Direct Pharmacological Action Research Articles

Cardiac arrhythmogenesis: roles of ion channels and their functional modification.

Cardiac arrhythmias cause significant morbidity and mortality and pose a major public health problem. They arise from disruptions in the normally orderly propagation of cardiac electrophysiological activation and recovery through successive cardiomyocytes in the heart. They reflect abnormalities in automaticity, initiation, conduction, or recovery in cardiomyocyte excitation. The latter properties are dependent on surface membrane electrophysiological mechanisms underlying the cardiac action potential. Their disruption results from spatial or temporal instabilities and heterogeneities in the generation and propagation of cellular excitation. These arise from abnormal function in their underlying surface membrane, ion channels, and transporters, as well as the interactions between them. The latter, in turn, form common regulatory targets for the hierarchical network of diverse signaling mechanisms reviewed here. In addition to direct molecular-level pharmacological or physiological actions on these surface membrane biomolecules, accessory, adhesion, signal transduction, and cytoskeletal anchoring proteins modify both their properties and localization. At the cellular level of excitation-contraction coupling processes, Ca2+ homeostatic and phosphorylation processes affect channel activity and membrane excitability directly or through intermediate signaling. Systems-level autonomic cellular signaling exerts both acute channel and longer-term actions on channel expression. Further upstream intermediaries from metabolic changes modulate the channels both themselves and through modifying Ca2+ homeostasis. Finally, longer-term organ-level inflammatory and structural changes, such as fibrotic and hypertrophic remodeling, similarly can influence all these physiological processes with potential pro-arrhythmic consequences. These normal physiological processes may target either individual or groups of ionic channel species and alter with particular pathological conditions. They are also potentially alterable by direct pharmacological action, or effects on longer-term targets modifying protein or cofactor structure, expression, or localization. Their participating specific biomolecules, often clarified in experimental genetically modified models, thus constitute potential therapeutic targets. The insights clarified by the physiological and pharmacological framework outlined here provide a basis for a recent modernized drug classification. Together, they offer a translational framework for current drug understanding. This would facilitate future mechanistically directed therapeutic advances, for which a number of examples are considered here. The latter are potentially useful for treating cardiac, in particular arrhythmic, disease.

HIV-Associated Apathy/Depression and Neurocognitive Impairments Reflect Persistent Dopamine Deficits.

Individuals living with human immunodeficiency virus type 1 (HIV-1) are often plagued by debilitating neurocognitive impairments and affective alterations;the pathophysiology underlying these deficits likely includes dopaminergic system dysfunction. The present review utilized four interrelated aims to critically examine the evidence for dopaminergic alterations following HIV-1 viral protein exposure. First, basal dopamine (DA) values are dependent upon both brain region andexperimental approach (i.e., high-performance liquid chromatography, microdialysis or fast-scan cyclic voltammetry). Second, neurochemical measurements overwhelmingly support decreased DA concentrations following chronic HIV-1 viral protein exposure. Neurocognitive impairments, including alterations in pre-attentive processes and attention, as well as apathetic behaviors, provide an additional line of evidence for dopaminergic deficits in HIV-1. Third, to date, there is no compelling evidence that combination antiretroviral therapy (cART), the primary treatment regimen for HIV-1 seropositive individuals, has any direct pharmacological action on the dopaminergic system. Fourth, the infection of microglia by HIV-1 viral proteins may mechanistically underlie the dopamine deficit observed following chronic HIV-1 viral protein exposure. An inclusive and critical evaluation of the literature, therefore, supports the fundamental conclusion that long-term HIV-1 viral protein exposure leads to a decreased dopaminergic state, which continues to persist despite the advent of cART. Thus, effective treatment of HIV-1-associated apathy/depression and neurocognitive impairments must focus on strategies for rectifying decreases in dopamine function.

Contact Lenses as Ophthalmic Drug Delivery Systems: A Review.

Ophthalmic drugs used for the treatment of various ocular diseases are commonly administered by eye drops. However, due to anatomical and physiological factors, there is a low bioavailability of the active principle. In order to increase the drug residence time on the cornea to adequate levels, therapeutic contact lenses have recently been proposed. The polymeric support that constitutes the contact lens is loaded with the drug; in this way, there is a direct and effective pharmacological action on the target organ, promoting a prolonged release of the active principle. The incorporation of ophthalmic drugs into contact lenses can be performed by different techniques; nowadays, the soaking method is mainly employed. To improve the therapeutic performance of drug-loaded contact lenses, innovative methods have recently been proposed, including the impregnation with supercritical carbon dioxide. This updated review of therapeutic contact lenses production and application provides useful information on the most effective preparation methodologies, recent achievements and future perspectives.

