Open field behaviour of rats after various mesencephalic lesions.
Hooded rats of the Long-Evans strain with small bilateral symmetric lesions of the pretectum (PR, n = 10), the nucleus commissurae posterioris (NCP, n = 14), area cuneiformis (CU, n = 10), area subcuneiformis (CUS, n = 11) and with combined lesions of CU and NCP (n = 6) were compared in an open field (OF) situation with sham-operated controls (C, n = 8). All lesioned rats showed significantly decreased crossing of 15 cm squares in the OF, which were controlled by infra-red beams. This decrease was stronger after dorsal lesions (55% of controls) than after ventral ones (80% of controls). In all lesioned groups with exception of CUS rats the duration of immobility was significantly prolonged, maximally after NCP lesions (980%). When NCP rats moved, they had a higher rate of crossings per second (150%) whereas CUS rats moved more slowly (71% crossings per second related to controls). The stay on peripheral fields was prolonged in PR rats and reduced in NCP rats. The number of rearings in all lesioned animals was less than 25% of control values. This was closely correlated with a strong reduction of climbings at the walls except after PR lesions. The third parameter of exploratory behaviour - the duration of sniffing - was significantly diminished except in CUS rats, in which sniffing was significantly enhanced compared with controls. Lesioned rats had shorter grooming latencies with a minimum in CUS rats (23% of controls) and prolonged grooming durations with a maximum in NCP-CU rats (267%). The results demonstrate that relatively small lesions in the anterior mesencephalic reticular formation (MRF) lead to remarkable changes in the spontaneous behaviour of rats with widely differing patterns of behavioural parameters depending on the locus of bilateral symmetric lesions. The data suggest in contrast to the hypothesis of an unspecific modulating function of the MRF, that their different parts play a specific role in the integration of various behavioural patterns.
D000818:Animals; D005106:Exploratory Behavior / Q000502:physiology*; D006120:Grooming / Q000502:physiology; D008297:Male; D008636:Mesencephalon / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D009928:Organ Specificity; D051381:Rats; D013238:Stereotaxic Techniques