A method of post-
stroke treatment at delayed timepoints with
sigma receptor agonists. Sigma receptors are promising targets for
neuroprotection following
ischemia. One of the key components in the demise of neurons following
ischemic injury is the disruption of
intracellular calcium homeostasis. The
sigma receptor agonist, DTG, was shown to depress [Ca2+]i elevations observed in response to
ischemia induced by
sodium azide and
glucose deprivation. Two
sigma receptor antagonists, metaphit and BD-1047, were shown to blunt the ability of DTG to inhibit
ischemia-evoked increases in [Ca2+]i. DTG inhibition of ischemia-induced increases in [Ca2+]i was mimicked by the sigma-1
receptor-selective agonists, carbetapentane, (+)-pentazocine and PRE-084, but not by the sigma-2 selective
agonist, ibogaine, showing that activation of sigma-1 receptors is responsible for the effects. Activation of sigma receptors can ameliorate [Ca2+]i dysregulation associated with ischemia in
cortical neurons, providing neuroprotective properties. The effects of 1,3-di-o-tolyguanidine (DTG), a high affinity sigma
receptor agonist, as a potential treatment for decreasing infarct area at
delayed time points was further examined in rats. DTG treatment significantly reduced infarct area in both cortical / striatal and cortical / hippocampal regions by >80%, relative to control rats. These findings were confirmed by immunohistochemical experiments using the neuronal marker, mouse anti-neuronal nuclei
monoclonal antibody (NeuN), which showed that application of DTG significantly increased the number of viable neurons in these regions. Furthermore, DTG blocked the
inflammatory response evoked by MCAO, as indicated by decreases in the number of reactive astrocytes and activated
microglia / macrophages detected by
immunostaining for
glial fibrillary acidic protein (GFAP) and binding of isolectin IB4, respectively. Thus, the sigma
receptor-selective agonist, DTG, can enhance neuronal survival when administered 24 hr after an
ischemic stroke. In addition, the
efficacy of sigma receptors for
stroke treatment at
delayed time points is likely the result of combined neuroprotective and anti-inflammatory properties of these receptors.