Modulation of voluntary ethanol consumption by beta-arrestin 2.

Beta-arrestin 2 is a multifunctional key component of the G protein-coupled receptor complex and is involved in mu-opiate and dopamine D2 receptor signaling, both of which are thought to mediate the rewarding effects of ethanol consumption. We identified elevated expression of the beta-arrestin 2 gene (Arrb2) in the striatum and the hippocampus of ethanol-preferring AA rats compared to their nonpreferring counterpart ANA line. Differential mRNA expression was accompanied by different levels of Arrb2 protein. The elevated expression was associated with a 7-marker haplotype in complete linkage disequilibrium, which segregated fully between the lines, and was unique to the preferring line. Furthermore, a single, distinct, and highly significant quantitative trait locus for Arrb2 expression in hippocampus and striatum was identified at the locus of this gene, providing evidence that genetic variation may affect a cis-regulatory mechanism for expression and regional control of Arrb2. These findings were functionally validated using mice lacking Arrb2, which displayed both reduced voluntary ethanol consumption and ethanol-induced psychomotor stimulation. Our results demonstrate that beta-arrestin 2 modulates acute responses to ethanol and is an important mediator of ethanol reward.

Plasticity and impact of the central renin-angiotensin system during development of ethanol dependence.

Pharmacological and genetic interference with the renin-angiotensin system (RAS) seems to alter voluntary ethanol consumption. However, understanding the influence of the RAS on ethanol dependence and its treatment requires modeling the neuroadaptations that occur with prolonged exposure to ethanol. Increased ethanol consumption was induced in rats through repeated cycles of intoxication and withdrawal. Expression of angiotensinogen, angiotensin-converting enzyme, and the angiotensin II receptor, AT1a, was examined by quantitative reverse transcription polymerase chain reaction. Increased ethanol consumption after a history of dependence was associated with increased angiotensinogen expression in medial prefrontal cortex but not in nucleus accumbens or amygdala. Increased angiotensinogen expression also demonstrates that the astroglia is an integral part of the plasticity underlying the development of dependence. The effects of low central RAS activity on increased ethanol consumption were investigated using either spirapril, a blood-brain barrier-penetrating inhibitor of angiotensin-converting enzyme, or transgenic rats (TGR(ASrAOGEN)680) with reduced central angiotensinogen expression. Spirapril reduced ethanol intake in dependent rats compared to controls. After induction of dependence, TGR(ASrAOGEN)680 rats had increased ethanol consumption but to a lesser degree than Wistar rats with the same history of dependence. These data suggest that the central RAS is sensitized in its modulatory control of ethanol consumption in the dependent state, but pharmacological or genetic blockade of the system appears to be insufficient to halt the progression of dependence.

c-fos reduces corticosterone-mediated effects on neurotrophic factor expression in the rat hippocampal CA1 region.

The transcription of neurotrophic factors, i.e., basic fibroblast growth factor (bFGF) and brain-derived neurotrophic factor (BDNF) is regulated by glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) activation despite the lack of a classical glucocorticoid response element in their promoter region. A time course for corticosterone (10 mg/kg, s.c.) in adrenalectomized rats revealed a peak hormone effect at the 4 hr time interval for bFGF (110-204% increase), BDNF (53-67% decrease), GR (53-64% decrease), and MR (34-56% decrease) mRNA levels in all hippocampal subregions using in situ hybridization. c-fos mRNA levels were affected exclusively in the dentate gyrus after 50 min to 2 hr (38-46% decrease). Furthermore, it was evaluated whether corticosterone regulation of these genes depends on interactions with the transcription factor complex activator protein-1. c-fos antisense oligodeoxynucleotides were injected into the dorsal hippocampus of adrenalectomized rats. Corticosterone was given 2 hr later, and the effects on gene expression were measured 4 hr later. In CA1, antisense treatment significantly and selectively enhanced the hormone action on the expression of bFGF (44% enhanced increase) and BDNF (38% enhanced decrease) versus control oligodeoxynucleotide treatment. In addition, an upregulation of c-fos expression (89% increase) was found. There were no effects of c-fos antisense on hippocampal GR and MR expression. Thus it seems that a tonic c-fos mechanism exists within CA1, which reduces GR- and MR-mediated effects on expression of bFGF and BDNF.

