Supranormal Stimulation of D₁Dopamine Receptors in the Rodent Prefrontal Cortex Impairs Spatial Working Memory Performance

TLDR

Dopamine normally supports prefrontal cortex function, but supranormal D1 receptor stimulation—especially under mild stress—has been shown to impair spatial working memory. The study aimed to test whether supranormal D1 receptor activation in the PFC impairs spatial working memory by infusing the agonist SKF 81297 during a delayed alternation task. Rats received intracerebral infusions of SKF 81297 into the PFC while performing a delayed alternation spatial working memory task. SKF 81297 caused a dose‑dependent impairment of delayed‑alternation performance that was reversed by the D1 antagonist SCH 23390, with the effect depending on infusion site and higher antagonist doses producing mild deficits.

Abstract

Although previous research has emphasized the beneficial effects of dopamine (DA) on functions of the prefrontal cortex (PFC), recent studies of animals exposed to mild stress indicate that excessive DA receptor stimulation may be detrimental to the spatial working memory functions of the PFC (Arnsten and Goldman-Rakic, 1990; Murphy et al., 1994, 1996a,b, 1997). In particular, these studies have suggested that supranormal stimulation of D 1 receptors may contribute to the detrimental actions of DA in the PFC (Murphy et al., 1994, 1996a). The current study directly tested this hypothesis by examining the effects of infusing a full D 1 receptor agonist, SKF 81297, into the PFC of rats performing a spatial working memory task, delayed alternation. SKF 81297 produced a dose-related impairment in delayed-alternation performance. The impairment was reversed by pretreatment with a D 1 receptor antagonist, SCH 23390, consistent with drug actions at D 1 receptors. SCH 23390 by itself had no effect on performance, although slightly higher doses impaired performance (Murphy et al., 1994, 1996a). There was a significant relationship between infusion location and drug efficacy; animals with cannulae anterior to the PFC were not impaired by SKF 81297 infusions. Taken together, these results demonstrate that supranormal D 1 receptor stimulation in the PFC is sufficient to impair PFC working memory function. These cognitive data are consistent with recent electrophysiological studies of D 1 receptor mechanisms affecting the PFC (Williams and Goldman-Rakic, 1995; Yang and Seamans, 1996). Increased D 1 receptor stimulation during stress may serve to take the PFC “off-line” to allow posterior cortical and subcortical structures to regulate behavior, but may contribute to the vulnerability of the PFC in many neuropsychiatric disorders.