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Biomedical subjects

T C Muir

Publications and source records attributed to T C Muir.

At least 55 records · Page 3Linked to original sources
PubMed1975

The electrical basis of excitation and inhibition in the rat anoccygeus muscle.

1. The transmembrane potential of smooth muscle cells of the rat anococcygeus muscle was studied with micro-electrodes. The muscle had a mean resting membrane potential of --61-5 mV and normally lacked spontaneous mechanical and electrical activity. 2. Stimulation of intramural nerves with single pulses produced a small depolarization and contraction. At frequencies greater than 0.5 Hz a second component occurred which had a maximum value of 35--51 mV with short trains at 30 Hz. Spike potentials were rarely seen. Depolarization was accompanied by a decrease in membrane resistance. 3. Noradrenaline (3 times 10-minus 5 M) and guanethidine (3 times 10-minus 5 M) both depolarized the membrane and produced contraction. Initially, oscillations in the membrane potential were oftern seen. 4. Intramural nerve stimulation in the presence of guanethidine damped the oscillations and produced relaxation. This was accompanied by neither hyperpolarization nor a change in membrane resistance. 5. TEA (1 mM) depolarized the membrane (--47-6 mV) and initiated spontaneous activity. Field stimulation evoked spikes with overshoot.

Action Potentials↗
PubMed1975

The effects of electrical stimulation of the autonomic nerves and of drugs on the size of salivary glands and their rate of cell division.

The effects of electrical stimulation of the sympathetic and of the parasympathetic nerves on the size of rat salivary glands have been investigated and compared with those caused by isoproterenol. Sympathetic nerve stimulation increased the size and the mitotic index in the parotid acini; in the submaxillary acini, only the size was increased. These responses varied with the gland studied and the duration of stimulation; the parotid showed the larger increase in the mitotic index and thymidine uptake, the submaxillary the greater degree of cell enlargement. Prolonged electrical stimulation beyond that required to produce the maximum increase in size reduced the enlargement. Sympathetic nerve stimulation caused no enlargement in the extraorbital lacrimal or major sublingual glands. The responses to sympathetic nerve stimulation were inhibited by propranolol (17 nmol/pg), normetanephrine (2 X 45 nmol/g) and mecamylamine (50 nmol/g) but not by phentolamine (13.0 nmol/g) or atropine (7.5 nmol/g). Electric stimulation of the parasympathetic nerves produced no increase in the size or in the mitotic index.

Animals↗
PubMed1971

Effect of iontophoretic application of cholinergic agonists and their antagonists to guinea-pig pelvic ganglia.

1. The electrical activity of guinea-pig pelvic ganglion cells following iontophoretically applied cholinergic drugs, alone and during orthodromic nerve stimulation via the hypogastric nerve, has been recorded intracellularly.2. Iontophoretic application of nicotine (Nic) and acetylcholine (ACh) reduced membrane resistance and caused a depolarization which in approximately 80% of cells led to the firing of action potentials. In the remainder, depolarization was unaccompanied by firing.3. Iontophoretic application of Nic and ACh reduced or abolished the amplitude of successively evoked orthodromic responses.4. ACh-induced depolarization, unlike that caused by tetanic stimulation, was not followed by a subsequent increase in the frequency of synaptic potentials.5. Di-hydrobetaerythroidine (DHbetaE) and atropine (Atr) inhibited the response to both orthodromic stimulation and iontophoretic application of Nic and ACh.6. There was no evidence for the existence of muscarinic receptors in guinea-pig pelvic ganglia. Iontophoretic application of muscarinic agonists alone and after tetanic stimulation of the hypogastric nerve produced no significant depolarization of the ganglion cell membrane.

Acetylcholine↗
PubMed1970

Species and tissue variation in extraneuronal and neuronal accumulation of noradrenaline.

1. The ability of arterial and non-arterial smooth muscle in five tissues (vas deferens, heart, bladder, colon, spleen) in four species (mouse, rabbit, rat, guinea-pig) to accumulate and retain noradrenaline (NA) was measured in thin tissue slices exposed to NA for 30 min, then washed in cold saline solution for 30 min. NA accumulation was assessed histochemically by measuring the fluorescence brightness of the tissue with the Leitz MPV microphotometer. In addition, similar measurements were made on smooth muscle in the cat spleen, on cardiac muscle and on the terminal adrenergic nerves.2. In general, arterial smooth muscle had a greater capacity to accumulate and retain NA than non-arterial smooth muscle, but there was a great species and organ variability. The ability to accumulate and retain NA was best developed in the mouse, followed by the rabbit, rat and guinea-pig in that order. Among organs the artery to the vas and the coronary arteries showed the greatest retention. Among non-arterial smooth muscle the mouse vas and the rabbit colon were notable.3. Cardiac muscle accumulates NA during exposure to the amine but, unlike smooth muscle, cannot retain it when washed with NA-free solution.4. Terminal adrenergic nerves in different tissues show some variability in fluorescence intensity, and this is increased after exposure to NA. This may indicate a variable capacity of these cells to accumulate and retain NA.

Animals↗