Roman Tashev

Antinociceptive effect of somatostatin microinjected into caudate putamen.

The effects of somatostatin microinjected bilaterally and unilaterally (left or right) at a dose of 10, 50 and 100 ng into the caudate putamen of male Wistar rats on nociception (analgesy-meter test) were studied. Somatostatin injected into caudate putamen resulted in analgesia. Bilateral microinjections of somatostatin significantly increased the pain threshold in a dose-dependent manner, i.e. somatostatin exerted antinociceptive effect. The pain threshold after left-side microinjections was significantly higher than that after injections into right-side. These findings suggest antinociceptive and asymmetric effects of somatostatin on pain in the caudate putamen.

Gastric antisecretory effects of synthetic cannabinoids after central or peripheral administration in the rat.

Previous studies have revealed that cannabinoid (CB)-receptor agonists inhibit gastric acid secretion stimulated by indirectly acting agents, but not by histamine. Aiming to investigate whether central or peripheral mechanisms are involved, the effects of the synthetic CB-receptor agonists WIN55,212-2 and HU-210, administered either intracerebroventricularly (i.c.v.) or intravenously (i.v.) to the anaesthetized rat with lumen-perfused stomach, against gastric acid secretion induced by pentagastrin were tested. Injected i.c.v., both WIN55,212-2 (50 and 100 microg/kg) and HU-210 (25, 50 and 100 microg/kg) were ineffective on either basal secretion or acid output induced by pentagastrin (7.7 microg/kg, i.v.). By contrast, i.v. injections of WIN55,212-2 (100 and 1000 microg/kg) or HU-210 (10-100 microg/kg) significantly inhibited pentagastrin-induced acid secretion, maximal reductions being 75.70 and 82.24% for WIN55,212-2 and HU-210, respectively. The gastric antisecretory effect of HU-210 was prevented by administration of the selective CB(1)-receptor antagonist SR141716A (1000 microg/kg, i.v.). These results show that CB(1)-receptors mediating inhibition of gastric acid secretion in the rat are mainly peripherally located.

Hippocampal asymmetry in serotonergic modulation of learning and memory in rats.

The modulation of learning and memory after left or right microinjections of the selective 5-HT1A receptor agonist 8-OH-DPAT and of the 5-HT1A receptor antagonist NAN190 into the hippocampal CA1 area of male Wistar rats was studied. Microinjections of 8-OH-DPAT (1 µg) into the right or left CA1 hippocampal area produced a significant decrease in the number of avoidances in a shuttle box. The impairing effect of 8-OH-DPAT was more pronounced when injected into the right hippocampus compared to the left one. Microinjections of NAN190 (1 µg) into the right or left CA1 hippocampal area produced a significant increase in the number of avoidances in a shuttle box. Right microinjections of NAN190 increased the number of avoidances more strongly than compared to left injections. These effects on learning and memory were more pronounced after injection of either of the serotonergic agents into the right CA1 hippocampal area compared to the left. The stronger memory-modulating effect after injection of 8-OH-DPAT or NAN190 into the right CA1 hippocampal area suggests a rightward bias in the rat.

Differential involvement of hippocampal vasoactive intestinal peptide in nociception of rats with a model of depression

The effects of VIP microinjected unilaterally (left or right) into the hippocampal CA1 area at a dose of 10 and 100 ng or bilaterally (10 ng), on nociception of male Wistar rats with a model of depression (bilateral olfactory bulbectomy-OBX) were studied. Nociception was examined applying mechanical pressure on the left hind paw of the rat (analgesy-meter test). It was found that in OBX rats the pain threshold is increased. VIP showed differential effects depending on the side and dose of administration. The pain threshold after left-side microinjections of VIP into the hippocampal CA1 area of OBX rats was significantly higher than that after injections into right-side. There are no significant differences between right-side VIP-treated and OBX rats. Bilateral microinjections of VIP also exerted antinociceptive effect. These findings suggest that the hippocampal lateralized antinociceptive effect of VIP in OBX rats depends on the hemisphere of injection and suggest that VIP-ergic neurons in the hippocampal CA1 area may play differential role in nociception of rats with a model of depression.

Behavioral effects of somatostatin microinjected into caudate putamen.

The present study examined the behavioral responses to bilateral microinjections of somatostatin (SRIF) into caudate putamen of male Wistar rats. SRIF locally administered at doses of 10, 50 and 100 ng/side dose-dependently affected locomotor activity, as reflected in both horizontal and vertical movements. SRIF modulated locomotor activity in a biphasic manner, exerting an inhibitory and a facilitatory effect. In the elevated plus-maze experiments, SRIF at doses of 50 and 100 ng/side microinjected bilaterally into caudate putamen decreased only the total number of entries in the open and closed maze arms, confirming the suppressing effect of SRIF on locomotion at the first 5 min.

Hippocampal asymmetry in exploratory behavior to vasoactive intestinal polypeptide

The effects of vasoactive intestinal polypeptide (VIP) microinjected uni- or bilaterally into the CA1 hippocampal area of male Wistar rats at a dose of 10, 50 and 100 ng on exploratory behavior were examined. VIP microinjected bilaterally at a high dose (100 ng) significantly decreased the horizontal movements, while at low doses (10 and 50 ng) had no effect on the exploratory activity. Microinjections of VIP into the left hippocampal CA1 area at doses 50 and 100 ng suppressed the exploratory activity, while right-side VIP administration at a dose 100 ng significantly increased horizontal movements compared to the respective controls. Vertical activity was stimulated only by VIP administered into the right hippocampal CA1 area at the three doses used. Neither bilateral nor left injections of VIP induced changes in the vertical movements. The main finding was the presence of hippocampal asymmetry in exploratory behavior to unilateral microinjections of VIP depending on the dose and the microinjected hemisphere.

