Lead (Pb) is a non physiological metal that has been implicated in toxic processes affecting several organs and biological systems, including the central nervous system. Several studies have focused on changes in lead-associated neurobehavioral and neurochemical alterations that occur due to Pb exposure. The present study evaluates the effects of acute and chronic Pb acetate exposure on serotoninergic and dopaminergic systems within the dorsal raphe nucleus, regarding motor activity and anxiety behaviours. Experiments were carried out on adult male Meriones shawi exposed to acute lead acetate intoxication (25 mg/kg b.w., 3 i.p. injections) or to a chronic lead exposure (0,5%) in drinking water from intrauterine age to adult age. Immunohistochemical staining demonstrated that both acute and chronic lead exposure increased anti-serotonin (anti-5HT) and tyrosine hydroxylase (anti-TH) immuno-reactivities in the dorsal raphe nucleus. In parallel, our results demonstrated that a long term Pb-exposure, but not an acute lead intoxication, induced behavioural alterations including, hyperactivity (open field test), and anxiogenic like-effects. Such neurobehavioral impairments induced by Pb-exposure in Meriones shawi may be related to dopaminergic and serotoninergic injuries identified in the dorsal raphe nucleus.