A. Donatini

Substance P levels are decreased in lesional skin of atopic dermatitis

Abstract There is increasing evidence that neuropeptides (NP) such as substance P (SP) and vasoactive intestinal polypeptide (VIP) are involved in the pathogenesis of atopic dermatitis (AD). Vasoactive intestinal polypeptide levels were found to be significantly elevated in lesional skin of AD as compared to controls. We evaluated by radioimmunoassay the SP content in whole skin homogenates from chronic lichenified lesions of patients with AD. The levels of SP were significantly decreased in lesional skin from AD patients as compared to control skin (0.25 ± 0.03 vs. 0.97 ± 0.24 pmol/g tissue, p < 0.01). The diminished SP levels as opposed to increased VIP concentrations could be consistent with different roles of these NP as modulatory agents in the mechanisms associated with AD.

Chronic intracerebroventricular cocaine differentially affects prodynorphin gene expression in rat hypothalamus and caudate-putamen

We investigated the effects of sustained administration of cocaine on the regulation of prodynorphin gene expression in rat brain. Intracerebroventricular (i.c.v.) infusion of cocaine hydrochloride (30 micrograms/day) for 7 days, by means of osmotic minipumps, elicited a significant 35% decrease of prodynorphin mRNA levels in rat hypothalamus and increase (22%) in caudate-putamen. At the same time and in the same animals, no significant changes were detected in the hippocampus or in the nucleus accumbens. These results indicate that continuously infused cocaine is able to modulate expression of the prodynorphin gene in opposite directions or has no effect on prodynorphin expression, depending on the brain region analysed. Cocaine, as well as opiates, might activate specific neuronal pathways, shared by different classes of drugs of abuse, involving, at least in part, the endogenous opioid system.

Early Changes in Prodynorphin mRNA and ir-Dynorphin A Levels after Kindled Seizures in the Rat

Prodynorphin mRNA and immunoreactive dynorphin A (ir‐dynorphin A) levels were measured in different brain areas at various time points after amygdala kindled seizures. In the hippocampus, striatum and hypothalamus, prodynorphin mRNA levels were not significantly changed in kindled rats (killed 1 week after the last stimulus‐evoked seizure), but they were significantly increased 1 h after seizures. The relative increase was the highest in the hippocampus (∼3‐fold). In the brainstem, midbrain and cerebral cortex no changes in prodynorphin mRNA were detected in kindled rats, 1 h or 1 week after a kindled seizure. ir‐Dynorphin A levels were significantly reduced in the hippocampus and in the striatum of kindled rats, as well as 5 and 60 min after kindled seizures, but they were increased back to control levels after 120 min. In the hypothalamus, ir‐dynorphin A levels were significantly increased 120 min after a kindled seizure. ir‐Dynorphin A levels were also significantly reduced in the brainstem and in the frontal, parietal and temporal cortex 120 min, but not 5 or 60 min, after a kindled seizure. Taken together, these data support the hypothesis that the dynorphinergic system is activated after amygdala kindled seizures, with different kinetics in different brain areas.

Long-term exposure to opioid antagonists up-regulates prodynorphin gene expression in rat brain

We investigated the effect of long-term administration of opioid antagonists on the regulation of prodynorphin gene expression in rat brain. Intracerebroventricular (i.c.v.) injections for seven days of nor-binaltorphimine (nor-BNI), the highly selective kappa opioid antagonist, naloxone and its longer acting analog naltrexone, both relatively selective antagonists for the mu opioid receptor, markedly raised prodynorphin mRNA levels in rat hypothalamus, hippocampus and striatum. Peptides, namely immunoreactive-dynorphin A (ir-dyn A), were unaffected after chronic treatment with all antagonists, in the same tissues. These results, taken together with our previous observations, suggest that chronic opioid antagonists, acting on kappa and mu opioid receptors, clearly up-regulate prodynorphin gene expression in discrete rat brain regions, activating its biosynthesis. Moreover, our data support the hypothesis that the endogenous opioid system plays a role in the mechanisms underlying the development of opiate tolerance.

