The acetylcholine release enhancer linopirdine induces Fos in neocortex of aged rats.

Centrally acting cholinergic agents induce the immediate early gene c-fos in the rat brain resulting in transient increases of Fos protein, most notably in the cerebral cortex. In this study we have monitored by Fos immunohistochemistry the effect of the acetylcholine release enhancer linopirdine (DUP996) on the immediate early gene c-fos in brains of 3 months and 30 months old rats. In young rats linopirdine had only a marginal effect on Fos expression. In contrast, in aged rats linopirdine caused widespread expression of Fos throughout neocortex. In somatosensory cortex, the induction of the c-fos gene by linopirdine was nearly completely blocked by atropine and scopolamine and strongly attenuated by the NMDA receptor blockers CPP and MK-801. The results suggest that the age-related decline in acetylcholine release in rodents can be partially compensated for by administration of linopirdine.

Effects of the memory enhancer linopirdine (Dup 996) on cerebral glucose metabolism in naive and hypoxia-exposed rats.

Linopirdine [DuP 996; 3,3-bis(4-pyrindinylmethyl)-1-phenylindolin-2-one] represents a novel class of compounds which enhance depolarization-activated (but not basal) release of acetylcholine, dopamine and serotonin in brain slices and improve learning and memory in rodents. The effects of linopiridine on local cerebral glucose metabolism were studied by the quantitative autoradiographic 2-deoxy-D-[1-14C]glucose method. Linopirdine administration in naive rats (0.01, 0.1, or 1.0 mg/kg, s.c.) did not significantly alter cerebral glucose metabolism in any of the regions analyzed. Since linopirdine protects against hypoxia-induced passive avoidance deficits in rats, we also examined the effects of linopirdine on cerebral metabolism after the rats were exposed to 30 min of hypoxia. Glucose metabolism was not significantly altered after hypoxic exposure, except for a small increase in some brain regions. Linopirdine administered after hypoxia decreased glucose metabolism in the hippocampus, limbic cortex, ventral hippocampal commissure, medial septum, striatum, subthalamic nucleus, zona incerta, lateral habenula, cerebral cortex, cerebellar vermis and a few thalamic nuclei. Statistically significant effects of linopirdine on glucose metabolism were observed in 22 of 56 brain regions sampled. In hypoxia-exposed rats, linopirdine altered glucose metabolism in brain regions that are implicated in learning and memory and are affected in Alzheimer's disease. Several of the affected regions are associated with the cholinergic system and may play a role in the cognitive enhancing properties of linopirdine.

[3H]linopirdine (DuP 996) labels a novel binding site in rat brain involved in the enhancement of stimulus-induced neurotransmitter release: autoradiographic localization studies.

A novel high-affinity binding site for linopirdine (DuP 996; 3,3-bis(4-pyrindinylmethyl)-1-phenylindolin-2-one), a cognitive enhancer which improves learning and memory in rodents and primates, has recently been identified in rat brain homogenates. [3H]Linopirdine binding sites were localized in rat brain using in vitro labeling, light microscopic autoradiography. Highest densities of binding sites were present in the hippocampus (CA1 to CA3 pyramidal cell layers and the granule cells of the dentate gyrus), the cerebral cortex (lamina IV), the dorsal raphe nucleus and the interpeduncular nucleus. Moderate densities were present in the olfactory bulb, olfactory tubercle, amygdala, subiculum and medial habenular nucleus. Lower levels of binding were present in the caudate/putamen, thalamus and hypothalamus. The localization of [3H]linopirdine binding sites in brain areas implicated in cognitive processes and affected in Alzheimer's disease suggest that ligands for this binding site may have therapeutic potential for the treatment of cognitive deficits seen in dementia.

Effects of IL-1 muteins on cartilage degradation and as inducers of acute inflammation.

IL-1 peptides with N-terminal amino acid mutations were cloned and expressed to help characterize structural requirements for activity. Addition of Thr-Asn to the N-terminus (DP516) or substitution of the first two residues (Ala-Pro) of mature, native IL-1 beta with Thr-Met (DuP118) had no effect on the potency of the muteins in stimulating proteoglycan breakdown and inhibiting proteoglycan synthesis in vitro, or inducing mouse paw swelling in vivo. When Arg in position 4 of DuP118 was replaced by Glu (Glu-4), proteoglycan-synthesis-inhibitory activity was reduced to 20% and proteoglycan-degrading activity to 2% of that induced by native IL-1 beta. Glu-4 was much less active in inducing mouse paw swelling and gave maximal swelling about 40% that of native IL-1 beta. The data suggest that the presence of the positively charged side chain of Arg in position 4 may be important for the activity of IL-1 and may be useful in designing specific IL-1 receptor agonists/antagonists.