Capsaicin 8% patch for treprostinil subcutaneous infusion site pain in pulmonary hypertension patients.

BACKGROUND: Treprostinil sodium improves haemodynamics and symptoms in pulmonary arterial hypertension (PAH) patients, but its subcutaneous (s.c.) administration can produce severe local site pain, and lead to discontinuation of vital treatment. Treprostinil is a prostacyclin analogue which stimulates prostacyclin receptors in skin nociceptor terminals, resulting in pain and cutaneous hypersensitivity, for which current pain remedies have limited effect. Capsaicin 8% patch relieves neuropathic pain for 3 months after a single 60 min cutaneous application; we investigated whether its pre-application can reduce s.c. trepostinil-induced pain. METHODS: A single-centre, double-blind, randomized, placebo-controlled, crossover study was conducted to assess the safety and efficacy of a single capsaicin 8% patch pre-application for s.c. treprostinil pain in 11 PAH patients, relative to control patch with low-dose capsaicin 0.075% cream. RESULTS: The primary efficacy endpoint, mean difference between the two treatment arms in an 11-point numerical pain rating scale from baseline to 2 weeks after patch applications, was significantly lower on the capsaicin 8% patch treatment arm [P=0.01, mean difference=-1.47 units, 95% credible interval (CI): -2. 59 to -0.38] in the patients who completed the study per protocol, although intention-to-treat analysis did not show significant difference (P=0.28). Heat pain thresholds were decreased (P=0.027, mean difference=5.43°C, 95% CI: 0.71-10.21) and laser Doppler flux increased (P=0.016, mean difference=370 units, 95% CI: 612 to 127.9) at the application site immediately after capsaicin 8% patch, confirming activity. CONCLUSIONS: Further investigation of the efficacy of capsaicin 8% patch in this indication is warranted.

Pittsburgh compound B (11C-PIB) and fluorodeoxyglucose (18 F-FDG) PET in patients with Alzheimer disease, mild cognitive impairment, and healthy controls.

Amyloid load in the brain using Pittsburgh compound B ((11)C-PIB) positron emission tomography (PET) and cerebral glucose metabolism using fluorodeoxyglucose ((18)F-FDG) PET were evaluated in patients with mild Alzheimer disease (AD, n = 18), mild cognitive impairment (MCI, n = 24), and controls (CTR, n = 18). ( 11)C-PIB binding potential (BP(ND)) was higher in prefrontal cortex, cingulate, parietal cortex, and precuneus in AD compared to CTR or MCI and in prefrontal cortex for MCI compared to CTR. For (18)F-FDG, regional cerebral metabolic rate for glucose (rCMRGlu) was decreased in precuneus and parietal cortex in AD compared to CTR and MCI, with no MCI-CTR differences. For the AD-CTR comparison, precuneus BP(ND) area under the receiver operating characteristic (ROC) curve (AUC) was 0.938 and parietal cortex rCMRGlu AUC was 0.915; for the combination, AUC was 0.989. ( 11)C-PIB PET BP(ND) clearly distinguished diagnostic groups and combined with (18)F-FDG PET rCMRGlu, this effect was stronger. These PET techniques provide complementary information in strongly distinguishing diagnostic groups in cross-sectional comparisons that need testing in longitudinal studies.

PIB is a non-specific imaging marker of amyloid-beta (Abeta) peptide-related cerebral amyloidosis.

The in vivo imaging probe [11C]-PIB (Pittsburgh Compound B, N-methyl[11C]2-(4'-methylaminophenyl-6-hydroxybenzathiazole) is under evaluation as a key imaging tool in Alzheimer's disease (AD) and to date has been assumed to bind with high affinity and specificity to the amyloid structures associated with classical plaques (CPs), one of the pathological hallmarks of the disease. However, no studies have systematically investigated PIB binding to human neuropathological brain specimens at the tracer concentrations achieved during in vivo imaging scans. Using a combination of autoradiography and histochemical techniques, we demonstrate that PIB, in addition to binding CPs clearly delineates diffuse plaques and cerebrovascular amyloid angiopathy (CAA). The interaction of PIB with CAA was not fully displaceable and this may be linked to the apolipoprotein E-epsilon4 allele. PIB was also found to label neurofibrillary tangles, although the overall intensity of this binding was markedly lower than that associated with the amyloid-beta (Abeta) pathology. The data provide a molecular explanation for PIB's limited specificity in diagnosing and monitoring disease progression in AD and instead indicate that the ligand is primarily a non-specific marker of Abeta-peptide related cerebral amyloidosis.

