Antagonism of xylazine plus chloral hydrate loss of the righting reflex in mice. A simple in vivo procedure for the evaluation of selective alpha 2-adrenoceptor antagonists

Xylazine-evoked depression of rat cerebral cortical neurons: a pharmacological study

1. Iontophoretic application of the veterinary tranquilizer xylazine suppressed the spontaneous firing of 134/137 neurons tested, an effect not antagonized by adenosine receptor and alpha-adrenergic receptor blocking agents. 2. Depressions in neuronal activity evoked by norepinephrine, gamma-aminobutyric acid or adenosine failed to be potentiated by xylazine. 3. However, the excitatory effects of acetylcholine and glutamate were both inhibited by xylazine. 4. Thus, the depressant effect of locally applied xylazine may involve a decrease in the excitability of the neuronal membrane.

Effect of intravenously-administered putative and potential antagonists of ethanol on sleep time in ethanol-narcotized mice

Groups of male CD-1 mice (n = 12/group) were injected intraperitoneally (IP) with 5 g ethanol/kg of body weight. After loss of righting reflex, they were given vehicle or one of 2-3 doses of reputed or potential antagonists of ethanol intravenously (IV). Sleep time was measured from loss to return of righting reflex. Mean sleep time (MST) was increased significantly (P less than 0.05) by a large dose of dl-amphetamine (24 mg/kg) and by 4-aminopyridine (1, 5 mg/kg). Significant (P less than 0.01) increases were also produced by small and large doses of aminophylline (25, 100 mg/kg) and by yohimbine (1, 5 mg/kg). MST was not altered significantly by small and medium doses of dl-amphetamine (6, 12 mg/kg), a medium dose of aminophylline (50 mg/kg), or by any doses of naloxone, thyrotropin-releasing hormone, propranolol, physostigmine, doxapram, or Ro 15-4513. When Ro 15-4513 was given IP 15 minutes before ethanol (n = 6/group), onset and duration of narcosis were not altered. None of the compounds tested was an effective IV antidote for deep ethanol narcosis because of drug side effects, toxicity, prolongation of MST, or insufficient shortening of MST.