Brain research
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The interactions of a steroid anaesthetic, alphaxalone, with the GABA receptor-ionophore complex were investigated by two different experimental approaches. In the rat cuneate nucleus slice, alphaxalone (0.1-10 microM) potentiated depolarizing responses to superfused GABA and muscimol, but not those to glycine. The potentiating effect of alphaxalone was unaltered by the benzodiazepine antagonist Ro 15-1788. ⋯ Analysis of binding curves for [3H]muscimol indicated that the steroid anaesthetic increases the affinity for [3H]muscimol of low affinity binding sites; this property is shared by pentobarbitone. The physiologically inactive beta-hydroxy isomer of the steroid was without activity in either of the experimental situations at 30 microM. It is suggested that alphaxalone and pentobarbitone share a common mode of action on the GABA system, which may be relevant to the mechanisms by which these drugs produce anaesthesia.
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Data obtained from neonatally treated rats are fairly consistent. However, there is disagreement as to whether mechanical and thermal nociceptive thresholds are elevated or unchanged in this group. There are at least two major areas of disagreement in adult animal capsaicin research. ⋯ Capsaicin-induced SP depletion in neonates is permanent. Systemic administration to adult depleted SP from much the same areas as observed in neonates, but all areas but the medulla exhibited a slow, regional recovery. Intraventricular injection of capsaicin depleted SP in the adult medulla only, while other SP-containing areas affected by systemic injection remained intact.(ABSTRACT TRUNCATED AT 400 WORDS)