The artificial zinc finger protein 'Blues' binds the enhancer of the fibroblast growth factor 4 and represses transcription.

The design of novel genes encoding artificial transcription factors represents a powerful tool in biotechnology and medicine. We have engineered a new zinc finger-based transcription factor, named Blues, able to bind and possibly to modify the expression of fibroblast growth factor 4 (FGF-4, K-fgf), originally identified as an oncogene. Blues encodes a three zinc finger peptide and was constructed to target the 9 bp DNA sequence: 5'-GTT-TGG-ATG-3', internal to the murine FGF-4 enhancer, in proximity of Sox-2 and Oct-3 DNA binding sites. Our final aim is to generate a model system based on artificial zinc finger genes to study the biological role of FGF-4 during development and tumorigenesis.

Behavioural and electrocortical effects after injection of two ornithine decarboxylase inhibitors into several areas of the brain in the rat.

The behavioural and electrocortical effects of alpha-methylornithine and alpha-difluoromethylornithine, two ornithine decarboxylase inhibitors, were evaluated after their infusion into several areas of the brain in the rat. Both compounds induced, in dose-dependent manner, similar epileptogenic effects, stereotyped behaviour and postural asymmetry, depending upon the site of injection. Unilateral injection of DFMO into the entopeduncular nucleus or the substantia nigra pars reticulata, caused an increase in locomotor activity. Unilateral injection of DFMO into the caudate nucleus or the substantia nigra pars compacta had no effect on locomotor activity. Among the areas of the brain studied, the most sensitive site from which electrocortical epileptogenic disorders were evoked, was the hippocampus. The GABA agonist muscimol, infused prior to DFMO, resulted in an anticonvulsant action, while DFMO, infused prior to putrescine, increased the convulsant properties of putrescine. In conclusion, these results indicate that DFMO and alpha-methylornithine produced epileptogenic effects after their intracerebral infusion and suggest that may act as analogues of putrescine.

Anticonvulsant effect of denzimol in DBA/2 mice.

The anticonvulsant activity of N-[beta-[4-beta-phenylethyl)phenyl]-beta-hydroxyethyl]-imidazole hydrochloride, denzimol, was studied following intraperitoneal administration in DBA/2 mice (seizures induced by sound). Protection against sound-induced seizures was observed after intraperitoneal administration of denzimol (3-15 mg/kg). The ED50 values for the suppression of tonic, clonic and wild running phases of sound-induced seizures were 1.24, 2.61 and 6.03 mg/kg, respectively. This protective action was significantly reduced by pretreatment with aminophylline (25 mg/kg i.p.), CGS 8216 (1 or 5 mg/kg i.p.) and Ro 15-1788 (2.5 mg/kg i.p). The present experiments suggest an involvement of purinergic and benzodiazepine mechanisms in the anticonvulsant action of denzimol.

1-Aryl-3,5-dihydro-4H-2,3-benzodiazepin-4-ones: novel AMPA receptor antagonists.

