Effect of intracisternal administration of prostaglandin E1 on waking and sleep in the rat

EFFECT OF INTRACrSTERNAL ADMINISTRATION OF PR~STAGLAND~N E, UN WAKING AND SLEEP fN THE RAT I(. M&K, 0. KAIILECOv~and N. I%s.XLf)VA, institute of P~rrna~lo~y,

Summary--lntracisternal

Czechosiovak Academy of Sciences, Prague. Czechoslovakirt

injection of SO pg/kg prostaglandin

E, (PGE,) to rats was followed by a

marked decrease of the paradoxical phase of sleep in the second and third hour after prostaglandin injection. The administration of &hydroxydopamine, which lowered the total level of noradrenaline to 40?;, and dopamine to 507; of control value, decreased the total time the animals spent in paradoxical sleep by 507;. The injection of PGE, to 6-hydroxydopamine-treated rats further decreased the time that animals spent in paradoxical sleep. However, the total time of paradoxical sleep in intact and 6-bydr~xydopamine-treated animals injected with PGE was about equal, i.e. i&15?;, of control values.

ProsEa~~~~dins of different types are found diffusely throughout the central nervous system, which also has the complete system for their synthesis and metabolism (SAMUELSON, 1972). A definite role of prostaglandins in the central nervous system is so far not clear. Originally it was thought that they might play the role of a transmitter, but more recent data suggests that they are modulators in neurotransmission (HEIXXJI~~and VONEULER, 1972). Prosta~landins of the E type (PGE) have been shown to induce in chickens and cats sedation, stupor and catatonia (HOLFUIE~ and HORTON,1968). lntraperitoneaf. adm~n~stratiun of PGE, to rats induced the behaviourat state characterized by sedation. diminished muscular tone and an activated EEG pattern which resembled paradoxical sleep (HAIJBRICH, PEREZ-CRUETand REID, 1973). The main aim of present paper was to investigate the effect of intracisternal injection of PGE, on different forms of sleep which would validate the original observation of HAUNCH et ul.(1973) and to decide whether the central noradrenergic neurones are involved in the effect of prostaglandin.

MATERIAL

AND

METHODS

The experiments were carried out on rats of the Wistar strain, housed in a constant tight-dark cycle at a temperature ranging from 22 to 23” C. Food and water were available ad lib. Sleep cycles were recorded by means of bipolar electrodes chronically implanted in the frontal cortex and dorsal hippocampus. The electrode for eiectromyographic (EMG) recording was introduced into the neck muscles. Seven days after surgery the adaptation of animals was begun. The rats were piaced for 3 consecutive days from 9 a.m. to 3 pm into a soundproof, weakly iihtminated experiment& box. The actual recording was begun i 5 min after the administration of prostag-

landin E, and lasted 6 hr. The electroencephaiographic (EEG) records were classified as described previously (KA~ILE~XIVA,MASEK, RA~KOVA and ROTTA. 1972) into 4 stages: wakefulness, non cyclic slow-wave sleep, cyclic slow-wave sleep and paradoxical sleep. For the determination of noradrenaline (NA) and dopamine (DA) ievels. the rats were killed at the end of EEG recording, i.e. 6 hr after injection of prostaglandin. The whole brain was quickly removed and homogenized in a gfass homogenizer with 4 vol. 0.4 M ice-cooled perchforic acid and the NA and DA levels were determined Spectro~uorometricaI~y as described previously (MASEK, KADLECOV~and RASIcuvA, 19735. In the case of ~-hydroxydopamine (f%OHDA)treated animals, 20 pl of the compound with ascorbic acid (200 ,ug of the free base) was injected intracisternally into each rat. Seven days later the sleep patterns of animals were recorded and the effect of prostaglandin E, was evaluated. Control animals were injected with an equal volume of isotonic saline solution containing OSS, of ascorbic acid. Anatomical controls on the site of injection were performed by the injection of Indian ink solution. Moreover, it was observed that when the injection was misdirected, the animals continually turned in one direction and these animals were discarded. Prostaglandin E, was kindly supplied by Dr. John Pike from Upjohn Laboratories, Kalamasoo, Michigan. and was made soluble in 0.9:; NaCl solution by converting it to PGE,-Na (STITT. 1973). Two doses of PGE, (S and 50 {*g/kg body weight) were injected intracisternally.

