No effect of acute tryptophan depletion on phosphodiesterase inhibition--related improvements of short-term object memory in male Wistar rats.

Abstract

OBJECTIVE To further explore the implication of the serotonin (5-HT) system in the improvement of rat short-term object recognition after administration of the type 2 phosphodiesterase inhibitor (PDE-I) BAY 60-7550 and the type 5 PDE-I vardenafil, the effect of PDE2 and PDE5 inhibition upon central amino acid levels, 5-HT, and related parameters were measured after applying acute tryptophan depletion (ATD). METHOD Wistar rats were orally administered saline or a protein-carbohydrate mixture with or without tryptophan (TRP). TRP-depleted animals additionally received an oral vehicle injection or the PDE inhibitors BAY 60-7550 or vardenafil at a dose known to improve object memory performance. RESULTS Although ATD significantly decreased TRP levels in the hippocampus 2 h after administration, 5-HT levels appeared only moderately affected, without any changes observed in the amount of 5-HIAA or 5-HT turnover rate. Moreover, no effects of PDE inhibition upon 5-HT or related parameters were observed. CONCLUSION Changes in 5-HT neurotransmitter activity might be excluded as a potential underlying mechanism of the previously reported ability of PDE inhibitors to improve short-term object memory in rats. It is suggested that a decrease in cerebral blood flow potentially underlies ATD-induced object memory deficits, most likely due to decrease in NO synthesis.

DOI: 10.1111/acps.12166

Cite this paper

@article{Donkelaar2013NoEO, title={No effect of acute tryptophan depletion on phosphodiesterase inhibition--related improvements of short-term object memory in male Wistar rats.}, author={Eva L. van Donkelaar and Jos HHJ Prickaerts and Sven Akkerman and Kris Rutten and Harry W. M. Steinbusch and Arjan A. J. Blokland}, journal={Acta psychiatrica Scandinavica}, year={2013}, volume={128 2}, pages={107-13} }