Microinjection of the melanin-concentrating hormone into the lateral basal forebrain increases REM sleep and reduces wakefulness in the rat

Abstract

AimsTo examine the effects of bilateral microinjection of melanin-concentrating hormone (MCH) 50 and 100ng into the horizontal limb of the diagonal band of Broca (HDB) on sleep variables during the light phase of the light–dark cycle of the rat. Main methodsMale Wistar rats were implanted for chronic sleep recordings. In addition, a guide cannula was implanted above the right and left HDB. Following the microinjection of MCH or control solution the electroencephalogram and the electromyogram were recorded for 6h. Data was collected and classified as either wakefulness (W), light sleep, slow wave sleep (SWS) or REM sleep (REMS). Latencies for SWS and REMS, as well as the number of REM periods and the mean duration of REM episodes were also determined. Key findingsMCH 50 and 100ng significantly decreased W during the first 2-h of recording. Moreover, MCH 100ng significantly reduced REMS latency and increased REMS time during the first 2-h block of the recording, due to an increase in the number of REM periods. SignificanceOur findings tend to suggest that the basal forebrain participates in the effects of MCH on W and REMS through the deactivation of cholinergic, glutamatergic and γ-aminobutyric acid (GABA)-ergic cells.