Our previous publication (Eur. J. Pharmacol. 1995, 294, 411-422) reported preliminary chemical and biological studies of some 2,3-benzodiazepines, analogues of 1-(4-aminophenyl)-4-methyl-7,8-(methylenedioxy)-5H-2,3-benzodiazepine (1, GYKI 52466), which have been shown to possess significant anticonvulsant activity. This paper describes the synthesis of new 1-aryl-3,5-dihydro-4H-2,3-benzodiazepin-4-ones and the evaluation of their anticonvulsant effects. The observed findings extend the structure-activity relationships previously suggested for this class of anticonvulsants. The seizures were evoked both by means of auditory stimulation in DBA/2 mice and by pentylenetetrazole or maximal electroshock in Swiss mice. 1-(4'-Aminophenyl)- (38) and 1-(3'-aminophenyl)-3,5-dihydro-7,8-dimethoxy-4H-2,3-benzodiazepin- 4-one (39), the most active compounds of the series, proved to be more potent than 1 in all tests employed. In particular, the ED50 values against tonus evoked by auditory stimulation were 12.6 micromol/kg for derivative 38, 18.3 micromol/kg for 39, and 25.3 micromol/kg for 1. Higher doses were necessary to block tonic extension induced both by maximal electroshock and by pentylenetetrazole. In addition these compounds exhibited anticonvulsant properties that were longer lasting than those of compound 1 and were less toxic. The novel 2,3-benzodiazepines were also investigated for a possible correlation between their anticonvulsant activities against convulsions induced by 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) and their affinities for benzodiazepine receptors (BZR). The 2,3-benzodiazepines did not affect the binding of [3H]flumazenil to BZR, and conversely, their anticonvulsant effects were not reversed by flumazenil. On the other hand the 2,3-benzodiazepines antagonized seizures induced by AMPA and aniracetam in agreement with an involvement of the AMPA receptor. In addition, both the derivative 38 and the compound 1 markedly reduced the AMPA receptor-mediated membrane currents in guinea-pig olfactory cortical neurons in vitro in a noncompetitive manner. The derivatives 25 and 38-40 failed to displace specific ligands from N-methyl-D-aspartate (NMDA), AMPA/kainate, or metabotropic glutamate receptors.

3,5-Dihydro-4H-2,3-benzodiazepine-4-thiones: a new class of AMPA receptor antagonists.

Synthesis and evaluation of anticonvulsant activity of a series of 2,3-benzodiazepin-4-ones (2) chemically related to 1-(4'-aminophenyl)-4-methyl-7,8-(methylenedioxy)-5H-2,3-benzodiazepine (1, GYKI 52466) have been reported in our recent publications. Compounds 2 manifested marked anticonvulsant properties acting as 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptor antagonists. In an attempt to better define the structure-activity relationships (SAR) and to obtain more potent and selective anticonvulsant agents, 1-aryl-3,5-dihydro-4H-2, 3-benzodiazepine-4-thiones 3 were synthesized from the corresponding isosteres 2. The evaluation is reported of their anticonvulsant effects, both in the audiogenic seizures test with DBA/2 mice and against the maximal electroshock- and pentylenetetrazole-induced seizures in Swiss mice. New derivatives 3 showed higher potency, less toxicity and longer-lasting anticonvulsant action than those of the parent compounds 2 in all tests employed. Analogous to derivatives 2, new compounds 3 do not affect the benzodiazepine receptor (BZR) while they do antagonize AMPA-induced seizures; their anticonvulsant activity is reversed by pretreatment with aniracetam but not with flumazenil, thus suggesting a clear involvement of AMPA receptors. Electrophysiological data indicate a noncompetitive blocking mechanism at the AMPA receptor sites for 3i, the most active of the series and over 5-fold more potent than 1.

Persistent muscarinic excitation in guinea-pig olfactory cortex neurons: involvement of a slow post-stimulus afterdepolarizing current.

The persistent excitatory effects of the muscarinic agonist oxotremorine-M were investigated in guinea-pig olfactory cortex neurons in vitro (28-30 degrees C) using a single-microelectrode current-clamp/voltage-clamp technique. In 40% of recorded cells (type 1), bath-application of oxotremorine-M (2-10 microM; 1-2 min) induced a strong membrane depolarization, an increase in input resistance and a sustained neuronal discharge lasting over 30 min following agonist washout. A large depolarizing stimulus applied during the action of oxotremorine-M, evoked a slow post-stimulus afterdepolarization (approximately 10-15 mV) lasting approximately 30 s. Injection of steady negative current at the peak of this response produced a slow repolarization of the membrane potential (half-time approximately 0.6 min) towards a plateau level ("hyperpolarization recovery"); these effects of oxotremorine-M were slowly reversed on washout or by application of atropine (1 microM). In a second population of neurons (type 2; 39% of total), oxotremorine-M produced a large depolarization, a resistance increase and repetitive firing that did not persist after agonist washout; these neurons failed to generate a prominent slow afterdepolarization on stimulation, and showed no hyperpolarization recovery effect. Their resting membrane properties were not significantly different from those of type 1 cells. The remaining proportion of cells (type 3) elicited little or no muscarinic response to oxotremorine-M and no slow afterdepolarization; these cells showed characteristics spike fractionation (pre-potentials) during an evoked train of action potentials.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of the muscarinic response and morphological properties of identified cells in the guinea-pig olfactory cortex in vitro.

