The effects of fatty acid amide hydrolase inhibitors on maintenance of cocaine and food self-administration and on reinstatement of cocaine-seeking and food-taking behavior in rats

Some empirical evidence suggests that the endocannabinoids (eCB) (e.g. anandamide) may play an important role in cocaine addiction. The eCB act as a retrograde messengers activating CB receptors at the presynaptic membrane and are degraded by enzymatic actions of fatty acid amide hydrolase (FAAH). The present study aimed to examine the effect of the FAAH inhibitors, phenylmethylsulphonyl fluoride (PMSF; i.p.) or cyclohexylcarbamic acid 3-carbamoyl biphenyl-3-yl ester (URB597; i.p.) on the cocaine- or food-maintained self-administration as well as on the cocaine-seeking or food-taking behaviors in rats. Male Wistar rats were implanted with a catheter (iv.) and trained to self-administer cocaine (0.5 mg/kg/infusion) on a fixed ratio 5 schedule of reinforcement with a conditioned stimulus (tone+light). After self-administration stabilized, extinction/reinstatement procedures were carried out during which the rats were tested for the response reinstatement induced by cocaine (10 mg/kg, ip) or a cue (light+tone). The food (sweetened milk) self-administration and extinction/reinstatement procedures were conducted in a manner resembling cocaine self-administration. Neither PMSF (30-120 mg/kg) nor URB597 (0.1-3 mg/kg) affected cocaine self-administration. PMSF, 60 mg/kg, significantly reduced cocaine-induced reinstatement and at 120 mg/kg (combined with the challenge dose of cocaine) it evoked behavioral disruption. PMSF (60-120 mg/kg) dose-dependently inhibited cue-induced reinstatement. URB597 (1-3 mg/kg) attenuated both cocaine- and cue-induced drug-seeking behaviors. PMSF (60 mg/kg) decreased food self-administration. Toward reinstatement of food-taking behavior PMSF (60-120 mg/kg) and URB597 (3 mg/kg) showed inhibitory effects. Our results indicate that FAAH inhibitors could be potent modulators of motivational and conditioned aspects of goal-directed behaviors with less prominent effects on consumatory behaviors.

Activation of endocannabinoid transmission induces antidepressant-like effects in rats

Recent reports indicate that endocannabinoid (eCB) system may be involved in depression and in the antidepressant-like activity demonstrated in experimental models. The present study examined the effects of the eCB uptake inhibitor 4-hydroxyphenyl-5Z,8Z,11Z,14Z-eicosatetraenamide (AM404; 0.1-3 mg/kg), the fatty acid amide hydrolase (FAAH) inhibitor cyclohexylcarbamic acid 3-carbamoylbiphenyl-3-yl ester (URB597; 0.03-0.3 mg/kg), the cannabinoid CB(1) receptor agonist (-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl) phenyl]-trans-4-(3-hydroxypropyl)-cyclohexanol (CP55,940; 0.03-0.3 mg/kg) and the CB(1) receptor antagonist rimonabant (0.3-3 mg/kg) on immobility time in the forced swim test (FST) in rats. Moreover, the effects of AM404, CP55,940 and URB597 on the antidepressant-like activity of imipramine and citalopram in the FST were also examined. We found that AM404 (0.3-3 mg/kg), CP55,940 (0.1 mg/kg) and URB597 (0.1-0.3 mg/kg) reduced the immobility time of rats, while rimonabant (0.3-3 mg/kg) was inactive in this respect. We also observed that the anti-immobility effects of AM404 (1 mg/kg), CP55,940 (0.1 mg/kg) and URB597 (0.3 mg/kg), but not of imipramine (30 mg/kg), were blocked by rimonabant (3 mg/kg). In another set of experiments we showed that the inactive dose of AM404 (0.1 mg/kg) potentiated the effects of the inactive doses of imipramine (15 mg/kg) or citalopram (30 mg/kg), while CP55,940 (0.03 mg/kg) and URB597 (0.03 mg/kg) enhanced the effect of imipramine only. None of the drugs studied, given alone or in combination, increased the basal locomotor activity of rats. Our results indicate that activation of the eCB system induces antidepressant-like effects in the FST in rats, and that these effects are mediated by CB(1) receptors. Moreover, they also indicate that agents activating eCB transmission enhance the anti-immobility responses to antidepressant drugs.

