Jeanette Georgieva

Nociceptin/Orphanin FQ Microinjected into Hippocampus Impairs Spatial Learning in Rats

The newly discovered peptide nociceptin/orphanin FQ has been found to increase reactivity to pain and to influence locomotor activity after intracerebroventricular administration. This study investigated the possible role of hippocampal nociceptin/orphanin FQ in spatial learning and in spontaneous locomotion. Male rats were trained in the Morris water task after microinjection of 10 nmol nociceptin/orphanin FQ or artificial cerebrospinal fluid (as control) into the CA3 region of the dorsal hippocampus. Nociceptin/orphanin FQ was found to severely impair spatial learning without interfering with swimming performance. Itrahippocampal injection of nociceptin/orphanin FQ markedly decreased exploratory locomotor activity including vertical movements (rearing). The data suggest that nociceptin/orphanin FQ is a potent modulator of synaptic plasticity within the hippocampus.

Hippocampal dynorphin B injections impair spatial learning in rats: a κ-opioid receptor-mediated effect

The hippocampus plays a central role in the acquisition and storage of information. Long-term potentiation in the mossy fibre pathway to the CA3 region in the hippocampus, an animal model of memory acquisition, is modulated by dynorphin peptides. This study investigated the possible role of hippocampal dynorphin in spatial learning. Male rats were trained in the Morris Water Task after microinjection with different doses of dynorphin B (1, 3.3 or 10 nmol/rat) or artificial cerebrospinal fluid (as control) into the CA3 region of the dorsal hippocampus. Dynorphin B was found to impair spatial learning at all tested doses. The synthetic kappa1-selective opiate receptor antagonist nor-binaltorphimine (2 nmol) also given into the hippocampus fully blocked the acquisition impairment caused by dynorphin B (10 nmol), while nor-binaltorphimine alone did not affect learning performance. These findings suggest that dynorphin peptides could play a modulatory role in hippocampal plasticity by acting on hippocampal kappa-receptors and thereby impair spatial learning.

In vivo metabolism of nociceptin/orphanin FQ in rat hippocampus.

The in vivo metabolism of the newly identified endogenous ligand for the ORL1 receptor, the opioid-like peptide nociceptin (orphanin FQ) in rat hippocampus was studied using size-exclusion chromatography linked to electrospray ionization mass spectrometry. The results show that nociceptin is metabolized step-wise in vivo into fragments (1-13) and (14-17) as well as (1-9) and (10-13), respectively. Interestingly, the (1-13) and (1-9) fragments have the same C-terminus, Arg-Ala-Lys, suggesting that this is a motif recognized by an enzyme which fragments the peptide in two consecutive steps. Injection of the (1-13) fragment into rat hippocampus had no effect on spatial learning or motor function under conditions where nociceptin is active, showing that this metabolic conversion reduces affinity for the ORL-1-receptor.

Ethanol alters the effect of kappa receptor ligands on dopamine release in the nucleus accumbens.

Repeated exposure to ethanol has previously been shown to induce alterations in both midbrain dopamine and dynorphin systems. The aim of this study was to investigate functional changes in the sensitivity of dynorphin/kappa-receptor systems following repeated ethanol administration, using dopamine as an indirect marker. The effects of kappa-opioid receptor ligands on dopamine release in the rat nucleus accumbens were investigated following repeated ethanol administration (2 g/kg body weight, twice daily for 7 days). The selective kappa-receptor agonist U50, 488H reduced dopamine levels in both ethanol- and saline-treated animals, although the decline had a later onset and lasted shorter in the ethanol-treated group. Nor-binaltorphimine, a kappa-antagonist, produced a significant increase of dopamine in ethanol-treated rats, but lacked effect in the saline-treated group. This change in responsiveness of dopamine neurons following repeated ethanol administration could be related to changes in the sensitivity of kappa-receptor systems and/or an increase in dynorphin tone in the nucleus accumbens.

Effects of single and dual administration of cocaine and ethanol on opioid and ORL1 receptor expression in rat CNS: an autoradiographic study.

The co-abuse of cocaine and ethanol is common among human addicts and has been reported to produce a stronger increase of euphoria as compared to either drug given alone. Both cocaine and ethanol increase the extracellular dopamine concentration in the nucleus accumbens, a terminal region in the mesolimbic dopamine pathway. In addition, both cocaine and ethanol affect the endogenous opioid system, which in turn alters the activity of the mesolimbic dopamine pathway. We have carried out quantitative autoradiography mapping of the opioid receptors as well as the opioid receptor-like 1 receptor in the brains of rats treated with both single and dual cocaine and ethanol. Rats received acute cocaine, ethanol or both drugs in combination. Ethanol alone or in combination with cocaine modulated the receptor densities in rat central nervous system. The kappa receptor densities were generally decreased, while both the mu and the opioid receptor-like 1 receptors were up-regulated. The mu opioid receptor levels were mainly increased in non-cortical regions, whereas the opioid receptor-like 1 receptors were increased in cortical structures. No changes in delta opioid receptors were observed. Cocaine alone did not influence the receptor levels in any of the treatment groups.

