The Novel, Orally Active, Delta Opioid RWJ-394674 Is Biotransformed to the Potent Mu Opioid RWJ-413216

Although the mu opioid receptor is the primary target of marketed opioid analgesics, several studies suggest the advantageous effect of combinations of mu and delta opioids. The novel compound RWJ-394674 [N,N-diethyl-4-[(8-phenethyl-8-azabicyclo]3.2.1]oct-3-ylidene)-phenylmethyl]-benzamide]; bound with high affinity to the delta opioid receptor (0.2 nM) and with weaker affinity to the mu opioid receptor (72 nM). 5'-O-(3-[(35)S]-thio)triphosphate binding assay demonstrated its delta agonist function. Surprisingly given this pharmacologic profile, RWJ-394674 exhibited potent oral antinociception (ED(50) = 10.5 micromol/kg or 5 mg/kg) in the mouse hot-plate (48 degrees C) test and produced a moderate Straub tail. Antagonist studies in the more stringent 55 degrees C hot-plate test demonstrated the antinociception produced by RWJ-394674 to be sensitive to the nonselective opioid antagonist naloxone as well as to the delta- and mu-selective antagonists, naltrindole and beta-funaltrexamine, respectively. In vitro studies demonstrated that RWJ-394674 was metabolized by hepatic microsomes to its N-desethyl analog, RWJ-413216 [N-ethyl-4-[(8-phenethyl-8-azabicyclo[3.2.1]oct-3-ylidene)-phenylmethyl]-benzamide], which, in contrast to RWJ-394674, had a high affinity for the mu rather than the delta opioid receptor and was an agonist at both. Pharmacokinetic studies in the rat revealed that oral administration of RWJ-394674 rapidly gave rise to detectable plasma levels of RWJ-413216, which reached levels equivalent to those of RWJ-394674 by 1 h. RWJ-413216 itself demonstrated a potent oral antinociceptive effect. Thus, RWJ-394674 is a delta opioid receptor agonist that appears to augment its antinociceptive effect through biotransformation to a novel mu opioid receptor-selective agonist.

Capsaicin for allergic rhinitis in adults

BACKGROUND

Allergic rhinitis represents a global health problem. Non-specific nasal hyperresponsiveness is an important feature of allergic and non-allergic rhinitis. This phenomenon is believed to result from the effect of allergic inflammation on the sensory nerves that supply the upper airway mucosa. A pharmacologic agent that has proved useful in the investigation of effects of neuronal stimulation is capsaicin, the pungent component of hot pepper. Intranasal capsaicin specifically stimulates afferent nerves consisting mostly of unmyelinated C fibers and some myelinated A-delta fibers. As a result it can trigger central and axonal reflexes, the latter being putatively mediated by the release of neuropeptides. Capsaicin as a blocking agent of neuropeptides, blocks the axon reflex and may exert a curative effect on allergic rhinitis.

OBJECTIVES

To assess the effectiveness of capsaicin for allergic rhinitis in adults.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2006), MEDLINE (1966 to 2006) and EMBASE (1974 to 2006). We assessed bibliographies from included studies, and contacted authors of known studies for additional information about published and unpublished trials. The date of the most recent search was January 2006.

SELECTION CRITERIA

Randomised controlled trials of capsaicin for allergic rhinitis in adults were included.

DATA COLLECTION AND ANALYSIS

Three reviewers read each paper, blind to its identity. Decisions concerning inclusion were made by simple majority. We all performed quality assessment independently.

MAIN RESULTS

One small trial did not find evidence that intranasal capsaicin had a therapeutic effect in allergic rhinitis. A small pharmacological effect on clinical histamine dose response was found. After treatment, leukotriene levels in nasal lavage did not increase in the capsaicin group.

AUTHORS' CONCLUSIONS

There is insufficient evidence to assess the use of capsaicin in clinical practice.

Functional characteristics of the parallel SI- and SII-projecting neurons of the thalamic ventral posterior nucleus in the marmoset