Effects of 1-methyl-1,2,3,4-tetrahydroisoquinoline on the behavioral effects of cocaine in rats

The efficacy of 1-methyl-1,2,3,4-tetrahydroisoquinoline (1MeTIQ), a member of endogenous tetrahydroisoquinolines, in cocaine- and food-maintained responding in self-administration procedures under a fixed ratio 5 schedule of reinforcement as well as in cocaine and food seeking behaviors in male Wistar rats was examined. The effects of 1MeTIQ on cocaine discrimination and on basal locomotor activity were also assessed. In rats trained to self-administered either cocaine (0.5 mg/kg/injection) paired with the cue (light+tone) or food under a fixed ratio 5 schedule of reinforcement, 1MeTIQ (25 - 50 mg/kg) dose-dependently decreased the cocaine-maintained responding, but did not alter the food-maintained responding. 1MeTIQ (25 - 50 mg/kg) decreased the cocaine seeking behavior reinstated by a noncontingent presentation of cocaine (10 mg/kg, i.p.), but altered neither behavior reinstated by a discrete cue (tone+light) nor food-induced reinstatement. In rats trained to discriminate cocaine (10 mg/kg) from saline in water-reinforced fixed ratio 20 task, pretreatment with 1MeTIQ resulted in neither substitution nor significant alterations in the cocaine (1.25 - 10 mg/kg)-induced discriminative stimulus effects. 1MeTIQ (25 - 50 mg/kg) did not produce also a significant changes in basal horizontal activity. In conclusion, our present results outline a significance of exogenously applied 1MeTIQ in attenuating drug-evoked relapses to cocaine as well as the direct rewarding properties of cocaine (that model the cocaine-induced "high"), but not cocaine subjective effects. Moreover, a dissociation between effects of 1MeTIQ on cocaine vs. food-maintained responding was demonstrated.

N-oleoyl-dopamine increases locomotor activity in the rat

N-oleoyl-dopamine (OLDA), a condensation product of oleic acid and dopamine (DA), is a bioactive lipid whose biological functions are not yet fully explored. The compound crosses the blood-brain barrier and might be considered as a carrier of DA into the brain. In this study we sought to determine whether OLDA would influence locomotor behavior and whether the central DA system would be involved in such influence. We addressed this issue by investigating horizontal locomotor activity in male Wistar rats after intraperitoneal administration of OLDA, 5-20 mg/kg, before and after pre-treatment with haloperidol, a D2 receptor antagonist. We found that OLDA caused a prompt stimulation of locomotor activity, with a bell-shaped dose-response. The maximum stimulatory effect was observed after 10 mg/kg of OLDA where the mean distance traveled by rats during a 2-hour test increased to 1213+/-196(SE) cm from the 403+/-89 cm in the vehicle-treated rats (P<0.05). This effect was dose-dependently antagonized by haloperidol (0.1-0.2 mg/kg). The results support the hypothesis that the OLDA-induced hyperlocomotion was mediated by the stimulation of DA systems. Using in vitro assays, we further demonstrated that OLDA is a stable compound that resists hydrolysis over a 2-hour period and thus the integral OLDA compound exerted DA-like effects. We conclude that OLDA is a potential brain modifier of motor behavior, the biological consequences of which remain to be explored.

