Effect of rapid eye movement sleep deprivation on sexual behaviour of male rats.

Rapid eye movement sleep deprivation for 3 to 4 days by the platform pedestal procedure produced an increase in sexual behaviour of male rats. The possible factors contributing towards the increase in sexual behaviour are discussed.

Inhibition of male sexual behavior by serotonin application in the medial preoptic area.

The study investigated the possible involvement of serotonin in the medial preoptic area in the regulation of sexual behavior of male rats. Injection of serotonin in the medial preoptic area resulted in an inhibition, whereas cyproheptadine (a serotonin antagonist) produced a slight facilitation, of male sexual behavior.

REM sleep deprivation and food intake.

The effect of REM-sleep deprivation (REM-SD) on diet preference was studied in rats. REM-SD for a period of 72 hrs produced an increase in day, night and 24 hrs (day plus night) intakes of Carbohydrate Rich diet (CRD) and Total diet (TD). Body weight (BWt) was also increased. The maximum increase in the above parameters were recorded on the 2nd day of REM-SD. During recovery period the intakes of TD fully recovered, but the BWt and consumption of CRD remained high. Intakes of Balanced diet (BD) remained significantly on the lower side when compared to the pre REM-SD mean values. During REM-SD, the rats preferred CRD than BD. The body temperature did not show any change. The increase in TD intake and BWt could be the result of an increase in insulin level and the change appears to be mediated by the activation of hypothalamic feeding centre.

Interrelationship of thermal and sleep-wakefulness changes elicited from the medial preoptic area in rats.

The study investigated the possible interrelationship between changes in sleep-wakefulness and body temperature, primarily induced by manipulation of the noradrenergic system in the medial preoptic area. Saline, norepinephrine, and its alpha- and beta-blockers were injected in the medial preoptic area and in some control areas of rats, during their sleeping and active periods. 5-Hydroxytryptamine was injected in the medial preoptic area in another group of animals. Simultaneous changes in sleep-wakefulness and the body temperature were continuously recorded. Norepinephrine produced hypothermia and arousal, whereas alpha-adrenergic blockers induced hyperthermia and sleep. These changes in body temperature and in sleep-wakefulness did not follow an identical time course. 5-Hydroxytryptamine induced hyperthermia without affecting sleep-wakefulness. It is suggested that there are different neuronal mechanisms in the medial preoptic area that bring about the drug-induced changes in temperature and sleep-wakefulness.

Correlation of preoptic neuronal activity with spontaneous and induced cortical EEG changes.

Preoptic area has neurons which change their firing rate along with spontaneous alterations of the cortical EEG between synchronization and desynchronization. The cortical EEG synchronization and desynchronization could be induced by stimulation of the caudal and the rostral brain stem respectively. This study was aimed at finding out whether stimulation of the brain stem structures produce the same change in the unit activity as that occurring during spontaneous alteration of the EEG. The changes in unit activity showed some concordance and dissociation between spontaneous and induced EEG alterations. The possible interaction of inputs from cortex and brain stem at the level of the preoptic area is discussed.

Alpha adrenergic system in medial preoptic area involved in sleep-wakefulness in rats.

The study is aimed at investigating the possible involvement of adrenergic mechanisms in the medial preoptic area (mPOA) for modulation of sleep-wakefulness in rats. In this study, saline, norepinephrine (NE), phenoxybenzamine (PBZ) and propranolol (PROP) were injected in the mPOA in different groups of male rats during the day and night. NE and PBZ were injected, during the day and the night respectively, in some control areas adjoining the mPOA in two other groups of animals. Arousal was produced by NE, and sleep by PBZ when they were applied in the mPOA. All other procedures, including application of NE and PBZ in the control areas and beta blocker (PROP) in the mPOA, did not produce alterations in sleep-wakefulness. These findings provide support for a physiological role played by the alpha adrenergic system in the mPOA for arousal, and area specificity of action of this system.

Blockade of ovulation by prostaglandins synthesis inhibitor in medial preoptic area.

Indomethacin, a known inhibitor of prostaglandins synthesis, injected into the medial preoptic area on the day of proestrus blocked ovulation in regularly cycling female rats. This finding provides evidence for a facilitatory role of endogenous prostaglandin synthesis, in the medial preoptic area, in the process of ovulation.

Comparison of rostro-caudal brain stem influence on preoptic neurons and cortical EEG.

The changes in activity of preoptic area (POA) neurons, and cortical EEG, upon stimulation of the caudal brain stem reticular formation (CBS) and the rostral brain stem reticular formation (RBS) are compared in this study. Low frequency (LF) stimulation of the CBS (which induced EEG synchronization) and the RBS (which generally did not affect the EEG) had an excitatory influence on a majority of the affected neurons of the POA. In contrast, high frequency (HF) stimulation of the CBS (which produced EEG desynchronization in many instances) and the RBS (which induced EEG desynchronization in all instances) resulted in inhibition of a majority of the affected POA neurons. A larger number of neurons responded to HF stimulation of both brain stem regions, as compared to LF stimulation. The changes induced in the POA neurons, upon stimulation of the two brain stem reticular structures, were not dependent on simultaneous changes in the cortical EEG, except during some cases of stimulation-induced EEG desynchronization.

