Experiments were conducted to investigate species-specific preferences in two closely related species of hamsters, Phodopus campbelli and Phodopus sungorus. Male hamsters that were raised with conspecifics spent more time investigating an anaesthetized conspecific male than a heterospecific male, and also spent more time investigating odours of conspecifics than those of heterospecifics (midventral gland, urine, and saccular secretion). Cross-fostered P. sungorus males reversed their normal preferences, spending more time investigating stimuli (anaesthetized males and all three odours) of the foster species. Cross-fostered P. campbelli males also investigated an anaesthetized male of the foster species more than a male of their own species, but did not show a preference for odours alone. Social experience during the 15 d immediately following weaning also influenced these preferences. If exposures during and after nesting were to heterospecifics the preference for heterospecifics was strengthened; if either period of experience was with a conspecific, this eliminated the preference for heterospecifics in P. sungorus but did not influence the lack of a preference in P. campbelli. Thus, early experience during both the nestling stage and the 15 d after weaning influenced responses to species-typical cues in both species, but it had a more pronounced effect in P. sungorus.
The character of interaction between two dominant foci (motivation hunger dominant and "animal hypnosis") which had been formed in the rabbit brain was ambiguous: the foci could either function simultaneously or compete. In the first case, summation food reactions were observed when the hunger dominant was tested during a hypnotic episode against the background of deep and continuous hypnotic state. Brain thermal activity was asymmetric the temperature being higher in the parieto-occipital areas of the left hemisphere. If the hypnosis inhibited the hunger dominant, summation reactions were absent and the brain temperature was higher in the parieto-occipital areas of the right hemisphere. In cases when despite the repeated immobilization sessions the hunger dominant prevented from induction of hypnosis, the left-hemisphere thermal dominance persisted against the background of general brain cooling.
The rat brain thermal fields were studied using the thermoencephaloscopic technique in three experimental conditions: the genetic catalepsy (GC rat strain), cataleptic phase of an audiogenic epileptic seizure (Krushinskiĭ-Molodkina strain), and pharmacological catalepsy produced by haloperidol injection (Wistar rats). Irrespective of the experimental conditions, the state of catalepsy, accompanied by a decrease in the muscle tone and inhibition of motor reactions, was characterized by total asymmetric cooling of the brain cortex with the dominance of the right hemisphere. Temperature difference between the parieto-occipital areas of the right and left hemispheres reached 0.3-0.6 degree C.
The character of interaction between two dominant foci (motivation hunger dominant and "animal hypnosis") which had been formed in the rabbit brain was ambiguous: the foci could either function simultaneously or compete. In the first case, summation food reactions were observed when the hunger dominant was tested during a hypnotic episode against the background of deep and continuous hypnotic state. Brain thermal activity was asymmetric the temperature being higher in the parieto-occipital areas of the left hemisphere. If the hypnosis inhibited the hunger dominant, summation reactions were absent and the brain temperature was higher in the parieto-occipital areas of the right hemisphere. In cases when despite the repeated immobilization sessions the hunger dominant prevented from induction of hypnosis, the left-hemisphere thermal dominance persisted against the background of general brain cooling.
Motivational states of hunger or thirst in rabbits were produced by the relevant deprivation of different duration (24 and 48 h). The distribution of brain thermal fields was studied by the method of thermoencephaloscopy. The thermal asymmetry was observed in the states of thirst and hunger the temperature of the left hemisphere being higher. Generalization of the brain temperature reaction depended on the level of motivational excitation. The interhemispheric brain asymmetry with higher temperature in the left hemisphere in the states of food and drinking deprivation had a pronounced trace effect, i.e., persisted for some time after satisfaction of the corresponding need. Evidently, the interhemispheric asymmetry with higher temperature of the left hemisphere reflects its predominant activation in the studied states.
The effects of neurotransplantation on development of audiogenic seizures (AS) were studied in Krushinsky-Molodkina (KM) rats genetically predisposed to AS and in Wistar rats especially selected for AS. Within 24 weeks after bilateral combined transplantation of the newborn striatum and cerebellum into the parietal cortex, the AS didn't develop in Wistar rats in 74% of tests. In control Wistar rats with cortical grafts or saline into the parietal cortex there were no significant changes in the AS development. In the experimental KM rats the grafting led to the 4-5-times increase in the AS latency. In 50% of rats it decreased the AS severity by 1-2. In the control KM rats these parameters didn't change. It was concluded that it was possible to suppress or decrease the AS development by the transplantation of the newborn striatal and cerebellar tissue into the cortex of rats predisposed to this kind of seizures.
The effects of neurotransplantation on development of audiogenic seizures (AS) were studied in Krushinskiĭ-Molodkina (KM) rats genetically predisposed to AS and in Wistar rats especially selected for AS. Within 24 weeks after bilateral combined transplantation of the newborn striatum and cerebellum into the parietal cortex, the AS didn't develop in Wistar rats in 74% of tests. In control Wistar rats with cortical grafts or saline injections into the parietal cortex there were no significant changes in the AS development. In the experimental KM rats the grafting led to the 4-5-times increase in the AS latency. In 50% of rats it decreased the AS severity by 1-2. In the control KM rats these parameters didn't change. It was concluded that it was possible to suppress or decrease the AS development by the transplantation of the newborn striatal and cerebellar tissue into the cortex of rats predisposed to this kind of seizures.
The cataleptic state is characterized by the presence of muscular rigidity, automatisms, and myoclonus. These symptoms frequently occur in epileptic patients. In animal models, a relation between catalepsy and epilepsy also is sometimes reported. Petrova et al. (J Vysh Nervn Deyar 1992;42: 1009-17) showed that genetic cataleptic rats have an increased predisposition for epileptoform activity, including signs of petit mal. In the present study, we investigated whether WAG/Rij rats, genetically endowed with generalized spike-wave discharges (SWD) are more sensitive for catalepsy. WAG/Rij and Wistar rats, implanted with chronic EEG electrodes, were recorded for 15 min; rats were exposed to photic stimulation of 3, 10, and 25 Hz for 2-min periods and several days later to acoustic stimulation with key ringing. WAG/Rij showed some behavioral signs of fear after both types of stimulation, and the EEG was periodically driven by the rhythm of the flashes; SWD were not observed. However, in the first 5 min after the end of the visual and auditory stimulation, 10 and I 1 of 13 WAG/Rij became motionless and retained an uncomfortable pose when forced to sit on their sacrum. The number of SWD gradually increased and reached a maximum 5-10 min after the end of the stimulation. Wistar rats remained active after visual and auditory stimulation and manifested no sign of pathology in behavior or in EEG. Genetically epileptic WAG/Rij are more susceptible than Wistar rats to induction of a cataleptic state, suggesting that the mechanisms responsible for SWD and for catalepsy might be related.
By the method of forced immobilization the rabbits were brought into the state of <<animal hypnosis>> (immobilization reflex), and their ECoG was recorded, which was further processed on the computer. It was found that during hypnosis a functional interhemispheric brain asymmetry was developed in rabbits with activity predominance in the right hemisphere. The <<animal hypnosis>> is a phasic process: in the ECoG of the rabbit under hypnosis a regular alternation of delta and theta activity takes place. Electrophysiological reconstructions in the rabbit brain during the change of its functional state correlate with the brain thermoreactions, revealed earlier.