An endogenous neuroprotectant substance, 1-methyl-1,2,3,4-tetrahydroisoquinoline (1MeTIQ), prevents the behavioral and neurochemical effects of cocaine reinstatement in drug-dependent rats

Drug abuse disorder is induced by a variety of substances and results from their interaction with the brain reward system. It is characterized by a high frequency of relapse, usually associated with to craving. In this study we investigated the effects of 1-methyl-1,2,3,4-tetrahydroisoquinoline, an endogenous compound with antidopaminergic and neuroprotective activity, on cocaine-induced reinstatement in cocaine-dependent, self-administering rats. 1-methyl-1,2,3,4-tetrahydroisoquinoline (50 mg/kg i.p.) completely inhibited the expression of reinstatement of cocaine self-administration and accompanying neurochemical changes induced by a single priming cocaine dose (10 mg/kg i.p.). The priming cocaine dose inhibited dopamine metabolism in the structures containing nerve endings (frontal cortex, nucleus accumbens, and striatum) but not in the substantia nigra and ventral tegmental area. A behaviorally active dose of 1-methyl-1,2,3,4-tetrahydroisoquinoline administered 30 min before a priming dose of cocaine significantly increased the dopamine concentration in the limbic structures, and strongly inhibited dopamine metabolism in the substantia nigra and ventral tegmental area. Cocaine also inhibited noradrenaline and serotonin metabolism, and 1-methyl-1,2,3,4-tetrahydroisoquinoline abolished the inhibition in noradrenaline metabolism, while it intensified the inhibition of serotonin metabolism. Our results strongly support the view that 1-methyl-1,2,3,4-tetrahydroisoquinoline, an endogenous compound, has considerable potential as a drug for combating substance abuse disease through the attenuation of craving.

[Toxic anterior segment syndrome]

The authors present two cases of TASS which occurred consequent upon anterior chamber administration of cefuroxime(Axetin). The ESCRS guidelines on prevention, investigation and management of postoperative endophthalmitis recommends intracameral injection of an antibiotic agent (cephalosporin) at the conclusion of surgery. In our group of patients TASS occurred. Elements of diagnosis and treatment in TASS are discussed. As a conclusion to our study we decided to discontinue cefuroxime administration.

A lymphoid conjunctival tumor--clinical aspects; therapeutical options

A female woman, 34 years old, having a history of 10 years of conjunctival allergy, came to our Clinic for a pale pink mass lesion, occupying both the upper and the lower fornices. The therapeutical and also investigational approach was to excise all suspected tissue and to biopsy to determine if benign or malignant (clinically indistinguishable). The conjunctival biopsy revealed a non-Hodgkin malignant conjunctival MALT lymphoma. A complete medical check-up performed by a hematologist-oncologist confirmed that the disease was localized. In this case, of ocular adnexal MALT lymphoma with localised disease, we took into account local treatment: external beam radiation therapy, topical use of chemotherapy agents and biologic therapy (subconjunctival injections with interferon-alpha). Systemic chemotherapy was avoided. Interesting results were obtained with

[Anterior uveal malignant melanoma with subconjunctival extension--a clinical case]

The authors present the case of a patient with intraocular tumour and secondary glaucoma, which has been surgically treated for acute angle-closure glaucoma in a local hospital. Patient sits for examination at the clinic 11 months after surgery. Multiple conjunctiva pigmented metastasis are present at physical examination. Chosen therapeutic approach: exenteration.

[Post-operatory biometry and refraction results estimated and refraction surprises--clinical study]

Preoperative biometry has a major influence on the success or failure of IOL implantation procedures. The paper wishes to demonstrate the significance of this manoeuvre for the refraction and visual outcome and for the postoperative satisfaction rate of the patients. The clinical study has rulled out for one year period and a number of 239 patients suffered a IOL implantation procedure (cataract or lens extraction for refractive purposes). The preoperative biometry was always necessary. We used one of the existing IOL power calculation formula (SRK II, SRK T, Holladay). The surgeon decided about the IOL power, always after discussing with the patient their postoperative refractive expectations. The postoperative refraction was, in the majority of cases, the estimated refraction and the errors were similar with those from the literature. Refractive surprises of several diopters were registered in high myopic and hyperopic eyes or in cases of coexisting ocular diseases which have modified the anatomical parameters of the eye. In conclusion, small errors in calculation can have large effects on visual outcome. This problem will be solved in the future, because the field is evolving rapidly driven by a new understanding of the anatomy of the eye and new hardware for measuring that anatomy.

