C. Heidbreder

Acamprosate modulates synaptosomal GABA transmission in chronically alcoholised rats

Male Sprague-Dawley rats were pulmonary alcoholised for 30 days. Six were treated with acamprosate (400 mg/kg/day, PO) during alcoholisation. The control nonalcoholised group also received acamprosate (400 mg/kg/day, PO) during the 30 days. At the end of the experiment, brains areas (cortex, hippocampus, thalamus, striatum, and olfactory bulbs) were dissected for the study of synaptosomal 3H-GABA uptake. In another experiment, GABA levels were determined in the same areas using HPLC with electrochemical detection. Blood ethanol levels were also measured during alcoholisation. Acamprosate treatment did not modify blood ethanol levels. In cortex and olfactory bulbs, alcoholisation increased 3H-GABA uptake (Vmax) with an increase in the affinity (Km). 3H-GABA uptake was not affected by alcoholisation in other brain areas. In hippocampus and thalamus, acamprosate treatment enhanced 3H-GABA uptake (Vmax) only in alcoholised rats. Moreover, in thalamus, alcoholisation enhanced GABA levels. The effect of alcohol and acamprosate on GABA presynaptic events is discussed and it is concluded that the action of ethanol and acamprosate on GABA transport could be, in part, responsible for the modulation by acamprosate treatment of ethanol behaviour.

Ethanol Differentially Affects Extracellular Monoamines and Gaba in the Nucleus-accumbens

The magnitude, direction, and time course of the effects of acute administration of ethanol (0.1 or 1.0 g/kg) on the extracellular levels of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), and GABA within the nucleus accumbens of the rat were analysed using microdialysis in conjunction with high-pressure liquid chromatography and electrochemical detection. IP injection of 0.1 g/kg ethanol failed to modify the extracellular concentration of DA, DOPAC, HVA, 5-HT, 5-HIAA, and GABA in the nucleus accumbens during the 120-min collection period. On the contrary, 1.0 g/kg IP ethanol significantly increased extracellular levels of DA, DOPAC, and 5-HIAA in microdialysates from the nucleus accumbens. The maximal increase in DA (314.87 +/- 6%), DOPAC (210.58 +/- 3%), and 5-HIAA (250.88 +/- 8%) was observed 40 min after administration of ethanol. Extracellular HVA was also enhanced (220.89 +/- 2%) at time point 100 min following injection of the same dose of ethanol. Finally, extracellular levels of 5-HT and GABA remained unchanged following 1.0 g/kg ethanol.

Opposite Effects of Cholecystokinin Octapeptide (cck-8) and Tetrapeptide (cck-4) After Injection Into the Caudal Part of the Nucleus-accumbens Or Into its Rostral Part and the Cerebral-ventricles

Neurons with colocalized cholecystokinin and dopamine are present predominantly in the ventral tegmental area and project mainly to the caudal part of the medial nucleus accumbens. The activity of this dopamine system can be evaluated by means of the intracranial self-stimulation behavior on male Wistar rats having chronic electrodes implanted into the medial forebrain bundle in the postero-lateral area of the hypothalamus. The direct injection of 150 pmol CCK-8 into the medio-caudal accumbens induced an increase of intracranial self stimulation while a similar administration into its rostral portion produced a slight decrease of intracranial self-stimulation. The administration of 300 pmol CCK-4 into the same medio-caudal part of the accumbens produced an inhibitory action on intracranial self stimulation lasting for 25 min. The injection of 70 to 1300 pmol CCK-4 into the cerebral ventricles produced no change on intracranial self-stimulation. The intracerebroventricular injection of 70 pmol CCK-8 induced a large decrease of intracranial self-stimulation lasting for 20 min. Sodium chloride 0.15 M or unsulphated CCK-8 injection were without effect in either case. These results support the ideas that intracerebroventricular CCK-8 injection inhibits accumbens dopaminergic activity but that CCK-8 injection into the medio-caudal part of the accumbens, where nerve terminals with colocalized CCK and DA are present, facilitates this dopaminergic activity. In addition at the level of medio-caudal accumbens, CCK-8 and CCK-4 have opposite effects.

