Genetic dissection of short-term and long-term facilitation at the Drosophila neuromuscular junction.

In a crayfish phasic neuromuscular junction, we have demonstrated low-frequency depression (LFD), high-frequency depression (HFD), and long-term facilitation (LTF) in response to different regimens of stimulation. Chronic stimulation of the phasic axon supplying the closer muscle of the claw in Procambarus clarkii resulted in diminished expression of HFD and LTF. Conversely, when impulse production in the phasic motoneuron was reduced by claw immobilization, both HFD and LTF were enhanced. LFD was insensitive to these manipulations. These results provide further evidence for long-term adaptation of the phasic neuromuscular junction to ongoing levels of impulse activity and illustrate the importance of a neuron's past history for synaptic plasticity. The ability of the neuron to adjust its short-term plasticity in response to altered experience constitutes an adaptive response that could be of general significance.

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Selected Contribution: Chronic intermittent hypoxia enhances respiratory long-term facilitation in geriatric female rats

Journal of Applied Physiology ◽

10.1152/japplphysiol.00476.2003 ◽

2003 ◽

Vol 95 (6) ◽

pp. 2614-2623 ◽

Cited By ~ 37

Author(s):

A. G. Zabka ◽

G. S. Mitchell ◽

E. B. Olson ◽

M. Behan

Keyword(s):

Intermittent Hypoxia ◽

Young Female ◽

Time Dependent ◽

Female Rats ◽

Chronic Intermittent Hypoxia ◽

Middle Aged ◽

Short Term ◽

Hypoxic Response ◽

Long Term Facilitation

Age and the estrus cycle affect time-dependent respiratory responses to episodic hypoxia in female rats. Respiratory long-term facilitation (LTF) is enhanced in middle-aged vs. young female rats ( 72 ). We tested the hypothesis that phrenic and hypoglossal (XII) LTF are diminished in acyclic geriatric rats when fluctuating sex hormone levels no longer establish conditions that enhance LTF. Chronic intermittent hypoxia (CIH) enhances LTF ( 41 ); thus we further predicted that CIH would restore LTF in geriatric female rats. LTF was measured in young (3-4 mo) and geriatric (20-22 mo) female Sasco Sprague-Dawley rats and in a group of geriatric rats exposed to 1 wk of nocturnal CIH (11 vs. 21% O2 at 5-min intervals, 12 h/night). In anesthetized, paralyzed, vagotomized, and ventilated rats, time-dependent hypoxic phrenic and XII responses were assessed. The short-term hypoxic response was measured during the first of three 5-min episodes of isocapnic hypoxia (arterial Po2 35-45 Torr). LTF was assessed 15, 30, and 60 min postepisodic hypoxia. Phrenic and XII short-term hypoxic response was not different among groups, regardless of CIH treatment ( P > 0.05). LTF in geriatric female rats was smaller than previously reported for middle-aged rats but comparable to that in young female rats. CIH augmented phrenic and XII LTF to levels similar to those of middle-aged female rats without CIH ( P < 0.05). The magnitude of phrenic and XII LTF in all groups was inversely related to the ratio of progesterone to estradiol serum levels ( P < 0.05). Thus CIH and sex hormones influence the magnitude of LTF in geriatric female rats.

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Time-dependent phrenic nerve responses to carotid afferent activation: intact vs. decerebellate rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1993.265.4.r811 ◽

1993 ◽

Vol 265 (4) ◽

pp. R811-R819 ◽

Cited By ~ 65

Author(s):

F. Hayashi ◽

S. K. Coles ◽

K. B. Bach ◽

G. S. Mitchell ◽

D. R. McCrimmon

Keyword(s):

