Open field behaviour of rats after various mesencephalic lesions
Mager, P.; Mager, R.; Klingberg, F.
Biomedica Biochimica Acta 42(10): 1257-1267
1983
ISSN/ISBN: 0232-766X PMID: 6372792 Document Number: 212228
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 IR 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 crossing S per second (150%) whereas CUS rats moved more slowly (71% crossings/s 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 < 25% of control values. This was closely correlated with a strong reduction of climbings at the walls except after PR lesions. The 3rd parameter of exploratory behavior, 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%). Relatively small lesions in the anterior mesencephalic reticular formation (MRF) lead to remarkable changes in the spontaneous behavior of rats with widely differing patterns of behavioral 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 behavioral patterns.