The functional organization of the primate somatosensory system at thalamocortical levels has been a matter of controversy, in particular, over the extent to which the primary and secondary somatosensory cortical areas, SI and SII, are organized in parallel or serial neural networks for the processing of tactile information. This issue was investigated for the marmoset monkey by recording from 55 single tactile-sensitive neurons in the lateral division of the ventral posterior nucleus of the thalamus (VPL) with a projection to either SI or SII, identified with the use of the antidromic collision technique. Neurons activated from the hand and distal forearm were classified according to their peripheral source of input and characterized in terms of their functional capacities to determine whether the direct thalamic input can account for tactile processing in both SI and SII. Both the SI- and SII-projecting samples contained a slowly adapting (SA) class of neurons, sensitive to static skin displacement, and purely dynamically sensitive tactile neurons that could be subdivided into two classes. One was most sensitive to high-frequency (> or =100 Hz) cutaneous vibration whose input appeared to be derived from Pacinian sources, while the other was sensitive to lower frequency vibration (< or =100 Hz) or trains of rectangular mechanical pulse stimuli, that appeared to receive its input from rapidly adapting (RA) afferent fibers presumed to be associated with intradermal tactile receptors. There appeared to be no systematic differences in functional capacities between SI- and SII-projecting neurons of each of these three classes, based on receptive field characteristics, on the form of stimulus-response relations, and on measures derived from these relations. These measures included threshold and responsiveness values, bandwidths of vibrational sensitivity, and the capacity for responding to cutaneous vibrotactile stimuli with phase-locked, temporally patterned impulse activity. The analysis indicates that low-threshold, high-acuity tactile information is conveyed directly to both SI and SII from overlapping regions within the thalamic VP nucleus. This direct confirmation of a parallel functional projection to both SI and SII in the marmoset is consistent with our separate studies at the cortical level that demonstrate first, that tactile responsiveness in SII largely survives the SI inactivation and second, that SI responsiveness is largely independent of SII. It therefore reinforces the evidence that SI and SII occupy a hierarchically equivalent network for tactile processing.

Piperazinyl benzamidines: synthesis and affinity for the delta opioid receptor

Piperazinyl benzamidines were prepared and found to bind to the rat delta (delta) opioid receptor. The most active compounds had a N,N-diethylcarboxamido group and a N-benzyl piperazine. The most potent among these was N,N-diethyl-4-[4-(phenylmethyl)-1-piperazinyl][2-(trifluoromethyl)phenyl]iminomethyl]benzamide (27) with a 1.22nM K(i) for the rat delta opioid receptor and ca. 1000 x selectivity relative to the mu opioid subtype.

Photodynamic action of actinomycin D: an EPR spin trapping study

Actinomycin D is one of the most widely studied anticancer antibiotic that binds to both double-stranded and single-stranded DNA, and this binding greatly enhances the DNA photosensitization. By use of electron paramagnetic resonance spin trapping techniques, both superoxide radical anion and the radical anion of actinomycin D were identified as important intermediates in the photodynamic process. A mechanism of electron transfer from a DNA base to excited actinomycin D was proposed. These novel findings may shed new light on future application of this drug in photodynamic therapy or cleavage of DNA in unique and controllable ways.

Functional studies of bradykinin receptors in Chinese hamster ovary cells stably expressing the human B2 bradykinin receptor

Bradykinin B1 and B2 receptors, members of the G-protein coupled receptor superfamily, are involved in inflammation and pain. Chinese hamster ovary (CHO) cells stably expressing the human B2 bradykinin receptor (CHO-B2) were used to characterize the signal transduction pathways associated with this receptor and its regulation. The selective B2 antagonist [3H]NPC17731 but not the selective B1 antagonist [3,4-prolyl-3,4-(3)H(N)]-[des-Arg10,Leu9]kallidin ([3H]DALKD) bound to CHO-B2 cell membranes with a Kd of 0.77 nM and a Bmax of 1087 fmol/mg protein. [3H]NPC17731 binding was inhibited by bradykinin ligands in the order: NPC17731 > bradykinin > kallidin >> DALKD > [des-Arg10] kallidin (DAKD), consistent with the pharmacological profile of B2 bradykinin receptors. The B2 agonist bradykinin and the B1/B2 agonist kallidin, but not the B1 agonist DAKD, increased [35S]GTP gamma S binding to the CHO-B2 cell membranes. The B2 bradykinin receptors were co-immunoprecipitated with G alpha q/11. In response to bradykinin stimulation, coupling of the B2 receptors to G alpha q/11 was increased by 10-fold. Bradykinin and kallidin, but not DAKD, induced intracellular calcium release in CHO-B2 cells, which was blocked by NPC17731 but not by DALKD. These results demonstrate that B2 bradykinin receptors directly coupled to G alpha q/11 to regulate intracellular calcium release. CHO-B2 cell is a useful system that can be applied to study the effect of potential agents that may influence the B2 receptor function.