Adenosine A2A agonists: a potential new type of atypical antipsychotic.

The systemic intraperitoneal (i.p.) administration of the adenosine A2A agonist CGS 21680 was found to dose-dependently antagonize spontaneous and amphetamine-induced (1 mg/kg i.p.) motor activity with similar ED50 values (about 0.2 mg/kg). The ratios between the ED50 values for induction of catalepsy and for antagonizing amphetamine-induced motor activity for CGS 21680, haloperidol, and clozapine were 12, 2, and > 30, respectively. Furthermore, CGS 21680 was comparably much stronger than haloperidol or clozapine at antagonizing the motor activity induced by phencyclidine (2 mg/kg subcutaneously) than motor activity induced by amphetamine (1 mg/kg i.p.). In conclusion, the present results show a clear "atypical" antipsychotic profile of the adenosine A2A agonist CGS 21680 in animal models.

Local 5,7-dihydroxytryptamine lesions of rat amygdala: release of punished drinking, unaffected plus-maze behavior and ethanol consumption.

Several serotonergic drugs are effective for anxiety disorders, but underlying mechanisms are unclear, and findings in experimental animals are difficult to reconcile with human data. It has been proposed that differential effects of serotonin within specific anatomical systems may account for these difficulties, and the amygdala has been suggested as one of the structures involved. To examine this hypothesis, the neurotoxin 5,7-dihydroxytryptamine was administered locally in rat amygdala. Within the amygdala, serotonin was depleted by approximately 80%, with other transmitters unaffected, and serotonin transporter labelling was decreased by approximately 85%. Cortical areas near the lesion site were also affected, although to a lesser degree. Other forebrain areas were unaffected. Lesions resulted in a specific anti-conflict effect in a punished drinking test, but did not influence elevated plus-maze behavior (under baseline conditions and after restraint stress), locomotor activity or ethanol intake. These data suggest that the punished drinking test and the elevated plus-maze may activate different components of fear circuitry, and that the serotonergic input to the amygdala specifically participates in fear-related behavioral suppression mediated by this structure.

The NMDA positive modulator D-cycloserine inhibits dopamine-mediated behaviors in the rat.

The NMDA positive modulator D-cycloserine (DCS), which failed to modify rat spontaneous behavior, inhibited the hypermotility induced by the dopamine releaser methamphetamine as well as the behavioral responses to the selective stimulation of D1 or D2 dopamine receptors (SKF 38393 induced grooming and LY 171555 elicited hyperactivity, respectively). In contrast, behavioral responses to different doses of apomorphine (hypermotility and stereotypies) were not modified by the administration of DCS. No change in apomorphine-induced stereotyped behavior was observed during DCS repeated treatment (21 days), but an antagonism of dopaminergic stimulation occurred when DCS was repeatedly administered together with low doses of D1 and D2 dopamine receptor blockers [SCH 23390 and (-)-sulpiride]. Five days following the combined repeated treatment, behavioral dopaminergic supersensitivity was observed. The results are consistent with the view that an increase in glutamatergic function could decrease the response to dopaminergic stimulation.

The modulation of dopaminergic transmission in the striatum by MK-801 is independent of presynaptic mechanisms.

This paper reports biochemical and behavioural experiments, planned to obtain a deeper knowledge on the mechanisms of the facilitating action of dopaminergic transmission, induced by the NMDA-sensitive glutamate receptor antagonist, dizocilpine (MK-801). Single or repeated administrations of MK-801 (0.25 mg/kg, i.p., daily for 21 consecutive days) failed to change levels of either dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) in the striatum of the rat or the haloperidol-induced (0.125 mg/kg, i.p.) accumulation of DOPAC. Consistently, the NMDA antagonist, given at a dose which did not affect the spontaneous motility of the animal (0.125 mg/kg, i.p.), failed to potentiate the behavioural stimulatory effect, induced by the dopaminomimetic agents, methamphetamine or nomifensine. All these results, taken together, exclude a facilitating action of MK-801 on dopaminergic neurotransmission. The possibility that the stimulatory effect of MK-801 on dopaminergic neurones is indirect and independent of presynaptic mechanisms is discussed.

Adenosine A2A and group I metabotropic glutamate receptors synergistically modulate the binding characteristics of dopamine D2 receptors in the rat striatum.