[Cataract surgery in Romania--2003]

AIM

to evaluate cataract surgery performed in Romania analyzing: --the number of cataract surgery performed in 2003; --the surgical technique used: intracapsular extraction, extracapsular extraction, phacoemulsification; --the number and type of intraocular lenses used; --the number of ophthalmologists that performed cataract surgery;

MATERIAL AND METHOD

--a questionnaire was sent to all ophthalmologists which do cataract surgery.

RESULTS

--38,000 surgeries for cataract were performed in 2003; --the surgical techniques used were : Phacoemulsification (18,000 cases), classic extracapsular extraction ( 19,000 cases) and intracapsular extraction (1000 cases); --28,500 rigid and 8,000 foldable intraocular lenses were implanted; - 223 ophthalmologists perform cataract surgery in Romania.

New concepts in etiology, clinic and management of postoperative endophthalmitis

THE AIM OF THE PAPER

In the last few years, as a result of the continuing changing of the ethiological, clinical and therapeutical aspects of the postoperative endophthalmitis, there are a lot of efforts to find the adequate means to prevent and to treat this severe complication of cataract surgery. So, the paper presents the most actual therapeutical approaches in the field.

MATERIAL AND METHODS

The goals of treatment of postoperative endophthalmitis are: to regain vision and to save the bulb. From the prophylactic techniques, preoperative povidone-iodine antisepsis is the most recommended procedure for decreasing the risk of endophthalmitis related to surgery. The main elements of the modern treatment of endophthalmitis are medical treatment by intravitreal injections or by systemic drugs and surgical treatment with vitrectomy.

CONCLUSIONS

Although endophthalmitis remains a potential cause of visual loss, both medical therapies and surgical techniques have evolved so that prognosis is not always as negative as it used to be.

[Particular aspects of treatment in diabetic eye cataract]

The knowing of the ocular consequences of diabetes is essential for the evaluation of the risk factors for the cataract surgery. The clinical study was made on a total number of 19 diabetic patients (3 with insulin dependent diabetes and the rest with noninsulin dependent diabetes), which were operated for cataract from september 2001 till march 2002. Preoperatory preparation presumed a good metabolic control of diabetes and a very carefully examination of the retina. The surgical technique was the extracapsular cataract extraction, followed by the implantation of a posterior chamber IOL, respectively phacoemulsification with the implantation of a foldable lens. The presence of a proliferative diabetic retinopathy, of a rubeosis iridis, of the neovascularization of the angle, or the preexistence of the vitreoretinal surgery (vitrectomy) were the main factors which dictated the anatomical and functional postoperatory prognosis. In conclusion, evenly the diabetic patient is a highly risk patient, the adequate preoperator preparation, the right treatment and a carefully follow-up could assure the success of the surgery in those cases.

[Laser in glaucoma treatment ; 1-year personal experience]

THE AIM OF THE PAPER

The paper establishes the role of the laser treatment in the complex treatment of glaucoma and realizes a comparison between our clinical results and the results from the literature.

MATERIAL AND METHODS

Along a period of one year, we have treated a number of 117 glaucoma patients: Open angle glaucoma (POAG), angle closure glaucoma (ACG), normal tension glaucoma (NTG) and symptomathic narrow anterior chamber. The complex treatment consists of medication, laser and/or surgery. To treat the patients, we have used the VISULAS 532 Combi laser, manufactured by Zeiss.

RESULTS

The results are presented in a synthetic way for different pathological entities and different methods of laser treatment.

CONCLUSIONS

In glaucoma, laser treatment represents a step between the medical treatment and surgery and is a very good alternative when the medication in inefficient or is not well tolerated. Our results are, in majority, similar with those from the literature.

Dry eye syndrome. Etiological and therapeutic aspects

"Dry eye syndrome" is a common disorder of the tear film that results from inadequate tear production, excessive tear evaporation or abnormality in mucin or lipid components of the tear film. A number of 53 patients suffering from dry eye syndrome were followed up for a period of 18 months. The study group was heterogeneous, including a lot of conditions accompanied by dry eye syndrome: Syogren's syndrome, lupus erythematous, ocular rosacea, patients with systemic treatments with antidepressants, betablockers, diuretics, oral contraceptives, glaucomatous patients with topical beta-blockers, postmenopausal women, aging people, computer users and long-term contact lens wearers. The therapeutical options were dictated by the severity of the syndrome: substitution therapy, treatment of the underlying eyelid diseases, modifying of the environmental conditions and treatment of the complications in the most severe cases. The new pathological approach is innovative and it may provide a real therapeutical measure for this condition: topical A Cyclosporine and androgen drops.

