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Biomedical subjects

E Marley

Publications and source records attributed to E Marley.

At least 55 records · Page 3Linked to original sources
PubMed1972

Effects of catecholamines and adenosine derivatives given into the brain of fowls.

1. Adult fowls (Gallus domesticus) with cannulae chronically implanted into the IIIrd cerebral ventricle and various other sites of the brain received microinfusions or injections of catecholamines, adenosine, 3',5'-cyclic AMP or its dibutyryl derivative. The effects of these substances on behaviour, electrocortical activity and body temperature were studied.2. Behavioural and electrocortical sleep with fall in body temperature were obtained with intraventricular noradrenaline, alpha-methylnoradrenaline and isoprenaline; dopamine was ineffective. The doses required to elicit sleep were smaller than those affecting body temperature. Following mebanazine, the effects of noradrenaline were prolonged and doses of dopamine, previously ineffective, lowered body temperature and induced behavioural and electrocortical sleep.3. Noradrenaline, alpha-methylnoradrenaline, isoprenaline and dopamine infused into the hypothalamus induced sleep and lowered body temperature. Effective doses of noradrenaline, alpha-methylnoradrenaline and isoprenaline infused into the hypothalamus were one-twentieth to one-fifth those for intraventricular injection. Tachypnoea developed with isoprenaline and dopamine. Additionally with dopamine, there was deviation of the head to the contralateral side, together with repetitive jerking movements of the head. These effects were prolonged and intensified by mebanazine, whereas the involuntary movements with dopamine were greatly reduced by haloperidol.4. Involuntary movements, but without sleep, were induced by infusing dopamine into the paleostriatum augmentatum; noradrenaline infused into this site was ineffective.5. In three of five fowls pretreated with aminophylline, 3',5'-cyclic AMP infused into the hypothalamus induced behavioural and electrocortical sleep; without aminophylline pretreatment, 3',5'-cyclic AMP was ineffective. Adenosine infused into the hypothalamus, following pretreatment of fowls with aminophylline, consistently induced behavioural and electrocortical sleep. Dibutyryl cyclic AMP infused into the hypothalamus of intact fowls elicited behavioural arousal, followed by bursts of electrocortical spikes (6 Hz) over both cerebral hemispheres, spikes subsequently becoming regular at 1 Hz. Clonic limb and body movements occasionally accompanied the bursts of spike activity, infrequently developing into convulsions. In fowl encéphale isolé preparations, in which dibutyryl cyclic AMP was infused into the hypothalamus, spike activity was confined to the ipsilateral hemisphere.

Adenosine↗
PubMed1972

Effects of muscarine given into the brain of fowls.

1. The effects of muscarine, given intraventricularly, in adult conscious fowls (Gallus domesticus) or microinfused into various brain regions of conscious young chicks, were tested on behaviour, electrocortical activity and respiratory rate. Its effects given intraventricularly or intravenously to anaesthetized fowls were also examined.2. After intraventricular injection, muscarine elicited immediate behavioural and electrocortical arousal; body temperature was unaffected. After a delay of 30-40 min, tachypnoea developed together with postural changes which included partial abduction of the wings away from the trunk, the back and tail becoming horizontal. These effects were prevented by intravenous or intraperitoneal atropine or hyoscine, but not by pempidine or methylatropine, and were potentiated by physostigmine. Hyoscine given intraventricularly or intravenously did not affect electrocortical activity.3. Intraventricular muscarine given to anaesthetized adult fowls produced brief apnoea. On return of respiration, amplitude of respiratory excursion was diminished for about 5 min; tachypnoea did not develop. Blood pressure also rose briefly. With larger doses of intraventricular muscarine, large amplitude electromyographic potentials developed in the dorsal neck muscles followed later by side-to-side neck movements.4. Muscarine given intravenously to anaesthetized adult fowls, raised blood pressure and perfusion pressure in a perfused hind limb, an effect most likely due to secretion of adrenal medullary catecholamines; these pressor effects were prevented by pempidine and phenoxybenzamine. Given directly to the perfused hind limb, muscarine lowered perfusion pressure.5. In young chicks, muscarine microinfused into the diencephalon or myelencephalon elicited intense bilateral electrocortical alerting associated with periods of alternating violent motor activity and quiescence. Microinfusion of muscarine into the telencephalon induced ipsilateral electrocortical desynchronization without affecting behaviour. These effects of muscarine were prevented by intravenous, intraperitoneal or intracerebral hyoscine, but once its effects were established could be antagonized only with difficulty; pempidine did not prevent these effects. Microinfusions of muscarine into the brain did not affect posture, respiration or temperature.

Alkaloids↗
PubMed1971

Actions of dexamphetamine and amphetamine-like amines in chickens with brain transections.