There is experimental evidence for the existence of interactions between metabotropic glutamate (mGlu), adenosine and dopamine receptors in the striatum. In membrane preparations from rat striatum the group I and II mGlu receptor agonist 1-aminocyclopentane-1S-3R-dicarboxylic acid (1S-3R-ACPD) was found to modulate the binding characteristics of D2 receptors in a similar manner as the A2A receptor agonist 2-[p-(2-carboxyethyl)phenthylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680), with a significant decrease in the affinity of the high-affinity state of D2 receptors for dopamine. The effect of 1S-3R-ACPD was mimicked by (+/-)-trans-ACPD (t-ACPD; a racemic mixture of 1S-3R-ACPD and its inactive isomer 1R-3S-ACPD) and by the selective group I mGlu receptor agonist 3,5-dihydroxyphenylglycine (DHPG) and it was counteracted by the selective group I mGlu receptor antagonist 1-aminoindan-1,5-dicarboxilic acid (AIDA), but not by the the group II and III mGlu receptor antagonist (RS)-alpha-methyl-4-tetrazolylphenylglycine (MTPG) or the adenosine receptor antagonist 8-phenyltheophylline. Furthermore, a strong synergistic effect was observed when the striatal membranes were exposed to both CGS 21680 and 1S-3R-ACPD. In agreement with the biochemical results, in unilaterally 6-OH-dopamine lesioned rats 1S-3R-ACPD counteracted the turning behaviour induced by the D2 receptor agonist quinpirole, but not by the D1 receptor agonist SKF 38393, and it synergistically potentiated the antagonistic effect of CGS 21680 on quinpirole-induced turning behaviour.

Evidence for a differential cholecystokinin-B and -A receptor regulation of GABA release in the rat nucleus accumbens mediated via dopaminergic and cholinergic mechanisms.

In the present study we characterized the cholecystokinin receptor regulation of (i) the dopamine D2 agonist binding sites in striatal sections including the nucleus accumbens and (ii) GABA and dopamine release in the central part of the rat nucleus accumbens, by combining the in vitro filter wipe-off and the in vivo microdialysis techniques. In the binding study we demonstrate that sulphated cholecystokinin octapeptide (1 nM) increased (219 +/- 30%) the KD value of the D2 agonist [3H]N-propylnorapomorphine binding sites in sections from the striatum including the accumbens. This effect was counteracted by the cholecystokinin-B antagonist PD134308 (50 nM). In a parallel study using microdialysis in the central nucleus accumbens, we found that local perfusion with sulphated cholecystokinin octapeptide (1 microM) induced an increase in GABA (135 +/- 7%) and dopamine (146 +/- 8%) release which was unaffected by the cholecystokinin-A antagonist L-364,718 (10 nM). In contrast, when the cholecystokinin-B antagonist PD134308 (10 nM) was co-perfused with the peptide it prevented the increase in dopamine and decreased GABA release (-24 +/- 2%). This reduction was counteracted by the addition to the perfusate medium of the cholecystokinin-A antagonist or the cholinergic muscarinic M2 receptor antagonist AF-DX 116 (0.1 microM). Taken together, these data demonstrate that the facilitation by sulphated cholecystokinin octapeptide of GABA and dopamine release in the central accumbens probably reflects an inhibitory effect of the peptide on both pre- and postsynaptic D2 receptors, mediated via cholecystokinin-B receptor activation. In addition, for the first time we provide evidence for a differential cholecystokinin-A and -B receptor-mediated regulation of GABA transmission in the central accumbens, where the cholecystokinin-B receptor exerts a dominant excitatory influence while the cholecystokinin-A receptor mediates an inhibition of GABA release via a local muscarinic M2 receptor.

The competitive NMDA antagonists CGP 43487 and APV potentiate dopaminergic function.

