Introduction receptors located on glutamatergic terminals [38,29]. Re-
Brain Research 883 2000 41–50 www.elsevier.com locate bres
Research report
Stimulation of 5-HT receptors reduces apoptosis after transient
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forebrain ischemia in the rat
Christine Schaper, Yuan Zhu, Maria Kouklei, Carsten Culmsee, Josef Krieglstein
¨ ¨
Institut f ur Pharmakologie und Toxikologie , Fachbereich Pharmazie, Philipps-Universitat Marburg, Ketzerbach 63, D-35032 Marburg, Germany
Accepted 15 August 2000
Abstract
It has recently been shown that 5-HT receptor stimulation reduced the infarct volume after occlusion of the middle cerebral artery in
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rats. Since there is increasing evidence that apoptosis is involved in neurodegenerative diseases and stroke, we investigated whether the 5-HT
agonist Bay x 3702 could protect neurons against apoptotic damage in a rat model of transient forebrain cerebral ischemia. Bay x
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3702 4 mg kg i.v. caused a 10 reduction of neuronal damage in the hippocampal CA1 subfield. Higher doses of Bay x 3702 40 and 12 mg kg i.v. did not cause any neuroprotective effect, most likely because of the strong reduction of mean arterial blood pressure during
the period of Bay x 3702 infusion. Bay x 3702 4 mg kg i.v. diminished DNA laddering in the hippocampus and striatum 4 days after 10 min forebrain ischemia. These results were confirmed by TUNEL-staining. The anti-apoptotic effect was abolished by additional
treatment with the 5-HT
receptor antagonist WAY 100635 1 mg kg. Taken together, the results suggest that Bay x 3702 can rescue
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hippocampal as well as striatal neurons from apoptotic cell death in vivo via stimulation of 5-HT receptors.
2000 Elsevier Science
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B.V. All rights reserved.
Theme : Disorders of the nervous system
Topic : Ischemia
Keywords : 5-HT
agonist; Forebrain ischemia; WAY 100635; Apoptosis; Neuroprotection
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1. Introduction receptors located on glutamatergic terminals [38,29]. Re-
cently it has been shown that stimulation of 5-HT
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It is well known that the stimulation of 5-HT re-
receptors inhibits apoptotic cell death in primary cultures
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ceptors can cause neuroprotection in vitro and in vivo of embryonic chick neurons [3,43] as well as in neuronal
[9,36,37,35]. Postsynaptic 5-HT receptors are highly
HN-2-5 cells [1]. There is growing evidence that apoptotic
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expressed in brain regions such as hippocampus or neocor- cell death occurs under pathological conditions, such as
tex [34,15]. In these regions the neurons are highly Alzheimer’s disease, Parkinson’s disease and Huntington’s
sensitive to damage induced by cerebral ischemia or brain disease [18,30]. It has also been reported that delayed
trauma [34,10]. The mechanism which leads to neuro- neuronal death, which is most likely apoptosis, can also
protection after activation of the 5-HT receptors is
appear after acute insults to CNS, such as cerebral
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thought to be due to the induction of hyperpolarisation of ischemia [27,28,19]. This demonstration of apoptosis after
neuronal membranes [12,14,4]. This effect is most likely cerebral ischemia suggests an increased time window for
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mediated by opening G protein-coupled K channels.
therapeutical intervention [26]. In the light of these data it Additionally, it has been reported that 5-HT
receptor is of interest to know whether stimulation of 5-HT
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agonists can reduce glutamate release [39], which is most receptors could lead to reduced apoptotic cell death in
likely mediated through activation of presynaptic 5-HT vivo. Therefore, we used the model of transient forebrain
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ischemia, where a maximum of apoptotic cells was de- tected at the fourth day after ischemia [51]. For 5-HT
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Corresponding author. Tel.: 149-6421-282-1311; fax: 149-6421-282-
receptor stimulation we used the highly potent 5-HT
8918.
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E-mail address : krieglstmailer.uni-marburg.de J. Krieglstein.
receptor agonist Bay x 3702 2-R-2-[4-[[3,4-dihydro-
0006-8993 00 – see front matter
2000 Elsevier Science B.V. All rights reserved. P I I : S 0 0 0 6 - 8 9 9 3 0 0 0 2 8 7 6 - 6
42 C
2H - 1 - benzopyran - 2 - ylmethyl]amino] - butyl] - 1, 2 - ben - removed, the blood was reinfused and NaHCO 50 mg
3
zisothiazol-32H-one 1,1-dioxide
monohydrochloride kg, i.v. was administered. Arterial pH, pCO , pO and
2 2
[15,16]. blood pressure were measured before and after ischemia.
The aim of this study was to investigate whether the The experiments were approved by the government ethics
5-HT agonist Bay x 3702 could cause an anti-apoptotic
committee. All efforts were made to reduce the suffering
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effect in vivo. In addition, we attempted to find out, of the animals during the experiments.
whether this anti-apoptotic effect could be blocked by the selective 5-HT
receptor antagonist WAY 100635 N-[2- 2.4. Drug administration
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[4-methoxyphenyl-piperazinyl]ethyl]-N-2-piperidinyl cy- clohexane carboxamide [20]. Electrophoresis and staining
Bay x 3702 40, 12 and 4 mg kg or saline were infused with terminal deoxynucleotidyl transferase TdT-mediated
i.v. with a perfusor Secura, Braun, Melsungen, Germany dUTP nick end labeling TUNEL were used to measure
immediately after ischemia for a period of 4 h. The DNA laddering and to detect internucleosomal DNA
infusion was given into the tail vein with a constant flow fragmentation in situ.
rate of 1 ml h. WAY 100635 1 mg kg was injected i.p. 60 min before ischemia. The body temperature was
maintained at 3760.58C with a heating lamp during the