Effectiveness of drugs acting on adrenergic receptors in the treatment for tobacco or alcohol use disorders: systematic review and meta-analysis.

To assess the efficacy of drugs directly acting on alpha- and beta-adrenergic receptors in the treatment of patients suffering from tobacco or alcohol use disorder. Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, studies were identified through PUBMED, EMBASE, the Cochrane Central Register of Controlled Trials and clinicaltrial.gov. We selected only randomized controlled trials with adult patients with tobacco or alcohol use disorders according to DSM-5 criteria. Interventions included any molecule having a direct pharmacological action on alpha- or beta-adrenergic receptors (agonist or antagonist). Comparators were placebo or other validated pharmacotherapies. The duration of the intervention was a minimum of 1month, with 3months of follow-up. Measurements included smoking cessation for tobacco; for alcohol, we selected abstinence, alcohol consumption (drinks per day or week) and heavy drinking days (HDD). Ten studies with tobacco and six with alcohol use disorder were included in the qualitative synthesis and fifteen studies in the quantitative analysis. We found that clonidine, an alpha-2 agonist, significantly increased smoking abstinence [relative risk=1.39 with a 95% confidence interval (CI)=1.04, 1.84]. Beta-blockers had no significant effect on smoking abstinence. The alpha-1 antagonists prazosin and doxazosin decreased alcohol consumption [SMD=-0.32 (-0.56, -0.07)] but had no effect on abstinence or HDD. The noradrenaline system may represent a promising mechanism to target in tobacco and alcohol use disorders.

Nocebo phenomena may be enhanced in aging: Implications for clinical practice

Nocebo effects, denoting unfavourable outcomes after a medical intervention because of negative expectations rather than a direct pharmacologic action, are an important cause of dropout from clinical trials and non-adherence to medication, and may be especially pertinent for older adults. Several characteristics of aging individuals and their medical care have a potential to augment nocebo susceptibility, such as depression and anxiety, neurodegenerative diseases and chronic pain states, adverse healthcare experiences, generic drug use, age-related stereotypes, and strained patient-physician communication. Nocebo-related research in older adults is hindered by under-representation in clinical trials, medical complexity of geriatric patients, and lack of validated tools to accurately assess susceptibility and efficacy of preventive efforts.

Compendium of Salvia officinalis: An Overview

The medicinal plants have enormous commercial potential throughout the globe. In the herbal boom worldwide, it is estimated that high quality phyto-medicinals will provide safe and effective medication. In India, Ayurveda, Siddha, Unani etc. consist of large number of herbal remedies, being used from ancient times. Many plant species containing active constituents that have a direct pharmacological action on the body. This plant Sage (Salvia officinalis Linn) is historically well known from the early 1960s till now by its therapeutic and culinary applications due to its high economic value. The plant is reported to contain alkaloids, triterpenoid, steroids, Phenolic compounds and essential oils. Sage plant is a rich source of antioxidant properties, for this reason sage has found increasing application in food industry. The core purpose of this review is to emphasize the origin, morphology, Phytochemistry and pharmacological aspects of Sage (Salvia officinalis Linn).

Direct posttranslational modification of astrocytic connexin 43 proteins by the general anesthetic propofol in the cerebral cortex

Propofol is widely used as a general anesthetic and is generally considered to exert its action by regulating neuronal firing via facilitation of GABAA receptors. However, accumulating evidence suggests that propofol also acts on astrocytes, including inhibitory effects on gap junctional coupling, but the underlying molecular mechanisms remain largely unknown. Here, using acute cortical brain slices prepared from mice, we characterize propofol-induced molecular changes in astrocytic gap junction protein connexin 43 (Cx43). Propofol does not change the protein expression level of Cx43 or its incorporation into gap junctional plaques, according to biochemical and immunohistochemical analyses. However, propofol alters migration pattern of Cx43 on western blot, suggesting changes in its posttranslational modifications. Indeed, this change is accompanied by an increase in the phosphorylation of Cx43 at serine 368, which is known to reduce permeability of Cx43 gap junctions. Finally, we show that this change occurs in the absence of neuronal firing or glutamatergic transmissions. Overall, these results show that propofol induces posttranslational modification of Cx43 directly on astrocytes at the site of gap junctional plaques, exerting direct pharmacological action on astrocytes in parallel with its action on neurons.