Synthesis and evaluation of 4-(N,N-diarylamino)piperidines with high selectivity to the delta-opioid receptor: a combined 3D-QSAR and ligand docking study

A series of 4-(N,N-diarylamino)piperidines are synthesized and evaluated for high affinity binding and selectivity to the delta-opioid receptor using a combination of 3D-QSAR and molecular docking techniques. Based on experimental ligand binding data to both mu- and delta- opioid receptors, CoMFA fields are generated and applied to identify potential ligand modifications to further optimize lead compounds. Molecular docking experiments to the delta-receptor are also reported that explain the CoMFA trends predicted as well as the differential binding and selectivity displayed by various compounds in the series. An analysis of the binding site model proposed indicates the piperidines take advantage of 3 key sites or binding domains within the delta-receptor. These include an aromatic pocket (approximately 1/3 into the receptor cavity), an aspartic acid residue (which serves as a docking point for the piperidinyl cationic amine) and a hydrophobic pocket at the extracellular boundary of the receptor cavity. Links are established between ligand modification and amino acid composition at these sites in mu and delta, providing new insight to the structural basis to binding and selectivity across the series and for related piperazines (i.e. SNC80 and BW373U86). Results are also presented that indicate delta- and mu-selectivity may be determined at alternate sites, suggesting opioid receptors may display multiple binding domains. The model is further supported by comparisons with opiate binding modes and site directed mutagenesis studies and is finally applied to suggest new strategies in ligand design.

Photosensitized formation of singlet oxygen by phycobiliproteins in neutral aqueous solutions

Phycobiliproteins (PBPs) are a type of promising sensitizers for photodynamic therapy (PDT). Upon irradiation (lambda>500nm) of an oxygen-saturated aqueous solution of phycobiliproteins, particularly, C-phycocyanin (C-PC), allophycocyanin (APC) or R-phycoerythrin (R-PE), the formation of singlet oxygen (1O2) was detected by using imidazole in the presence of p-nitrosodimethylaniline (RNO). The bleaching of RNO caused by the presence of imidazole in our system showed typical concentration dependence with a maximum at about 8mM imidazole, which is in agreement with the formation of 1O2. In addition, the generation of 1O2 was verified further in the presence of D2O and specific singlet oxygen quencher 1,4-diazabicyclo [2,2,2] octane (DABCO) and sodium azide (NaN3). Our experimental results indicated that APC possesses high ability to generate reactive oxygen species and the relative quantum yields of photogeneration of 1O2 by PBPs are as follows: APC > C-PC > R-PE.

Synthesis and binding affinities of 4-diarylaminotropanes, a new class of delta opioid agonists

A series of 4-diarylaminotropanes has been prepared. Both endo and exo diastereomeric forms bound to the delta opioid receptor but the endo isomers were more potent and selective versus the mu opioid receptor than the exo isomers. The most potent delta opioid agonist (14) exhibited a delta opioid Ki of 0.2 nM and was 860-fold selective over mu.

Characterization of the transient species generated by the photoexcitation of C-phycocyanin from Spirulina platensis: a laser photolysis and pulse radiolysis study

Nanosecond laser flash photolysis and pulse radiolysis were used to generate and characterize the triplet state and cation radical of C-phycocyanin (C-PC) from Spirulina platensis. The transient absorption spectra of C-PC were measured from direct excitation and acetone sensitization in aqueous solution at room temperature by KrF (248 nm) laser flash photolysis. Laser-induced transient species have been characterized by the method of acetone sensitization and one-electron oxidation. In nitrous oxide-saturated phosphate buffer saline (pH = 7.0) of C-PC, the produced intermediates are assigned to the excited triplet state and the radical cation. Using acetone as photosensitizer, the C-PC excited triplet states produced via triplet-triplet energy transfer and the C-PC radical cation from electron transfer reaction were further confirmed. Furthermore, the corresponding kinetic parameters were determined. To our knowledge, the transient absorption spectra of C-PC have been reported for the first time.

Effect of antisense oligodeoxynucleotides directed to individual calmodulin gene transcripts on the proliferation and differentiation of PC12 cells