[High-altitude retinopathy]

High-altitude retinopathy is a very rare ocular disease in our country, which can occur isolately or as a part of high-altitude illness. This paper presents the case of a patient with high-altitude illness and the diagnosis and treatment problems of this case.

[Choroidal neovascularization]

Choroidal neovascularization (CNV) may occur in any ocular condition affecting the integrity of the choriocapillaris-Bruch's membrane-retinal pigment epithelium-outer retinal layer complex. CNV in the macula is a major cause of severe central visual loss. A variety of clinical symptoms suggest the diagnosis of CNV. Fluorescein and indocyanine green angiography play a very important role in the detection and precise localization of CNV in relation to the centre of the foveal avascular zone. In the present, CNV benefits by many treatment possibilities. The goal of treatment is specifically to decrease the risk of visual acuity loss.

Effects of 5-HT1B receptor ligands microinjected into the accumbal shell or core on the cocaine-induced locomotor hyperactivity in rats

The present study was designed to examine the effect of 5-HT1B receptor ligands microinjected into the subregions of the nucleus accumbens (the shell and the core) on the locomotor hyperactivity induced by cocaine in rats. Male Wistar rats were implanted bilaterally with cannulae into the accumbens shell or core, and then were locally injected with GR 55562 (an antagonist of 5-HT1B receptors) or CP 93129 (an agonist of 5-HT1B receptors). Given alone to any accumbal subregion, GR 55562 (0.1-10 microg/side) or CP 93129 (0.1-10 microg/side) did not change basal locomotor activity. Systemic cocaine (10 mg/kg) significantly increased the locomotor activity of rats. GR 55562 (0.1-10 microg/side), administered intra-accumbens shell prior to cocaine, dose-dependently attenuated the psychostimulant-induced locomotor hyperactivity. Such attenuation was not found in animals which had been injected with GR 55562 into the accumbens core. When injected into the accumbens shell (but not the core) before cocaine, CP 93129 (0.1-10 microg/side) enhanced the locomotor response to cocaine; the maximum effect being observed after 10 microg/side of the agonist. The later enhancement was attenuated after intra-accumbens shell treatment with GR 55562 (1 microg/side). Our findings indicate that cocaine induced hyperlocomotion is modified by 5-HT1B receptor ligands microinjected into the accumbens shell, but not core, this modification consisting in inhibitory and facilitatory effects of the 5-HT1B receptor antagonist (GR 55562) and agonist (CP 93129), respectively. In other words, the present results suggest that the accumbal shell 5-HT1B receptors play a permissive role in the behavioural response to the psychostimulant.

The effect of amphetamine sensitization on mouse immunoreactivity

Recent studies indicate a role of the immune system in the behavioral effects of amphetamine in rodents. In the present study we attempted to find a connection between the behavioral changes induced by repeated, intermittent administration of amphetamine and some immunological consequences of sensitization to amphetamine in mice. Male Albino Swiss mice were treated repeatedly (for 5 days) with amphetamine (1 mg/kg, i.p.). On day 9, they received a challenge dose of amphetamine (1 mg/kg). Acute administration of amphetamine increased their locomotor activity by ca. 40%. In animals treated repeatedly with amphetamine, the challenge dose of the psychostimulant induced behavioral sensitization, i.e. the higher locomotor activation as compared with that after its first administration to mice. Immune functions were evaluated by the ability of splenocytes to proliferate and to produce cytokines such as interferon gamma (IFN-gamma), interleukin (IL)-4 and IL-10. Acute amphetamine administration significantly decreased, by ca. 30% and 25%, the proliferation of splenocytes in response to an optimal and a suboptimal dose of concanavalin A (Con A), respectively, and increased their ability to produce IL-4. Chronic intermittent treatment with amphetamine significantly decreased, by ca. 65% and 50%, the proliferative response of T cells to an optimal and a suboptimal dose of Con A, respectively, and diminished by 20% the metabolic activity of splenocytes. The above data showed that both acute and chronic amphetamine administration diminished some aspects of the cell-mediated immunity; nevertheless, immunosuppression was particularly evident in amphetamine-sensitized mice. Our findings seem to indicate possible importance of monitoring and correcting immune changes in the therapy of amphetamine addiction.

