ELECTROPHYSIOLOGICAL RECORDINGS FROM OXYTOCINERGIC NEURONES DURING SUCKLING IN THE UNANAESTHETIZED LACTATING RAT

1981 ◽  
Vol 90 (2) ◽  
pp. 255-265 ◽  
Author(s):  
A. J. S. SUMMERLEE ◽  
D. W. LINCOLN
Keyword(s):  
High Frequency ◽  
Action Potentials ◽  
Milk Ejection ◽  
Extracellular Recordings ◽  
Electrophysiological Recordings ◽  
Oxytocin Release ◽  
Anaesthetized Rats ◽  
Freely Moving ◽  
Frequency Burst ◽  
Stimulation Of

A method is described for making extracellular recordings of the spontaneous activity of single hypothalamic neurones in unanaesthetized, freely moving, lactating rats using chronically implanted micro-wire electrodes. Extracellular recordings taken from individual neurones were maintained for periods of between 1 and 12 days. These records were not affected by any normal movement of the animal. As several micro-wires were implanted into each animal it was possible to make simultaneous recordings from several different hypothalamic sites in the same animal. Some recordings were identified as those from magnocellular neurones in the paraventricular nucleus on the basis of antidromic invasion after electrical stimulation of the neurohypophysis. Milk ejection in response to the prolonged sucking of ten or more pups was intermittent, and individual milk ejections recurred at intervals of 2–10 min throughout each period of nursing. The rise in intramammary pressure at milk ejection was associated with a vigorous extensor response from the pups. This was monitored by radar to provide an index of milk ejection in the unanaesthetized rat. Eleven antidromically identified neurones were recorded through 321 milk ejections. Eight of these neurones displayed a transient (2–6 s) and very substantial acceleration in discharge at the time predicted for oxytocin release, i.e. 10–12 s before milk ejection. The background discharge of these cells was 0·1–2·6 action potentials/s; this increased to 16–50 action potentials/s during the brief period of accelerated activity. Twenty-five neurones were studied during 365 milk ejections in rats which did not have a stimulating electrode implanted in the neurohypophysis. Thirteen of these neurones displayed a burst of high frequency discharge before each milk ejection, similar to that described for the antidromically identified neurones. Two of the non-responsive cells displayed a phasic pattern of discharge, characteristic of vasopressinergic neurone discharge recorded in anaesthetized rats. These observations of putative oxytocinergic neurones in unanaesthetized, freely moving rats are identical with those previously made on anaesthetized rats, and establish that the high frequency burst of electrical activity displayed by magnocellular neurones some 10–12 s before milk ejection is responsible for oxytocin release under normal physiological circumstances.

Electronmicroscopic and electrophysiological studies of the teat branch of the XIII thoracic nerve: relationship with lactation in the rat

1988 ◽  
Vol 118 (3) ◽  
pp. 471-483 ◽  
Author(s):  
L. M. Voloschin ◽  
E. Décima ◽  
J. H. Tramezzani
Keyword(s):  
Electrical Stimulation ◽  
Conduction Velocity ◽  
Action Potentials ◽  
Silent Period ◽  
High Amplitude ◽  
Milk Ejection ◽  
Nerve Activity ◽  
Thoracic Nerve ◽  
Myelinated Fibres ◽  
Stimulation Of

ABSTRACT Electrical stimulation of the XIII thoracic nerve (the 'mammary nerve') causes milk ejection and the release of prolactin and other hormones. We have analysed the route of the suckling stimulus at the level of different subgroups of fibres of the teat branch of the XIII thoracic nerve (TBTN), which innervates the nipple and surrounding skin, and assessed the micromorphology of the TBTN in relation to lactation. There were 844 ± 63 and 868 ± 141 (s.e.m.) nerve fibres in the TBTN (85% non-myelinated) in virgin and lactating rats respectively. Non-myelinated fibres were enlarged in lactating rats; the modal value being 0·3–0·4 μm2 for virgin and 0·4–0·5 μm2 for lactating rats (P > 0·001; Kolmogorov–Smirnov test). The modal value for myelinated fibres was 3–6 μm2 in both groups. The compound action potential of the TBTN in response to electrical stimulation showed two early volleys produced by the Aα- and Aδ-subgroups of myelinated fibres (conduction velocity rate of 60 and 14 m/s respectively), and a late third volley originated in non-myelinated fibres ('C') group; conduction velocity rate 1·4 m/s). Before milk ejection the suckling pups caused 'double bursts' of fibre activity in the Aδ fibres of the TBTN. Each 'double burst' consisted of low amplitude action potentials and comprised two multiple discharges (33–37 ms each) separated by a silent period of around 35 ms. The 'double bursts' occurred at a frequency of 3–4/s, were triggered by the stimulation of the nipple and were related to fast cheek movements visible only by watching the pups closely. In contrast, the Aα fibres of the TBTN showed brief bursts of high amplitude potentials before milk ejection. These were triggered by the stimulation of cutaneous receptors during gross slow sucking motions of the pup (jaw movements). Immediately before the triggering of milk ejection the mother was always asleep and a low nerve activity was recorded in the TBTN at this time. When reflex milk ejection occurred, the mother woke and a brisk increase in nerve activity was detected; this decreased when milk ejection was accomplished. In conscious rats the double-burst type of discharges in Aδ fibres was not observed, possibly because this activity cannot be detected by the recording methods currently employed in conscious animals. During milk ejection, action potentials of high amplitude were conveyed in the Aα fibres of the TBTN. During the treading time of the stretch reaction (SR), a brisk increase in activity occurred in larger fibres; during the stretching periods of the SR a burst-type discharge was again observed in slow-conducting afferents; when the pups changed nipple an abrupt increase in activity occurred in larger fibres. In summary, the non-myelinated fibres of the TBTN are increased in diameter during lactation, and the pattern of suckling-evoked nerve activity in myelinated fibres showed that (a) the double burst of Aδ fibres, produced by individual sucks before milk ejection, could be one of the conditions required for the triggering of the reflex, and (b) the nerve activity displayed during milk-ejection action may result, at least in part, from 'non-specific' stimulation of cutaneous receptors. J. Endocr. (1988) 118, 471–483