Calmodulin (CaM) is encoded by three different genes that collectively give rise to five transcripts. In the present study, we used antisense oligodeoxynucleotides targeted to unique sequences in the transcripts from the individual CaM genes to selectively block the expression of the different genes and to investigate the roles these individual genes play in the proliferation and nerve growth factor (NGF)-induced differentiation of PC12 cells. Culturing PC12 cells in the presence of oligodeoxynucleotide antisense to the transcripts from CaM genes I and II caused a significant decrease in the proliferation and a significant delay in the NGF-induced differentiation of PC12 cells when compared with untreated cells and with cells treated with the corresponding randomized oligodeoxynucleotides. However, an oligodeoxynucleotide antisense to CaM gene III did not significantly alter the proliferation or the NGF-induced differentiation of PC12 cells. The inhibition of cell proliferation could be reversed by washing out the antisense oligodeoxynucleotides. The levels of CaM in cells treated with oligodeoxynucleotides antisense to CaM genes I or II were reduced 52% or 63%, respectively, of the levels found in the control cells. However, the levels of CaM were not significantly reduced in PC12 cells treated with CaM gene III antisense oligodeoxynucleotide. None of the randomized oligodeoxynucleotides had any effect on the levels of CaM in PC12 cells. The reduced levels of CaM in PC12 cells treated with an oligodeoxynucleotide antisense to CaM gene I were accompanied by a reduction in the levels of the CaM gene I mRNAs, supporting a true antisense mechanism of action for these oligodeoxynucleotides. These results suggest that altering the level of CaM by using antisense oligodeoxynucleotides targeted to the dominant CaM transcripts in a particular cell type will specifically inhibit their proliferation and, in the case of neuronal cells, alter the course of their differentiation.

Characterization of bradykinin receptors in human lung fibroblasts using the binding of 3[H][Des-Arg10,Leu9]kallidin and [3H]NPC17731

Bradykinin (BK) receptors are involved in pain and inflammation. Two BK receptor subtypes, B1 and B2, have been defined based on their pharmacological properties. Both B1 and B2 receptors are G-protein coupled membrane receptors. B1 receptors are present in smooth muscle tissue, whereas B2 receptors are found in both smooth muscle tissue and neurons. [Des-Arg10,Leu9]kallidin (DALKD) is a selective B1 receptor antagonist, and NPC17731 is a selective B2 receptor antagonist. To develop binding assays for the two known BK receptor subtypes, [3H]DALKD and [3H]NPC17731 were used as selective ligands for B1 and B2 receptors respectively. Both ligands bound to the CCD-16 human lung fibroblast membranes reaching equilibrium at 25 degrees C within 30 min. Binding was stable for at least 60 min. The Kd of [3H]DALKD was 0.33 nM and Bmax was 52 fmol/mg membrane protein. The Kd of [3H]NPC17731 was 0.39 nM and Bmax was 700 fmol/mg membrane protein. Competition for [3H]DALKD binding with BK receptor agonists was in the order: [des-Arg10]KD (DAKD) > KD >> [des-Arg9]BK (DABK) > BK, and competition for [3H]DALKD binding with BK receptor antagonists was in the order: DALKD > [des-Arg10]Hoe 140 (DAHoe 140) > [des-Arg9,Leu8]BK (DALBK) > NPC17731 > Hoe 140 > DNMFBK, suggesting that [3H]DALKD bound selectively to B1 receptors. By contrast, competition for [3H]NPC17731 binding by BK agonists was in the order: BK > KD >> DAKD > DABK, and competition for [3H]NPC17731 binding by BK antagonists was in the order: NPC17731 = Hoe 140 >> DNMFBK > DAHoe 140 > DALBK > DALKD, indicating that [3H]NPC17731 labeled B2 receptors selectively. These results demonstrate that [3H]DALKD and [3H]NPC17731 can be used with CCD-16 human lung fibroblast membranes to provide a pair of binding assays for the simultaneous evaluation of B1 and B2 BK receptor subtypes.

D2 dopamine antisense RNA expression vector, unlike haloperidol, produces long-term inhibition of D2 dopamine-mediated behaviors without causing Up-regulation of D2 dopamine receptors

Long-term inhibition of D2 dopamine receptors using classic D2 dopamine receptor antagonists such as haloperidol often causes a compensatory up-regulation of the D2 dopamine receptors. We investigated whether the long-term inhibition of D2 dopamine receptors using an eukaryotic expression vector housing a cDNA sequence encoding an antisense RNA directed to the D2 dopamine receptor transcript (D2 antisense vector) would also produce up-regulation of the D2 receptors. Single, bilateral injections of the D2 antisense vector into the corpora striata of mice inhibited the stereotypy induced by acute challenge injections with the D2/D3 dopamine receptor agonist quinpirole but did not inhibit the grooming induced by acute challenge injections with the D1 agonist SKF 38393. Similar treatment with the D2 antisense vector produced a long-term (>1 month) cataleptic response without producing tolerance to challenge injections with haloperidol. By contrast, catalepsy induced by a single injection of haloperidol lasted only approximately 2 days, and tolerance developed to its effects after long-term treatment. Repeated treatment of mice with haloperidol resulted in an inhibition of apomorphine-induced climbing behavior throughout the time of treatment with haloperidol, but the climbing behavior markedly increased to levels significantly higher than that of the control mice immediately after withdrawal from haloperidol treatment. This increased climbing was accompanied by increased levels of D2 dopamine receptors in the striatum. By contrast, single, bilateral intrastriatal injections of the D2 antisense vector significantly inhibited apomorphine-induced climbing for approximately 30 days but failed to increase the climbing behavior or the levels of D2 dopamine receptors in striatum over those of the control values. These results suggest that a single injection of a D2 antisense RNA expression vector into mouse striatum produces specific, long-term inhibition of D2 dopamine receptor behaviors without causing a compensatory increase in the levels or function of D2 dopamine receptors.

