RELATION OF EXPLORATORY-BEHAVIOR OF RATS IN ELEVATED PLUS-MAZE TO BRAIN RECEPTOR-BINDING PROPERTIES AND SERUM GROWTH-HORMONE LEVELS

Forty-five male Wistar rats were selected according to their behavior in the elevated plus-maze. They were separated as follows: animals wit h low exploratory activity ('anxious'), an 'intermediate' group and an imals having high exploratory activity ('non-anxious'). Various recept or binding studies and hormonal assays were also performed in these se lected rats. The affinity of 5-hydroxytryptamine 5-HT2A receptors in t he frontal cortex was lower in the 'anxious' rats compared to home-cag e controls and 'non-anxious' animals. Moreover, the number of cholecys tokinin (CCK) receptors in the hippocampus was significantly elevated in the 'anxious' group compared to home-cage control animals. The bloo d levels of growth hormone (GH) were significantly lower in the 'non-a nxious' rats compared to 'anxious' counterparts. In conclusion, it see ms likely that the decreased exploratory activity of rats is related t o the increased 5-hydroxytryptamine (5-HT) and CCK mediated neurotrans mission in the brain. The different serum levels of GH in the selected rats probably reflect alterations in the activity of 5-HT and CCK. (C ) 1997 Elsevier Science B.V.