Learning-induced changes in D2 receptors of rat brain are sexually dimorphic

PubMed ID: 1409820Pharmacological agents known to stimulate monoamine systems improve memory, and destruction of the dopaminergic systems or dopamine depletion lead to impairments in various learning-related tasks. These reported effects of the central dopaminergic system imply the involvement of D2 receptors. The aim of the present study was to investigate changes in [3H]spiroperidol binding in seven areas of rat brain following informal and active avoidance learning. Littermate male and female rats were reared until 3 months of age in standard colony conditions and treated as active controls or in enriched environmental conditions and exposed to pole-jump active avoidance trials. Female rats acquired avoidance behavior more rapidly than males. Among the brain regions, only the hippocampus showed significant variations in D2 receptor binding between the groups; sex differences and learning-sex interaction were observed in the corpus striatum. There was an inverse correlation between learning performance and hippocampal D2 receptor binding. Our results show that learning affects hippocampal D2 receptors in a sexually dimorphic pattern. © 1992.This study was supported by Grant 1987/068 from Ege University Research Funds. The authors thank Hatice Arsoy for excellent assistance in behavioral testing. -

Sex difference in up-regulation of nicotine acetylcholine receptors in rat brain

PubMed ID: 9315514This study tested for sex differences in the effects of chronic nicotine administration and withdrawal on nicotine acetylcholine receptor binding in brain. Rats received nicotine (0.6 mg/kg, sc) or saline once daily fore 15 days, and were sacrificed 1 or 20 days after termination of treatment. Saturation studies of nAChR binding were performed using [3H]cystine as the radioligand in whole brains minus cerebellum taken from animals in the chronic treatment groups and from native rats. Male but not female rats that received chronic nicotine had higher receptor densities than corresponding control groups; up-regulation of nAChR was not seen 20 days after withdrawal. Furthermore, in groups that showed no up-regulation (controls and rats withdrawn for 20 days), nAChR densities were higher in female rats than males. The findings underscore the importance of sex differences in pharmacological responses as well as in basal neurochemical parameters

Free amino acid level determinations in normal and schizophrenic brain

PubMed ID: 27488561. Some disturbances in brain amino acids are reported with regard to pathological changes in schizophrenia: a reduction in GABA content and a reduced activity at some glutamatergic synapses. 2. Comparison of post-mortem brain tissue from control subjects and schizophrenic patients can provide evidence for amino acid alterations in disease. 3. The present study was undertaken to measure free amino acid concentrations in 20 brain regions obtained at autopsy, from normal persons and schizophrenics. Amino acids were extracted, esterified and separated by gas chromatography. 4. The distribution and levels of amino acids in normal persons is in accordance with similar values reported in human post-mortem brain samples by other investigators. 5. The differences in amino acids found in schizophrenic brain samples support the view of disturbed neurotransmission especially with regard to GABAergic and glutamatergic systems in schizophrenia and suggest the possible involvement of other amino acids as well. © 1989.:025/84This study was supported by the Ege University Research Foundation Grant No:025/84. -

Recovery of dopamine transporter binding and function after intrastriatal administration of the irreversible inhibitor RTI-76 {3ß-(3p-chlorophenyl)tropan-2ß-carboxylic acid p-isothiocyanatophenylethyl ester hydrochloride}

PubMed ID: 8858994Effects of in vivo, intrastriatal administration of RTI-76 {3ß-(3-p-chlorophenyl)tropan-2ß-carboxylic acid p-isothiocyanatophenylethyl ester hydrochloride}, an irreversible inhibitor of dopamine transporter (DAT) binding in vitro, on [125I]RTI-55 {3ß-[4-iodophenyl]tropan-2ß-carboxylic acid methyl ester tartrate} binding to striatal DAT in vitro were examined in male rats. Effects on [3H]DAT and D1 dopamine receptor binding in vitro after intrastriatal RTI-76 injection were also determined. One hour after direct intrastriatal injection, RTI-76 caused a dose-related increase in KD for [125I]RTI-55 binding in vitro in striatal tissue, without affecting transporter maximum binding (Bmax). In contrast, 24 hr after administration, RTI-76 caused a dose-related decrease in striatal DAT Bmax without affecting KD, a decrease that reversed over the next several days. Transport of [3H]dopamine into synaptosomes was decreased similarly. Intrastriatal injection of reversible inhibitors of DAT, such as cocaine or WIN-35428 {3ß-[4-fluorophenyl]tropan-2ß-carboxylic acid methyl ester tartrate}, was without effect on transporter binding 1 and 6 days after administration. RTI-76 had little effect on [3H]SCH-23390 {R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine} binding 1 or 24 hr after intrastriatal injection, indicating at least some selectivity of RTI-76 for DAT. The RTI-76-induced decrease in Bmax, as well as the concurrent decrease in [3H]DAT, were reversible, with the T1/2 of transporter recovery estimated to be 6 days

