Neuropharmacology
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In a maternal fetal rat model, we investigated the behavioral and neurotoxic effects of fetal exposure to isoflurane. Pregnant rats at gestational day 21 were anesthetized with 1.3% isoflurane for 6h. Apoptosis was quantified in the hippocampus and cortex at 2 and 18h after exposure in the fetal brain and in the postnatal day 5 (P5) pup brain. ⋯ Rat fetal exposure to isoflurane at pregnancy day 21 through maternal anesthesia significantly decreased spontaneous apoptosis in the hippocampal CA1 region and in the retrosplenial cortex at 2h after exposure, but not at 18h or at P5. Fetal exposure to isoflurane did not impair subsequent juvenile or adult postnatal spatial reference memory and learning and, in fact, improved spatial memory in the juvenile rat. These results show that isoflurane exposure during late pregnancy is not neurotoxic to the fetal brain and does not impair memory and learning in the juvenile or adult rat.
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We have previously demonstrated that gabapentin supraspinally activates the descending noradrenergic system to alleviate neuropathic pain. In this study, we investigated whether pregabalin, an antiepileptic and analgesic drug that is also designed as a structural analogue of gamma-aminobutyric acid (GABA), exhibits supraspinal analgesic effects similar to those of gabapentin involving the descending noradrenergic system. Both systemically (intraperitoneally; i.p.) and locally (intracerebroventricularly or intrathecally; i.c.v. or i.t.) injected pregabalin reduced thermal and mechanical hypersensitivity in a murine chronic pain model that was prepared by partial ligation of the sciatic nerve (the Seltzer model), suggesting that pregabalin acts at both supraspinal and spinal loci. ⋯ Depletion of spinal noradrenaline (NA) or pharmacological blockade of spinal alpha(2)-adrenoceptors with yohimbine (i.p. or i.t.), but not alpha(1)-adrenoceptors with prazosin (i.p.), reduced the analgesic effects of pregabalin (i.p. or i.c.v.) on thermal and mechanical hypersensitivity. Moreover, i.c.v.-administered pregabalin dose-dependently increased the spinal 4-hydroxy-3-methoxyphenylglycol (MHPG) content and the MHPG/NA ratio only in mice with neuropathic pain, whereas the concentrations of NA, serotonin, 5-hydroxyindoleacetic acid and dopamine were unchanged, demonstrating that supraspinal pregabalin accelerated the spinal turnover of NA. Together, these results indicate that pregabalin supraspinally activates the descending noradrenergic pain inhibitory system coupled with spinal alpha(2)-adrenoceptors to ameliorate neuropathic pain.