[Verification of a surgical technique using a new biotitanium cage in degenerative diseases of the lumbar spine--experimental study]

PURPOSE OF THE STUDY

Authors performed experimental PLIF operations on cadavers to verify appropriate shape and size of cage made from bioactive titan material. The approach for application into intervertebral space of the lumbar spine and appearance on X-ray and CT scans was also investigated.

MATERIAL

In experiment on cadavers five implantations of interbody cages were performed, two of them in interbody space L3/L4 and three of them in L4/L5. Subtotal discectomy and end platec preparation was done before cage insertion. Our type of cage is made from bioactive titan material and fastened in the application instrument that we developed for this purpose.

METHOD

To verify operational approach we used midline incision and opened spinal canal through laminectomy, partial hemilaminectomy or partial medial facetectomy. This phase was followed by discectomy and end plates preparation. Stability of inserted cages in intervertebral space is ensured by rotation and anchorage of cage wings in end plates. Operated motion segment was taken out and evaluated by X-rays and CT scans.

RESULTS

The operational approach through partial hemilaminectomy and partial medial facetectomy was fully sufficient for cage application with respect to operated segment. All implantations were successful and position of cages satisfactory. Thanks to less robust gripping instrument the approach was more thrifty compared to glass-ceramic cage and comparable with commercially produced cages that we have experience with (Spine Tech, Stryker, Comesa). Due to cage radio opaque, proper position of cages is easy to control on X-ray and CT scans and allows good peroperative monitoring by X-ray magnifier.

DISCUSSION

Usage of bioactive materials in spinal surgery started by introduction of glass ceramics. Based on our experience we determined suitable indications. To eliminate some of te disadvantages of glass ceramics (mainly mechanical properties), a cage made from bioactive material was developed. This type of cage does not require bone harvesting to fill the cage. This fact results in better comfort for patient in postoperative period and eliminates complications from bone graft harvesting. Bioactive surface of the cage with osseo conductive and osseo integrative features creates prerequisites for solid fusion without bone grafts. Titanium material guarantees mechanical strength and makes possible to produce a wide range of shapes and sizes. Strength of the material enables more advantageous gripping of cage in application instrument. The cage is well visible on X-ray and in MRI scans artifacts are considerably reduced. Operational approach and technique are similar to other commercially produced cages and the extent of destabilization is limited to minimum.

CONCLUSION

Experimentally we repeatedly verified operational approach, suitable shape and applicability of bioactive titanium cage into intervertebral space. For clinical use bioactive titanium could be a possible way how to replace bone grafts. For spinal surgeons it represents a chemically and mechanically stable material capable of interaction in an environment where it is implanted. Even in difficult conditions the level of osseo integration is high.

[Laser phacoemulsification--a method of cataract surgery]

Today, ultrasound phacoemulsification is the most used method of cataract surgery. Because the side effects (injury of corneal endothelium and other nearly tissues), was tried to find alternative energy forms. Erbium laser was proven to be the most effective method among all of these.

Does combined treatment with novel antidepressants and a dopamine D3 receptor agonist reproduce cocaine discrimination in rats?

