Modifications of sleep parameters in the rat by (+)- and (-)-3-PPP.

The effects of subcutaneous administration of the two enantiomers of 3-(3-hydroxyphenyl)-N-n-propylpiperidine (3-PPP), a new dopamine analogue, were studied with regard to their effects on sleep parameters in the rat. The studies with both enantiomers were carried out taking into account their different effects on central dopaminergic receptors. At low doses they act preferentially as autoreceptor agonists; at higher doses the (+)-form is also an agonist while the (-)-form acts as an antagonist at postsynaptic dopamine receptors. The results showed the following: (1) with the high dose of (+)-3-PPP there was no change in REM sleep, but a marked increase in wakefulness; (2) with the high dose of (-)-3-PPP there was a significant increase in REM sleep and in the mean duration of REM episodes; (3) with the low dose of (+)-3-PPP similar results to those described for high-dose (-)-3-PPP were obtained; (4) there was no significant alteration of sleep parameters with the low dose of (-)-3-PPP. The data are discussed in terms of an active role for dopamine in the regulation of REM sleep.