Alterations in t-butylbicyclophosphorothionate binding in the brains of lidocaine-kindled rats

Expression of proopiomelanocortin and proenkephalin mRNA in sexually dimorphic brain regions are altered in adult male and female rats treated prenatally with morphine

The present study demonstrates that prenatal morphine exposure on gestation days 11-18 differentially alters proopiomelanocortin (POMC) and proenkephalin (pENK) mRNA in the hypothalamus and limbic system of adult male and female rats. In adult, prenatally morphine-exposed male rats POMC mRNA levels are decreased in the arcuate nucleus of the hypothalamus (ARC), while the pENK mRNA levels are increased in the paraventricular nucleus of the hypothalamus (PVN) and in the ventrolateral subdivision of the ventromedial nucleus of the hypothalamus (VMH), specifically in the ventrolateral subdivision of the VMH. In adult, prenatally morphine-exposed female rats, POMC mRNA levels in the ARC are increased in ovariectomized (OVX) but not in OVX, estradiol benzoate- (EB) or EB- and progesterone- (P) treated females. In contrast, pENK mRNA levels are decreased in the VMH of morphine-exposed, OVX females and increased in EB-treated females. Further, prenatal morphine exposure decreases pENK mRNA in the ARC and increases it in the medial pre-optic area independently of female gonadal hormones. Finally, POMC mRNA levels are increased in the ARC of saline-exposed, EB- or EB- and P-treated females but not in OVX females. Thus, the present study suggests that prenatal morphine exposure sex and brain region specifically alters the level of POMC and pENK mRNA.

Repeated exposure to trimethylolpropane phosphate induces central nervous system sensitization and facilitates electrical kindling

Trimethylolpropane phosphate (TMPP), pentylenetetrazol (PTZ) and N-methyl-beta-carboline-3-carboxamide (FG-7142) were evaluated and compared for facilitation of electrical kindling in freely moving rats. Stimulating/recording electrodes were implanted in the left amygdala (LAD), right amygdala (RAD) and left bed nucleus (LBN) of the stria terminalis. TMPP (0.275 mg/kg), PTZ (20 mg/kg), FG-7142 (7.5 mg/kg) or vehicle was administered intraperitoneally (i.p.) to separate groups of rats 3 times/week for 10 weeks. Stimulation of the LAD (0.1 Hz, 0.1-ms duration, 280-1500 microA, 20 pulses) 24 h following the drug administration evoked epileptiform after-discharges (ADs) in the LBN and RAD of 12.5% and 17% of rats after the seventh dose of TMPP and PTZ, respectively, and in 20% of rats from the LBN and RAD after the ninth and nineteenth dose of FG-7142, respectively. The same stimulation also induced myoclonic jerks after nine doses of TMPP or PTZ, or after thirteen doses of FG-7142 in 25%, 30% and 20% of animals tested, respectively. Chemically kindled clonic seizures were observed in 100% of TMPP or FG-7142 and 50% of PTZ treated rats by the thirtieth dosing. Control animals exhibited neither behavioral nor electrographic seizures to vehicle injection or to the LAD stimulation. Kindling stimulation applied to the LAD (60 Hz, 2-s train duration, 20-1500 microA, 0.1-ms pulse duration) 4 weeks following the completion of drug treatments evoked epileptic after-discharges from the LAD, LBN and RAD in all treated groups, with generally decreased threshold and latency to onset of after-discharges, compared to vehicle controls. The present study suggests that repeated exposure of rats to sub-convulsive doses of TMPP, PTZ and FG-7142 induces long-term central nervous system sensitization that may be related to both chemical kindling and the facilitation of electrical kindling.