Ro 19-4603

Different functional effect of Ro 15-4513 and Ro 19-4603 on synaptic responses of Purkinje cells in the rat cerebellar slice.[Pubmed:7895057]

Brain Res. 1994 Dec 5;665(2):222-8.

Modulation of GABA-mediated neurotransmissions by Ro 15-4513 in cerebellar slices was assessed following stimulation of the parallel fibre input, which, in this preparation, preferentially activates the inhibitory interneurones innervating Purkinje cells. Peristimulus-time histogram analysis of inhibitory responses of spontaneously-active Purkinje cells showed only a decrease in the duration of inhibition induced by Ro 19-4603. This is consistent with inverse agonism on the BZ1 receptors associated with postsynaptic GABAA receptors on Purkinje cells. 1 microM Ro 15-4513 induced a similar response but 100 nM Ro 15-4513 induced a biphasic response, with an increase in duration of inhibition preceding the decrease during continued perfusion of the compound. At lower concentrations of Ro 15-4513 the increase in inhibition predominated, the minimal effective concentration being 10 pM. 1 microM flumazenil blocked both components of this response to 100 nM Ro 15-4513, but at 100 nM flumazenil only blocked the decrease in inhibition. The ability of Ro 15-4513 but not Ro 19-4603 to enhance inhibition and its relative insensitivity to 100 nM flumazenil, parallel the affinities of these compounds for diazepam-insensitive (DI) binding sites in the cerebellum. These data suggest that the enhancement of inhibition induced by Ro 15-4513 results from its inverse agonist activity on DI receptors causing disinhibition of both granule cells and their parallel fibres and increased sensitivity to the electrical stimuli inducing activation of the inhibitory interneurones innervating Purkinje cells.

Ro 19-4603, a benzodiazepine receptor inverse agonist, attenuates voluntary ethanol consumption in rats selectively bred for high ethanol preference.[Pubmed:1965120]

Alcohol Alcohol. 1990;25(5):449-52.

The effect of Ro 19-4603, a novel potent partial inverse agonist of benzodiazepine (BZ) receptors, on voluntary ethanol intake was examined in a rat line selectively bred for ethanol preference (Sardinian ethanol preferring, sP, rats). Ro 19-4603, 1 mg/kg i.p., three times daily, reduced voluntary ethanol consumption by about 40% during 7 days of treatment, but failed to reduce water intake. The results suggest that the GABA/BZ receptor complex may play a role in the reinforcing property of ethanol.

Convulsant action of a benzodiazepine receptor agonist/inverse agonist Ro 19-4603 in developing rats.[Pubmed:7845475]

Naunyn Schmiedebergs Arch Pharmacol. 1994 Oct;350(4):393-7.

An inverse benzodiazepine receptor agonist Ro 19-4603, administered intraperitoneally, was found to induce two types of motor seizures, i.e. minimal, predominantly clonic and major, generalized tonic-clonic, in rats at all developmental stages studied (7, 12, 18 and 25 days old). The developmental profile of the two types of seizure was different. Minimal seizures could be induced easily in the two youngest groups, whereas there were no marked differences in the induction of major seizures between the age groups. A lethal outcome was more common in 18- and 25-day-old rats than in younger animals. The convulsant action of the benzodiazepine agonist/inverse agonist Ro 19-4603 shows only quantitative changes during post-natal development in the rat.

Anxiogenic effects of a benzodiazepine receptor partial inverse agonist, RO 19-4603, in a light/dark choice situation.[Pubmed:2165618]

Pharmacol Biochem Behav. 1990 Jul;36(3):593-6.

In a light/dark choice procedure, the imidazothienodiazepinone Ro 19-4603, given alone, induced a dose-dependent decrease in the time spent by mice in the lit box as well in the number of transitions between the two boxes. These data confirm the anxiogenic intrinsic properties of inverse agonists of the benzodiazepine receptor. Since Ro 19-4603 also reversed the anxiolytic effects of ethanol and exhibited proconvulsant properties, it is suggested that the antagonistic action of this drug against ethanol could be due to an additive rather than an interactive process.

The novel benzodiazepine inverse agonist RO19-4603 antagonizes ethanol motivated behaviors: neuropharmacological studies.[Pubmed:9518641]

Brain Res. 1998 Feb 16;784(1-2):256-75.