The administration to rats of different doses of the non competitive NMDA receptor blocker MK-801 (0.03-1 mg/kg IP) induced stimulation or reduction of locomotor activity, depending on the dose, whereas the competitive NMDA antagonists CGP 43487 (0.188-6 mg/kg IP) and APV (2.5-20 micrograms/rat ICV) inhibited locomotion at the highest doses. Unlike MK-801 and APV treatment, the administration of CGP 43487 did not induce impairment of rota-rod test performance. Both competitive and non-competitive NMDA antagonists, at doses devoid of any behavioral effect per se, potentiated the responses elicited by apomorphine (0.25 mg/kg SC). In particular, the occurrence of episodes of licking was weakly affected by MK-801 administration, but significantly increased by CGP 43487 and APV treatment; the presence of gnawing was augmented by all the pretreatments; sniffing, locomotion, grooming and rearing occurrence were not affected by the administration of NMDA antagonists. The results suggest that the competitive antagonists which facilitated dopaminergic function without causing motor impairment could be useful supplements in the treatment of Parkinson's disease.

Effect of NMDA receptor antagonists on D1, D2 and D1/D2 mediated behaviors in intact rats.

The effect of treatment with the competitive (CGP 43487) and non-competitive (MK-801) NMDA antagonists on behaviors induced by the stimulation of D1 (SKF 38393 induced grooming), D2 (LY 171555 elicited hypermotility) or D1/D2 (apomorphine induced locomotion and stereotypies) was observed in intact rats. The administration of low doses of MK-801 (0.03 and 0.06 mg/kg) or CGP 43487 (0.375 and 0.75 mg/kg), which were without effect by themselves on animal locomotion, reduced the hyperactivity induced by LY 171555 (0.15 mg/kg) and did not change the stimulating motor effect of a low dose of apomorphine (0.15 mg/kg). Spontaneous grooming behavior was inhibited by both NMDA antagonists, whereas the administration of CGP 43487 but not of MK-801 potentiated grooming response to SKF 38393 (10 mg/kg). Both antagonists increased stereotyped behavior induced by 0.25 mg/kg apomorphine. The results, according to those obtained by other authors in DA depleted/lesioned animals, support the view of interaction between NMDA/D1,D2 receptors in intact rats.

Multiple intramembrane receptor-receptor interactions in the regulation of striatal dopamine D2 receptors.

Adenosine A2A, group I mGlu and neurotensin receptors have been previously found to modulate the binding characteristics of dopamine D2 receptors in membrane preparations from rat striatum. In the present study it is shown that stimulation of different combinations of striatal A2A, group I mGlu and neurotensin receptors induce different effects on the modulation of D2 receptor binding to those obtained when they are separately stimulated using maximal effective concentrations. In competitive inhibition experiments of dopamine versus the D2 receptor antagonist [3H]raclopride the addition of the A2A receptor agonist CGS 21680, the group I mGlu receptor agonist DHPG or neurotensin induced a decrease in the affinity of the high affinity state of the dopamine D2 receptors for dopamine. When added together CGS 21680 plus neurotensin induced the same effect as when administered alone, CGS 21680 plus DHPG induced a synergistic effect and DHPG plus neurotensin lost their modulating effect on D2 receptor binding. These results demonstrate the existence of multiple intramembrane receptor-receptor interactions in the regulation of striatal D2 receptors.

Endothelin-1 induced lesions of the frontoparietal cortex of the rat. A possible model of focal cortical ischemia.

Endothelin-1 (ET-1) was unilaterally applied onto the surface of the dorsal frontoparietal cortex of the rat. Cortical blood flow measurements using laser-Doppler flowmetry demonstrated dose-dependent reductions of frontoparietal cortical blood flow. Histological analysis demonstrated dose-related lesions and the time course was followed using MRI. The lesions appear to be associated with a large penumbra area indicated by morphological characteristics. Thus, cortical surface exposure to ET-1 may produce graded lesions of the frontoparietal cortex related to local ischemia.

The secretory trypsin inhibitor like-peptide, PEC-60 increases dopamine D2 receptor agonist induced inhibition of GABA release in the dorsolateral neostriatum of the awake freely moving rat. An in vivo microdialysis study.