1. A method for preparing the encéphale isolé preparation in young fowls is described. Certain important differences were found between electrocortical activity of chicken and mammalian encéphale isolé preparations. Electrocortical effects of excitant sympathomimetic amines and their antagonism were readily quantified because of stable electrocortical activity of the chick encéphale isolé preparation.2. Amphetamine-like excitant amines ((+)- and (-)-amphetamine, alpha-methyltryptamine, tryptamine, beta-phenethylamine, cyclopentamine, beta-tetrahydronaphthylamine and tuaminoheptane) evoked electrocortical desynchronization in chick encéphale isolé preparations, confirming the central origin of these effects. Behavioural changes were also observed.3. The electrocortical response to these amines was antagonized by methysergide, a selective tryptamine antagonist and by a catecholamine, alpha-methylnoradrenaline. Behavioural changes were also antagonized.4. Electrocortical desynchronization to dexamphetamine was prevented by an anterior transection of the brain which separated the telencephalon from the diencephalon. More posterior transections reduced the duration of the electrocortical response to dexamphetamine; intensity of response was either increased or decreased.

Amines↗
PubMed1970

Mode of action of alpha-methylnoradrenaline on temperature and oxygen consumption in young chickens.

1. Temperature, oxygen consumption, electromyographic activity, plasma non-esterified fatty acids and blood sugar were estimated in conscious unrestrained young chickens under conditions of thermoneutrality (31 degrees C) and below thermoneutrality (16 degrees C). In some chickens carotid arterial pressure was also recorded.2. At thermoneutrality, alpha-methylnoradrenaline lowered temperature and oxygen consumption in intact or chronically vagotomized chicks. alpha-Methylnoradrenaline was ineffective on temperature in chicks with transection of the brain-stem posterior to the hypothalamus but anterior to the respiratory centre. Hypothermia due to alpha-methylnoradrenaline was associated with a significant reduction of plasma non-esterified fatty acids but blood sugar was not significantly altered. Lowering of temperature by alpha-methylnoradrenaline occurred despite vasoconstriction which would hinder heat loss.3. Temperature and oxygen consumption were reduced by alpha-methylnoradrenaline in chronically thyroidectomized chicks to the same extent as in intact chicks but recovery did not occur unless the chicks were taken from the metabolism chamber and warmed artificially. In contrast, chronically thyroidectomized chicks given replacement thyroxine were relatively resistant to alpha-methylnoradrenaline.4. Oxygen consumption of tissue slices from different parts of the chick's brain, including the diencephalon, was not altered by alpha-methylnoradrenaline over an extensive dose range. The effects of alpha-methylnoradrenaline on temperature and oxygen consumption in intact chickens were unlikely, therefore, to be due to depressed metabolism of neurones.5. In an environment below thermoneutrality (16 degrees C) temperature was considerably reduced and carotid arterial pressure fell 40-50 mmHg. In contrast, electromyographic activity, oxygen consumption and plasma non-esterified fatty acids were markedly raised whereas blood sugar was insignificantly elevated.6. In experiments at 16 degrees C, alpha-methylnoradrenaline markedly reduced oxygen consumption although values were still higher than those at thermoneutrality. Temperature fell further, but whereas the reductions in oxygen consumption and temperature were long-lasting, electromyographic activity (shivering) was only transiently diminished. Plasma non-esterified fatty acids were reduced after alpha-methylnoradrenaline but not significantly so; blood sugar was not significantly altered. The time-course for recovery of oxygen consumption following a-methylnoradrenaline paralleled recovery from its blood pressure effects but the effect on oxygen consumption was not a consequence of the blood pressure changes. The effects of a-methylnoradrenaline on temperature, oxygen consumption and electromyographic activity were similar to those of another central depressant, pentobarbitone.

Animals↗
PubMed1970

Effects of catecholamines infused into the brain of young chickens.

1. (-)-Noradrenaline, (-)-alpha-methylnoradrenaline and (-)-isoprenaline were infused into various brain regions of 12-21 day chicks. When infused into the hypothalamic area, but not the cerebral hemisphere or posterior mesencephalon, these amines produced behavioural sleep, lowered temperature and blood pressure and reduced oxygen consumption; electrocortical sleep activity usually ensued but this was not marked and frequently dissociation between electrocortical activity and behaviour occurred. After monoamine oxidase inhibition, which prolonged the action of noradrenaline, dopamine had similar effects.2. The effects of the catecholamines were prevented or substantially reduced by pretreatment with phenoxybenzamine given intravenously or into the hypothalamus but not by intravenous injection of propranolol. However, intrahypothalamic infusion of propranolol prevented the temperature, but not the behavioural effects of noradrenaline. The implications of this are discussed.3. That the effects were similar but more intense, apart from electrocortical changes, and of longer duration than those seen after intravenous injection of catecholamines suggests that in young chicks these amines penetrate from the blood into the brain and elicit their effects through a localized region, presumably the hypothalamus.

Animals↗