The neuroprotective effects of the acetylenic tryptamine derivative, PF9601N, against excitotoxic damage

Bolea I2, Ballini C1, Colivicchi MA1, Fattori M1, Torre E1, Marco JL3, Unzeta M2 & Della CorteL1 1Dip. Farmacologia Preclinica e Clinica, Università di Firenze, Italia; 2Dep. Bioquimica i Biologia Molecular, Institut de Neurociències, Universitat Autònoma de Barcelona, Spain; 3Inst. Quimica Organica General (CSIC), Madrid, Spain.

Selegiline, an irreversible monoamine oxidase B inhibitor, has been shown to have neuroprotective properties. It has been used alone and as an adjunct to levodopa therapy in Parkinson’s disease A new series of acetylenic and allenic derivatives of tryptamine has been described by Unzeta and co-workers (e.g., Sanz et al., 2004). In particular, N-(2-propynyl)-2-(5-benzyloxy-indolyl) methylamine (PF9601N) behaved as a MAO B inhibitor that was more potent and selective than selegiline, both in vitro and in vivo. It also showed an inhibitory capacity towards dopamine reuptake in human caudate similar to that of selegiline. Furthermore, PF9601N was shown to exert neuroprotective effects against intrastriatallly administered 6-hydroxydopamine (6-OHDA) and, in vitro, against an excess of dopamine.

The aim of the present work was to investigate the neuroprotective effects of PF9601N in vivo against excitotoxic damage induced by the non-NMDA glutamatergic agonist, kainic acid (KA, 1 mM), applied intrastriatally by vertical microdialysis.

Wistar male rats (220-250 g body weight) were anaesthetised (chloral hydrate, 400 mg/kg i.p.) and microdialysis vertical probes (3 mm tip) implanted stereotaxically in the right striatum (co-ordinates relative to bregma: AP 0.7; L 3.2; DV 5.5 mm). After 24 h, the probes were perfused (1.5 µl/min) with artificial cerebrospinal fluid (aCSF in mM: NaCl 140, KCl 3, CaCl2 1.2, Mg Cl2 1.0, Na2HPO4 1.2, NaH2PO4 0.27 and glucose 7.2, pH 7.4) for 2 h, before collecting samples at 20 min intervals up to 4 h. Amino acid levels were monitored in the dialysates by HPLC with fluorimetric detection (Bianchi et al., 1999). After the first 3 samples (basal values), perfusion with aCSF containing KA (1 mM for 20 min) induced a statistically significant (ANOVA) increase in the extracellular levels (nM, mean± ESM) of the excitotoxic amino acids, aspartate (140± 42) and glutamate (354± 81), accompanied by an increase of the inhibitory neuroprotective amino acid taurine (1231± 134). Post-mortem histological examination of the tissue, 48 h after KA administration, using TUNEL staining, showed apoptotic degeneration of 70.1% (± 13 %) of the nuclei. When the animals were treated i.p. with PF9601N (30 mg/kg body weight) 3 h before KA administration, the KA-evoked release of glutamate (-7± 15) was significantly reduced, whereas the evoked release of taurine was significantly increased (1858± 131). Furthermore, the percentage of apoptotic nuclei was drastically reduced (3.2± 1.1 %), down to values observed in the control group (3.8± 3.0 %). These data demonstrate the neuroprotective effects of PF9601N against excitotoxic damage, both in terms of a reduced release of the excitotoxic amino acid glutamate and an increased release of the neuroprotective amino acid, taurine.

The combined neurochemical and histological approach used in the present study provides new data in support of the value of PF9601N as a potential drug for the therapy of neurodegenerative diseases, such as Parkinson’s and Alzheimer’s diseases, as well as for other pathological conditions, such as cerebral ischemia, that also involve excitotoxic damage and apoptotic neuronal degeneration.

Bianchi et al. (1999) J. Chromatogr. B723: 47-59.
Sanz et al. (2004) Med. Sci. Monit. 10: BR477-484.

Supported by COST D34.