences are in accordance with temperature conditions of habitats (Fatt and Dougherty, 1963; Fodor et al., 1983). Nevertheless interspecific differences in tolerance to temperature extremes are still uninvestigated.

Therefore we compared resistance to high temperature extremes of C. elegans (strain N2) and C. briggsae (strain AF16). Experiments were carried out with young adults grown in Petri dishes with NGM and E.coli OP50 at 23°C. Resistance to constant temperature 36°C or 37°C was measured for worms incubated individually in 1 ml of liquid medium (NGM without agar, peptone, cholesterol).

Results of our experiments show that organism’s resistance to extreme high temperature is significantly higher in C. briggsae than in C. elegans:

1. Mean time of reversible disturbances of swimming induced by intensive mechanic stimulus (shaking of test tube) was similar at 36°C in C. elegans and at 37°C in C. briggsae.
2. Mean time of heat death was rather more in C. briggsae at 37°C than in C. elegans at 36°C.

Rapid adaptations of worms to temperature elevation by 2 hour incubation at 30°C or by heat hardening (1 hour at 33°C followed by 1 hour at 23°C) increased behavior resistance to short-term heat stress (36°C for C. elegans and 37°C for C. briggsae). Efficiency of both adaptations was similar in C. elegans and C. briggsae.

Therefore we conclude that adaptation of C. elegans and C. briggsae to different temperature conditions of habitats changed only base resistance to extreme high temperature.

It is known that the upper temperature limit for reproduction of C. elegans N2 is 26.5°C (Fatt and Dougherty, 1963), while C. briggsae AF16 can grow at 27.5°C (Gupta et al., 2007). Therefore our data indicate that evolution of Caenorhabditis thermotolerance involves unidirectional adaptive changes of the upper limits of temperature for reproduction and resistance to short-term heat stress. This pattern reveals in the evolution of most poikilotherms.

Thus soil nematodes Caenorhabditis may be used as convenient model organisms for study thermotolerance evolution.

It is known that the first ethanol metabolite acetaldehyde (AA) is the mediator and modulator of ethanol actions in the human brain. Basic enzymes of ethanol metabolism, such as alcoholdehydrogenase and aldehyde dehydrogenase (ALDH) are very conservative in evolution. Therefore it is possible that AA plays an important role in ethanol effects upon the simple nervous systems of invertebrates.

Results of our experiments revealed AA involvement in the tolerance to ethanol of simple nervous system of C. elegans (wild type strain N2): (i) Elevation of AA concentration during ethanol metabolism by inhibition of ALDH (preliminary 16-hours exposition of worms on agar plates containing selective inhibitor of ALDH disulfiram (antabus) in concentration 0.8 mg/ml and seeded with E. coli OP50) protected worms’ behavior against disturbances induced by ethanol. These disturbances revealed in numerous reversible incoordinations of swimming induced by mechanical stimulus in experiments with worms incubated singly in liquid medium with ethanol (1-3%); (ii) Low concentrations of exogenous AA (30–75 µg/ml) mimics protective effect of disulfiram in the ethanol containing medium.

It is known that AA mediates many unfavorable effects of alcohol in human nervous system. However our data indicate that AA can’t be the mediator of negative effect of ethanol upon C. elegans swimming: (i) Exogenous AA (75–300 µg/ml) induces very specific form of behavior disturbance similar to kinked motion and coiled posture of unc-1 and unc-8 mutants (Park, Horvitz, 1986; Hecht et al., 1996), and this form of behavior disturbance was not revealed among swimming disturbances induced by ethanol; (ii) Disulfiram sensitizes human organism to adverse ethanol action but has opposite protective effect on C.elegans locomotion in the medium containing alcohol; (iii) Low concentrations of AA protect C.elegans locomotion against unfavorable ethanol effect; (iv) Low concentrations of ethanol (0.5-1.0 %) prevent worms’ kinking and coiling induced by AA.

In general our data suggest cross modulation of unfavorable effects of ethanol and its first metabolite upon C. elegans behavior. This cross modulation can be adaptive for C. elegans since in all known natural habitats of this nematode (compost soils) constantly or periodically there are conditions for fermentation, such as substrates for fermentation and oxygen deficit resulting from metabolism of aerobic microorganisms, and ethanol and other alcohols are volatile chemoattractants for C. elegans.