The electrophysiological and morphological characteristics of neurons in the guinea-pig olfactory cortex brain slice were investigated using a combined intracellular recording and neurobiotin-dye filling technique, in an attempt to show whether a clear relation existed between cell morphology and excitatory muscarinic response profile. Out of 46 sampled neurons, 25 (termed type 1), responded to bath-application of the muscarinic agonist oxotremorine-M (10 microM, 2-3 min) with a strong and persistent excitation coupled with the appearance of a slow depolarizing afterpotential (10-20 mV amplitude) following a large depolarizing stimulus. These neurons were identified as deep pyramidal cells located in cortical layer III, with characteristic pyramidal/ovoid shaped cell bodies, prominent apical dendrites with branches extending to the surface, and extensive basal dendritic trees. The cells showed a regular spiking pattern in response to injected depolarizing current, with no evidence of bursting behaviour. Nine cells (termed type 2), were strongly excited by oxotremorine-M, but only generated a weak depolarizing afterpotential (< 5 mV) following stimulation. These neurons (located in layer III or at layer II-III border) had a variable, non-pyramidal morphology with either a fusiform/tripolar, stellate/multipolar or bipolar/bi-tufted appearance, respectively. Apart from a more prominent post-spike afterhyperpolarization observed in some type 2 cells, their resting membrane properties and firing patterns were indistinguishable from those of type 1 responding cells. Twelve cells (termed type 3) showed little or no excitatory response to oxotremorine-M, and never generated a post-stimulus slow afterdepolarization. These cells (within compact layer II) had the morphological features of superficial pyramidal cells, typified by their short apical trunks and well-developed apical dendritic trees. They could be distinguished electrophysiologically by their ability to show spike fractionation during injection of large depolarizing current pulses. The morphology and laminar position of neurobiotin-filled cells was also compared with those of cells stained by the Golgi-Cox method. Some factors that may have contributed to the observed differences in muscarinic response profile are discussed. It is proposed that the selective muscarinic induction of the slow depolarizing afterpotential phenomenon in deep pyramidal cells may be important in olfactory cortical learning and memory processes.

Investigation of the role of intracellular Ca(2+) stores in generation of the muscarinic agonist-induced slow afterdepolarization (sADP) in guinea-pig olfactory cortical neurones in vitro.

1. Intracellular recordings were made from guinea-pig olfactory cortical brain slice neurones to assess the possible role of intracellular Ca(2+) stores in the generation of the slow post-stimulus afterdepolarization (sADP) and its underlying tail current (I(ADP)), induced by muscarinic receptor activation. 2. Caffeine or theophylline (0.5 - 3 mM) reduced the amplitude of the I(ADP) (measured under 'hybrid' voltage clamp) induced in the presence of the muscarinic agonist oxotremorine-M (OXO-M, 10 microM) by up to 96%, without affecting membrane properties or muscarinic depolarization of these neurones. 3. The L-type Ca(2+) channel blocker nifedipine (1, 10 microM) also inhibited I(ADP) (by up to 46%), while ryanodine (10 microM) (a blocker of Ca(2+) release from internal stores) produced a small ( approximately 10%) reduction in I(ADP) amplitude; however, neither 10 microM dantrolene (another internal Ca(2+) release blocker) nor the intracellular Ca(2+) store re-uptake inhibitors thapsigargin (3 microM) or cyclopiazonic acid (CPA, 15 microM) affected I(ADP) amplitude. 4. IBMX (100 microM), a phosphodiesterase inhibitor, also had no effect on I(ADP). Furthermore, inhibition of I(ADP) by caffeine was not reversed by co-application of 100 microM adenosine. 5. Caffeine (3 mM) or nifedipine (10 microM) reduced the duration of presumed Ca(2+) spikes revealed by intracellular Cs(+) loading. When applied in combination, nifedipine and caffeine effects were occlusive, rather than additive, suggesting a common site of action on L-type calcium channels. 6. We conclude that Ca(2+)-induced Ca(2+) release (CICR) from internal stores does not contribute significantly to muscarinic I(ADP) generation in olfactory cortical neurones. However caffeine and theophylline, which enhance CICR in other systems, blocked I(ADP) induction. We suggest that this action might involve a combination of L-type voltage-gated Ca(2+) channel blockade, and a direct inhibitory action on the putative I(ADP) K(+) conductance.