Learning induces changes in the central cholinergic system of the rat in a sexually dimorphic pattern

PubMed ID: 1522028The involvement of the central cholinergic system in learning and the possible sexual dimorphism in related brain responses were investigated. Rats were exposed to different environmental conditions and to active avoidance learning. The resulting changes were studied using the following approaches: muscarinic receptor binding (MRB), acetylcholinesterase (AChE) and choline acetyltransferase (CAT) activities. The statistical evaluation of the data reveal that learning induces changes, especially in the postsynaptic component of the central cholinergic system, which shows some sexual dimorphism, and that males and females respond with different levels of increased cholinergic activity to informal and associative learning. © 1992.1987/067s studyw as supportedb y the Ege Univer-esearchF oundation Grant No: 1987/067. The authors thank Mrs. Hatice Arsoy for her excellenta ssistancein learningt rials. -

The effect of clomiphene citrate on osteoporosis in ovariectomized rats

PubMed ID: 18193254Objective: The aim of this study was to investigate whether clomiphene citrate (CC) administration could be a new therapeutic agent in case of contraindication of estrogen therapy for hormone-dependent osteoporosis and to show the changes in bone structure by histomorphometric analysis in ovariectomized rats administered CC. Study design: This study was carried out in the Experimental Surgery Laboratory of the Brain Research Centre of the Medical Faculty of Ege University. Four-month-old Sprague-Dawley rats were used for the experiment. The study was carried out on six groups of animals each consisted of eight rats. Four groups of rats were ovariectomized and 2 groups of rats were used as control group. For 6 weeks every day, rats were injected physiological saline solution (1 ml/kg), clomiphene citrate (1 or 10 mg/1 ml/kg, Organon), 17ß-estradiol (50 µg/1 ml/kg, within susame oil, Sigma) or susame oil (1 ml/kg, Sigma). Drug administrations were carried out according to the weekly weight measurements. Group 1(PSS), n = 8, non-ovariectomized, were injected with physiological saline solution. Group 2(CC-1), n = 7, non-ovariectomized, were injected with CC (1 mg/1 ml/kg). Group 3(OVX + CC-1), n = 7, ovariectomized, were injected with CC (1 mg/1 ml/kg). Group 4(OVX + CC-10), n = 6, ovariectomized, were injected with CC (10 mg/1 ml/kg). Group 5(OVX + E), n = 8, ovariectomized, were injected with 17ß-estradiol (50 µg/1 ml/kg). Group 6(OVX), n = 8, ovariectomized, were injected with susame oil (1 ml/kg) Bone-specific serum alkaline phosphatase (ALP) levels were measured and statistical analyses were made by Kruskal Wallis test. Left femur bone histomorphometric studies were done. The uteri were dissected out to measure their weight and ANOVA was used to show the intergroup differences. Results: The level of ALP in group 3 was significantly higher than the other five groups. Bone histomorphometric examination showed that total bone volume in group 3, 4, and 5 was higher than group 6, and group 4 had the highest level of bone volume compared to the rest of the groups. Uterus weights in group 1 were significantly higher than group 3 and 6 (P = 0.02, P = 0.01) and uterus weights in group 5 were significantly higher than group 3 and 4 (P = 0.00, P = 0.01) Conclusions: In ovariectomized rats, treatment with CC is seen as effective as estrogen treatment in preventing osteoporosis, without causing uterin hyperstimulation. Nevertheless, further investigations on more rats are needed to assess whether it is an alternative treatment method to estrogen. © 2007 Springer-Verlag