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Biomedical subjects

C R House

Publications and source records attributed to C R House.

At least 37 records · Page 2Linked to original sources
PubMed1980

A calcium-readmission response recorded from Nauphoeta salivary gland acinar cells.

1. When cockroach salivary glands are exposed to bathing solutions without added calcium, reintroduction of calcium causes the acinar cells to hyperpolarize. The effect ('readmission response') may be very prolonged if the conditioning solution contains 5 mM-cobalt. 2. Evidence is presented against the possibility that the readmission response is mediated by transmitter released from the salivary nerves. 3. The readmission response is shown to reflect an increase in potassium conductance.

Animals↗
PubMed1979

Ion and water transport by isolated cockroach salivary glands.

When the isolated salivary glands of the cockroach Nauphoeta cinerea Oliver are stimulated by dopamine, the putative neurotransmitter, they secrete a fluid containing (mM):Na, 121; K, 47; Cl, 143. Stimulation of glands by 5-hydroxytryptamine or the neuro-transmitter evokes a secretion identical in Na composition to this. Dopamine-evoked secretion is abolished in the absence of extracellular Na. The relationship between the rates of fluid secretion and Na transport is linear. However, at very low rates of secretion the Na concentration falls. Calcium, K and Cl ions can be removed from the bathing solution without abolishing fluid secretion. Our evidence suggests that (i) the primary secretion is formed by active transport of Na in the acini, and (ii) the ionic composition of this secretion is modified by re-absorption of Na and an independent secretion of K in the ducts.

Biological Transport↗
PubMed1979

On the effect of ionophoretically applied dopamine on salivary gland cells of Nauphoeta cinerea.

1. Responses to ionophoretically applied dopamine ('ionophoretic responses') have been recorded with an intracellular micro-electrode from acini of isolated salivary glands of the cockroach, Nauphoeta cinerea. They resembled responses to nerve stimulation ('neural responses') but they usually decayed more slowly and were sometimes more rapid in onset. 2. As already described for neural resonses, ionophoretic responses (i) included a secondary phase of depolarization (although more rarely than neural responses), (ii) increased in duration with increased amplitude and (iii) when small, added superlinearly. These features therefore reflect post-synaptic processes. By contrast, tachyphylaxis was much more marked for neural responses and is therefore mainly of presynaptic origin. 3. Ionophoretic and neural responses were affected similarly by increase in temperature. The times-to-peak of both decreased with values for Q10 of about 3. 4. The differences between the onset and decay of ionophoretic and neural responses can probably be explained by the inherently different conditions of application of the agonist. The similarities therfore provide further support for dopamine as the neurotransmitter.

Animals↗
PubMed1979

On the time course of the electrical response of salivary gland cells of Nauphoeta cinerea to ionophoretically applied dopamine.

1. An attempt has been made to account for the latency and slow time course of the electrical responses of salivary gland cells of Nauphoeta cinerea (Olivier) to nerve stimulation and ionophoretically applied dopamine from a pipette placed as close as possible to the acinar surface. 2. The effects have been investigated on the time course of the ionophoretic response of changes in the distance of the pipette from the acinar surface and of the amount of dopamine ejected. 3. The observed changes were smaller than those predicted by models in which the rate limiting step was assumed to be diffusion or slow receptor kinetics. Indirect evidence suggests that the time course of the response is determined by processes subsequent to receptor activation.

Animals↗
PubMed1978

On the receptors involved in the nervous control of salivary secretion by Nauphoeta cinerea Olivier.

1. It has been shown that the isolated salivary glands of Nauphoeta cinerea Olivier produce fluid secretion in response to nerve stimulation or bath applications of dopamine, noradrenaline, adrenaline and 5-HT. These catecholamines, of which dopamine is the most potent, evoked maximal responses matching that to nerve stimulation whereas 5-HT was less effective. 2. The receptors combining with 5-HT could be distinguished from those for the catecholamines and the transmitter at this salivary neuroglandular junction. 3. The results of experiments where glands were stimulated by dopamine in the presence of noradrenaline or adrenaline suggested that there are receptors with specific binding sites for dopamine. 4. The effects of several antagonists (Ginsborg, House & Silinsky, 1976) of the hyperpolarizing responses from acinar cells to nerve stimulation and the above agonists have been examined. Phentolamine reversibly suppressed the secretory responses to these stimuli whereas methysergide had no effect and ergometrine elicited fluid secretion in a dose-dependent manner.

Animals↗
PubMed1978

Competitive antagonism by phentolamine of responses to biogenic amines and the transmitter at a neuroglandular junction.

1. A quantitative study has been made of phentolamine's inhibition of the electrical and secretory responses of the isolated salivary glands of Nauphoeta cinerea Olivier to nerve stimulation and bath applications of agonists. 2. The results suggested that phentolamine is a competitive antagonist having an affinity constant of about 1 micrometer-1 for the receptors for dopamine, noradrenaline, adrenaline and the neurotransmitter. 3. Phentolamine also inhibited responses to 5-hydroxytryptamine in a manner seemingly more complex than competitive antagonism. Attempts to estimate the affinity constant gave values of about 0.08 and 0.015 microgram-1 for inhibition of the secretory and electrical responses respectively. 4. This investigation showed that phentolamine discriminates between two kinds of receptor in this gland, one binding 5-hydroxytryptamine and the other combining with catecholamines and the neurotransmitter.

Animals↗
PubMed1976

On the actions of compounds related to dopamine at a neurosecretory synapse.