The effects of local perfusion with the secretory trypsin inhibitor like-peptide, PEC-60 on dopamine and gamma-aminobutyric acid (GABA) release in the dorsolateral neostriatum and GABA release in the globus pallidus were studied using in vivo microdialysis in the awake freely moving rat. Local perfusion with PEC-60 (500 nM and 1 microM) increased dopamine release in the dorsolateral neostriatum while the highest (1 microM) concentration of PEC-60 decreased striatal but not pallidal GABA release. An inactive form of the peptide, S-carboxyamidomethylated PEC-60 (1 microM) failed to influence either striatal dopamine and GABA or pallidal GABA release. In addition, when PEC-60, at a dose which did not affect striatal and pallidal GABA release (100 nM), was co-perfused together with the dopamine D2 receptor agonist pergolide (500 nM), a potentiation in the ability of pergolide to reduce GABA release in the dorsolateral neostriatum was observed and this effect was counteracted by co-perfusion with the selective dopamine D2 receptor antagonist raclopride (1 microM). In contrast, the pergolide induced inhibition of striatal dopamine release was unaffected by PEC-60 (100 nM). These data indicate that PEC-60 differentially regulates dopamine and GABA release in the dorsolateral neostriatum by a selective and facilitory interaction with the postsynaptic dopamine D2 receptor possibly involving high-affinity PEC-60 like-peptide binding sites located on local axon collaterals of a discrete subpopulation of efferent GABA neurons and/or on GABA interneurons.

Age-related alteration of the adenosine/dopamine balance in the rat striatum.

An antagonistic interaction between adenosine A2A- and dopamine D2-receptors has been described. Radioligand binding experiments showed a predominant reduction in the number of D2 vs. A2A-receptors in the striatum of aged compared to young rats. The A2A-receptor-mediated antagonistic modulation of D2-receptor binding remained unchanged in aged animals. In striatal homogenates a significant increase in adenosine and no change in dopamine content was found in aged vs. young rats. These results reveal the existence of an age-dependent imbalance of adenosine vs. dopamine in favor of adenosine, which involves both presynaptic and postsynaptic mechanisms.

Differential effects of selective adenosine A1 and A2A receptor agonists on dopamine receptor agonist-induced behavioural responses in rats.

The effects of the systemic (i.p.) administration of the selective adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) and the selective adenosine A2A receptor agonist sodium 2-p-carboxyethyl)phenylamino-5'-N-carboxamidoadenosine (CGS 21680) on different dopamine receptor agonist-induced behaviours were studied in the male rat. CGS 21680 (1 micromol/kg), but not CPA, was found to counteract the stereotypies induced by the non-selective dopamine receptor agonist apomorphine (0.25 mg/kg s.c.). Low doses of CGS 21680 (0.1 micromol/kg) and high doses of CPA (3 micromol/kg) counteracted yawning induced by the dopamine D2 selective agonist quinpirole (0.05 mg/kg). On the other hand, low doses of CPA (0.3 micromol/kg) antagonized grooming induced by the selective dopamine D1 receptor-selective agonist SKF 38393 (10 mg/kg i.p.), while CGS 21680 was ineffective. These results are consistent with the proposed existence of a selective antagonistic modulation of dopamine D1 and D2 receptors by adenosine A1 and A2A receptors, respectively. The ability of CGS 21680 to counteract apomorphine-induced stereotypies is weaker compared to its previously reported antagonistic effect of amphetamine-induced motor activity. This supports the hypothesis that adenosine A2A receptor agonists may be potential antipsychotic drugs with a low potential for extrapyramidal side effects.

Blockade of central neuropeptide Y (NPY) Y2 receptors reduces ethanol self-administration in rats.

Activation of central neuropeptide Y (NPY) receptors is known to produce several behavioral effects, including feeding, modulation of memory and antagonism of behavioral effects of stress. In addition, experiments in knock-out and transgenic mice have suggested a possible role of NPY regulation of voluntary ethanol intake. NPY receptors involved in this action are not known. Here, we examined the effects of a selective NPY-Y2 receptor antagonist, BIIE0246, on operant responding for ethanol in a sweetened solution, or the sweetened solution without ethanol, during 30 min sessions of free choice between the two. BIIE0246 produced a robust suppression of responding for ethanol (40% reduction, P=0.013) at an intracerebroventricular dose of 1.0 nmol, but not 0.3 nmol. Responding for the saccharin solution was not significantly affected. The dose range examined was selected since preliminary experiments with doses of 3 nmol and higher indicated sedative effects, but such effects were absent up to 1.0 nmol, as shown by unaffected exploratory locomotor activity. In summary, antagonism at central NPY-Y2 receptors seems to selectively suppress operant self-administration of ethanol. This suggests that Y2 receptors might be candidate targets for developing novel pharmacological treatments of alcoholism.

