GIF-0173 protects against cerebral infarction through DP1 receptor activation.

The neuroprotective effects and mechanism of action of GIF-0173, a Delta12-prostaglandin J analogue, were investigated in the early phase of cerebral ischemia. GIF-0173 was administered intravenously immediately following middle cerebral artery occlusion (MCAO) in photochemically induced thrombosis model of rat. Neurological scores and infarct sizes were examined at 24 h after MCAO. Cerebral blood flow (CBF) was monitored by laser-Doppler flowmetry for 1 h after MCAO. In cultured cortical neurons obtained from 1-day-old rats, the effects of GIF-0173 on the excitotoxicity induced by glutamate were examined. Morphological changes, neuronal death, and changes in intracellular calcium concentration ([Ca(2+)](i)) were also examined. GIF-0173 improved neurological scores and reduced the infarct size in a dose-dependent manner following MCAO. But GIF-0173 did not improve CBF after MCAO. GIF-0173 also prevented glutamate-induced neuronal death and acute cellular swelling in primary cultures in a dose-dependent manner, indicating that it inhibited neuronal necrosis. GIF-0173 dose-dependently suppressed the glutamate-induced increase in [Ca(2+)](i), but could not inhibit NMDA-induced calcium influx. The effects of GIF-0173 against glutamate-induced [Ca(2+)](i) increase were reversed by addition of non-specific prostaglandin D (PGD(2)) receptor antagonist and were comparable to the effects of PGD(2) DP1 receptor agonist, which prevented [Ca(2+)](i) increase and neuronal death. We conclude that GIF-0173 reduces cerebral infarction and protects cultured neurons against glutamate-induced excitotoxicity by inhibiting [Ca(2+)](i) increase through DP1 receptor activation.

A synthetic kainoid, (2S,3R,4R)-3-carboxymethyl-4-(phenylthio)pyrrolidine-2-carboxylic acid (PSPA-1) serves as a novel anti-allodynic agent for neuropathic pain.

In spite of prominent progress in basic pain research, neuropathic pain remains a significant medical problem, because it is often poorly relieved by conventional analgesics. Thus this situation encourages us to make more sophisticated efforts toward the discovery of new analgesics. We previously showed that i.t. administration of acromelic acid-A (ACRO-A), a Japanese mushroom poison, provoked prominent tactile pain (allodynia) at an extremely low dose of 1 fg/mouse. In the present study we synthesized ACRO-A analogues (2S,3R,4R)-3-carboxymethyl-4-phenoxypyrrolidine-2-carboxylic acid (POPA-2) and (2S,3R,4R)-3-carboxymethyl-4-(phenylthio)pyrrolidine-2-carboxylic acid (PSPA-1) chemically and examined their ability to induce allodynia in conscious mice. Whereas POPA-2 induced allodynia at extremely low doses from 1 to 100 fg/mouse, similar to ACRO-A, PSPA-1 did not induce allodynia; rather, it inhibited the ACRO-A-induced allodynia with an ID(50) value (95% confidence limits) of 2.19 fg/mouse (0.04-31.8 fg/mouse). Furthermore, PSPA-1 relieved neuropathic pain produced by L5 spinal nerve transection on day 7 after the operation in a dose-dependent manner from 1 to 100 pg/mouse. In contrast, it did not affect thermal or mechanical nociception or inflammatory pain. PSPA-1 reduced the increase in neuronal nitric oxide synthase activity in the spinal cord of neuropathic pain mice assessed by NADPH-diaphorase histochemistry and blocked the allodynia induced by N-methyl-d-aspartate. These results demonstrate that PSPA-1 may represent a novel class of anti-allodynic agents for neuropathic pain acting by blocking the glutamate-nitric oxide pathway.