1 The effects of a number of substances related to dopamine, including all its methylated derivatives, were investigated on the membrane potential and response to nerve stimulation of cockroach salivary gland cells. 2 Only N-methyldopamine (epinine), N,N-dimethyldopamine and N,N-dimethylnoradrenaline, all with unsubstituted hydroxyl groups, directly resembled dopamine in producing a hyperpolarization which could be as large as that caused by maximal nerve stimulation. During the continued presence of these substances the hyperpolarization waned and responses to nerve stimulation declined. 3 Many of the compounds caused one or both of two other effects, namely an increase in the rate of 'spontaneous miniature hyperpolarizations' and an enhancement of the submaximal responses to single nerve stimuli. There were no obvious structural requirements for these effects.

Animals↗
PubMed1976

The morphology of spinocervical tract neurones in the cat.

1. The morphology of physiologically identified spinocervical tract (SCT) neurones was studied using the intracellular injection of Procion dyes in anesthetized and decerebrate cats. 2. Extracellular recordings were made from SCT neurones at depths between 1000 and 2850 mum from the cord surface but neurones were only stained at depths between 1100 and 2400 mum. 3. The dendritic trees of stained SCT neurones were reconstructed in the transverse plane of the spinal cord. All SCT neurones had well developed dorsal dendrites but despite this it is not possible to consider the twenty-two SCT cells in out sample as consituting a morphologically homogenous population. 4. There was no correlation between the form of the dendritic trees and the depth of SCT neurones in the dorsal horn as determined both from measurements from the dorsal grey-white border and the position of cells with respect to the border between Rexed's laminae II and III. 5. Six types of SCT neurones were identified on the basis of the form of their dendritic trees as viewed in the transverse plane: (1) radially symmetrical, (2) semicircular, (3) large elliptical, (4) bilobed, (5) triangular, (6) small elliptical. Each of these types was found only in a certain region across the dorsal horn although any one region could contain more than one type. 6. Spinocervical tract neurones with small elliptical dendritic trees always had receptive fields encompassing part of the hip or thigh and were unique in being located in the lateral portions of the horn. 7. There was no correlation between the morphology of SCT neurones and their excitatory cutaneous inputs, receptive field size, axonal conduction velocity or depth in the dorsal horn.

Action Potentials↗
PubMed1976

The responses to nerve stimulation of the salivary gland of Nauphoeta cinerea Olivier.

A study has been made with intracellular electrodes of the responses of acini of the salivary gland of Nauphoeta cinerea Olivier to salivary duct nerve stimulation. The gland is a paired structure and offers the possibility of investigating the interaction between ipsi- and contralateral nerve stimulation. 2. The characteristics of the responses are as previously described for field stimulation (House, 1973). The latency is of the order of 1 sec and almost independent of the amplitude of the response which may attain a hyperpolarization of about 80 mV. The depolarization which sometimes follows can be disassociated from the preceding hyperpolarization and is presumably an independent response. 3. The stimulus-response relationship shows that acini are multiply innervated. Those close to the mid line recieve axons from both ipsi- and contralateral salivary duct nerves. The response to a test stimulus T can be augmented by an immediately preceding conditioning stimulus C, the joint response being greater than the sum of the separate responses. This effect occurs even when C and T are delivered to different nerves. For longer intervals between C and T, the response to T is depressed.

Action Potentials↗
PubMed1976

On the receptors which mediate the hyperpolarization of salivary gland cells of Nauphoeta cinerea Olivier.

The actions of sympathomimetics and of catecholamine antagonists have been investigated on the membrane potential and responses to nerve stimulation of acinar cells of the salivary gland of Nauphoeta cinerea Olivier. 2. Hyperpolarizations such as those evoked by nerve stimulation and by low concentrations of adrenaline, noradrenaline and dopamine were not produced by the alpha-agonists amidephrine and methoxamine. Isoprenaline was active, but only in concentrations above 100 muM. 3. Tyramine, an indirectly acting sympathomimetic, and high concentrations of methoxamine caused an increase in the rate of the small transient hyperpolarizations sometimes seen in the absence of stimulation. 4. The response to nerve stimulation was unaffected by propranolol (20 muM) an alpha-adrenergic antagonist. Phentolamine, an alpha-adrenergic antagonist, reduced matching responses to nerve stimulation and to dopamine to about the same extent. 5. As on other systems responsive to low concentrations of dopamine, apomorphine was active, although only in high concentration, and ergometrine and methysergide were antagonistic both to nerve stimulation and to dopamine.

Adrenergic alpha-Agonists↗
PubMed1976

The actions of some putative neurotransmitters on the cockroach salivary gland.

1. Certain putative transmitters were applied to the innervated cockroach salivary gland and their effects on the resting potential and the neurally evoked secretory potential of the acinar cells were observed. 2. gamma-Aminobutyric acid, glutamate, glycine, aspartate and alanine had no significant effect on the resting potential. However, gamma-aminobutyric acid and glutamate reduced the neurally evoked secretory potential but only at concentrations above 10(-3) M3. Acetylcholine and carbachol appeared to act by modifying transmitter output from the salivary nerves. These substances failed to have any effect on the resting potential. 4. The biogenic amines, adrenaline, dopamine, noradrenaline, 5-hydroxy-tryptamine and octopamine, produced hyperpolarizing responses, graded according to concentration. 5. It is suggested that dopamine, the most potent of the biogenic amines tested, is the transmitter at this junction.

Acetylcholine↗