Metabotropic glutamate receptor subtypes mediating slow inward tail current (IADP) induction and inhibition of synaptic transmission in olfactory cortical neurones.

1. The pharmacological features of the pre- and postsynaptic metabotropic glutamate receptors (mGluRs) present in the guinea-pig olfactory cortex, were examined in brain slices in vitro by use of a conventional intracellular current clamp/voltage clamp recording technique. 2. Bath-application of trans-aminocyclopentane-1,3-dicarboxylic acid (trans-ACPD) (50 microM) produced a sustained membrane depolarization, increase in cell excitability and induction of a post-stimulus inward (after depolarizing) tail current (IADP) (measured under 'hybrid' voltage clamp) similar to those evoked by the muscarinic receptor agonist oxotremorine-M (OXO-M, 2 microM). 3. L-Glutamate (0.25 1 mM. in the presence of 20 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 100 microM-DL-amino-5-phosphono valeric acid (DL-APV)) or the broad spectrum mGluR agonists 1S,3R-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD, 10 microM), 1S,3S-ACPD (50 microM), ibotenate (Ibo; 25 microM. in the presence of 100 microM DL-APV), the selective mGluR I agonists (S)-3,5-dihydroxyphenylglycine ((S)-3,5-DHPG, 10 microM), (S)-3-hydroxyphenylglycine ((S)-3HPG, 50 microM), or quisqualate (10 microM, in the presence of 20 microM CNQX), but not the mGluR II agonist 2S,1'S,2'S-2-(2'-carboxycyclopropyl)-glycine (L-CCG1,1 microM) or mGluR III agonist L(+)-2-amino-4-phosphonobutyric acid (L-AP4, 1 mM), were all effective in producing membrane depolarization and inducing a post-stimulus IADP. Unexpectedly, the proposed mGluR II-selective agonist (2S,1'R,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)-glycine (DCG-IV, 10 microM, in the presence of 100 microM DL-APV) was also active. 4. The excitatory effects induced by 10 microM 1S,3R-ACPD were reversibly antagonized by the mGluR I/II antagonist (1)-alpha-methyl-4-carboxyphenylglycine ((+)-MCPG, 0.5 1 mM), as well as the selective mGluR I antagonists (S)-4-carboxyphenylglycine ((S)-4CPG) and (S)-4-carboxy-3-hydroxyphenyl glycine ((S)-4C3HPG) (both at 1 mM), but not the nonselective mGluR antagonist L(+)-2-amino-3-phosphonopropionic acid (L-AP3, 1 mM) or the selective mGluR III antagonist (S)-alpha-methyl-L-AP4 (MAP4, 1 mM). 5. The excitatory postsynaptic potentials (e.p.s.ps), induced by single focal stimulation of cortical excitatory fibre tracts, were markedly reduced by 1S,3R-ACPD or L-AP4 (both at 10 microM), and by the selective mGluR II agonists (mGluR 1 antagonists) (S)-4CPG or (S)-4C3HPG (both at 1 mM) but not (S)-3,5-DHPG or (S)-3HPG (both at 100 microM). 6. The inhibitory effects of 1S-3R-ACPD, but not L-AP4, were reversibly blocked by (+)-MCPG (1 mM), whereas those produced by L-AP4, but not 1S,3R-ACPD, were blocked by the selective mGluR III antagonist MAP4 (1 mM). 7. It is concluded that a group I mGluR is most likely involved in mediating excitatory postsynaptic effects, whereas two distinct mGluRs (e.g. group II and III) might serve as presynaptic inhibitory autoreceptors in the guinea-pig olfactory cortex.

Microinfusion of clonidine and yohimbine into locus coeruleus alters EEG power spectrum: effects of aging and reversal by phosphatidylserine.