Effects of clozapine on adipokine secretions/productions and lipid droplets in 3T3-L1 adipocytes

Clozapine, a second-generation antipsychotic (SGA), is a cause of side effects related to metabolic syndrome. The participation of serotonin 5-HT2C and histamine H1 receptors in the central nervous system has been reported as a mechanism of the weight gain caused by clozapine. In the present study, we investigated the direct pharmacological action of clozapine on the 3T3-L1 adipocytes and compared it to that of blonanserin, an SGA with low affinity for both receptors. Short-term exposure to clozapine decreased secretion and mRNA expression of leptin. Long-term exposure decreased leptin as well as adiponectin secretion, and further increased lipid droplets accumulation. However, short- and long-term exposures to blonanserin did not affect these parameters. A selective serotonin 5-HT2C, but not a histamine H1, receptor antagonist enhanced the decreased secretion of leptin induced by short-term exposure to clozapine, but did not affect the increased accumulation of lipid droplets. Our findings indicate that clozapine, but not blonanserin, strongly and directly affected the secretion of adipokines, such as leptin, in adipocytes and caused adipocyte enlargement.

Effect of Chronic Low-dose Tadalafil on Penile Cavernous Tissues in Diabetic Rats

To assess the effect of chronic low-dose administration of tadalafil (Td) on penile cavernous tissue in induced diabetic rats. The study investigaged 48 adult male albino rats, comprising a control group, sham controls, streptozotocin-induced diabetic rats, and induced diabetic rats that received Td low-dose daily (0.09 mg/200 g weight) for 2 months. The rats were euthanized 1 day after the last dose. Cavernous tissues were subjected to histologic, immunohistochemical, morphometric studies, and measurement of intracavernosal pressure and mean arterial pressure in anesthetized rats. Diabetic rats demonstrated dilated cavernous spaces, smooth muscles with heterochromatic nuclei, degenerated mitochondria, vacuolated cytoplasm, and negative smooth muscle immunoreactivity. Nerve fibers demonstrated a thick myelin sheath and intra-axonal edema, where blood capillaries exhibited thick basement membrane. Diabetic rats on Td showed improved cavernous organization with significant morphometric increases in the area percentage of smooth muscles and elastic tissue and a significant decrease of fibrous tissue. The Td-treated group showed enhanced erectile function (intracavernosal pressure/mean arterial pressure) at 0.3, 0.5, 1, 3, and 5 Hz compared with diabetic group values at the respective frequencies (P<.05) that approached control values. Chronic low-dose administration of Td in diabetic rats is associated with substantial improvement of the structure of penile cavernous tissue, with increased smooth muscles and elastic tissue, decreased fibrous tissue, and functional enhancement of the erectile function. This raises the idea that the change in penile architecture with Td treatment improves erectile function beyond itshalf-life and its direct pharmacologic action on phosphodiesterase type5.

P-1126 - Sensitization induced by haloperidol and olanzapine is situationally specific

Repeated administration of haloperidol and olanzapine causes a progressively enhanced disruption of conditioned avoidance responding and a progressively enhanced inhibition of phencyclidine (PCP)-induced hyperlocomotion in rats. Both actions are thought to reflect the intrinsic antipsychotic activity. The present study examined to the extent to which antipsychotic-induced sensitization in one model (e.g. conditioned avoidance response model) can be transferred or maintained in another (e.g. PCP hyperlocomotion model). Methods : We first induced behavioral sensitization in one model through repeated administration of haloperidol or olanzapine to male Sprague-Dawley rats, then tested its expression in another model, and finally retested its expression back in the first model. Repeated haloperidol and olanzapine induced a robust behavioral sensitization in both models. Its expression was highly situational specific as it only manifested itself in the model in which it was being induced. Based on these and other findings, we propose that three behavioral mechanisms regulate antipsychotic sensitization and its situational specificity : (1) Repeated antipsychotic treatment induces an unconditioned and nonassociative enhanced behavioral effect (i.e. sensitization) by progressively decreasing motivational salience of stimuli, an effect attributable to the direct pharmacological action of a drug; (2) Distinct contextual cues develop an association with unconditional drug effects via a Pavlovian conditioning process, thus acquiring the ability to elicit antipsychotic-like effects. This associative learning process may potentiate the sensitized behavioral response in an expected situation; (3) Contextual stimuli and interoceptive drug state also serve as occasion-setters to modulate the expression of sensitized responses.

