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Biomedical subjects

T J Biscoe

Publications and source records attributed to T J Biscoe.

At least 73 records · Page 4Linked to original sources
PubMed1972

Effect of etorphine, morphine and diprenorphine on neurones of the cerebral cortex and spinal cord of the rat.

1. The actions of etorphine, morphine and diprenorphine were investigated on neurones of the cerebral cortex and spinal cord of rats anaesthetized with pentobarbitone.2. In the cerebral cortex, intravenous etorphine increased the latency of the primary evoked response to a peripheral nerve stimulus and suppressed the rhythmical after-discharge. Diprenorphine reversed this effect. These actions were demonstrated on both field potentials and unit firing.3. Morphine had no effect on the primary response but the frequency of after-discharge bursts was reduced and there was an increase in firing between bursts.4. In the cerebral cortex, electrophoretically applied etorphine reduced after-discharges when applied for long periods but had no effect on the depressant actions of glycine and gamma-aminobutyric acid (GABA) nor on the excitant action of acetylcholine and L-glutamate. Similarly there was no alteration by etorphine of the effects of glycine, GABA and L-glutamate on spinal cord neurones.5. It is concluded that etorphine may act pre-synaptically in the cerebral cortex.

Analgesics↗
PubMed1970

The relation between carotid body chemoreceptor discharge, carotid sinus pressure and carotid body venous flow.

1. Activity in forty-two single chemoreceptor afferent fibres from the carotid body in thirty-nine cats was measured when the carotid body was naturally and artificially perfused. In nine of these cats, carotid body venous flow was also measured.2. When pressure within the carotid sinus segment was suddenly raised or lowered, chemoreceptor activity changed in the opposite direction within the first 5-10 sec by an amount which was significantly greater than the variation of activity in the control period. Thereafter activity stabilized at a level which was not different from control.3. Whether the carotid body was naturally or artificially perfused, carotid body chemoreceptor activity, following this initial transient change, was unaffected in eight out of twelve fibres by alterations in carotid sinus pressure within the range 60-160 mm Hg and carotid body venous flow 10-60 mul./min, blood gas tensions and pH being maintained constant. In the four remaining fibres, chemoreceptor activity increased slightly but significantly as pressure was lowered in this range. Chemoreceptor activity increased in all fibres tested when pressure was lowered below 50-60 mm Hg.4. Chemoreceptor response curves to changes in P(a,O2) (30-450 mm Hg), P(a,CO2) (27-62 mm Hg) or [H(+)](a) (3-7 x 10(-5) m-equiv/l.) were not significantly different whether the carotid body was perfused (a) naturally at the prevalent systemic pressure, (b) artificially at the same pressure, or (c) artificially at one higher pressure, 130 or 140 mm Hg.5. These results indicate that the carotid body chemoreceptors are relatively unaffected by sustained changes in arterial pressure or in total carotid body flow within the physiological range.

Animals↗
PubMed1970

The frequency of nerve impulses in single carotid body chemoreceptor afferent fibres recorded in vivo with intact circulation.

1. The responses of single afferent fibres of carotid body chemoreceptors to independent changes in arterial O(2) and CO(2) tensions and pH were studied in the cat in vivo.2. The response curve obtained relating chemoreceptor activity to changes in arterial P(O2) was similar to an hyperbola; the frequency of nerve impulses at first decreased rapidly as the P(a,O2) was raised and then more slowly. The arterial P(O2) at which the slow decrease was reached varied among the different fibres; the mean level was 190 mm Hg (S.D. +/- 40 mm Hg).3. Single chemoreceptor afferent fibres continued to discharge even when the arterial P(O2) was more than 600 mm Hg.4. The discharges of single chemoreceptor afferent fibres increased both with increasing P(a,CO2) at constant pH and P(a,O2), and with increasing arterial H(+) at constant P(a,CO2) and P(a,O2).5. It is concluded that single carotid body chemoreceptor afferent fibres of the cat can be activated in vivo by an increase in either arterial H(+) or arterial P(CO2) as well as by a decrease in arterial P(O2).

Action Potentials↗
PubMed1970

Electron microscopic and electrophysiological studies on the carotid body following intracranial section of the glossopharyngeal nerve.

1. The innervation of carotid body Type I cells has been investigated in seventeen cats. At a sterile operation the glossopharyngeal and vagus nerve roots were cut intracranially on one side.2. From 1(1/2) to 378 days after the operation the carotid bodies were fixed in situ and prepared for electron microscopy. Nerve endings on Type I cells were found to degenerate with a prolonged time course. In each cat there was a decrease in the number of nerve endings on the operated side as compared with the non-operated side.3. Before the carotid bodies were fixed, recordings were made from chemoreceptor, and baroreceptor, afferent fibres in the sinus nerve on the operated side. The chemoreceptors responded in the usual way to changes in arterial O(2), CO(2) and pH; the injection of cyanide evoked a brisk response.4. It is concluded that the nerve endings on Type I cells are efferent rather than afferent and the cell bodies of their axons are probably in the brain stem.

Action Potentials↗