The novel imidazothienodiazepine inverse agonist RO19-4603 has been reported to attenuate EtOH intake in home cage drinking tests for at least 24 h post-drug administration after systemic administration. In the present study, selectively bred alcohol-preferring (P) rats were trained under a concurrent (FR4-FR4) operant schedule to press one lever for EtOH (10% v/v) and another lever for saccharin (0.05% or 0.75% g/v), then dose-response and timecourse effects of RO19-4603 were evaluated. Systemic RO19-4603 injections (0.0045-0.3 mg/kg; i.p.) profoundly reduced EtOH responding by as much as 97% of vehicle control on day 1. No effects were seen on saccharin responding except with the highest dose level (0.3 mg/kg). In a second experiment, microinjections of RO19-4603 (2-100 ng) directly into the nucleus accumbens (NA) suppressed EtOH responding on day 1 by as much as 53% of control: Control injections dorsal to the NA or ventral tegmental area did not significantly alter EtOH or saccharin responding. On day 2, rats in both experiments received no RO19-4603 treatments; however, all 7 of the i.p. doses, and all 3 of the intra-NA infusions continued to significantly suppress EtOH responding by 43-85% of vehicle control levels. In addition, i.p. injections of RO19-4603 produced a dose-dependent decrease in the slope of the cumulative record for EtOH responding, while concomitantly producing a dose-dependent increase in the slope for saccharin responding. RO19-4603's actions appear to be mediated via recognition sites at GABAA-BDZ receptors which regulate EtOH reinforcement, and not via mechanisms regulating ingestive behaviors. Based on recent in situ hybridization studies in our laboratory, we hypothesize that occupation of alpha4 containing GABAA diazepam insensitive (DI) receptors in the NA, may mediate in part, the RO19-4603 suppression of EtOH responding in EtOH-seeking P rats.

Effects of the benzodiazepine inverse agonist RO19-4603 on the maintenance of tolerance to a single dose of ethanol.[Pubmed:7562476]

J Pharmacol Exp Ther. 1995 Sep;274(3):1105-12.

The time course of the novel benzodiazepine inverse agonist, RO19--4603 (0.075 or 0.150 mg/kg) in antagonizing the depressant effects of ethanol (EtOH) (0.50, 1.0 and 1.5 g/kg) and the development of tolerance on locomotor behaviors (e.g., ambulatory count, total distance and stereotypy count) were investigated in Sprague-Dawley rats given EtOH injections spaced at 24-hr intervals. A single dose of RO19--4603 prevented the development of tolerance to the 0.50- and 1.0-g/kg EtOH doses 24-hr post-RO19--4603 administration on most locomotor behaviors. On Day 1, the 0.150-mg/kg RO19--4603 dose prevented the reduction of motor behaviors after the 1.0- and 1.5-g/kg EtOH doses, whereas the 0.075-mg/kg RO19--4603 dose prevented the reduction of motor behaviors only after the 1.5-g/kg EtOH dose. The 0.075- and 0.150-mg/kg RO19--4603 doses also prevented the EtOH-induced reduction of motor behaviors after the 1.5-g/kg EtOH dose 24-hr post-RO19--4603 administration. RO19--4603 was without effect on activity when given alone. These data suggest that the motor impairing effects of EtOH and the development of tolerance to them may involve gamma-aminobutyric acidA-benzodiazepine receptor mechanisms that when occupied, even briefly by certain benzodiazepine inverse agonists, produce long-lasting effects on locomotion and tolerance.

High affinity ligands for 'diazepam-insensitive' benzodiazepine receptors.[Pubmed:1311690]

Eur J Pharmacol. 1992 Jan 14;225(1):63-8.

Structurally diverse compounds have been shown to possess high affinities for benzodiazepine receptors in their 'diazepam-sensitive' (DS) conformations. In contrast, only the imidazobenzodiazepinone Ro 15-4513 has been shown to exhibit a high affinity for the 'diazepam-insensitive' (DI) conformation of benzodiazepine receptors. We examined a series of 1,4-diazepines containing one or more annelated ring systems for their affinities at DI and DS benzodiazepine receptors, several 1,4-diazepinone carboxylates including Ro 19-4603, Ro 16-6028 and Ro 15-3505 were found to possess high affinities (Ki approximately 2.6-20 nM) for DI. Nonetheless, among the ligands examined, Ro 15-4513 was the only substance with a DI/DS potency ratio approximately 1; other substances had ratios ranging from 13 to greater than 1000. Ligands with high to moderate affinities at DI were previously classified as partial agonists, antagonists, or partial inverse agonists at DS benzodiazepine receptors, but behaved as 'GABA neutral' (antagonist) substances at DI. The identification of several additional high affinity ligands at DI benzodiazepine receptors may be helpful in elucidating the pharmacological and physiological importance of these sites.