Placebo analgesia: cognitive influences on therapeutic outcome

The therapeutic response to a drug treatment is a mixture of direct pharmacological action and placebo effect. Therefore, harnessing the positive aspects of the placebo effect and reducing the negative ones could potentially benefit the patient. This article is aimed at providing an overview for clinicians of the importance of contextual psychosocial variables in determining treatment response, and the specific focus is on determinants of the placebo response. A better understanding of the physiological, psychological, and social mechanisms of placebo may aid in predicting which contexts have the greatest potential for inducing positive treatment responses. We examine the evidence for the role of psychological traits, including optimism, pessimism, and the effect of patient expectations on therapeutic outcome. We discuss the importance of the patient-practitioner relationship and how this can be used to enhance the placebo effect, and we consider the ethical challenges of using placebos in clinical practice.

Thinking Outside the Synapse: Pharmacokinetic-Based Medications for Cocaine Addiction

Thinking Outside the Synapse: Pharmacokinetic-Based Medications for Cocaine Addiction

Suppressive Effects of Intrathecal Paeoniflorin on Bee Venom-Induced Pain-Related Behaviors and Spinal Neuronal Activation

Recently, paeoniflorin (PF) administered systemically was found to have analgesic effects against inflammatory pain and hypersensitivity in a naloxone-reversible manner. In the present study, we adopted intrathecal administration to evaluate whether PF has direct antinociceptive actions at the spinal level. Pain-related behaviors and spinal c-Fos expression were induced by subcutaneous injection of bee venom (BV) into one hind paw of a rat. Intrathecal pretreatment of PF resulted in an inhibition of the BV-induced persistent spontaneous nociception and partially suppressed the occurrence of both thermal and mechanical hypersensitivity. Moreover, the PF-produced antinociception was completely reversed by naloxone. We further evaluated the intrathecal effects of the drug on the BV-induced c-Fos expression. The result showed that intrathecal PF preconditioning was effective to suppress spinal c-Fos expression in both superficial (lamina I–II) and deep (lamina IV–VI) layers of the L_4–5 dorsal spine. This result showed that PF has a direct pharmacological action in the spinal cord dorsal horn via activation of opioid receptors.

Aliskiren reduces prorenin receptor expression and activity in cultured human aortic smooth muscle cells

The recent discovery of a specific receptor for renin/prorenin (PRR) has added new interest to the potential pharmacological actions of aliskiren, the first direct renin inhibitor. In the present study, to gain new insights into the pharmacological properties of aliskiren, we investigated the effect of aliskiren on PRR expression and activity in cultured human smooth muscle cells (HSMCs). Co-incubation of HSMCs with angiotensinogen (ANG) (1.5 × 10(-7)M) and prorenin (10(-8)-10(-7)M) resulted in an efficient production (within 4h) of angiotensin I, almost completely inhibited by 10(-5)M aliskiren (-86.0 ± 14.0%). In HSMCs stimulated with both ANG and prorenin, a 24h incubation with aliskiren (10(-6)-10(-5)M) resulted in a concentration-dependent reduction of PRR mRNA levels (IC(50) 4.6 × 10(-6)M). The cell surface expression of PRR determined by flow cytometry analysis was also reduced after incubation with aliskiren in a concentration-dependent manner. The lower levels of PRR were associated with a reduced expression of TGF-β, PAI-1 and type I collagen mRNA. These results suggest a direct pharmacological action of aliskiren on PRR expression and its signalling pathway in HSMCs. This reported action of aliskiren may reveal a new scenario of the pharmacological properties of aliskiren.