Repeated administrations of (-)-deprenyl increase [3H]MK801 binding in rat brain and antagonize the impairment of passive avoidance conditioning induced by N-methyl-D-aspartate receptor antagonists.

Repeated but not single administrations of the MAO type B inhibitor (-)-deprenyl (1 mumol/kg s.c. for 21 consecutive days) antagonized the impairment of passive avoidance retention induced by the N-methyl-D-aspartate (NMDA) receptor antagonists 2-amino-5-phosphonovalerate (APV), ketamine and dizocilpine (MK801), in rats. In well-washed membranes prepared from the hippocampi of rats repeatedly treated with (-)-deprenyl, the [3H]MK801 specific binding was increased. In contrast, repeated MAO B-selective doses of pargyline or (+)-amphetamine, as well as single injections with (-)-deprenyl failed to change [3H]MK801 binding. It is suggested that the effects of repeated (-)-deprenyl administrations upon NMDA receptors and upon the impairment of acquisition of a passive avoidance task induced by NMDA antagonists could be independent of MAO inhibition.

PEC-60 increases dopamine but not GABA release in the dorsolateral neostriatum of the halothane anaesthetized rat. An in vivo microdialysis study.

The effect of striatal perfusion with the intestinal peptide PEC-60 on endogenous dopamine (DA) and gamma-aminobutyric acid (GABA) release in the dorsolateral striatum and GABA release in the globus pallidus was monitored using in vivo microdialysis in the halothane anaesthetized rat. The results show that PEC-60 (100 nM) increases DA release in the dorsolateral striatum without influencing GABA release in the dorsolateral striatum or in the globus pallidus. In addition, PEC-60 failed to influence the extracellular striatal 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels. The PEC-60 induced increase in striatal DA was abolished by the addition of tetrodotoxin (1 microM) to the perfusion medium. These data suggest that PEC-60 plays a role in modulating striatal DA release but not DA metabolism and that this effect is primarily targeted on the presynaptic DA terminals of the nigrostriatal DA pathway rather than on the postsynaptic striatopallidal GABA projection neurons in the dorsolateral striatum.

"Atypical" neuromodulatory profile of glutapyrone, a representative of a novel 'class' of amino acid-containing dipeptide-mimicking 1,4-dihydropyridine (DHP) compounds: in vitro and in vivo studies.

Glutapyrone, a disodium salt of 2-(2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydropyridine-4-carboxamido)- glutaric acid, is a representative of a novel 'class' of amino acid-containing 1,4-dihydropyridine (DHP) compounds developed at the Latvian Institute of Organic Synthesis, Riga, Latvia. Conceptually, the glutapyrone molecule can be regarded as a dipeptide-mimicking structure formed by the "free" amino acid (glutamate) moiety and "crypto" (built into the DHP cycle) amino acid ("GABA") elements. Both of these amino acids are joined by the peptide bond. This compound unlike classical DHPs lacks calcium antagonistic or agonistic properties. Our previous studies revealed a profound and long-term anticonvulsant, stress-protective and neurodeficit-preventive activities of glutapyrone. In view of structural properties the role of glutamatergic mechanisms in the mediation of central effects of glutapyrone was considered. In the present study glutapyrone at the concentration range of 1 microM(-1) mM failed to effect both NMDA ([3H]TCP) and non-NMDA ([3H]KA and [3H]AMPA) receptor ligand binding in the rat cortical membranes in vitro. The compound markedly enhanced motor hyperactivity induced by the NMDA antagonist PCP and the dopamine releasing compound D-amphetamine in the rats. Glutapyrone displayed activity in a variety of animal models relevant for affective/depressive disorders in humans i.e. reserpine-induced ptosis and hypothermia, forced swimming test and open field test. These data indicate that the unusually "broad" pharmacological spectrum of glutapyrone might involve concomitant actions on multiple neurotransmitter systems, particularly, GABA-ergic and the catecholamines. It is discussed whether these functional properties are secondary to action on intracellular events, predominantly, G protein-related since glutapyrone appears to lack direct interactions with a number of receptors including ionotropic glutamate and GABA(A)/Bzd receptors.