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Serotonin and Carbachol Induced Suppression of Synaptic Excitability in Rat CA1 Hippocampal Area: Effects of Corticosteroid Receptor Activation (1998)

Hesen, W. ; Karten, Y. J. G. ; Van de witte, S. V. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Journal of neuroendocrinology 10 (1998), S. 0

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ISSN: 1365-2826

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Medicine

Notes: Serotonin (5HT) and the cholinergic analogue carbachol (CCh) act on neurons in the hippocampal CA1 area through pre- and post-synaptic receptors. Previously, it was shown that post-synaptic actions of 5HT and CCh are affected by corticosteroids: predominant activation of high affinity mineralocorticoid receptors resulted in small hyperpolarizing responses to 5HT and small depolarizing responses to CCh; additional activation of low affinity glucocorticoid receptors led to increased 5HT and CCh responses. In the present study, we examined the consequences of steroid modulation of these post-synaptic membrane effects and/or possible pre-synaptic effects by 5HT and CCh for the excitability in the CA1 area, using extracellular field potential or intracellular recordings from individual pyramidal neurons. Steroid treatment by itself did not affect the amplitude or paired pulse properties of synaptic responses. In slices from adrenally intact rats, both 5HT (3–30 μM) and CCh (1–10 μM) induced a dose-dependent suppression of the synaptic field responses evoked in the CA1 area by stimulation of the Schaffer collaterals. No changes in these transmitter effects were observed after adrenalectomy. The 5HT induced suppression of the population spike amplitude was, however, reduced after selective occupation of mineralocorticoid receptors. Intracellularly, no significant steroid dependent modulation of (pre-synaptic) 5HT evoked changes in synaptic responses was observed. These data suggest that the steroids modulate post-synaptic but not pre-synaptic 5HT effects and that this modulation is reflected in the excitability of the CA1 region. The CCh induced suppression of the population spike was not affected by corticosteroid receptor activation, indicating that the previously found steroid modulation of post-synaptic CCh effects has no clear consequences for the CA1 excitability.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2826.1998.00167.x

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Microsatellite Variation in Two Populations of Free-Ranging Yellow Baboons (Papio hamadryas cynocephalus) (1998)

St. George, D. ; Witte, S. M. ; Turner, T. R. ; [et al.]

Springer

International journal of primatology 19 (1998), S. 273-285

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ISSN: 1573-8604

Keywords: Papio ; microsatellite loci ; DNA polymorphism ; population structure

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We investigated genetic variation at six microsatellite (simple sequence repeat) loci in yellow baboons (Papio hamadryas cynocephalus) at two localities: the Tana River Primate Reserve in eastern Kenya and Mikumi National Park, central Tanzania. The six loci (D1S158, D2S144, D4S243, D5S1466, D16S508, and D17S804) were all originally cloned from and characterized in the human genome. These microsatellites are polymorphic in both baboon populations, with the average heterozygosity across loci equal to 0.731 in the Tana River sample and 0.787 in the Mikumi sample. The genetic differentiation between the two populations is substantial. Kolmogornov–Smirnov tests indicate that five of the six loci are significantly different in allele frequencies in the two populations. The mean F ST across loci is 0.069, and Shriver's measure of genetic distance, which was developed for microsatellite loci (Shriver et al., 1995), is 0.255. This genetic distance is larger than corresponding distances among human populations residing in different continents. We conclude that (a) the arrays of alleles present at these six microsatellite loci in two geographically separated populations of yellow baboons are quite similar, but (b) the two populations exhibit significant differences in allele frequencies. This study illustrates the potential value of human microsatellite loci for analyses of population genetic structure in baboons and suggests that this approach will be useful in studies of other Old World monkeys.