Strategies to maintain the credibility of sham acupuncture used as a control treatment in clinical trials

Many clinical trials concerning acupuncture are flawed by methodological problems. One of the major difficulties is the appropriate selection and use of a placebo control. This article evaluates the use of sham acupuncture as a placebo control and analyzes its credibility as a control treatment. Sixty-four subjects were assessed for their perception of whether they were receiving sham or real acupuncture while participating in a clinical trial of acupuncture. It was found that if used under specific experimental conditions, sham acupuncture can function as a credible control. Specific strategies are suggested to maintain the credibility of sham acupuncture as a placebo control.

Quantitative analysis of cuneate neurone responsiveness in the cat in association with reversible, partial deafferentation

1. Partial deafferentation, based on peripheral nerve section or local anaesthetic blockade, has been reported to induce both immediate loss of responsiveness and/or immediate reorganization in receptive fields of neurones in the somatosensory system. In the present study, in anaesthetized cats, we have used a rapid, reversible deafferentation procedure based on cold block of the median nerve in order to evaluate quantitatively the response characteristics of cuneate neurones (n = 39) before, during and after partial deafferentation. 2. The first hypothesis tested was that cuneate neurones with input from ulnar or superficial radial nerve fields in the vicinity of the median nerve field should undergo, in association with median nerve blockade, an increased level of responsiveness to tactile stimuli within the ulnar or radial nerve zone, and an expansion of their cutaneous receptive fields. However, among eighteen cuneate neurones of this type, there was no evidence for any systematic enhancement of responsiveness nor, in at least sixteen of the eighteen neurones, any evidence for receptive field expansion. 3. The second hypothesis tested was that cuneate neurones whose input came from both the median nerve and another peripheral nerve source should undergo, in association with median nerve blockade, an increase in responsiveness to the remaining input and an expansion of the receptive field into the field of that remaining nerve source. However, in none of thirteen neurones of this type tested was there evidence of such a change. 4. The third hypothesis was that cuneate neurones whose control' receptive fields were within the median nerve zone of deafferentation should show an emergence of novel receptive fields and responsiveness from areas around the field of innervation of the median nerve. However, in none of eight neurones of this type was there evidence for such changes in adjacent skin areas. 5. In conclusion, with the use of cold block of the median nerve for partial deafferentation, the present study has confirmed previous findings of denervation-related loss of responsiveness in dorsal column nuclei neurones. The conflicting findings in studies of central nervous system plasticity indicate the need to understand better factors that do and do not lead to acute central changes.

Expression of a D2 dopamine receptor antisense RNA in brain inhibits D2-mediated behaviors

Drugs currently used to treat disorders of dopamine-mediated behaviors in the central nervous system are non-selective in that they interact not only with more than one isoform of dopamine receptor but also with receptors for other neurotransmitters. A new strategy to inhibit the actions of individual dopamine receptor subtypes is to inhibit the synthesis of the receptors through the use of oligonucleotides antisense to the transcripts encoding the different receptors. Earlier studies showed that oligodeoxynucleotides antisense to the D1 or D2 dopamine receptor messenger RNAs specifically inhibited the biological actions mediated by these individual isoforms of the dopamine receptor. However, these actions were relatively short-lasting. To determine whether one can achieve long-lasting inhibition of dopamine responses, while still taking advantage of the highly selective nature of an antisense strategy, an expression vector was employed that generates antisense RNA to the transcript encoding the D2 dopamine receptor. A single intrastriatal injection of this vector generated an antisense RNA to the D2 dopamine receptor, selectively reduced the levels of D2 dopamine receptors, and caused selective, long-term inhibition of behaviors mediated by D2 dopamine agonists. Such an antisense RNA strategy may find use in studying the function of dopaminergic receptors and in disorders associated with dopaminergic hyperactivity.