It is established that dopamine (DA) neurotransmission plays a critical role in the behavioral (e.g. discriminative stimulus) effects of cocaine in rodents. Nonetheless, research has also demonstrated that reciprocal signaling between DA and monoamine neurotransmitters, i.e. serotonin (5-HT) and norepinephrine (NE) has important implication for understanding the actions of cocaine. The present study was focussed on the ability of novel antidepressant drugs (milnacipram, reboxetine and venlafaxine), which affect either NE or both 5-HT and NE reuptake mechanism, to alter (enhance or antagonize) the discriminative stimulus effects of cocaine. Moreover, we investigated if the combined treatment with those drugs and a DA D3 receptor agonist (pramipexole) could reproduce cocaine discrimination. Male Wistar rats were trained to discriminate cocaine (10 mg/kg, ip) from saline (ip) in a two-choice, water-reinforced fixed-ratio 20 drug discrimination paradigm. Given alone, none of antidepressant drugs induced substitution for the cocaine-lever responses. Pramipexole (0.25 mg/kg) produced a partial substitution for cocaine (i.e. 43-52% cocaine-lever responding). In combination experiments, milnacipram (10 mg/kg) or reboxetine (10 mg/kg) given with submaximal doses of cocaine (1.25-5 mg/kg) did not affect the cocaine dose-response curve or its ED50 values. Venlafaxine (10 mg/kg) given in combination with submaximal doses of cocaine (0.6-5 mg/kg) produced significant enhancement of cocaine discrimination with a leftward shift in the cocaine dose-response curve and a decrease in its ED50 value. Pretreatment with either milnacipram (10 mg/kg) or reboxetine (10 mg/kg) failed to modulate the partial substitution evoked by pramipexole (0.25 mg/kg). On the other hand, venlafaxine (10 mg/kg) given in combination with a submaximal dose of pramipexole (0.25 mg/kg), which separately elicited 16 and 42% the cocaine-lever responses, produced significant enhancement of cocaine discrimination (up to 99% of the drug-lever responding). These results indicate that the discriminative stimulus effects of cocaine in rats can be enhanced by venlafaxine or mimicked by the combination with this antidepressant drug and the DA D3 receptor agonist. This finding, together with the recent data reporting the lack of rewarding properties of venlafaxine and the attenuation of morphine dependence and withdrwal signs in rats by the drug, may indicate a possible therapeutic use of this antidepressant in cocaine abuse.

Differential regulation of the mesoaccumbens circuit by serotonin 5-hydroxytryptamine (5-HT)2A and 5-HT2C receptors

Serotonin [5-hydroxytryptamine (5-HT)] 5-HT(2A) and 5-HT(2C) receptors (5-HT(2A)Rs and 5-HT(2C)Rs), which innervate the dopamine mesoaccumbens pathway, may play an important role in the behavioral effects of cocaine. To test this hypothesis, the present study measured cocaine-evoked locomotor activity after bilateral microinjection of selective 5-HT(2A)R and 5-HT(2C)R antagonists into the ventral tegmental area (VTA) or the nucleus accumbens (NAc) shell. Locomotor activity was measured after intracranial microinjection of saline (0.2 microl/side), the selective 5-HT(2A)R antagonist R-(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidine methanol (M100907) (0.1 or 0.3 microg. 0.2 microl(-1). side(-1)), or the selective 5-HT(2C)R antagonist 8-[5-(2,4-dimethoxy-5-(4-trifluoromethylphenylsulfon-amido)phenyl-5-oxopentyl)]-1,3,8-triazaspiro[4.5]decane-2,4-dione hydrochloride (RS 102221) (0.05-0.5 microg. 0.2 microl(-1). side(-1)) followed by an injection of saline (1 ml/kg, i.p.) or cocaine (10 mg/kg, i.p.). Microinjection of M100907 (0.1-0.3 microg/side) into the VTA or RS 102221 (0.15-0.5 microg/side) into the NAc shell attenuated cocaine-induced hyperactivity in a dose-related manner. However, hyperactivity evoked by cocaine was not altered by microinjection of RS 102221 into the VTA or M100907 into the NAc shell. No changes in basal activity were observed after microinjection of M100907 or RS 102221 into either brain region. These findings are the first to demonstrate that the behavioral effects of cocaine are generated in part by activation of 5-HT(2A)Rs in the VTA and by activation of 5-HT(2C)Rs in the NAc shell. The selective regulation of the mesoaccumbens circuit by 5-HT(2A)Rs and 5-HT(2C)Rs implicates these 5-HT receptors as important in the behavioral outcomes of systemic cocaine administration.