1. The behavioural and electrocortical (ECoG) power spectrum effects of clonidine, and yohimbine, an agonist and an antagonist at alpha 2-adrenoceptors, after their unilateral microinfusion into the rat locus coeruleus (LC) in young (50-70 days old) and old (13-15 months old) rats were studied. 2. Clonidine (0.09, 0.19, 0.28 and 0.56 nmol) microinfused into the LC of young rats induced dose-dependent behavioural and ECoG slow wave sleep (SWS) with a significant increase in total voltage power and power in the lower frequency bands. In contrast, yohimbine (1.3 and 2.6 nmol) infused into the LC of young rats produced ECoG desynchronization and a significant decrease in total voltage power. 3. In contrast to young rats, clonidine (0.19 and 0.28 nmol) given into the LC did not affect behaviour and the ECoG power spectrum in old rats. However, after higher doses of clonidine (0.56 and 1.2 nmol) a small and short-lasting period of behavioural and ECoG SWS was still evident. Similarly, in old rats yohimbine, at a dose (1.3 nmol) which was stimulative in young animals, did not significantly affect behaviour and ECoG power spectrum. Higher doses of yohimbine (2.6 and 5.2 nmol) were required to induce behavioural and ECoG changes similar to those observed with lower doses of yohimbine in young rats. 4. Chronic treatment with phosphatidylserine (30 mg kg-1, orally, daily for 21 and 30 days), was able gradually to restore in old rats, in comparison with a vehicle-treated group, the responsiveness of alpha 2-adrenoceptors to clonidine and yohimbine given into the LC.

Evidence that locus coeruleus is the site where clonidine and drugs acting at alpha 1- and alpha 2-adrenoceptors affect sleep and arousal mechanisms.

The behavioural and electrocortical (ECoG) effects of clonidine were studied after microinjection into the third cerebral ventricle, or microinfusion into some specific areas of the rat brain rich in noradrenaline-containing cell bodies (locus coeruleus) or into areas receiving noradrenergic terminals (dorsal hippocampus, amygdaloid complex, thalamus, frontal and sensimotor cortex). The ECoG effects were continuously analysed and quantified by means of a Berg-Fourier analyser as total power and as power in preselected bands of frequency. Clonidine (9.4 to 75 nmol) given into the third cerebral ventricle produced behavioural sedation and sleep and a dose-dependent increase in ECoG total voltage power as well as in the lower frequency bands. Much lower doses were required to produce similar behavioural and ECoG spectrum power effects after either unilateral or bilateral microinfusion of clonidine into the locus coeruleus. Doses of clonidine equimolar to those given into the third cerebral ventricle, were almost ineffective in inducing behavioural and ECoG sleep after their microinfusion into the dorsal hippocampus. In addition, a dose (0.56 nmol) of clonidine which, given into the locus coeruleus, produced marked behavioural sleep and ECoG synchronization, lacked effects when given into the ventral or anterior thalamus, into the amygdaloid complex or onto the frontal and sensimotor cortex. The behavioural and ECoG spectrum power effects of clonidine given into the third cerebral ventricle or into the locus coeruleus were prevented by antagonists of alpha 2-adrenoceptors but not by alpha 1-adrenoceptor antagonists. Intraventricular microinjection, or microinfusion into the locus coeruleus, of yohimbine, a selective alpha 2-adrenoceptor antagonist, produced behavioural arousal, increase in locomotor and exploratory activity, tachypnoea and ECoG desynchronization with a significant reduction in total voltage power. Similar stimulatory effects were also observed after microinjection of phentolamine into the same sites. No significant effects on behaviour and ECoG activity were evoked after intraventricular injection or microinfusion into the locus coeruleus of prazosin or methoxamine.

Effects of pertussis toxin on the behavioural and ECoG spectrum changes induced by clonidine and yohimbine after their microinfusion into the locus coeruleus.