Adverse drug reactions to biologics

The use of biologics has rapidly expanded since the introduction of the first diagnostic antibodies; they are now widely employed in oncology, autoimmune disorders, inflammatory diseases and transplantation medicine. Their widespread use has resulted in an increase in adverse drug reactions. Adverse effects result from both direct pharmacological actions and immunological actions, as well as through induction of a specific immune response. The nomenclature, particularly of the monoclonal antibodies, identifies the target structure and organ as well as the species of origin, which then helps predict their effects and antigenic properties. Depending on the extent of foreign protein, anti-allotypic or anti-idiotypic antibodies with or without neutralizing properties may be induced. Adverse drug reactions from biologics often depend on the target and may be explained by activation or inhibition of particular cytokine pathways. Adverse drug reactions are classified by their pathomechanism, which enhances understanding of the pathogenesis and facilitates both allergologic diagnostic measures and planning of premedication in future treatments. This review emphasizes immunostimulatory and hypersensitivity reactions.

Role of Hydrogen Sulfide Production in Inhibitory Action of L-Cysteine on Isolated Porcine Irides

Purpose: To investigate the direct pharmacological actions of L-cysteine, a substrate for the production of H2S, on isolated porcine irides in the presence of tone induced by muscarinic receptor stimulation. Furthermore, we examined the underlying mechanism of action of L-cysteine in this smooth muscle.Methods: Isolated porcine iris muscle strips were set up in organ baths containing oxygenated Krebs buffer solution at 37°C. Longitudinal isometric tension was recorded via a grass FT03 Force-Displacement Transducer and analyzed using the PolyView computer software. The relaxant action of L-cysteine on carbachol-induced tone was studied in the absence and presence of inhibitors of enzymes of the biosynthetic pathways for H2S, and prostanoids. In addition, we also examined the effect of ATP-sensitive K+ (KATP) channel antagonist, glibenclamide on relaxations induced by L-cysteine.Results: L-cysteine (30 nM–1 mM) evoked concentration-dependent relaxations of carbachol-induced tone in isolated porcine irides, reaching a maximum inhibition of 43% at 1 mM. This response was enhanced significantly (P < 0.001) in the presence of the COX inhibitor, flurbiprofen (3 μM). Additionally,in the presence of flurbiprofen, the H2S donors, NaHS and Na2S, mimicked the relaxations produced by L-cysteine, yielding IC50 values of 5.8 μM and 180 μM, espectively. Both the inhibitor of cystathionine β-synthase, AOA (30 μM) and the KATP channel antagonist, glibenclamide (100 μM) caused significant (P < 0.001) rightward shifts in the concentration-response curves to L-cysteine and attenuated the maximum inhibitory response. Conversely, the inhibitor of cystathionine γ-lyase, PAG (1 mM) blocked only relaxations caused by high concentrations of L-cysteine (> 100 μM).Conclusions: The inhibitory action of L-cysteine in isolated porcine irides is dependent on the endogenous production of H2S by cystathionine γ-lyase and cystathionine β-synthase. Furthermore, prostanoids and KATP channels are involved in the inhibitory action of L-cysteine in this tissue.

Changes in CREB Phosphorylation and BDNF Plasma Levels during Psychotherapy of Depression

Background: The cyclic adenosine monophosphate response element-binding proteins (CREB) and their interaction with brain-derived neurotrophic factor (BDNF) are essential elements in signal transduction pathways important for cellular resilience and neuroplasticity. They play a decisive role in the concept of altered neuroplasticity in major depression. We have previously demonstrated that the increase in phosphorylated CREB (pCREB) in T lymphocytes is significantly associated with clinical improvement in patients treated with antidepressants. In the present study, we focused on patients treated only with psychotherapy to exclude direct pharmacological actions. In addition to pCREB, we also measured the BDNF plasma levels. Methods: pCREB in T lymphocytes was determined by Western blot; the BDNF plasma levels with solid-phase ELISA. Psychopathology was evaluated with the Hamilton Rating Scale for Depression (HAMD). Thirty patients meeting DSM-IV criteria for major depressive episodes (MDE) were recruited into this 6-week study. They received interpersonal psychotherapy (IPT) twice weekly. Results: After 6 weeks of IPT, 17 patients responded (reduction of ≥50% of baseline HAMD); after 1 week of treatment pCREB increased significantly compared to the nonresponder group. Measurement of the BDNF plasma levels revealed no differences between the responder and nonresponder groups. Furthermore, the correlations between BDNF plasma levels and pCREB were not significant. Conclusions: The early increase in pCREB is related to treatment response and does not depend on pharmacological interventions or BDNF plasma levels. For the first time, cellular biological markers could be associated with response to psychotherapy.