Phrenic Nerve ◽

Carotid Sinus ◽

Carotid Sinus Nerve ◽

Short Term ◽

Nerve Activity ◽

A Value ◽

Afferent Activation ◽

Term Potentiation ◽

Long Term Facilitation

The objectives were to determine 1) respiratory responses to carotid chemoreceptor inputs in anesthetized rats and 2) whether the cerebellar vermis plays a role in these responses. A carotid sinus nerve was stimulated (20 Hz) with five 2-min trains, each separated by approximately 3 min. During stimulation, respiratory frequency (f), peak amplitude of integrated phrenic nerve activity (integral of Phr), and their product (f x integral of Phr) immediately increased. As stimulation continued, integral of Phr progressively increased to a plateau [short-term potentiation (STP)], but f and f x integral of Phr decreased [short-term depression (STD)] to a value still above control. Upon stimulus termination, integral of Phr progressively decreased but remained above control; f and f x integral of Phr transiently decreased below baseline. After the final stimulation, integral of Phr remained above control for at least 30 min [long-term facilitation (LTF)]. Repeated 5-min episodes of isocapnic hypoxia also elicited STP, STD, and LTF. Vermalectomy lowered the CO2-apneic threshold and eliminated LTF. In conclusion, carotid chemoreceptor activation in rats elicits STP and LTF similar to that in cats; the vermis may play a role in LTF. A new response, STD, was observed.

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Long-term facilitation alters transmitter releasing properties at the crayfish neuromuscular junction

Journal of Neurophysiology ◽

10.1152/jn.1986.55.3.484 ◽

1986 ◽

Vol 55 (3) ◽

pp. 484-498 ◽

Cited By ~ 40

Author(s):

J. M. Wojtowicz ◽

H. L. Atwood

Keyword(s):

Neuromuscular Junction ◽

Synaptic Transmission ◽

Time Course ◽

Muscle Fibers ◽

Low Frequencies ◽

Before And After ◽

Binomial Parameter ◽

Small Muscle ◽

Long Term Facilitation

Synaptic transmission at the neuromuscular junction of the excitatory axon supplying the crayfish opener muscle was examined before and after induction of long-term facilitation (LTF) by a 10-min period of stimulation at 20 Hz. Induction of LTF led to a period of enhanced synaptic transmission, which often persisted for many hours. The enhancement was entirely presynaptic in origin, since quantal unit size and time course were not altered, and quantal content of transmission (m) was increased. LTF was not associated with any persistent changes in action potential or presynaptic membrane potential recorded in the terminal region of the excitatory axon. The small muscle fibers of the walking-leg opener muscle were almost isopotential, and all quantal events could be recorded with an intracellular microelectrode. In addition, at low frequencies of stimulation, m was small. Thus it was possible to apply a binomial model of transmitter release to events recorded from individual muscle fibers and to calculate values for n (number of responding units involved in transmission) and p (probability of transmission for the population of responding units) before and after LTF. In the majority of preparations analyzed (6/10), amplitude histograms of evoked synaptic potentials could be described by a binomial distribution with a small n and moderately high p. LTF produced a significant increase in n, while p was slightly reduced. The results can be explained by a model in which the binomial parameter n represents the number of active synapses and parameter p the mean probability of release at a synapse. Provided that a pool of initially inactive synapses exists, one can postulate that LTF involves recruitment of synapses to the active state.

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Short-term and long-term facilitation of goose grazing by livestock in the Dutch Wadden Sea area

Journal of Coastal Conservation ◽

10.1007/bf02788956 ◽

2002 ◽

Vol 8 (2) ◽

pp. 179-188

Author(s):

A. J. Graaf ◽

D. Bos ◽

M. J. J. E. Loonen ◽

M. Engelmoer ◽

R. H. Drent

Keyword(s):

Wadden Sea ◽

Short Term ◽

Long Term Facilitation ◽

Sea Area

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Neuromuscular Facilitation in Crayfish: Dependence on Potassium and Strophanthidin

Journal of Experimental Biology ◽

10.1242/jeb.86.1.39 ◽

1980 ◽

Vol 86 (1) ◽

pp. 39-47

Author(s):

C. LEO ORTIZ ◽

R. K. ORKAND

Keyword(s):

Neuromuscular Junctions ◽

Short Term ◽

Presynaptic Terminals ◽

Potential Amplitude ◽

Junctional Potential ◽

Long Term Facilitation

1. Long-term facilitation (LTF) and short-term facilitation (STF) at excitatory neuromuscular junctions were studied under conditions of varying [K+]0 and with the addition of strophanthidin. 2. The magnitude of LTF varied inversely with [K+]0, while STF was unaffected. 3. Strophanthidin concentrations greater than 10−5 M greatly increased LTF, but not STF. 4. Both LTF and STF were unaffected by large decreases in excitatory junctional potential amplitude produced by the addition of GABA or Mn+2. 5. The results support the hypothesis that LTF is a consequence of Na+ accumulation in presynaptic terminals and behaves independently of STF.

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