Dissociation between cognitive and motor/motivational deficits in the delayed matching to position test: effects of scopolamine, 8-OH-DPAT and EAA antagonists

Abstract

The effects of the muscarinic antagonists scopolamine HBr and MeBr, the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), and the N-methyl-d-aspartate (NMDA) antagonists MK-801 and CGS-19755 on performance of rats in a delayed matching-to-position task were examined. Pretreatment with scopolamine HBr (0.05 and 0.1 mg/kg), resulted in a delay-dependent decrease in the percentage of correct responses and discriminability (log d), but had no effect on either the latency to complete trials, or the rate of trial completion during the fixed duration session. Scopolamine MeBr (0.1 mg/kg) did not impair percent correct or increase the response latency but did decrease the rate of trial completion. 8-OH-DPAT (up to 0.3 mg/kg), had no effect on percent correct, but did induce a small decrease in discriminability. The impairment in discriminability occurred only at a dose that substantially reduced the rate of trial completion. Both MK-801 (0.05 mg/kg) and CGS 19755 (10 mg/kg) induced a delay-independent impairment in percent correct, discriminability and a reduction in the rate of trial completion without affecting latency. A lower dose of CGS 19755 (5.0 mg/kg) induced a slight impairment in discriminability without significantly affecting the other measures. Taken together, these results demonstrate some dissociation between drug-induced cognitive and motor/motivational deficits in the DMTP test. However, the data question the specificity of putative cognitive impairments reported in many previous studies with the 5-HT1A agonist 8-OH-DPAT.

Effects of low‐dose scopolamine on locomotor activity: No dissociation between cognitive and non‐effects

“…Results showed that the increase in locomotor activity is due to the central effect of the drug, because scopolamine MeBr does not cross the blood-brain barrier, unlike scopolamine HBr. This is in parallel with the observed effects of scopolamine on cognitive tasks such as memory in other studies (36)(37)(38)(39)(40)(41)(42). In these studies, scopolamine HBr was found to affect NEUROSCIENCE RESEARCH COMMUNICATIONS, VOL.…”

Scopolamine Effects Under a Titrating-Delayed-Nonmatching-to-Position Procedure

“…Our findings, too, suggest that the effects of scopolamine may not be confined to working memory, in that the most effective dose (0.06 mg/kg SC) disrupted all measures of performance, not just the highest delay attained. interestingly, Stanhope, McLenachan, and Dourish (1995) found that low doses of scopolamine (0.05 and 0.1 mg/kg iP) produced delay-dependent reductions in the accuracy of rats performing a DMTS task without reducing the number of trials completed. This finding is suggestive of selective impairment of working memory.…”

The glycine transporter 1 inhibitor SSR504734 enhances working memory performance in a continuous delayed alternation task in C57BL/6 mice

“…Here, this possibility had been reduced by requiring the subjects to press a centrally located lever to activate the availability of a choice (illumination of both magazine lights), thus ensuring that the mouse would always be in the same location when the choice was presented. Furthermore, the installation of partition walls between the lever and magazines also reduced the use of simple motor pattern as mediating strategy, although this possibility can never be completely eliminated (see Stanhope et al 1995). Most critically, however, the use of mediating behaviour is expected to assist performance at short rather than at long delays (Rawlins and Tsaltas 1983).…”