Environment and central neurotransmitters in relation to learning, memory and behavior

Comparison of the inhibitory action of aminobeclamide and beclamide on socially offensive behaviour

The inhibitory effects of aminobeclamide (N-(p-aminobenzyl)-beta-chloropropionamide) on socially offensive behaviour has been studied and compared with those of the parent drug beclamide (N-benzyl-beta-chloropropionamide). Following oral administration in mice which had been individually housed for a 28 day period then paired with normal group-housed opponents, aminobeclamide and beclamide both produced significant and dose-related inhibition of socially offensive behaviour. Aminobeclamide (20-150 mg kg-1 p.o.) and beclamide (50-250 mg kg-1 p.o.) gave increased offense onset latency whilst at the same time they reduced the incidence of offense encounters/animal and decreased the group percentage of animals displaying offense behaviour. It is likely that both drugs have similar monoamine modifying effects though this animal study suggests that aminobeclamide is 1.5 to 2.7 times more potent than beclamide against socially offensive behaviour.

Neurochemical changes in experimental African trypanosomiasis in voles and mice

Dopamine, norepinephrine, serotonin and related metabolites were measured in the brain of meadow voles and mice after infection with Trypanosoma brucei gambiense with the goal of understanding the neurochemical changes accompanying infection with this parasite. Serotonin and 5-HIAA levels both fell by 26%, and HVA levels rose by 56%, in vole brains during infection. Dopamine, DHPG and norepinephrine levels, however, remained unchanged. In mice, serotonin levels dropped by 17 and 23%, respectively, in the pons-medulla and midbrain regions after infection; 5-HIAA and dopamine levels remained unaffected by infection in mice. The possible causes and the significance of these changes are discussed.

Changes in brain concentrations of catecholamines and indoleamines in Toxoplasma gondii infected mice

Brain concentrations of dopamine, homovanillic acid, norepinephrine, serotonin and 5-hydroxyindoleacetic acid were measured in mice with acute and chronic, adult-acquired toxoplasmosis. Mice with acute infections showed a 40% rise in homovanillic acid levels as compared with controls; dopamine levels, however, remained unchanged. Norepinephrine levels in this group were 28% lower than in controls. Dopamine levels were 14% higher in the mice with chronic infections than controls. Serotonin and 5-HIAA levels were not altered in infected mice. These neurochemical changes may be factors contributing to mental and motor abnormalities that accompany or follow toxoplasmosis in rodents and possibly in man.

Effects of African trypanosomiasis on brain levels of dopamine, serotonin, 5-hydroxyindoleacetic acid, and homovanillic acid in the rabbit

Serotonin (5-HT) levels fell by 21% in the mid-brain-thalamus-hypothalamus (MTH) region of the rabbit brain after chronic infection with the protozoan Trypanosoma brucei gambiense. 5-HT did not decrease significantly in the caudate/putamen (CP) or the pons/medulla (PM) region. 5-Hydroxyindoleacetic acid (5-HIAA) levels were unchanged in the MTH and caudate/putamen (CP) but increased by 17% in the pons/medulla (PM) after infection. Dopamine (DA) levels rose by 19% and homovanillic acid (HVA) by 33% in the PM during infection. DA and HVA tended to be lower in the CP of infected rabbits, but the apparent decreases were not statistically significant. DA and HVA levels in the MTH were also unchanged by infection. These neurochemical changes may be involved in the behavioral symptoms that frequently accompany this disease in man and cattle.

Behavioural comparisons between individually- and group-housed male rats: effects of novel environments and diurnal rhythm

Individually-housed rats, when compared with group-housed controls, have been previously shown to be hyper-reactive when exposed to an openfield at the beginning of the dark-phase; this was not due to elevated spontaneous activity. In the present experiments locomotor and rearing activities were determined immediately after exposing animals to a novel environment, and after 6 and 24 h of habituation to the test-environment. Additionally, after 24 h of adaptation, animals' responses towards a modification of the test-environment were examined. Four parallel experiments were carried out, each starting at a different time in the light/dark cycle. Individually-housed rats were hyper-reactive in novel environments and showed a slower habituation at all time points tested. Part of behavioural parameters show clearcut day/night variations, but differences between individually- and group-housed rats do not seem to be influenced by the time of day.

Synaptosomal uptake studies on recombinant inbred mice; neurotransmitter interaction and behavioral correlates

The uptake of noradrenaline, choline and GABA into whole brain synaptosomes from the mice inbred strains C57BL/6By, BALB/cBy, their reciprocal crosses and seven recombinant inbred strains derived from the F2 crosses was measured in order to study the relation between different neurotransmitter systems and their possible correlations with behavioral parameters. Analysis of variance demonstrated significant differences in both Vmax and Km for each substrate between the inbred strains studied. Only the Km for GABA uptake did not reach significance although a strong trend (P = 0.07) was apparent. For none of the uptake parameters clear strain distribution patterns were found. A positive phenotypic as well as genotypic correlation was found between the Vmax and Km for noradrenaline, choline and GABA uptake. A genetic analysis showed a positive correlation between the Vmax for noradrenaline and choline uptake. Since prior to these neurochemical studies, all subjects were tested in a variety of behavioral paradigms, phenotypic and genotypic correlations between behavioral and neurochemical parameters could be calculated. The most consistent correlations were found between noradrenaline and choline uptake and water consumption and the preference ratio as measured in a conditioned taste aversion test.