CSF and blood oxytocin concentration changes following intranasal delivery in macaque.

Oxytocin (OT) in the central nervous system (CNS) influences social cognition and behavior, making it a candidate for treating clinical disorders such as schizophrenia and autism. Intranasal administration has been proposed as a possible route of delivery to the CNS for molecules like OT. While intranasal administration of OT influences social cognition and behavior, it is not well established whether this is an effective means for delivering OT to CNS targets. We administered OT or its vehicle (saline) to 15 primates (Macaca mulatta), using either intranasal spray or a nebulizer, and measured OT concentration changes in the cerebral spinal fluid (CSF) and in blood. All subjects received both delivery methods and both drug conditions. Baseline samples of blood and CSF were taken immediately before drug administration. Blood was collected every 10 minutes after administration for 40 minutes and CSF was collected once post-delivery, at the 40 minutes time point. We found that intranasal administration of exogenous OT increased concentrations in both CSF and plasma compared to saline. Both delivery methods resulted in similar elevations of OT concentration in CSF, while the changes in plasma OT concentration were greater after nasal spray compared to nebulizer. In conclusion our study provides evidence that both nebulizer and nasal spray OT administration can elevate CSF OT levels.

Reversal of peripheral nerve injury-induced hypersensitivity in the postpartum period: role of spinal oxytocin.

BACKGROUND: Physical injury, including surgery, can result in chronic pain; yet chronic pain following childbirth, including cesarean delivery in women, is rare. The mechanisms involved in this protection by pregnancy or delivery have not been explored. METHODS: We examined the effect of pregnancy and delivery on hypersensitivity to mechanical stimuli of the rat hindpaw induced by peripheral nerve injury (spinal nerve ligation) and after intrathecal oxytocin, atosiban, and naloxone. Additionally, oxytocin concentration in lumbar spinal cerebrospinal fluid was determined. RESULTS: Spinal nerve ligation performed at mid-pregnancy resulted in similar hypersensitivity to nonpregnant controls, but hypersensitivity partially resolved beginning after delivery. Removal of pups after delivery prevented this partial resolution. Cerebrospinal fluid concentrations of oxytocin were greater in normal postpartum rats prior to weaning. To examine the effect of injury at the time of delivery rather than during pregnancy, spinal nerve ligation was performed within 24 h of delivery. This resulted in acute hypersensitivity that partially resolved over the next 2-3 weeks. Weaning of pups resulted only in a temporary return of hypersensitivity. Intrathecal oxytocin effectively reversed the hypersensitivity following separation of the pups. Postpartum resolution of hypersensitivity was transiently abolished by intrathecal injection of the oxytocin receptor antagonist, atosiban. CONCLUSIONS: These results suggest that the postpartum period rather than pregnancy protects against chronic hypersensitivity from peripheral nerve injury and that this protection may reflect sustained oxytocin signaling in the central nervous system during this period.

CSF levels of prostaglandins, especially the level of prostaglandin D2, are correlated with increasing propensity towards sleep in rats.

The concentration of PGD2, PGE2, and of PGF2 alpha was measured in the cerebrospinal fluid (CSF) collected from the cisterna magna of conscious rats (n = 29), which, chronically implanted with a catheter for the CSF sampling, underwent deprivation of daytime sleep. Significant elevation of the CSF level of PGD2 was observed following 2.5-h sleep deprivation (SD), and the elevation became more marked following 5- and 10-h SD, apparently reaching the maximum at 5-h SD (703 +/- 140 pg/ml (mean +/- S.E.M.) for baseline vs. 1734 +/- 363 pg/ml for SD, n = 10). The levels of PGE2, and PGF2 alpha also significantly increased following 5- and 10-h SD, but not following 2.5-h SD. It is unlikely that these changes were simply caused by some responses of the animals to stress stimuli, because stress stimuli derived from restraint of the animal at the supine position to a board for 1 h did not produce any acute responses in the CSF levels of prostaglandins (n = 13). In a different group of animals (n = 11) implanted with electrodes for recording electroencephalogram (EEG) and electromyogram (EMG) in addition to the catheter, the levels of the prostaglandins in CSF were determined for slow-wave sleep (SWS) and wakefulness in the day and for SWS and wakefulness in the night. The highest PGD2 value was obtained at daytime SWS, whereas the lowest was at night wakefulness; furthermore, a significant difference was observed between SWS and wakefulness rather than between day and night. The CSF level of PGE2 also showed a similar tendency. In an additional group of animals (n = 6), not only PGD2 but also PGE2 and PGF2 alpha significantly increased the sleeping time of the animal when applied into the subarachnoid space underlying the ventral surface area of the rostral basal forebrain, the previously defined site of action for the sleep-promoting effect of PGD2. The promotion of sleep by PGE2 applied to the subarachnoid space was an effect completely opposite to the well-established awaking effect of the same prostaglandin demonstrated in the hypothalamic region in a series of previous studies. Based on these results, we conclude that increases in CSF levels of prostaglandins, especially that of PGD2, are correlated in rats with heightened propensity towards sleep and further with the depth of sleep under normal as well as SD conditions.