RESUMEN
The role of medial septum in the genesis of slow-wave sleep and the inhibition of rapid eye movement sleep has been established using neurotoxic lesion and chemical stimulation of the medial septum. Intracerebroventricular injection of endocannabinoids (anandamide) decreases wake and increases slow-wave and rapid eye movement sleep in rats. Central cannabinoid (CB1) receptors are localized in the rat medial septum; however, the role of cannabinoid receptors at the medial septum on the regulation of sleep-wakefulness in rats lacks evidence. In this study, we have examined the changes in sleep architecture of 21 male Wistar rats, divided into three groups. Initially, 6 rats were used for dose standardization. Subsequently, one group (n = 6) was microinjected with CB1 receptor agonist, R-(+)-WIN 55,212-2 mesylate salt, the second group (n = 6) received microinjection of CB1 receptor antagonist LY 320,135, and the third group (n = 5) was microinjected with the vehicle, DMSO at the medial septum using stereotaxy. The sleep-wake cycle was recorded using electroencephalogram, electro-oculogram, and electromyogram. Microinjection of CB1 receptor agonist at the medial septum decreased slow-wave sleep and increased total sleep time. The increase in total sleep time was due to an increased percentage of rapid eye movement sleep. After the third and fourth hour of CB1 receptor antagonist microinjection at the medial septum, slow-wave sleep decreased when compared to vehicle injection, while rapid eye movement sleep decreased compared to baseline. We conclude that the endocannabinoid system at the septal nucleus acts through CB1 receptors to increase rapid eye movement sleep in rats.
Asunto(s)
Endocannabinoides , Vigilia , Animales , Masculino , Microinyecciones , Ratas , Ratas Wistar , SueñoRESUMEN
Spatio-temporal dynamics of activated brain areas induced by drinking were investigated and visualized in behaving rats using functional magnetic resonance imaging (fMRI). The rats were trained to drink in the magnet bore, and the images were taken during and after drinking glucose and distilled water. During glucose ingestion, the signal intensity was increased continuously and maximally in the lateral hypothalamic area (LHA) and the ventromedial hypothalamus (VMH). Somewhat less intense activation in the central nucleus of the amygdala (AMc), and transient activation in the piriform cortex and the mediodorsal nucleus of the thalamus were observed. The signal intensities of other regions measured were largely unchanged. During post-ingestive periods, the signals re-increased in the hypothalamic areas and AMc. When water was given, LHA and VMH were similarly activated, however, the signal intensity in the amygdala was not significantly increased. The results indicate that these brain regions are activated differentially during drinking behavior, and that LHA and VMH play a central role in the control of not only feeding but also drinking. The regional activities in LHA and VMH are not principally related to the gustatory sensation, and the reactivation after drinking may be related to satisfaction or post-ingestive nutritional information. Also, the responses of AMc are probably due to reward value difference. To the best of our knowledge, this is the first report of mapping of brain areas using fMRI in behaving rats. The improved method described in this study for collecting fMRI data in behaving animals will be useful for studying functional network during animal behavior.