Granulocyte-macrophage colony-stimulating factor modulates rapid eye movement (REM) sleep and non-REM sleep in rats

Abstract

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic cytokine that may affect various functions of the CNS because the molecule and its receptors are expressed in the brain. The present study examines the effects of GM-CSF on sleep using rats and the secretion of three neurotransmitters/hormones that are involved in sleep regulation. When infused intracerebroventricularly at doses as low as 10 pmol for 10 hr during the dark period, GM-CSF promoted predominantly rapid eye movement (REM) sleep and moderate amounts of non-REM sleep without eliciting fever. An injection of GM-CSF (3.0 pmol) into the arcuate nucleus increased the release of nitric oxide (NO) from the hypothalamus but did not alter plasma levels of growth hormone. The release of somatostatin (SRIF) from the medial basal hypothalamus was stimulated by 1 x 10(-)(11) M GM-CSF. These findings indicated that centrally administered GM-CSF stimulates SRIF release through activation of the NO system in the hypothalamus. Because SRIF promotes REM sleep, it may also mediate the effects of GM-CSF on REM sleep. The present study indicates a novel central effect of GM-CSF that modulates sleep, supporting the notion that hematopoietic cytokines also play roles in the CNS.

Fig. 1.

Effects of GM-CSF (10 pmol) on sleep and brain temperature (Tbr). Data points indicate 1 hr averages of changes in Tbr (n = 6) and time spent in non-REM sleep (non-REMS) and REM sleep (REMS) (n = 7). Each symbol represents mean ± SE (white, day 1; black, day 2; gray, day 3). Horizontal gray barindicates GM-CSF infusion for 10 hr on day 2; otherwise the rats were infused intracerebroventricularly with saline during the entire 3 d period. Horizontal open bar, Light period;horizontal hatched bar, dark period. ANOVA for Tbr between days 1 and 2 during the dark period,F_(1,5) = 16.15; p< 0.01; ANOVA for non-REMS between days 1 and 2 during postinfusion hr 1–3, F_(1,6) = 26.57;p < 0.01; for REMS between day 1 versus days 2 and 3 during the dark period, F_(2,12) = 13.58; p < 0.001; for REMS between days 1 and 2 versus day 3 during the light period,F_(2,12) = 8.12; p< 0.01.

Fig. 2.

Effects of anti-GM-CSF antibodies (10 μg) on sleep and brain temperature (Tbr). Data points indicate 1 hr averages of changes in Tbr (n = 3) and time spent in non-REMS and REMS (n = 5). Each symbol represents mean ± SE (white, day 1; black, day 2; gray, day 3).Horizontal gray bar indicates the period when anti-GM-CSF was infused for 10 hr on day 2; otherwise the rats were infused intracerebroventricularly with saline during the entire 3 d period. Horizontal open bar, Light period;horizontal hatched bar, dark period. ANOVA between days 1 and 2 versus day 3 during the dark period for NREMS,F_(2,8) = 5.09; p < 0.05, for REMS F_(2,8) = 9.24;p < 0.001.

Fig. 3.

Effects of GM-CSF on the release of NOx from the hypothalamus. Top panel, Data points indicate typical changes (%) in NOx release during and after local administration of norepinephrine (NE; 30 nmol/0.5 μl saline;triangles) in the Arc of the hypothalamus, compared with the level before administration (pre). Bottom panel,Data points ± SE indicate changes (%) in NOx release during and after local saline administration (open circles) and GM-CSF (3 pmol/0.5 μl; solid circles) in the Arc (n = 6 each). ANOVA between control and GM-CSF-injected groups F_(1,200) = 134.1; p < 0.001. *Statistical difference from preinjection baseline; p < 0.05.

Fig. 4.

Locomotor activity after the local injection of GM-CSF into the hypothalamus. Locomotor activity was simultaneously monitored while NOx was measured (Fig. 3). Arrowsindicate timing of saline or GM-CSF injection. Locomotion intensity is shown as variable densities in vertical columns. Horizontal open bar, Light period; horizontal hatched bar, dark period.

Fig. 5.

Plasma levels of GH after local GM-CSF injection into the hypothalamus. Data points ± SEM indicate plasma levels of GH after local saline and GM-CSF administration (3 pmol/0.5 μl each) to the Arc of the hypothalamus. ANOVA between control saline and GM-CSF-injected groups (n = 5 each),F_(1,56) = 0.75; p> 0.05.

Fig. 6.

Effects of GM-CSF on SRIF release from the hypothalamus in vitro. Height ± SE of columns and symbols indicate quantities of SRIF released into the medium incubated without (KRB only) or with GM-CSF. Numbers represent number of explants of the MBH in each group. ANOVA among all groups,F_(2,23) = 4.04; p< 0.01. *Statistical difference from KRB control;p < 0.05.