Contrasting effects of systemic and intracerebral infusions of the 5-HT 1A receptor agonist 8-OH-DPAT on spatial short-term working memory in rats

Abstract

The present study compared the effects of systemic 8-OH-DPAT (0.05, 0.1 and 1.0 mg/kg) with intra-raphe and intra-hippocampul infusions of 8-hydroxy-2-(di- n-propylamino)tetralin (8-OH-DPAT) (10, 30 100 ng) on delayed non-matching-to-position (DNMP) performance in rats. The highest dose of 8-OH-DPAT administered systemically impaired DNMP performance in a delayindependent manner, increased premature responding and increased response bias. Infusions of 8-OH-DPAT (100 ng) into the median raphé nucleus improved performance accuracy, independent of delay whilst having no effect on any other response measure. Infusions of 8-OH-DPAT into the dorsal raphe nucleus had no effect on performance at any dose tested. Infusions of 8-OH-DPAT into the dorsal hippocampus produced a small impairment in performance which was also independent of delay. However, this decrement in performance accuracy was not accompanied by any changes in other response measures. These findings demonstrate a dissociation between the effects of stimulation of pre- and post-synaptic 5-HTIA receptors on performance of a DNMP task although the changes in performance cannot be accounted for by changes in mnemonic function.