Alterations of prodynorphin gene expression in the rat mesocorticolimbic system during heroin self-administration

Opiate-induced alterations in the gene expression of the opioid propeptides prodynorphin (PDYN) and proenkephalin (PENK) in the brain have previously been described. However, there are no studies examining opioid propeptide system alterations due to long-lasting heroin self-administration. In our study, using in situ hybridization, we measured PDYN and PENK mRNA levels in the dorsal striatum, central nucleus of amygdala (CEA), and nucleus accumbens (NAcc) shell and core in rats after 6 weeks of heroin self-administration (fixed ratio 5, 0.02 mg/kg/infusion of heroin i.v.) and their respective saline or heroin “yoked” control. Our results show an increase in the PDYN mRNA level in the CEA and NAcc shell and no changes of PENK gene expression after heroin self-administration. In addition, to dissociate pharmacological effects of heroin from those produced by motivational processes driving active heroin intake on the PDYN and PENK gene expression, we compared effects of response-dependent (contingent) and response-independent (noncontingent — “yoked” heroin control) heroin administration. We found no differences between contingent and noncontingent groups of rats. In conclusion, our results indicate neuroadaptations in the PDYN but not PENK gene expression in rat limbic forebrain during heroin self-administration. We show that such changes depend on direct pharmacological actions of heroin rather than contingent heroin intake. These neuroalterations probably occur as an adaptation to long-lasting heroin exposure and may underlie changes leading to compulsive drug use and addiction.

Active versus passive cocaine administration: Differences in the neuroadaptive changes in the brain dopaminergic system

There is considerable evidence that chronic exposure to cocaine is associated with low striatal dopamine D 2 receptor availability. In the present study we wished to determine whether neuroadaptive changes in densities of D 2 receptors were due to direct pharmacological actions of cocaine or they reflected motivational states that were present when cocaine injection depended on active drug-seeking behavior and whether these changes were related to the actual expression of D 2 mRNA. To achieve this goal we utilized a “yoked” procedure in which rats were tested simultaneously in groups of three, with only one rat actively self-administering cocaine while the other two received yoked injections of either cocaine or saline. Only passively administered cocaine produced a decrease in dopamine D 2 receptor levels in the anterior and central regions of caudate/putamen, and both the shell and core of the nucleus accumbens, as measured by in vitro quantitative autoradiography. In contrast, examination of D 2 receptor gene expression using in situ hybridization analysis revealed that there was an increase in D 2 receptor mRNA levels in the ventral tegmental area of rats actively self-administered cocaine. We conclude that the reductions in striatal D 2 receptor densities may be related to the chronic administration of cocaine per se and not to the motivated process of reinforced responding. Our results also suggest that increases in D 2 receptor mRNA levels in limbic regions do not necessarily result in increased receptor densities and these changes likely reflect motivational states that were present when cocaine injection dependent on active drug self-administration.

Contingency does not contribute to the effects of cocaine self-administration on prodynorphin and proenkephalin gene expression in the rat forebrain

Neuroadaptations in the brain opioid systems produced by chronic exposure to drugs of abuse may contribute to the drug dependence and addiction. Although regulation of the gene expression of the opioid propeptides proenkephalin (PENK) and prodynorphin (PDYN) by psychostimulants has previously been described, little attention has been paid to dissociating effects of pharmacological actions of the drugs from those produced by motivational processes driving active drug intake in self-administration paradigms. In the present study, effects of response-dependent (contingent) and response-independent (noncontingent) cocaine administration on the PENK and PDYN gene expression in the rat forebrain have been directly compared using the “yoked” self-administration procedure. The i.v. cocaine treatment lasted for 5 weeks, and rats were sacrificed 24 h after the last self-administration session. In situ hybridization analysis revealed that levels of the PDYN mRNA were significantly increased in the caudate/putamen, to the same extent in rats self-administering cocaine as in animals receiving noncontingent injections of the drug at the same frequency and dosage. No changes in the expression of the PDYN gene were detected in the nucleus accumbens or in the central nucleus of amygdala. Levels of the PENK mRNA remained unaltered in all the above-mentioned forebrain regions of rats receiving contingent or noncontingent cocaine injections. The obtained data indicate that up-regulation of the PDYN gene expression in the caudate/putamen results from direct pharmacological actions of cocaine rather than from the motivational and cognitive processes underlying active self-administration of the drug.