In vivo antisense inhibition of prodynorphin expression in rat striatum: dose-dependence and sequence specificity ☆ ☆☆

An antisense oligodeoxynucleotide (ODN) corresponding to a region downstream from the translation initiation codon of rat prodynorphin mRNA was constructed and obtained in its phosphothioated form. Sense and randomized ODNs were also used. Each ODN was continuously infused for 3 days into dorsal striatum of Sprague-Dawley rats, at three different concentrations, followed by measurement of radioimmunoactive dynorphin A and met-enkephalin, as well as total protein content in striatal tissue. Dynorphin A levels were reduced in a dose-dependent manner following both antisense and sense probes, but not by a control random sequence. Thus, antisense as well as sense ODNs specifically inhibited prodynorphin gene expression in striatum. These results indicate that direct continuous infusion of antisense ODNs into a defined brain region can be used to inhibit late-response gene expression.

Involvement of a c-fos-dependent mechanism in caffeine-induced expression of the preprotachykinin A and neurotensin/neuromedin N genes in rat striatum.

Striatal c‐fos induction was blocked by local administration of phosphorothioated c‐fos antisense oligonucleotides (AS‐ODN) to examine the possible role of caffeine‐induced c‐fos expression in transcriptional regulation of striatal preproenkephalin, prodynorphin, preprotachykinin A and neurotensin/neuromedin N. Caffeine (100 mg/kg i.p.) induced both c‐fos mRNA and Fos‐protein, and this induction was significantly attenuated by intrastriatal injection of 4 (but not 1) nmol c‐fos AS‐ODN. This suggests that, in addition to translational arrest, other mechanisms may be involved in the mediation of antisense action. The action of the AS‐ODN was sequence specific. The antisense blockade of c‐fos reduced the effect of caffeine on the expression of mRNAs for preprotachykinin A and neurotensin/neuromedin N in the ventrolateral caudate–putamen. Levels of preproenkephalin and prodynorphin transcripts were unaffected. Thus caffeine induction of striatal preprotachykinin A mRNA and neurotensin/neuromedin N mRNA, but not of preproenkephalin mRNA or prodynorphin mRNA, may at least in part be mediated by a pathway involving Fos protein. The findings illustrate the utility of blockade of gene expression with antisense oligonucleotides for in vivo studies of drug actions.

Differential effects of intrastriatally infused fully and endcap phosphorothioate antisense oligonucleotides on morphology, histochemistry and prodynorphin expression in rat brain

In the present study, we investigated the selectivity and specificity associated with continuous intrastriatal treatment with antisense oligonucleotides. Rats were given intrastriatal infusions for 72 h with phosphodiester, and fully and endcap phosphorothioated oligonucleotide probes complementary to prodynorphin mRNA. Dynorphin (Dyn) peptide levels were measured by radioimmunoassay. The integrity of three other striatal transmitter systems, the neuropeptide Y (NPY)-ergic interneurons, the cholinergic interneurons and the dopaminergic afferent innervation, was assessed histochemically. The gross morphology of the striatum and the distribution of fluorescently labelled antisense probes were also investigated. Brains infused with phosphodiester probes had tissue Dyn levels not different from control. They also showed little or no change in staining for NPY, acetylcholinesterase (AChE) and tyrosine hydroxylase (TH) and essentially normal striatal gross morphology. In contrast, brains treated with fully phosphorothioated oligonucleotides showed significant decreases in striatal Dyn levels but also severe tissue damage accompanied by massive cell infiltration and decreases in immunoreactivities for the striatal neurochemical markers. Fluorescently labelled phosphorothioate probes were observed widely in the striatum and adjacent structures and, presumably retrogradely transported, in the dopamine cell bodies in the substantia nigra, also revealing the presence of abnormal cellular structures within the striatum. By comparison, endcap probes significantly reduced striatal Dyn levels and showed good tissue penetration without inducing major changes in tissue morphology or histochemistry of non-dynorphinergic systems, except for cell infiltration. The deleterious tissue effects of fully phosphorothioated oligonucleotides and the ineffectiveness of phosphodiester oligonucleotides in inhibiting protein synthesis suggest that, of the probes examined in this study, endcap oligonucleotides are the most useful for in vivo studies in the central nervous system.

Long-acting olanzapine injection during pregnancy and breastfeeding: a case report

We present one case of a woman treated with the intramuscular depot formulation of the atypical antipsychotic, olanzapine pamoate (ZypAdhera®), during pregnancy and breastfeeding. Data on olanzapine distribution in breast milk as well as on plasma concentration in the nursed infant are provided. The present case report demonstrates that olanzapine was excreted in the breast milk, but the breast-fed infant had very low olanzapine concentrations, which did not result in any adverse effects.

Brainstem Auditory Evoked Potentials for diagnosing Autism Spectrum Disorder, ADHD and Schizophrenia Spectrum Disorders in adults. A blinded study.

The aim of the present study was to examine the clinical utility of complex auditory brainstem response (c-ABR) and investigate if c-ABR is helpful in the diagnostic procedure. Thirty-one adult psychiatric patients, thoroughly diagnosed with autism spectrum disorder (ASD) (n=16), ADHD (n=8), or schizophrenia spectrum disorder (SSD) (n=7) and 15 healthy controls (HC), were blindly assessed with SensoDetect BERA. This c-ABR correctly identified psychiatric diagnoses in 4 patients (13%) and provided partially correct diagnoses in 11 more patients. Of the 15 HC, 6 were misclassified as psychiatric patients. The Cohen´s kappa coefficient (κ) was substantial for HC (κ=0.67), fair for SSD (κ=0.37), slight for ADHD (κ=0.09) and without agreement in ASD (κ=-0.03). In conclusion, we found the c-ABR method unhelpful and unreliable as a tool in clinical diagnostics.