BESLX~S The intracisternai ~dmin~stmt~on of 50 pgjkg prostaglandin E, to rats caused evident sedation which

K. MA&K.

492

0. KAULECOVA and

set

WAKEFULNESS

SLOW

WAVE

N

P&SHLOVA

SLEEP set

PARADOXICAL

SLEFP

lOOOr

---CONTROL --GE,

Fig. 1. Effect of 50 pg/kg PGE, on waking and sleep in rats. The pomts on the curves represent the mean values from six animals. Statistically significant results are denoted by asterisks * P < 0.05: **p < 0.01.

started a few minutes after PGE, injection and persisted for several hours. The animals had minimal spontaneous movements and lay with closed eyes. The ten times smaller dose of PGE, (5 pg/kg) was without noticeable effect. The EEG recording clearly demonstrated that the dose of 50 pg/kg PGE, induced marked changes in the sleep pattern of rats. While the duration of paradoxical sleep in the second and third hour after prostaglandin injection was significantly decreased, the wakefulness in corresponding hours increased. The observed decrease in the total time of slow-wave sleep (cyclic and non cyclic) was not statistically significant (Fig. 1). The injection of 6-OHDA into the cerebrospinal fluid produces degeneration of the sympathetic nerve DOPAMINE

terminals. The dose I mg/kg 6-OHDA caused a substantial decrease of both brain monoamines 7 days after injection in our experiments; NA being decreased to 407” and DA to 509b of control values. The intracisternal administration of 50 pg/kg PGE, alone had no effect on the level of NA and DA measured 6 hr after PGE, administration (Fig. 2). The partial destruction of catecholaminergic nerve terminals with a corresponding reduction of brain NA and DA resulted in about a 50”;; decrease of the total time the animals spent in paradoxical sleep during the first 3 hr. The injection of 50 pg/kg PGE, to 6-OHDA-treated animals decreased the duration of paradoxical sleep to about same extent as in intact animals. However, the sleep recordings 24 hr later showed a rebound phenomenon in intact animals, i.e. a significant increase of total time of paradoxical sleep, whereas paradoxical sleep deprivation was not

-de

PARADOXICAL

SLEEP

*

400.

% t t 200.

0

CONTROL

f36-

&ZZJ

PGE,

m6-OHDA+PGE,

OHDA

Control

PGE,

6-OHDA

6-?HDA

PGE,

6-OFDA

PGE,

Fig. 2. Effect of drugs on NA and DA levels in tl7e I of rats. PGE, was given in a dose of 50 pg/kg intracisternally and the animals were killed 6 hr later. 6-Hydroxydopamine (I mg/kg) was given by the same route and the effect of prostaglandin was tested 7 days later. Columns represent the mean value of six animals with their fiducial limits. Statistically significant results are denoted by an asterisk (P < 0.05).

PGEI 24tlr

later

Fig. 3. Effect of 6-OHDA (1 mgjkg) and PGE, (50 pg/kg) on the total time of paradoxical sleep during the first 3 hr. The sleep patterns of rats were recorded 15 min after injection of PGE, and 24 hr later. Columns represent the mean value of six animals with their fiducial limits. Statistically significant results are denoted by an asterisk (P < 0.05).

ERect

followed by rebound in the animals with S-OHDA (Fig. 3).

of PGE,

treated previously

DISCUSSION The main pbarmacologi~l effect of pros&gland& of the E series on the central nervous system, irrespective of the route of administration, seems to be the sedation of animals (HORTON, 1964). However, much higher doses of prostaglandins are required to produce the effect after intravenous, intraperitoneal or subcutaneous administration. This is understandable, since only little or no prostaglandins reach the CNS by these routes of administration (NAKANO, 1970). Qnly small amounts of prastaglandins are taken up by brain tissue even after intracerebral administration (HOLMESand Ho~ron, 1968). The most prominent change in waking and sleep in our experiments was a marked decrease of paradoxical sleep in the second and third hour after prostaglandin injection. Instead there was a significant increase of wakefulness. Our findings differ from those of &UBRICH et ai. (i973), who suggested that prostaglandin El appears to induce a state of persistent paradoxical sleep. The apparent reason for this discrepancy may be in the different design of the two sets of experiments. While PGE, was administered intracisternally in our experiments, HAUBRICH et af. (1973) employed jntraper~toneal administration. Different results have also been previously obtained in the effect of prostaglandins on body temperature. While intracerebral administration caused an increase in temperature in the experiments of a number of workers (FELDBERG and SAXENA, 1971; MILTON and WENDLANUT, 1971; STKT, 1973) the intraperitoneal administration in Haubrich’s experiments produced a marked decrease of body temperature (HAUBRICH et al., 1973). The important role of central monoaminergic neurones in the onset and maintenance of different forms of sleep is now generally accepted (FUXE and LIDBRINK, 1974). Since BIXOS.SR~&%, FARNEBOand FUXE (1973) recently suggested that the prostagiandins might also reduce catecholamine release from central neurones in manner similar to that in the peripheral sympathetic system (HEr>~vrs~ and VON EULER, 19723, it was of interest to know whether the effect of PGEr on sleep is related to the central noradrenergic neurones. We therefore foliowed waking and sleep after prostagfandin administration in the rat with a relatively selective destruction of sympathetic pathways induced by intracisternal injection of 6UHL)A. The adm~nistratiou of &OHDA, which decreased the total levef of NA to 40% and DA to 5O”i, of control value.