Kindled seizure-induced c-fos and prodynorphin mRNA expressions are unrelated in the rat brain

Levels of mRNA for c‐fos and prodynorphin were studied by in situ hybridization in adjacent coronal sections taken from kindled rats 30–60 min after the last seizure. Within this time frame, expression of both genes was induced in multiple brain areas. Anatomical colocalization of the induced gene expressions was found in the hippocampus. Induction of c‐fos in the dentate gyrus was bilateral and symmetrical in a subgroup of rats, ipsilateral in another subgroup and absent in a third subgroup. However, no relative increase was observed in the ipsilateral compared with the contralateral prodynorphin expression in the dentate gyrus when c‐fos expression was induced ipsilaterally only. These observations suggest that, at variance with other experimental situations, Fos is not involved in the mechanisms of kindled seizure‐induced activation of prodynorphin transcription in the rat forebrain.

Region-specific changes in prodynorphin mRNA and ir-dynorphin A levels after kindled seizures.

The opioid peptide dynorphin is thought to be implicated in specific types of seizures.In particular,complex partial seizures have been shown to cause release of dynorphin,activation of prodynorphin gene expression,and new peptide synthesis in the hippocampus.In this study, the kinetics of the seizure-induced changes in prodynorphin mRNA and ir-dynorphin Alevels in the hippocampus have been compared with those induced in the temporal and frontal cortex, i.e.,in other regions involved in the pathophysiology of complex partial seizures.Experiments have been run using kindling,one of the most valuable models of partial epilepsy.In the hippocampus (1)prodynorphin mRNA levels transiently increase (threefold)1 h after kindled seizures,and return to baseline by 2 h,and (2)dynorphin Alevels are slightly decreased at 1 h, but increase (twofold)at 2 h and return to baseline by 6 h.In the temporal and in the frontal cortex,a late (beginning at 2 h)and prolonged (up to 24 h)decrease in both prodynorphin mRNA and ir-dynorphin A levels have been observed.These data suggest that differential changes in dynorphin metabolism occur in different brain areas after seizures.The mechanisms and functional implications of this observation remain to be investigated.

Methamphetamine alters prodynorphin gene expression and dynorphin A levels in rat hypothalamus

Chronic administration of morphine or cocaine affects opioid gene expression. To better understand the possible existence of common neuronal pathways shared by different classes of drugs of abuse, we studied the effects of methamphetamine on the gene expression of the opioid precursor prodynorphin and on the levels of peptide dynorphin A in the rat brain. Acute (6 mg/kg, intraperitoneally, i.p.) and chronic (6 mg/kg, i.p. for 15 days) methamphetamine markedly raised prodynorphin mRNA levels in the hypothalamus, whereas no effect was observed in the hippocampus. Dynorphin A levels increased after chronic treatment in the hypothalamus and in the striatum, whereas no significant changes were detected after acute treatment. These results indicate that methamphetamine affects prodynorphin gene expression in the hypothalamus, which may be an important site (also for its relevant neuroendocrine correlates) for opioidergic mechanisms activated by addictive drugs.

Binding profile of benextramine at neuropeptide Y receptor subtypes in rat brain areas.

Binding studies in rat whole brain, frontoparietal cortex and brainstem membrane preparations revealed that benextramine displaced [3H]neuropeptide Y specific binding from a low and a high affinity site with IC50 values in the microM (36 +/- 2, 4.4 +/- 1.4 and 300 +/- 120 microM, respectively) and the pM (29.3 +/- 12.1, 0.35 +/- 0.11 and 0.42 +/- 0.03 pM, respectively) range, whereas in rat hippocampus benextramine displaced [3H]neuropeptide Y specific binding from one site only with an IC50 value of 22.8 +/- 5.7 microM. With the exception of frontoparietal cortex binding assay, benextramine was not able to completely inhibit [3H]neuropeptide Y specific binding revealing the presence of a benextramine nonsensitive third binding site. Benextramine pretreatment followed by membrane washing demonstrated that benextramine inhibited irreversibly both high and low affinity sites.

Opioid antagonists up-regulate prodynorphin gene expression in rat brain ☆

Neurochemical alterations in opioid receptor function and post-transductional events have been demonstrated to occur during the development of opiate tolerance (1). In addition, it has been recently shown that chronic opiate agonists, acting on μ, κ and δ receptors, induce a down-regulation of the biosynthesis of the endogenous opioid system in rat brain (2,3). In order to better understand the mechanisms underlying this phenomenon, the present study was carried out to investigate the effect of chronic intracerebroventricular (icv) exposure to selective opioid antagonists: the preferential μ naltrexone (NTX), the selective κ norbinaltorphimine (nor-BNI) and the selective μ naltrindole (NTI), on opioid gene expression in rat brain