1. Pertussis toxin, a substance which interferes selectively with receptor-mediated signal transduction mechanisms, was injected into the locus coeruleus of rats 1, 2, 3, 6 or 10 days before the microinjection of clonidine or yohimbine into the same site. 2. Clonidine produced in control rats typical behavioural sedation and/or sleep and ECoG synchronization while yohimbine produced behavioural arousal and ECoG desynchronization. 3. The behavioural and ECoG effects of both compounds were blocked in animals pretreated with pertussis toxin. This activity was more marked from 2 to 6 days after pertussis toxin pretreatment and was restored 10 days after toxin administration. In addition, the behavioural and ECoG slow-wave sleep observed after intraperitoneal administration of clonidine (0.2 mumol kg-1) was significantly reduced by prior (3 days) microinfusion of pertussis toxin into the locus coeruleus. 4. These results are consistent with the hypothesis that the behavioural and ECoG effects of clonidine and yohimbine are mediated via a guanine regulatory protein which is affected by pertussis toxin.

Tripelennamine enhances buprenorphine-, but not pentazocine-induced hyperactivity in mice.

The opioid agonist-antagonist pentazocine (1-30 mg/kg) and the partial agonist buprenorphine (0.05-0.25 mg/kg) were tested, alone or in combination with the histamine H1-receptor antagonist tripelennamine (1, 2.5, 5 or 10 mg/kg), on locomotor activity in mice of the CD-1 strain. When given alone, pentazocine produced slight and non-dose-related activity increments, while buprenorphine induced strong and dose-related locomotor stimulation. Tripelennamine slightly increased activity by itself and enhanced buprenorphine-, but not pentazocine-induced hyperactivity. The results are discussed in relation to the hypothesis that antihistaminic agents specifically interfere with locomotor effects of opioids.

Chronic (-)baclofen or CGP 36742 alters GABAB receptor sensitivity in rat brain and spinal cord.

Administration of the GABAB receptor agonist, (-)-baclofen 10 mg kg-1, i.p. daily for 21 days to rats prevented (-)-baclofen-induced hyperpolarizing responses and synaptically-evoked late inhibitory potentials (IPSPs) in olfactory cortical neurones recorded intracellularly from 450 microns brain slices. In contrast, pre-treatment with CGP 36742 induced a significant increase in (-)-baclofen-mediated post-synaptic responses and late IPSP amplitude. In the spinal cord, the potency of (-)-baclofen in inhibiting electrically-evoked substance P-like immunoreactivity or amino acid release was significantly reduced or increased in slices from rats pre-treated with the GABAB agonist or antagonist, respectively. These data suggest that functional responses to GABAB receptor activation in the mammalian central nervous system can be up- or down-regulated.

The amygdala mediates the impairing effect of the selective kappa-opioid receptor agonist U-50,488 on memory in CD1 mice.

The effect of the selective kappa-opioid receptor agonist U-50,488 on passive avoidance behaviour was studied in CD1 mice bearing lesions of the amygdaloid complex. The results have shown that post-trial injections of U-50,488 in unoperated mice as well as lesions of the amygdaloid complex in untreated mice decreased retention performances. No further impairment was observed in lesioned mice treated with U-50,488, indicating that amygdala is involved in the mediation of the effects of kappa-opioid receptor agonists on memory. The possibility that kappa-opioid receptors could modulate the memory retention of CD1 mice by influencing their emotional state is discussed.

Blocking of morphine-induced locomotor hyperactivity by amygdaloid lesions in C57BL/6 mice.

Bilateral lesions of the amygdaloid complex in C57BL/6 mice prevented the occurrence of morphine-induced hypermotility (running fit). This effect, that was different from that observed after hippocampal lesions but similar to that observed after caudate lesions, confirms the role of the basal ganglia catecholaminergic system in the development of the motor stimulation consecutive to the administration of this opiate receptor agonist.

Trans-ACPD induces a slow post-stimulus inward tail current (IADP) in guinea-pig olfactory cortex neurones in vitro.

The metabotropic glutamate receptor agonist trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid (trans-ACPD) produced a slow, persistent excitation of guinea-pig olfactory cortical neurones in vitro, and the appearance of a prominent post-stimulus after depolarization. The corresponding slow inward tail current (IADP) revealed under voltage clamp was insensitive to tetrodotoxin (or atropine) but was blocked by Cd2+ or tetrabutylammonium. The IADP properties resembled those of the slow inward tail current induced by muscarinic agonists in these neurones, suggesting a common intracellular transduction mechanism.