Differential effects of somatostatin on exploratory behavior after unilateral injections into rat neostriatum

The effects of somatostatin (SRIF) microinjected unilaterally (left or right) at a dose of 10, 50, and 100 ng into the neostriatum of male Wistar rats on exploratory behavior were studied. Unilateral injections of SRIF suppressed dose-related the exploratory activity as decreased the number of horizontal and vertical movements compared to the respective controls. The effect was more pronounced when SRIF was microinjected into the right neostriatum as compared to the left neostriatum. These findings suggest some asymmetric effects of SRIF, depending on the dose and the microinjected hemisphere.

Lateralized learning and memory effects of vasoactive intestinal peptide infused into the rat hippocampal CA1 area

The effects of VIP microinjected unilaterally (left or right) and bilaterally (left and right) at a dose of 50 ng into hippocampal CA1 area of male Wistar rats on learning and memory (shuttle-box) were studied. Bilateral VIP microinjections impaired learning and memory, i.e., decreased the number of avoidances during the second training day and memory tests, compared to the respective controls. When infused into the left CA1 area, VIP exerted a marked inhibitory effect. Right-side VIP microinjections did not change the number of avoidances during the learning and memory tests. Compared to the right-side, left-side VIP infusions provoked a threefold decrease of the number of avoidances on the second training day and on the memory tests (24 h after the 2nd training day and on 7th day). These findings reveal lateralized inhibitory effects of VIP on cognitive processes in hippocampus.

Memory Effects Of Aronia Melanocarpa Fruit Juice In A Passive Avoidance Test In Rats

ABSTRACT AIM: To study the effect of Aronia melanocarpa fruit juice on memory in male Wistar rats. MATERIALS AND METHODS: The juice was administered orally for 7, 14, 21 and 30 days at doses of 2.5 ml/kg, 5 ml/kg and 10 ml/ kg. Memory was assessed in the one-way passive avoidance task (step through) which consisted of one training session and two retention tests (3 hours and 24 hours after training). The variables measured were the latency time to step into the dark compartment of the apparatus and the learning criterion (remaining in the illuminated compartment for at least 180 sec). RESULTS: Oral administration of Aronia melanocarpa fruit juice for 7 and 14 days resulted in a dose-dependent tendency to increase the latency time and the learning criterion compared to saline-treated controls but the effect failed to reach statistical signifi cance. After 21 days of treatment, the juice dose-dependently prolonged the latency time at the retention tests, the effect being significant at doses of 5 ml/kg and 10 ml/kg. Applied for 30 days, the juice in all the tested doses increased signifi cantly the latency time at the retention tests and the dose of 10 ml/kg significantly increased the percentage of rats reaching the learning criterion. CONCLUSION: These fi ndings suggest that Aronia melanocarpa fruit juice could improve memory in rats. The effect is probably due to the polyphenolic ingredients of the juice which have been shown to be involved in learning and memory processes. РЕЗЮМЕ ЦЕЛЬ: Настоящая работа ставит себе целью исследовать эффект сока Aronia melanocarpa на память мужских крыс породы Wistar. МАТЕРИАЛЫ И МЕТОДЫ: Плодовый сок Aronia melanocarpa применен перорально в течение 7, 14, 21 и 30 дней в дозах 2.5 мл/кг, 5 мл/кг и 10 мл/кг. Память оценивали с помощью метода обучения однонаправленному пассивному избежанию - step through, состоящему из одной тренировочной сессии и двух тестов, предназначенных для определения памяти (3 часа и 24 часа после тренировки). Прослежены латентное время перехода в темное отделение аппарата и критерий обученности (оставание в освещенное отделение не менее 180 секунд). РЕЗУЛЬТАТЫ: Применен в течение 7 и 14 дней сок Aronia melanocarpa вызывает доза-зависимую тенденцию к повышению латентного времени и критерия обученности по сравнению с контрольной группой крыс, получившей физиологический раствор, но эффект оказался статистически незначительным. После применения сока в течение 21 дня доза-зависимо удлиняет латентное время в тестах для определения памяти, при чем эффект статистически значим при дозах 5 мл/кг и 10 мл/кг. После 30-идневного применения все исследованные дозы сока значимо удлиняют латентное время в тестах для определения памяти, а доза 10 мл/кг значимо увеличивает и процент крыс, достигших критерия обученности. ЗАКЛЮЧЕНИЕ: Полученные авторами результаты показывают, что сок Aronia melanocarpa может улучшить память крыс. Этот эффект вероятно можно объяснить полифенольными составляющими сока, о которых доказано, что участвуют в процессах обучения и памяти.

EFFECTS OF ACUTELY APPLIED CANNABINOID CB1 LIGANDS ON NOCICEPTION IN RATS WITH A MODEL OF DEPRESSION

The effects of CB1 receptor agonist HU-210 and cannabinoid CB1 receptor antagonist SR 141716A on nociception of male Wistar rats with a model of depression (bilateral olfactory bulbectomy, OBX) were studied. HU-210 (5 g) and SR 141716A (3 g) were acutely microinjected i.c.v. on the developed depression background. Nociception was examined as applied mechanical pressure on the left hind paw of the rat (analgesy-meter test, Randall & Sellitto). In the OBX rats, it was found that the pain threshold was increased. HU-210 significantly increased the pain threshold in OBX rats, i.e. decreased the pain sensitivity as compared to saline-treated OBX controls and to sham-operated controls, suggesting an implication of CB1 receptors in nociception of OBX rats. SR 141716A did not affect the nociception in OBX rats. These results suggest that stimulation of CB1 receptors in rats with a model of depression exerted antinociceptive effect.