Sleep-wake and eeg effects following adenosine a1 agonism and antagonism: similarities and interactions with sleep-wake and eeg effects following a serotonin reuptake inhibitor in rats.

Adenosine is currently being investigated as a possible mediator of a homeostatic sleep need. Reports from different laboratories suggest that both adenosine A1 agonists and selective serotonin reuptake inhibitors (SSRI) increase deep slow wave sleep (SWS-2) after an interval. In this study, the sleep-wake effects of the adenosine A1 agonist N6-cyclopentyladenosine (CPA) and the SSRI zimeldine are directly compared in the same animals. Since the SWS-2 increase following SSRIs may be secondary to increased adenosine levels during the initially increased waking, it was also investigated whether the adenosine A1 antagonist 8-cyclopentyltheofylline (CPT) would inhibit the SWS-2 increase following the serotonin reuptake inhibitor. Both the adenosine A1 agonist CPA and the SSRI zimeldine increased SWS-2 after an interval. Both drugs increased slow wave activity and decreased 9-20 Hz activity during SWS-2. Both the adenosine A1 antagonist CPT, zimeldine and the two drugs combined initially increased waking and subsequently increased SWS-2 after 2 or 4 h. All treatments increased 2-6 Hz activity in SWS-2 after 2h. Thus, CPT did not antagonize the SWS-2 increase of zimeldine. Based on the sleep and power spectral effects it is suggested that the adenosine A1 antagonist potentiated the zimeldine effect, possibly due to antagonism of adenosine A1 inhibition of serotonin release. The data indicate that the delayed SWS-2 and slow wave activity increases following zimeldine are not due to increased stimulation of adenosine A1 receptors following the initial sleep loss.