Balance of glutamate and dopamine in the nucleus accumbens modulates self-stimulation behavior after injection of cholecystokinin and neurotensin in the rat brain

Subpopulations of dopamine (DA) neurons in the ventral mesencephalon have been reported to contain cholecystokinin (CCK) and neurotensin (NT), giving rise to DA, DA/NT, NT/CCK and DA/CCK/NT projections. More precisely, colocalized DA/CCK neurons project mainly to the caudal part of the medial nucleus accumbens, whereas its rostral portion receives CCK and DA nerve terminal networks that are structurally independent. We investigated the respective effects of both CCK and NT on the intracranial self-stimulation behavior (ICSS) from the posterolateral hypothalamus after their direct administration into the lateral ventricle (ICV), into both portions of the nucleus accumbens, into the ventral tegmental area (VTA), and into the subiculum of the hippocampal formation (SUB). The ICV injection of 150 pmol CCK8 induced a decrease in the rate of ICSS. By contrast, the direct administration of 150 pmol CCK8 into the mediocaudal part of the nucleus accumbens induced an enhanced rate of ICSS while a similar injection into its rostral portion gave rise to a slight transient decrease of ICSS. When injected into the SUB, both CCK8 and glutamate produced decreased rates of ICSS at femtomolar doses one thousand-fold under the picomolar concentrations used for ICV injections. Neurotensin induced similar behavioral profiles to that observed after the ICV injection of CCK8 or into both portions of the nucleus accumbens. Neurotensin and CCK8 displayed opposite effects on ICSS when administered into the SUB or into the VTA, suggesting they may regulate ICSS most probably through different synaptic mechanisms and through different anatomical pathways.

Inhibition of enkephalin metabolism and activation of mu- or delta-opioid receptors elicit opposite effects on reward and motility in the ventral mesencephalon

The coexistence of endogenous opioid systems and dopaminergic neurones in the midbrain tegmental area suggests functional interactions between dopamine and enkephalins. Nevertheless, the identification of the specific opioid receptors associated with modulation of tegmental dopamine activity and its behavioural concomitants on motility and reward is far from clear, considering the mixed nature of the ligands usually employed. In this way, kelatorphan, a potent inhibitor of enkephalinases and selective agonists for mu- and delta-opioid receptor subtypes (DAGO and DSTBULET, respectively) were infused directly into the ventral tegmental area of the rat to study the role of endogenous enkephalins and opioid receptors in regulating spontaneous motor activity and intracranial self-stimulation behaviour. A greater increase in the rate of intracranial self-stimulation behaviour was found after activation of mu-opioid receptors in the ventral tegmental area, as compared to activation of delta-opioid receptors, whereas enhancement of endogenous enkephalins by inhibiting their metabolism through kelatorphan, reduced the rate of intracranial self-stimulation behaviour. On the contrary, spontaneous motor activity was reduced by the delta-opioid receptor agonist, whereas kelatorphan increased the movements of the animal. Taken together, these results show that inhibition of the metabolism of enkephalins in the ventral tegmental area decreased positive reinforcement from the lateral hypothalamic medial forebrain bundle and increased spontaneous movements. On the contrary, activation of both mu- or delta-opioid receptors in the ventral tegmental area significantly increased self-stimulation and decreased spontaneous motor activity, supporting the view that different mechanisms underlie the behavioural effects, resulting from enhancement of endogenous enkephalins and from activation of specific opioid receptors in the ventral mesencephalon.

Regional amines levels in the rat brain following intra-accumbens cholecystokinin and intraperitoneal amphetamine pre-treatment

Cholecystokinin octapeptide (CCK8) coexists with dopamine (DA) in a subpopulation of mesolimbic DA neurons including the projections to the nucleus accumbens. In this structure, CCK8 has been reported to exert agonist-like or antagonist-like effects on DA-mediated behaviours and on amphetamines locomotor-activating effects in rodents. These findings raise the possibility that CCK8 plays a role in modulating the neurochemical mechanisms underlying the effects of DA and amphetamine in the mesolimbic DA system. The purpose of this study was to determine regional tissue monoamine levels in the rat brain and their modulation following injection of CCK8 in the nucleus accumbens. The same paradigm was used to determine the effects of this octapeptide on changes in amine levels induced by amphetamine administered intraperitoneally. DA, norepinephrine (NE), serotonin (5-HT) and their primary metabolites, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were measured using a reversed-phase ion pair high-pressure liquid chromatography system with electrochemical detection (HPLC-ED). Frontal cortex displayed the highest DOPAC/DA ratio and the lowest DOPAC/HVA ratio in contrast to the olfactory tubercle. The intraperitoneal injection of amphetamine (1 mg/Kg) followed by the intra-accumbens administration of 0.15M saline decreased the levels of DOPAC and increased DA, 5-HT and 5-HIAA both in nucleus caudatus and nucleus accumbens. The DA agonist induced a decrease in the level of NE in olfactory tubercle and frontal cortex. The direct administration of CCK8 (300 pmol) into the nucleus accumbens decreased the level of DA, DOPAC and 5-HT mainly in olfactory tubercle and nucleus accumbens itself.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of caerulein and bombesin on the ethanol intake in the rat.