Tonic activity of medial preoptic norepinephrine mechanism for body temperature maintenance in sleeping and awake rats.

The study was aimed at investigating the possible involvement of tonic activity of the adrenergic receptors in the medial preoptic area (mPOA) for maintenance of body temperature in rats. Differences in drug-induced changes in body temperatures during sleep and wakefulness--during the day and at night--were also investigated. Norepinephrine injected in the mPOA, produced a fall in body temperature, whereas phenoxybenzamine produced an increase. Saline and propranolol produced no alteration. Norepinephrine and phenoxybenzamine produced alterations in sleep-wakefulness also. These changes in sleep-wakefulness did not completely explain the thermal changes. The findings highlight the need for taking into account the basal activity and the time of application of drug in studies on thermo-regulation, using free moving animals.

Mapping of regions in the caudal brain stem that produce stimulus-bound synchronization in the cortical EEG.

This study was aimed at filling the lacunae in our knowledge regarding the localization of the regions in the caudal brain stem that bring about cortical EEG synchronization on electrical stimulation and characteristic features of synchronized waves elicited from those regions. Studies were conducted on 40 encéphale isolé cats. Stimulation of ventromedial regions of the caudal brain stem, with low frequency, elicited stimulus-bound synchronized waves in the cortex which were more prominent ispsilaterally. On the other hand, low-frequency stimulation of dorsal and lateral areas produced synchronized waves which were either equally prominent on both sides, or more prominent on the contralateral side. The loci in the brain stem that produce synchronization were very specific. The induced synchronized waves showed amplitude modulation and did not outlast the train of stimuli. The results are further confirmation of the role of caudal brain stem structures in cortical EEG synchronization. They also provide information regarding the nature of cortical synchronization elicited from these brain stem structures.

Alterations in preoptic unit activity on stimulation of caudal brain stem EEG-synchronizing structures.

Effects of stimulation of EEG-synchronizing structures of the caudal brain stem reticular formation with low (6 Hz) and high (100 Hz) frequencies were studied on 42 neurons of the preoptic area, in encéphale isolé cats. Though low-frequency stimulation produced excitation and inhibition, the majority of the influenced neurons of the preoptic area had effects of the former type. Cortical EEG synchronization was also induced by low-frequency stimulation of the caudal brain stem. High-frequency stimulation, on the other hand, produced inhibition in a majority of the influenced neurons and induced, mostly, desynchronization of the cortical EEG. A majority of the neurons that were inhibited on high-frequency stimulation, remained unaffected during low-frequency stimulation. The influence induced on the preoptic area neurons by low-frequency stimulation could be obtained even in the absence of cortical EEG synchronization. Changes induced on preoptic neurons by high-frequency stimulation may be partially related to induced cortical EEG desynchronization.

Sleep-awake responses elicited from medial preoptic area on application of norepinephrine and phenoxybenzamine in free moving rats.

The study makes an attempt to find out the action of norepinephrine (NE) and phenoxybenzamine (PB), applied at medial preoptic area (mPOA), in altering the sleep-awake responses, in free moving rats, which has not yet been reported. Effects of application of NE during day and PB during night, at mPOA, on sleep-awake responses, were compared with application of saline during identical periods. Application of NE produced arousal, whereas, PB produced the opposite effect. The findings are suggestive of the involvement of NE terminals at mPOA in normal arousal.

Influence of ascending reticular activating system on preoptic neuronal activity.

There is evidence to suggest that the reticular activating system may have an influence on the neurons of the preoptic area (POA). We studied the responses of POA neurons and their relation to the cortical EEG, on stimulation of the midbrain reticular formation (MRF) at various frequencies, in unanesthetized, encéphale isolé cats. Stimulation of the MRF at high frequency produced inhibition of the firing rate in a majority of the responsive neurons of the POA. Stimulation of the MRF with lower frequencies, on the other hand, induced excitation in a majority of the responsive POA neurons. The possibility exists of a summation of stimuli and an involvement of structures bringing about changes in the EEG in causing the shift in the POA neuronal excitability.

Responses of preoptic neurons to stimulation of caudal and rostral brain stem reticular structures.

Effect of stimulation (1 Hz) of rostral and caudal brain stem reticular formation was studied on 41 neurons of preoptic area in encéphale isolé cats. Primary excitation was seen on almost all the 25 neurons influenced by stimulation of either of the areas. Many of these influenced neurons received inputs from both areas and showed poststimulatory oscillations in excitability. The two brain stem reticular structures, which have antagonistic influence on cortical EEG, cortical and subcortical neuronal activity, had identical influence on preoptic area neurons when stimulated at 1 Hz.

Cholinergic activation of medial preoptic area by amygdala for ovulation in rat.

Ovulation blocked by amygdalar lesion was restored by carbachol injection into medial preoptic area (mPOA) in rats on the afternoon of proestrus. Both spontaneous and carbachol-induced ovulation was blocked by application of nicotinic and muscarinic cholinergic antagonists (mecamylamine and atropine) to mPOA. The effect was more pronounced in the latter case. The study suggests amygdalar facilitatory control of ovulation to be mediated via mPOA through the involvement of cholinergic mechanisms.