Experimental animal models can be used to help understand how oestrogen modulates autoimmune arthritis. We have previously shown that castration of female DBA/1 mice exaggerates arthritis induced with type II collagen. This report shows that treatment of castrated DBA/1 mice with low doses (0.2 micrograms twice a week) of beta-oestradiol reduces the incidence (37% vs 78% in controls) and severity (3.9 vs 5.6 mean scores) of arthritis. Levels of IgG anti type II collagen antibodies are decreased whereas levels of IgM antibodies are increased in the beta-oestradiol treated mice. The T cell response, as measured by a 3H-thymidine assay, is reduced in the beta-oestradiol treated mice. The results suggest that treatment with low doses of beta-oestradiol exerts a suppressive effect on both development of collagen arthritis as well as T cell dependent immune reactivity towards type II collagen.
This study examined the functional effects of long-term elevated brain GABA concentrations. The increase in GABA was achieved by use of the GABA-aminotransferase (GABA-T) inhibitor, ethanolamine O-sulphate (EOS). Forms of exploratory behaviour pre viously demonstrated to be sensitive to GABAergic receptor stimulation were measured over a 4 week period of EOS treatment. The most pronounced behavioural effect was an increased duration of investigating behaviour following 2-21 days of EOS treatment. This effect was accompanied by an accumulation of GABA in the substantia nigra and the corpus striatum. After 28-30 days of EOS treatment the GABA concentration was still significantly elevated, whereas the investigating behaviour was no longer different from controls.
Abstract: There is an increasing demand for appropriate methods for analysing the pharmacological and toxicological action of chemical agents on behavioural patterns. The present study describes a non‐instrumental approach to the study of exploratory and socio‐sexual behaviours in the laboratory male rat. The behaviours were differentiated in terms of latency of onset, incidence, frequency and duration. Castrated and intact males were tested under three defined test situations. One test was focused on exploratory behaviour and two tests in which the male encountered an oestrous female or a castrated male were set up to study social and sexual behaviours. A multivariate statistical method was used to analyse differences in the behavioural profiles observed in the different tests. The data show that simultaneous recording of several spontaneous behaviours may be a useful technique for investigating how a compound influences behavioural processes.
The capacities of 11 progestins to induce general anesthesia and to activate estrous behavior were studied in the ovariectomized rat. The lordosis response was used as an indicator that the female was in heat. The different progestins were administered subcutaneously 48 hr after a standard dose of estradiol benzoate, 2.5 μg/kg. The loss of the righting reflex after intravenous injection of the steroids tested was used as a criterion of anesthetic action. No correlation was obtained between the efficiency of the injected progestins to activate estrous behavior and their ability to induce general anesthesia. On the contrary, a positive correlation was revealed on comparison of the data in the estrous behavior assay and the ability to maintain pregnancy in the spayed rat. It is suggested that progesterone activates estrous behavior in the estrogen-treated ovariectomized rat by a specific action on the central nervous system which is different from the general anesthetic effect. (Endocrinology81: 369, 1967)
Vasopressin-containing neurosecretory cells are partly regulated by GABAergic neurons present both at the hypothalamic and the pituitary level. In the present work, we compared GABA effects on vasopressin release from posterior pituitaries of Sprague-Dawley (SPD), Wistar (W), Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Release of vasopressin was studied in vitro by placing neurointermediate lobes in perfusion chambers. It was stimulated twice by 50 mM KC1 (S1 and S2) and the ratio between the first and the second stimulation was calculated (S2/S1). The basal and stimulated release of vasopressin was enhanced in the SHR. There was no difference in vasopressin content in the pituitary between the WKY and the SHR but the levels were lower compared to the SPD rat. Muscimol, a GABA-A receptor agonist, was added during S2. Muscimol inhibited in a dose-dependent manner the stimulated release of vasopressin, with an ED50 about 3 µM. The effect of muscimol was not statistically different between the strains expressed in ratios. The actual inhibition was apparently greater in the SHR, as both basal and stimulated vasopressin release was larger.
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