Antisense strategies in neurobiology

The use of antisense oligodeoxynucleotides, targeted to the transcripts encoding biologically active proteins in the nervous system, provides a novel and highly selective means to further our understanding of the function of these proteins. Recent studies of these agents also suggest the possibility of their being used therapeutically for a variety of diseases involving neuronal tissue. In this paper we review studies showing the in vitro and in vivo effects of antisense oligodeoxynucleotides as they relate to neurobiological functions. Particular attention is paid to the behavioral and biochemical effects of antisense oligodeoxynucleotides directed to the various subtypes of receptors for the neurotransmitter dopamine. An example is also provided showing the effects of a plasmid vector expressing an antisense RNA targeted to the calmodulin mRNAs in the PC12 pheochromocytoma cell line. The advantages of antisense oligodeoxynucleotides over traditional pharmacological treatments are assessed, and the advantages of using vectors encoding antisense RNA over the use of antisense oligodeoxynucleotides are also considered. We also describe the criteria that should be used in designing antisense oligodeoxynucleotides and several controls that should be employed to assure their specificity of action.

Antisense strategies in dopamine receptor pharmacology

Recent advances in molecular biology have provided pharmacologists the opportunity of developing an entirely new type of agent for studying and treating a variety of biological disorders. These agents, termed antisense oligodeoxynucleotides, have as their target the messenger RNAs encoding specific proteins. They act by binding to selected portions of these mRNAs through complimentary interactions and thereby prevent the synthesis of these proteins. These novel pharmacological tools have the promise of being easier to design and being more selective and predictable in their actions. In addition, insofar as agents targeted to receptors for neurotransmitters are concerned, unlike the classical pharmacological agents, these new compounds may not lead to the upregulation of the very receptors the drugs are designed to inhibit. The present review summarizes briefly studies on the effect of oligodeoxynucleotides antisense to the mRNAs encoding the various subtypes of the dopamine receptor. The studies show that oligodeoxynucleotides antisense to the D2 dopamine receptor when intracerebroventricularly into brains of rodents are rapidly taken up into the brain tissue, distributed to brain cells, and produce effects characteristic of highly selective D2 dopamine antagonists. The compounds also produced specific reductions in the levels of D2 dopamine receptor mRNA and D2 dopamine receptors. Similarly, injecting an antisense oligodeoxynucleotide targeted to the D1 dopamine receptor mRNA produces effects characteristic of D1 dopamine receptor antagonists. Other studies using these agents has produced evidence that there is a small pool of receptors that turn over very rapidly and which constitute the functional pool of these receptors. The evidence suggests further that antisense oligodeoxynucleotides inhibit the synthesis of this small functional pool of dopamine receptors, thereby providing an explanation of why there is often a discordance between changes in dopaminergic function and changes in the levels of dopamine receptors. Studies of antisense oligodeoxynucleotides targeted to the other subtypes of dopamine receptor may help reveal the biological roles that these and other newly discovered subtypes of neurotransmitter receptors have. They may also provide an entirely new and potentially more selective therapeutic regimen for altering the functions of these receptors.

Reduced level of calmodulin in PC12 cells induced by stable expression of calmodulin antisense RNA inhibits cell proliferation and induces neurite outgrowth

The role calmodulin plays in the growth and differentiation of nerve cells was assessed by altering the levels of calmodulin in the PC12 rat pheochromocytoma cell line and determining the effects of altering these levels on cellular proliferation and differentiation. Calmodulin levels in the PC12 cells were increased or decreased by transfecting the cells with a mammalian expression vector into which the rat calmodulin gene I had been cloned in the sense or antisense orientation, respectively. The cells transfected with the calmodulin sense gene showed increased levels of calmodulin immunoreactivity and increased levels of calmodulin messenger RNA as ascertained by immunocytochemistry and slot-blot analysis, respectively. Cells transfected with the calmodulin antisense construct showed reduced levels of calmodulin immunoreactivity. Reducing the levels of calmodulin by expression of antisense calmodulin messenger RNA resulted in a marked inhibition of cell growth, whereas increasing the levels of calmodulin by overexpressing calmodulin messenger RNA resulted in an acceleration of cell growth. Transfected PC12 cells having reduced levels of calmodulin immunoreactivity exhibited spontaneous outgrowth of long, stable and highly branched neuritic processes. PC12 cells in which calmodulin was overexpressed showed no apparent changes in cell morphology, but did show an altered response to the addition of nerve growth factor. While nerve growth factor slowed cellular proliferation and induced extensive neurite outgrowth, in parental PC12 cells nerve growth factor induced little or no neurite outgrowth and little inhibition of cell proliferation in transfected cells overexpressing calmodulin. These results indicate that calmodulin is essential for the proliferation of nerve cells and for the morphological changes that nerve cells undergo during differentiation. The study also suggests the possibility that a calmodulin antisense approach may be used to inhibit the proliferation of neuronal tumors.

