REGIONAL DIFFERENCES IN RAT BENZODIAZEPINE BINDING IN RESPONSE TO NOVELTY AND CAT ODOR

Laboratory rats exhibit innate behavioural and corticosterone response s when exposed to cat odour. However, not all are responsive and diffe rences in benzodiazepine receptor binding between responders and non-r esponders were explored. Rats were exposed to cat odour for 5 min and based on time spent sheltering were divided into responders (n = 21; m ean h SEM = 244 +/- 8.2 sec) or non-responders (n = 20; 43.9 +/- 4.8 s ec). Four days later, both groups were randomly allocated among 3 expe rimental conditions: home-cage, neutral or cat odour, and killed 30 mi n after exposure. [H-3]flunitrazepam binding was performed at two liga nd concentrations (2 and 10 nM); where significant differences in sing le point binding were found, Scatchard analysis was performed on poole d samples. In hippocampus and frontal cortex responders had significan tly lower binding than non-responders. In hippocampus this was most ap parent when the rats were exposed to the novel test situation, i.e. ne utral odour and was due to a reduction in affinity (K-d = 0.4 and 1.2 nM non-responders and responders). In frontal cortex, differences were significant only following exposure to cat odour (B-max = 2663 and 15 01 fmol/mg protein in non-responders and responders). The changes in a mygdala were not significant.