Behavioural and adrenocortical responses to nicotine measured in rats with selective lesions of the 5‐hydroxytryptaminergic fibres innervating the hippocampus

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Abstract
1 The effects of acute and subchronic (7) injections of nicotine (0.4 mg kg−1, s.c.) and of selective lesions of the 5-hydroxytryptaminergic (5-HTergic) pathways innervating the hippocampus on the spontaneous behaviour of rats in an elevated X-maze composed of two open and two enclosed runways have been examined. 2 Subchronic, but not acute, nicotine increased total spontaneous activity. Neither acute nor subchronic nicotine altered the ratio of open:closed runway entries. 3 Destruction of the 5-HTergic pathways innervating the hippocampus with 5,7-dihydroxytryptamine caused a reduction in the ratio of open:enclosed runway entries. 4 Acute, but not subchronic, nicotine caused a significant increase in plasma corticosterone. The lesion had no effects on the plasma levels of this hormone. 5 No significant interactions between the lesion and the responses to nicotine were observed. 6 The data failed to provide any evidence that hippocampal 5-HTergic systems may be implicated in the effects of nicotine on the spontaneous behaviour of the rat.