3alpha-OL-5-beta-pregnan-20-one hemisuccinate, a steroidal low-affinity NMDA receptor antagonist improves clinical rating scores in a rabbit multiple infarct ischemia model: synergism with tissue plasminogen activator.
We previously showed that the neuroactive steroid 3alpha-ol-5-beta-pregnan-20-one hemisuccinate (ABHS), a low-affinity NMDA receptor antagonist, improves behavior in rabbits following spinal cord ischemia. The present study assessed whether this also occurs following cerebral ischemia. We used the rabbit small clot embolic stroke model (RSCEM), a model of multiple infarct ischemia, which has a well-defined behavioral endpoint. Quantal analysis for each treatment determines microclots (mg) that produce neurologic dysfunction in 50% of a group of animals (P(50)), with treatment considered beneficial if it increases the P(50) compared to controls. ABHS (25 mg/kg) injected 5 min post-embolization significantly (P = 0.046) increased the P(50) to 2.60 +/- 0.69 mg compared to 1.15 +/- 0.19 mg in controls but was ineffective at longer intervals. For combination studies with tissue plasminogen activator (tPA), a cumulative control curve (P(50) = 1.18 +/- 0.25 mg) was used for statistical comparisons. Low-dose tPA (0.9 mg/kg) and ABHS, given 60 min post-embolization, improved behavior synergistically (P(50) = 2.44 +/- 0.44 mg), compared to tPA (P(50) = 1.25 +/- 0.25 mg) or ABHS (P(50) = 1.05 +/- 0.24 mg) alone. A standard tPA dose (3.3 mg/kg) significantly increased the P(50) at 60 (2.69 +/- 0.19 mg) but not 180 min (1.28 +/- 0.31 mg) post-embolization. However, when combined with ABHS, an effect was evident even 180 min post-embolization (P(50) = 2.31 +/- 0.48 mg). Although the therapeutic window for ABHS is limited, it significantly enhanced neuroprotection by low-dose tPA and increased the therapeutic window for tPA, suggesting that it may be most useful as a co-therapy with thrombolytics for stroke.
Lapchak
Paul A
PA
Department of Neuroscience, University of California San Diego, 9500 Gilman Drive, MTF 316, La Jolla, 92093-0624, USA. plapchak@ucsd.edu
D000818:Animals; D002545:Brain Ischemia / Q000517:prevention & control*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D018691:Excitatory Amino Acid Antagonists / Q000627:therapeutic use; D005343:Fibrinolytic Agents / Q000627:therapeutic use*; D008297:Male; D011280:Pregnanolone / Q000627:therapeutic use*; D011817:Rabbits; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000627:therapeutic use*; D016896:Treatment Outcome
D018691:Excitatory Amino Acid Antagonists; D005343:Fibrinolytic Agents; D016194:Receptors, N-Methyl-D-Aspartate; D011280:Pregnanolone; D010959:Tissue Plasminogen Activator