Intrastriatal administration of an oligodeoxynucleotide antisense to the D2 dopamine receptor mRNA inhibits D2 dopamine receptor-mediated behavior and D2 dopamine receptors in normal mice and in mice lesioned with 6-hydroxydopamine

Previous studies have shown that the intracerebroventricular injection of antisense oligodeoxynucleotides targeted to the mRNAs encoding the different subtypes of dopamine receptors inhibited behaviors mediated by these receptors. The present studies were designed to determine whether such antisense oligodeoxynucleotides could produce similar effects when injected into a discrete brain area. A D2 dopamine receptor antisense oligodeoxynucleotide (D2 antisense) was repeatedly injected into one corpus striatum of either normal mice or mice with unilateral lesions of the striatum induced by 6-hydroxydopamine. In the latter, intrastriatal injection of D2 antisense blocked the contralateral rotational behavior induced by the parenteral administration of the D2 dopamine receptor agonist quinpirole. The inhibitory effect of D2 antisense was dose- and time-related and was reversed upon cessation of D2 antisense treatment. This inhibitory effect was also selective in that D2 antisense treatment inhibited the rotational behavior induced by quinpirole but not that induced by the D1 dopamine receptor agonist SKF 38393 or by the muscarinic cholinergic agonist oxotremorine. Following repeated intrastriatal injections of D2 antisense into normal mice, parenteral administration of quinpirole caused rotational behavior ipsilateral to the side in which the D2 antisense was injected. No such rotational behavior was seen when similarly treated mice were challenged with SKF 38393 or oxotremorine. The quinpirole-induced rotational behavior in mice given intrastriatal injections of D2 antisense disappeared upon cessation of D2 antisense treatment. Repeated intrastriatal administration of D2 antisense also caused a significant reduction in the levels of D2, but not D1, dopamine receptors in striatum, as determined by receptor autoradiography. The levels of D2 dopamine receptors returned to normal upon cessation of D2 antisense treatment. Intrastriatal administration of an oligodeoxynucleotide with randomly placed nucleotides failed to alter the rotational response to quinpirole in either 6-hydroxydopamine-lesioned or normal mice and failed to alter the levels of D2 dopamine receptors in striatum. These results show that selective inhibition of behavioral responses mediated by D2 dopamine receptors can be achieved by the direct injection of a D2 antisense oligodeoxynucleotide into a discrete brain area.

Neural control of vocalization: respiratory and emotional influences

Previous research has shown that a region of the midbrain, the periaqueductal gray matter (PAG), is critical for vocalization. In this review, we describe the results of previous investigations in which we sought to find out how PAG neurons integrate the activity and precise timing of respiratory, laryngeal, and oral muscle activity for natural-sounding vocalization using the technique of excitatory amino acid microinjections in cats. In these studies, all surgical procedures were carried out under deep anaesthesia. In the precollicular decerebrate cat two general types of vocalization, classified as voiced and unvoiced, could be evoked by exciting neurons in the lateral part of the intermediate part of the PAG. The patterns of evoked electromyographic activity were strikingly similar to previously reported patterns of human muscle activity. Coordinated patterns of activity were evoked with just-threshold excitation leading to the conclusion that patterned muscle activity corresponding to the major categories of voiced and voiceless sound production are represented in the PAG. In a parallel series of human and animal experiments, we also determined that the speech and vocalization respiratory patterns are integrated and coordinated with afferent signals related to lung volume. These data have led to the proposal of a new hypothesis for the neural control of vocalization: that the PAG is a crucial brain site for mammalian voice production, not only in the production of emotional or involuntary sounds, but also as a generator of specific respiratory and laryngeal motor patterns essential for human speech and song.