Male Wistar rats were allowed to drink either water or water mixed with ethyl alcohol (4%, 8% and 12%) as part of a water-deprived procedure. The decapeptide caerulein (1, 3 and 6 micrograms/kg i.p.), a cholecystokinin analog, decreased the intake of ethanol while the consumption of tap water remained unchanged in a choice paradigm. The addition of quinine (a bitter substance) in drinking bottles did not significantly modify the fluid consumption while the i.p. injection of caerulein produced a significant decrease in the consumption of the saccharin containing bottle. The i.p. administration of bombesin (10 and 20 micrograms/kg) failed to modify the intake of water or ethanol solution in water-deprived animals. Interpretations are given in terms of the action of the cholecystokinin analog on differences in the taste intensity induced by the beverage or in terms of a direct consequence of the caerulein-induced decreased gastric emptying effect leading to an accumulation of ethanol in the gut.

Similar potencies of CCK-8 and its analogue BOC(Nle28;Nle31)CCK27-33 on the self-stimulation behaviour both are antagonized by a newly synthesized cyclic CCK analogue.

Neurons with co-localized cholecystokinin (CCK) and dopamine (DA) are present predominantly in the ventral tegmental area (VTA) and project mainly to the caudal part of the medial nucleus accumbens. The activity of this dopaminergic system can be evaluated by means of the intracranial self-stimulation behaviour (ICSS) on male Wistar rats having chronic electrodes implanted into the medial forebrain bundle in the postero-lateral area of the hypothalamus. The direct injection of the CCK analogue BOC(Nle28;Nle31)CCK27-33 (BDNL-CCK7) into a lateral ventricle decreased the electrical self-stimulation of the medial forebrain bundle. Nevertheless, this decrease in self-stimulation was steeper (immediately after the injection vs a delay of +/- 5-10 min.) than the CCK8-induced ICSS depletion. The intracerebroventricular (ICV) injection of 150 pmol and 1000 pmol BC-197 (BOC-D.Asp-Tyr(SO3H)-Nle-D.Lys-Trp-Nle-Asp-Phe-NH2) was ineffective to modify the self-stimulation behaviour when administered alone while a 150 pmol BC-197 dosage was able to antagonize the decreasing effect of 150 pmol CCK-8 on ICSS. Nevertheless, a dosage 6 times as important, i.e. 1000 pmol BC-197, was needed to antagonize the depression induced by 150 pmol BDNL-CCK7 on ICSS behaviour. These results support the equipotence of BDNL-CCK7 to CCK-8 in decreasing the self-stimulation behaviour after their direct administration into the lateral ventricle. They further give evidence of the relevance of BC-197 in antagonizing the respective effects of both compounds on the ICSS.

Cortical Microvascular Changes in Chronological Aging, Cortical Insults and Chronic Alcohol-intoxication in Rats - Effects of Antihypoxic Drug On These Phenomena

Chronic alcohol pulmonary exposure in rats produced a cortical hypervascularization from one to four weeks after the onset of the alcoholization procedure. This alcohol-induced cortical hypervascularization, resembling closely the enhanced cortical vascular network observed in chronologically aged rats as well as around a lesion-induced cavity performed on the cortex, was significantly reduced by a concomitant treatment with Sabeluzole, a chemically benzothiazol derivative with antihypoxic and antiischaemic properties. The blood alcohol level of rats treated with the antihypoxic agent remained stable and constant at a mean level of 1 g/l during a whole 2-week-alcoholization duration in contrast to that of untreated rats which was directly related to the increased alcohol concentration of the atmosphere insufflated in the alcoholization chamber. Finally, a free-choice paradigm achieved after the chronic intoxication also revealed that Sabeluzole-treated rats chose to drink less alcohol as compared to untreated rats suggesting Sabeluzole well modulated the alcohol-induced behavioral preference.