Alterations in behavior and opioid gene expression induced by the novel tropane analog WF-31

"Binge" cocaine differentially alters preproenkephalin mRNA levels in guinea pig brain

Male Hartley guinea pigs were administered i.p. injections of cocaine or saline for 2 or 7 days in a "binge" paradigm. RNA was isolated from dissected brain regions and levels of preproenkephalin mRNA and total RNA were quantified by RNase protection assays. Following 2 days of "binge" cocaine administration, no significant alterations in preproenkephalin mRNA levels were detected in six brain regions. Following 7 days of cocaine administration, however, lower levels of preproenkephalin mRNA were observed in the nucleus accumbens and hypothalamus of cocaine-treated animals and higher levels in the frontal cortex and amygdala. These findings differed from previous studies in the rat, so an additional experiment was performed with animals treated at the 7 day time point. For increased statistical power, data from the two experiments were combined and examined by two-way ANOVAs; in this combined analysis, increases in preproenkephalin mRNA were observed in frontal cortex, amygdala, and hippocampus, decreases were found in the nucleus accumbens and hypothalamus, with no change in thalamus, caudate putamen, or cerebellum. These observed differences between guinea pigs and rats make this species an interesting model for neurobiological studies of cocaine-induced alterations in neuropeptide gene expression in the mammalian brain.

Synthesis of 2beta-acyl-3beta-(substituted naphthyl)-8-azabicyclo[3.2.1]octanes and their binding affinities at dopamine and serotonin transport sites

A series of 3beta-naphthyltropane derivatives were synthesized and found to show high affinity at both the dopamine and serotonin transporter sites, leading to some of the most potent inhibitors known based on the tropane structure. Comparative molecular field analysis (CoMFA) models were developed for both dopamine and serotonin transporter binding data. These models provide insights into those factors that influence binding at the two transporters.

Chronic GBR 12909 administration differentially alters prodynorphin gene expression compared to cocaine

The effect of the selective dopamine uptake inhibitor 1-[2-[bis(4-flourophenyl)methoxy]ethyl]-4-[3-phenylpropyl]piperazine dihydrochloride (GBR 12909) was examined on prodynorphin gene expression. GBR 12909 or vehicle was continuously infused for 7 days via osmotic minipump, or injected daily into male rats. Both continuous infusions and daily injections of GBR 12909 produced significant decreases in prodynorphin expression in the hypothalamus (37% and 31% decreases, respectively). There were no significant changes in the caudate putamen, hippocampus or nucleus accumbens. One injection of GBR 12909 had no effects on prodynorphin expression in any of the brain regions studied, suggesting that the effect in the hypothalamus is not an acute effect. As previously reported for other treatment regimens, continuous infusion of cocaine produced a 35% significant decrease in the hypothalamus, consistent with the effects of GBR 12909. In contrast to GBR 12909, however, cocaine also produced a significant increase in prodynorphin expression in the caudate putamen. Thus, chronic inhibition of dopamine uptake can regulate prodynorphin expression in the hypothalamus. In contrast, the increase in the caudate putamen following cocaine administration may not be related to the inhibition of dopamine uptake, since it was not produced by a selective dopamine uptake inhibitor. These findings suggest that regulation of prodynorphin gene expression by cocaine in the caudate putamen may be mediated by the inhibition of norepinephrine or serotonin uptake, by a combination of effects on two or three monoamine transporters, or by a mechanism unrelated to transporter inhibition.

Molecular mechanisms of actions of interleukin-6 on the brain, with special reference to serotonin and the hypothalamo-pituitary-adrenocortical axis

Biological activities of the multifunctional cytokine, interleukin-6 (IL-6) include stimulation of B cell proliferation, immunoglobulin production, and initiation of the acute-phase response. IL-6 affects the CNS in that it activates the hypothalamo-pituitary-adrenocortical (HPA) axis and increases brain tryptophan and serotonin metabolism. IL-6 has been proposed as an important mediator of interaction between the neuroendocrine and immune systems. The peripheral and central effects of IL-6 are presumably mediated through its membrane receptor (IL-6R). IL-6, IL-6R and their respective mRNAs have been detected in several brain regions. Although the functions of cytokines overlap considerably, each displays its own characteristic properties. Expression of IL-6 in the brain has been observed in several CNS disorders, some of which have been associated with disorders of serotonin metabolism. It is proposed that interactions between IL-6 and brain serotonin is a complex process which involves corticotropin-releasing factor (CRF) and opioid peptides. It is likely that the molecular mechanisms underlying the actions of IL-6 on the HPA axis and its other brain functions involve the integrated effects of glutamate, Ca2+, 3',5'-cyclic AMP, protein kinase C, and other metabolic pathways.