Uptake and distribution of fluorescein-labeled D2 dopamine receptor antisense oligodeoxynucleotide in mouse brain

To determine the uptake and distribution of oligodeoxynucleotides in brain, a 20-mer phosphorothioated oligodeoxynucleotide complementary to a portion of the D2 dopamine receptor mRNA was fluorescently labeled with fluorescein isothiocyanate (FITC) and injected into the lateral cerebral ventricles of mice. At various survival times after the injection, the brains were removed, fixed, sectioned, and viewed under a fluorescent microscope. The results showed that the oligodeoxynucleotide was rapidly taken up into the brain. Initially the label was relatively diffusely spread throughout the interstitial spaces of the brain, then became redistributed to the cellular compartments. The signal extended from those forebrain nuclei located immediately in contact with the ventricles, such as the corpus striatum, septum, and hippocampus, to areas further removed from the ventricles, such as the cerebral cortex, nucleus accumbens, and substantia nigra. When the FITC-labeled D2 antisense oligodeoxynucleotide was given once daily for 4 d, the signal intensity seen 24 h after the last injection appeared to be of greater intensity overall compared to that seen after a single injection. At early time-points the oligodeoxynucleotide signals appeared to be punctuated and were found in cell bodies as well as in proximal dendritic processes. However, not all cells were equally labeled, suggesting an uneven uptake and accumulation of the D2 antisense into the various cell types. At later time-points the fluorescent signal appeared granular; at these times the injected material was largely degraded. These studies show that a D2 dopamine receptor antisense oligodeoxynucleotide is rapidly taken up from cerebral ventricles into brain, becomes widely distributed throughout the brain tissue to areas far removed from direct contact with the ventricles, and appears to accumulate to a different extent in the various brain areas and cell types.

Brain stem integration of vocalization: role of the nucleus retroambigualis

1. The descending pathways that mediate the periaqueductal gray (PAG)-evoked coordination of respiratory, laryngeal, and orofacial activity for vocalization have yet to be delineated. Two hypotheses have been offered. One theory is that this activity is mediated by a diffuse descending projection to parvocellular reticular interneurons, adjacent to the relevant laryngeal and orofacial motoneuronal pools. The second hypothesis is that the motor activity for vocalization is integrated via a projection from the PAG to a caudal medullary column of neurons, the nucleus retroambigualis (NRA). These hypotheses were tested with the use of a series of medullary transections combined with PAG stimulation. Transections that eliminated, in a series of caudal-to-rostral steps, the NRA, also eliminated the PAG-evoked cricothyroid and most of the thyroarytenoid laryngeal motor activity. These results indicate that the final common pathway for much of the laryngeal activity in PAG-evoked vocalization includes un initial synapse in the caudal medulla, presumably in the NRA. 2. The electromyographic changes evoked by microinjection of D,L-homocysteic acid (DLH) in the NRA of the unanesthetized, precollicular decerebrate cat were analyzed in order to delineate the NRA contribution to the coordinated respiratory, laryngeal, and oral muscle changes in vocalization. A total of 415 DLH injection sites were located at or caudal to the level of the obex. Vocalization was evoked at 46 of these sites, which were all confined to a restricted region of the ventrolateral medulla 1-3 mm caudal to the obex. This region corresponded to the rostral half of the NRA and the immediately adjacent medullary tegmentum. 3. In all experiments evidence was obtained that variable muscle activation, rather than functional and integrated muscle patterns, was represented within the NRA. Vocalization evoked by DLH microinjection in the NRA was usually associated with excitation of the cricothyroid, thyroarytenoid, external oblique, internal oblique, internal intercostal, and diaphragm muscles that occurred in a different manner from site to site. That is, injection at sites separated by 0.3-0.5 mm evoked quite different responses. 4. NRA-evoked vocalization was compared with PAG-evoked vocalization using small injections (1.5-4.5 nl) into each region. As well, larger microinjections (15-120 nl) into NRA were made for comparison with previous results from the PAG using similar doses. Within the PAG, stereotyped and relatively "fixed" patterns of muscle activity are represented, whereas within the NRA there was no representation of specific muscle patterns, but rather a partial topographic separation of "premotor neurons" regulating different muscles. Correspondingly, stereotyped vocalizations were never evoked from the NRA. Further, most NRA-evoked vocalizations were unusual in quality and would not be identified generally as feline. 5. Evidence was obtained for a separation of pathways from the PAG regulating sound production and orofacial modulation of that sound. In contrast to the results from the PAG, excitation of NRA neurons rarely evoked activity in the oral muscles (genioglossus or anterior belly of digastric) or orofacial modulation of sound production. 6. Our finding suggests that the NRA serves as an important substrate for the generation of respiratory pressure and larynges adduction, which are two essential aspects of not only vocalization but also several behaviors involving Valsava maneuvers such as coughing, vomiting, and defecation.