Behavioural and Biochemical Evidence that Cholinergic or Dopaminergic Stimulation in the Nucleus Accumbens Differentially Alters Dopaminergic Activities in Rat Ventrolateral Striatum
Unilateral turning is usually considered to arise from unequal stimulation of dopamine receptors on each side of the brain, resulting in an asymmetrical striatal output and forcing animals to rotate away from the side with the greatest dopaminergic stimulation (Ungerstedt, 1971). This turning is believed to involve two processes, thus the process of postural asymmetry, which keeps the animal curved in one direction (postural component), and the process of locomotion (locomotion component), which is the drive for active circling in the direction of the postural asymmetry (Pycock 1980; Pycock and Marsden, 1978). The process of postural asymmetry has been ascribed to the striatum, whereas the process of locomotion has been ascribed to the nucleus accumbens (Ziegler and Szechtman, 1990, 1988; Kelly and Moore, 1976). This so-called two-component hypothesis was based upon studies with unilaterally lesioned rats. However, it is preferable to investigate these mechanisms in intact brains rather than to rely on lateral imbalances caused by denervation supersensitivity induced by chemical or physical lesions. This can be optimally achieved in intact rats by unilateral injections of agonists and antagonists into discrete regions of the brain, a technique which has the additional advantage of permitting both selective receptor stimulation and blockade (Saigusa et al., 1995, 1993; Konitsiotis and Kafetzopoulos, 1990; Koshikawa et al., 1990; Costali et al., 1983).
KeywordsNucleus Accumbens Dopamine Release Dopaminergic Treatment Dopaminergic Stimulation Unilateral Injection
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