LONG-TERM BEHAVIORAL AND NEUROENDOCRINE CHANGES IN ROMAN HIGH-(RHA VERH) AND LOW-(RLA-VERH) AVOIDANCE RATS FOLLOWING NEONATAL HANDLING/

Roman high-(RHA/Verh) and low-(RLA/Verh) avoidance rats, originally se lected and bred for rapid vs poor acquisition of a two-way active avoi dance response, differ in emotional reactivity and coping style. These differences are associated with particular neuroendocrine and neuroch emical characteristics. New data are presented here to show that the b ehavioural changes specifically induced by neonatal handling, i.e. dec reased emotional reactivity, are associated with marked changes in the neuroendocrine responses of (hyperemotional) RLA/Verh rats to a novel environment. Eight months after neonatal handling, self-grooming beha viour, a reliable marker of emotional reactivity in this line of rats, was significantly decreased in RLA/Verh rats. Defecation scores were also significantly reduced in both lines. Moreover, there was a signif icant reduction in prolactin and corticosterone release following expo sure to a novel environment in neonatally-handled RLA/Verh rats as com pared to control, non-handled rats. No effects on prolactin and cortic osterone release were observed in RHA/Verh rats. There was also no app arent effect of neonatal handling on coping style i.e. RLA/Verh rats d id not increase their spontaneous exploration of novel environments. T hus, the phenotypic expression of basic traits of(high) neuroendocrine /emotional reactivity was specifically modulated by neonatal handling in RLA/Verh rats, whereas both the (hypo-emotional) RHA/Verh rats as w ell as coping style in both lines remained unaffected. Changes in emot ional reactivity were still apparent at 12 months of age when rats fro m the same groups were tested for hyponeophagia. These results suggest that psychogenetically selected lines such as RHA/RLA rats are suitab le animal models to investigate interactions between genes and the env ironment in determining individual sensitivity to stress and coping st yles, as well as potential vulnerability (or resistance) to the develo pment of maladaptive syndromes similar to anxiety and mood disorders i n humans. (C) 1998 ISDN. Published by Elsevier Science Ltd.