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Total sleep deprivation induces EEG oscillations in rats with absence epilepsy
127
Early ontogeny Dominique
of agonistic
interactions
and of social recognition
in chickens
Domken, Sabine Suys, Rene Zayan and Veronique Sohet
Psychobiology Unit, UCL, 1 place Croix du Sud, 1348 Louvain-la-Neuve, Belgium
Two experiments
were conducted with artificially-incubated
chicks which were placed
in small groups immediately after hatching. The animals were of two strains: White Leghorn (W), and Rhode Island Red CR). In one experiment (Exp. I), the chicks were housed in observation cages to form either single-strain groups (W or R groups), or mixed-strain groups (WR groups). Group sizes were n = 4 or n = 6; the same floor area per bird was provided in the groups of the two sizes. The groups were systematically observed, without being handled, during their first week of life. The chicks of the other experiment (Exp. 2) were obtained simultaneoulsy as those of Exp. 1, but they were selected only to form single-strain pairs and groups of sizes n = 3, n = 4, n = 6 and n = 8. The aims of the experiments were: (I) to describe accurately the repertoire of behavioural interactions among chicks at the earliest stage of their ontogeny. Particular reference was made to all the possible types of pecks that could be observed; (2) to test the hypothesis that agonistic interactions would increase both in frequency and intensity as group size increases; and (3) to test the hypothesis that agonistic interactions would be less frequent and less intense among members of the mixed-strain groups than among those of the single-strain groups, because in the former groups individual recognition would be easier and would enhance the stability of affiliative relationships. The results have clearly confirmed the two hypotheses. As to the ethological observations, they have revealed that aggressive pecks, feather pecking (a precursor of cannibalism>, threats and even bouts of fighting occurred at such an early stage of the ontogeny. Allo-preening, a ritualised behaviour indicative of both affiliation and conflict, was also frequently recorded.
Total sleep deprivation Pim Drinkenburg,
induces EEG oscillations
in rats with absence epilepsy
Gilles van Luijtelaar and Anton Coenen
Department of Psychology, University of Nijmegen,
The Netherlands
Total sleep deprivation (TSD) is often used as a provocation method for the diagnosis of epilepsy. It induces a state favourable for the occurrence of absence seizures. Generally, absences occur during intermediate levels of vigilance, during sleep-wake transitions. Rats of the WAC/Rij strain show spontaneously occurring spike-wave discharges (SWD) in the cortical EEG as well as clinical signs of absence epilepsy. Furthermore, they show a prolonged intermediate stage and various spindle-like 8-l 0 Hz oscillations.
128
In the present study, it is investigated whether the occurrence of SWD and of other oscillations is facilitated by TSD. Eight male adult WAG/Rij rats were chronically provided with cortical EEC and nuchal EMC electrodes. Animals were recorded for 24 h to obtain a base-line; next they were deprived of total sleep for 12 h during the light phase. TSD was accomplished with an arousal technique: at detection of sleep-onset the cage of the animal was shaken until the rat awakened. TSD appeared to be effective: a reduction of 78% was accomplished, eliminating all REM sleep and almost all deep sleep. The number of SWD was enhanced during the first four hours of the TSD period, followed by a decrease after eight deprivation hours. These results may be explained by the presence of an initial increase in sleep pressure and in transitions into light slow wave sleep, gradually changing into the presence of periods during which awakenings were immediately followed by quick transitions into deep sleep; the latter state being unfavourable for the appearance of SWD. Furthermore, another result was that in the course of the TSD, arousing of the animal was followed by oscillations in the EEC about 2 s after the shaking of the cage had ended.The probability of an oscillation to occur following an arousal increased about 4.3 times as TSD proceeded. These results indicate that TSD facilitates the occurrence of two types of oscillations: first, the characteristic SWD in the beginning of the TSD period, and later on the short lasting rhythmic phenomena. Whether both types of oscillations should be considered as representatives of one class is an important question for future research, as well as the question whether the arousal-induced rhythmic oscillations are a common phenomenon or unique to epileptic rats.