On the role of serotonin2A/2C receptors in the sensitization to cocaine

Apart from showing involvement of dopamine, recent studies also indicate a role of serotonin (5-HT) in the behavioral effects of cocaine in rodents. In the present study we investigated the role of 5-HT2A/2C receptors in the development or expression of sensitization to cocaine in rats, using ketanserin, an antagonist at these receptors. Since ketanserin also shows a high affinity for alpha1-adrenoceptors, prazosin, a comparative antagonist at those receptors was also examined. Male Wistar rats were treated repeatedly (for 5 days) with cocaine (10 mg/kg) in combination with either vehicle, or ketanserin (1-3 mg/kg) or prazosin (3 mg/kg); afterwards, on day 10, they received a challenge dose of cocaine (10 mg/kg). In another experiment, the animals were given either with vehicle or cocaine (10 mg/kg) for 5 days, and were then challenged with cocaine (10 mg/kg) in combination with vehicle, or ketanserin (1-3 mg/kg) or prazosin (3 mg/kg) on day 10. Acute administration of cocaine increased the locomotor activity in rats; that hyperactivation was inhibited by ketanserin (3 mg/kg), but not by prazosin. In animals treated repeatedly with cocaine, the locomotor hyperactivity induced by a challenge dose of the psychostimulant was ca. 2-3 times higher than that after its first administration. No difference was observed in the response to cocaine challenge in rats treated repeatedly with cocaine, ketanserin+cocaine, or prazosin+cocaine. In animals treated repeatedly with the psychostimulant, the behavioral response to a challenge dose of cocaine was dose-dependently decreased when the drug was combined with ketanserin, but not with prazosin. The above findings indicate a role of 5-HT2A/2C receptors (but not alpha1-adrenoceptors) in the acute locomotor hyperactivity, as well as in the expression (but not development) of cocaine sensitization. Since chronic use of cocaine by humans may lead to psychoses or craving for this drug of abuse, our findings also seem to indicate possible importance of 5-HT2A/2C receptor antagonists in the therapy of cocaine addiction.

Serotonin1B receptor ligands in the nucleus accumbens shell do not affect the discriminative stimulus effects of amphetamine in rats

Enhanced dopamine neurotransmission particularly, in the target area of the mesolimbic system, i.e. the nucleus accumbens (NAc), seems to be critical for the behavioral effects of amphetamine in rodents. Nonetheless, recent findings have also demonstrated a modulatory role of 5-hydroxytryptamine (5-HT; serotonin) in these effects. In the present study, we examined whether 5-HT1B receptors in the NAc shell are engaged in the discriminative stimulus of amphetamine. To this end male Wistar rats were trained to discriminate amphetamine (1 mg/kg, ip) from saline (ip) in a two-lever, water reinforced fixed ratio (FR) 20 task. After acquiring the amphetamine-saline discrimination, rats were stereotaxically implanted with bilateral cannulae aimed at the NAc shell and then infused with selective 5-HT1B receptor ligands. The ability of these drugs to substitute for or to alter (enhance or antagonize) the discriminative stimulus effects of amphetamine was examined. When given systemically, amphetamine (0.125-1 mg/kg) produced a dose-dependent increase in drug-lever responding. In substitution studies, microinjection of the 5-HT1B receptor agonist CP 93129 (1-10 microg/side) or the 5-HTIB receptor antagonist GR 55562 (1-10 microg/side) into the NAc shell did not evoke amphetamine-lever responding. Combination tests of 5-HT1B receptor ligands demonstrated that local injection with fixed doses of CP 93129 (1 or 10 microg/side) or GR 55562 (1 or 10 microg/side) with the submaximal doses of amphetamine (0.125-0.5 mg/kg) did not modify dose-response curves of the psychostimulant, nor did it affect its ED50 value. Our results seem to exclude a role for the NAc shell 5-HT1B receptors in the control of the discriminative stimulus effects of amphetamine. These findings also show that pharmacological stimulation of those receptors does not affect the amphetamine discrimination in rats.