decreased the total time the animals spent in paradoxical sleep by SOY&This is in good agreement with the hypothesis that noradrenergic neurones, besides their role in the process of waking also have a role in the induction af paradoxical sleep (JOUVET, 1972). The injection of PGE, to Ci-OHDA-treated rats

493

on deep

decreased the time which animals spent in paradoxical deep. However the total time of paradoxical sleep in intact and GOHDA-treated animals injected with PGEr was about equal, i.e. lU-i5”i, of control values. The measurement of c3H)-NA release from rat midbrain and medulla oblnngata after intracisternal administration of 20 )tg PGE, revealed the slowdown of [‘HI-NA release (MAQEK and KADLEC, 1975) and this in uiuo finding is in good agreement with the in vitro results of BERGSTRB~~ CCal. (1973) and suggests that at least part of the effect of PGE, on sleep patterns might be related to noradrenergic neurones. However, the possible involvement of other systems which have been suggested to play a role in control of waking and sleep, such as Shydroxytryptaminergic and parasympathetic systems cannot be excluded (JOUVET, 1972). In fact a growing body of data supports the concept of a close interplay of these systems in the control of sleep. The effect of prostaglandin E, on rr4C]5-hydroxytryptamine release from rat brain has also been studied by our group (MAW further

and KADLEC, 1975).

It should be borne in mind that prostag~and~~s might in&.tence the cerebral circulation and this may contribute to the changes in sleep patterns. So far no data are available as to whether and how the prostagfandins infhtence cerebral circulation after intracerebral injection. fntracarotid infusion of PGE, caused a vasod~~atat~on in the study of DENTON, WHITEand ROBERTSON(1972) and vasoconstr~ctio~ in work of YAMAMOTO, FEINDEL, WOLFE, KA~OT)W and HODGE f 1972). In the normal rat the effect of PGE, was short term and the evaluation of waking and sleep the fol-

lowing day showed a rebound phenomenon, i.e. an increase in the total time spent in paradoxical sleep, but no such effect was observed in 6-OHDA-treated animals. This further supports the concept that intact central noradrenergic pathways are of key importance for the induction of paradoxical sleep and therefore also for the rebound phenomenon.

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HEDQVIST, P. and VON EULER. U.S. (1972). Prostagiandininduced neurotransmissiotl failure in field stimulated vas deferens. ~euro~~r~colog~ 11: i 77-187. HOLMES, S. W. and HORTON,E. W. (1968). The distribution of tritium labelled prostaglandin E, injected in amounts sufficient to produce central nervous effects in cats and chicks. Br. J. Pharmuc. 34: 32-37. HORTON, E. W. (1964). Action of prostaglandin E,. E2 and E, on the central nervous system. Br. J. Pkatwuc. 22: 189-192. JOUVET. M. (1972). The role of monoamines and acetylcholine-containing neurons in the regulation of sleep-waking cycle. Erg&n. Physioi. 64: 168-307. KAULLCOVA0.. MASEK. K.. KASKOVA.H. and Ro? TA. J. (1972). Fever and sleep cycle im~~irn~cnt after streptococcal mucopeptide adminjstration. Toyicott 10: 473477. MASEK. K. and KADLFC. 0. (1975). The effect of prostagktndin of E-type on peripheral and central release of neurotransmitters. Interrxuiorzal Cor$wttcr of1 Prosfugh&m, Florence, May 26-30. 1975. Abstracts pp. 17 18.

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