Transition frequencies as additional activity in the elevated plus-maze test
measurements
for
assessing
anxiolytic
drug
U. Falter, J. Gobert and A.J. Cower UCB-Pharma,
CNS Department,
Chemin
du Foriest, B-1420
Braine-I’Alleud,
Belgium
The elevated plus-maze is a standard rodent test of anxiety aimed at detecting potential new anxiolytic drugs. It consists of a cross-maze, mounted 70 cm above floor level, with two open and two closed arms, like arms facing one another. As rodents spontaneously tend to avoid the open arms, anxiolytic activity is classically inferred from the ease with which drug-treated animals increase the number of visits onto and/or the time spent on the open arms. Recent studies (Moser, 1989) have shown that these measurements are not sufficient to reliably detect new anxiolytic compounds. The aim of the present experiments was to investigate whether information provided by the spatial exploration strategy could contribute to a better appreciation of the anxiolytic activity of drugs in this test. Besides the standard measurements, we therefore also calculated arm-transition frequencies, expressed as percentage of closed-closed, or open-open transitions, and percentage of open-closed, or closed-open transitions. Chlordiazepoxide (CDP), O-20 mg/kg po 60 min, or O-IO mg/kg ip 30 min, was used as the reference drug and its effects were evaluated either on a
Early ontogeny Dominique
of agonistic
interactions
and of social recognition
in chickens
Domken, Sabine Suys, Rene Zayan and Veronique Sohet
Psychobiology Unit, UCL, 1 place Croix du Sud, 1348 Louvain-la-Neuve, Belgium
Two experiments
were conducted with artificially-incubated
chicks which were placed
in small groups immediately after hatching. The animals were of two strains: White Leghorn (W), and Rhode Island Red CR). In one experiment (Exp. I), the chicks were housed in observation cages to form either single-strain groups (W or R groups), or mixed-strain groups (WR groups). Group sizes were n = 4 or n = 6; the same floor area per bird was provided in the groups of the two sizes. The groups were systematically observed, without being handled, during their first week of life. The chicks of the other experiment (Exp. 2) were obtained simultaneoulsy as those of Exp. 1, but they were selected only to form single-strain pairs and groups of sizes n = 3, n = 4, n = 6 and n = 8. The aims of the experiments were: (I) to describe accurately the repertoire of behavioural interactions among chicks at the earliest stage of their ontogeny. Particular reference was made to all the possible types of pecks that could be observed; (2) to test the hypothesis that agonistic interactions would increase both in frequency and intensity as group size increases; and (3) to test the hypothesis that agonistic interactions would be less frequent and less intense among members of the mixed-strain groups than among those of the single-strain groups, because in the former groups individual recognition would be easier and would enhance the stability of affiliative relationships. The results have clearly confirmed the two hypotheses. As to the ethological observations, they have revealed that aggressive pecks, feather pecking (a precursor of cannibalism>, threats and even bouts of fighting occurred at such an early stage of the ontogeny. Allo-preening, a ritualised behaviour indicative of both affiliation and conflict, was also frequently recorded.
Total sleep deprivation Pim Drinkenburg,
induces EEG oscillations
in rats with absence epilepsy
Gilles van Luijtelaar and Anton Coenen
Department of Psychology, University of Nijmegen,
The Netherlands
Total sleep deprivation (TSD) is often used as a provocation method for the diagnosis of epilepsy. It induces a state favourable for the occurrence of absence seizures. Generally, absences occur during intermediate levels of vigilance, during sleep-wake transitions. Rats of the WAC/Rij strain show spontaneously occurring spike-wave discharges (SWD) in the cortical EEG as well as clinical signs of absence epilepsy. Furthermore, they show a prolonged intermediate stage and various spindle-like 8-l 0 Hz oscillations.
128
In the present study, it is investigated whether the occurrence of SWD and of other oscillations is facilitated by TSD. Eight male adult WAG/Rij rats were chronically provided with cortical EEC and nuchal EMC electrodes. Animals were recorded for 24 h to obtain a base-line; next they were deprived of total sleep for 12 h during the light phase. TSD was accomplished with an arousal technique: at detection of sleep-onset the cage of the animal was shaken until the rat awakened. TSD appeared to be effective: a reduction of 78% was accomplished, eliminating all REM sleep and almost all deep sleep. The number of SWD was enhanced during the first four hours of the TSD period, followed by a decrease after eight deprivation hours. These results may be explained by the presence of an initial increase in sleep pressure and in transitions into light slow wave sleep, gradually changing into the presence of periods during which awakenings were immediately followed by quick transitions into deep sleep; the latter state being unfavourable for the appearance of SWD. Furthermore, another result was that in the course of the TSD, arousing of the animal was followed by oscillations in the EEC about 2 s after the shaking of the cage had ended.The probability of an oscillation to occur following an arousal increased about 4.3 times as TSD proceeded. These results indicate that TSD facilitates the occurrence of two types of oscillations: first, the characteristic SWD in the beginning of the TSD period, and later on the short lasting rhythmic phenomena. Whether both types of oscillations should be considered as representatives of one class is an important question for future research, as well as the question whether the arousal-induced rhythmic oscillations are a common phenomenon or unique to epileptic rats.
Transition frequencies as additional activity in the elevated plus-maze test
measurements
for
assessing
anxiolytic
drug
U. Falter, J. Gobert and A.J. Cower UCB-Pharma,
CNS Department,
Chemin
du Foriest, B-1420
Braine-I’Alleud,
Belgium
The elevated plus-maze is a standard rodent test of anxiety aimed at detecting potential new anxiolytic drugs. It consists of a cross-maze, mounted 70 cm above floor level, with two open and two closed arms, like arms facing one another. As rodents spontaneously tend to avoid the open arms, anxiolytic activity is classically inferred from the ease with which drug-treated animals increase the number of visits onto and/or the time spent on the open arms. Recent studies (Moser, 1989) have shown that these measurements are not sufficient to reliably detect new anxiolytic compounds. The aim of the present experiments was to investigate whether information provided by the spatial exploration strategy could contribute to a better appreciation of the anxiolytic activity of drugs in this test. Besides the standard measurements, we therefore also calculated arm-transition frequencies, expressed as percentage of closed-closed, or open-open transitions, and percentage of open-closed, or closed-open transitions. Chlordiazepoxide (CDP), O-20 mg/kg po 60 min, or O-IO mg/kg ip 30 min, was used as the reference drug and its effects were evaluated either on a