Biomedical subjects
Publications and source records attributed to B Sparf.
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This study was undertaken with the aim of determining whether the postsynaptic alpha-adrenergic receptor population of the cat urethra differed from that of other isolated tissues (rabbit aorta and rat vas deferens) and if so the possibility of selectively affect these receptors. For this purpose the substances 2-methylammonio-1-(spiro[cyclopentane-1,1'-indene]-3'-yl)ethanol (KABI 2023), noradrenaline (NA) and dopamine (DA) were used. KABI 2023 and NA acted as full agonists on all three tissues investigated. DA was a full agonist on the vas deferens but was almost inactive on urethra. The contractile response of urethra to KABI 2023 was of an alpha-adrenergic nature, as it could be blocked with phentolamine. Compared with NA, KABI 2023 showed a 10 times higher selectivity for the receptors of urethra than for those of aorta. Affinity constants (log KB) for phentolamine and haloperidol with use of the various agonists were estimated. The affinity of phentolamine was found to be significantly different when using NA and KABI 2023 as agonists on the urethra but not on the aorta. Corresponding findings were obtained with haloperidol. On the vas deferens a greater difference in log KB values than that on the urethra was found. On the basis of the results, it is suggested that the population of postsynaptic alpha-adrenoceptors in the urethra (cat) differs from that in the aorta (rabbit). On the vas deferens a heterogenicity of postsynaptic receptors seem to exist which makes the interpretation of the results more difficult on this organ. In the presence of phentolamine and haloperidol the maximum responses to NA were potentiated on the aorta and vas deferens, but not on the urethra. Investigations to evaluate this difference are now in progress.
The effects of prolonged treatment with phenobarbital, diazepam, and oxazepam on behaviour and on the plasma half-life of antipyrine have been studied in the dog. In this species the biotransformation of diazepam and oxazepam is known to be very similar to man. After equipotent doses of phenobarbital (25 mg/kg) and diazepam (35 mg/kg), antipyrine half-life was found to decrease 80 and 40%, respectively, while after treatment with oxazepam (150 mg/kg) there was an increase of 20%. The behavioural effects declined in the dogs during the course of treatment with diazepam but were rather constant during treatment with oxazepam.
The effect of atropine on the acetylcholine (ACh) turnover in the mouse brain has been studied and related to the central effect (motor activity) of the drug. At the threshold dose for maximal increase in motor activity, atropine had no measurable effect in the brain on the initial rate of formation of labelled ACh from labelled choline (Ch) i.v. injected. However, if atropine was injected 3 min after the injection of labelled Ch, when the labelled ACh had reached its peak value in the brain, there was a more rapid exponential decline of labelled ACh. This was assumed to be an indication that atropine increases the turnover of ACh in the brain. The specific radioactivity of ACh was not changed 2-17 min after the atropine injection, which indicates that atropine does not preferentially increase the release of newly synthetized ACh.