Effect of stimulation intensity on oxytocin release before, during and after machine milking

2003 ◽  
Vol 70 (3) ◽  
pp. 349-354 ◽  
Author(s):  
Daniel Weiss ◽  
Alen Dzidic ◽  
Rupert M Bruckmaier
Keyword(s):  
Dairy Cows ◽  
Milk Production ◽  
Threshold Level ◽  
Flow Profile ◽  
Milk Ejection ◽  
Machine Milking ◽  
Milk Flow ◽  
Oxytocin Release ◽  
Stimulation Period ◽  
Stimulation Of

Release of oxytocin (OT) is essential for milk ejection in dairy cows (Lefcourt & Akers, 1983; Bruckmaier & Blum, 1998). During milk ejection, alveolar milk is shifted into the cistern, which causes an increase of intracisternal pressure (Bruckmaier et al. 1994). To initiate maximum milk ejection at the start of milking, increasing OT concentration beyond a threshold level is sufficient (Schams et al. 1983). Increasing OT concentration beyond this threshold has no additional effect on intracisternal pressure, i.e., milk ejection (Bruckmaier et al. 1994). Stimulatory effects of milking by hand or by machine or by suckling are well documented (Gorewit et al. 1992; Bar-Peled et al. 1995; Tancin et al. 1995; Bruckmaier & Blum, 1996). At the start of milking, stimulatory effects of machine milking without pre-stimulation or with a manual pre-stimulation and subsequent machine milking cause the release of comparable amounts of OT (Gorewit & Gassman, 1985; Mayer et al. 1985; Bruckmaier & Blum, 1996), whereas the timing of the applied pre-stimulation is important for the shape of the milk flow curve. Should the pre-stimulation period be too short, or absent altogether, the start of the main milk flow is delayed resulting in a bimodal milk flow profile (Bruckmaier & Blum, 1996). Furthermore, the stimulation of only one teat causes an OT release similar to that caused by stimulation of all four teats (Bruckmaier et al. 2001). However, milk production is greater for hand milking or suckling than for machine milking, possibly owing to higher OT concentrations (Gorewit et al. 1992; Bar-Peled et al. 1995).

ETHANOL AND THE INHIBITION OF OXYTOCIN RELEASE IN LACTATING RATS

1969 ◽  
Vol 62 (3) ◽  
pp. 546-554 ◽  
Author(s):  
Anna-Riitta Fuchs
Keyword(s):  
Mammary Gland ◽  
Dose Level ◽  
Milk Yield ◽  
Complete Inhibition ◽  
Milk Ejection ◽  
Oxytocin Release ◽  
Anaesthetized Rats ◽  
Peripheral Effect ◽  
Higher Doses

ABSTRACT The effect of ethanol on the release of oxytocin in the rat was studied using suckling as the oxytocin releasing stimulus. Milk removal on 30 min suckling by a litter of 8 after 18 h separation from the mother on postpartum day 13–16 was used as a parameter of oxytocin liberation. Under these conditions 25 mU intravenously injected oxytocin permitted normal milk removal in anaesthetized rats, whereas after injection of 10 mU oxytocin only about half of the normal milk yield was obtained. Ethanol in doses varying from 1.0 to 5.0 g/kg was injected intraperitoneally into the dam as 10 to 20 % solution in saline 30 to 60 min before nursing commenced and the milk yield was compared with saline injected control rats. At the dose level of 1.0 g/kg ethanol had no effect on milk removal but 2.0 g/kg caused a significant reduction to about 60 % of normal, and with higher doses a further reduction of the milk yield occurred. At 3.5 g/kg about 14% of normal milk yield was obtained, and at 5.0 g/kg a complete inhibition of milk ejection was observed. Oxytocin administration permitted normal milk removal in all ethanol treated rats indicating that there was no peripheral effect on the mammary gland. The experiments suggest that ethanol inhibits oxytocin release also in the rat.

Modulation of synaptic transmission at Ia-afferent fiber connections on motoneurons during high-frequency stimulation: role of postsynaptic target

1991 ◽  
Vol 65 (3) ◽  
pp. 590-597 ◽  
Author(s):  
H. R. Koerber ◽  
L. M. Mendell
Keyword(s):  
High Frequency ◽  
Afferent Fiber ◽  
High Frequency Stimulation ◽  
Excitatory Postsynaptic Potential ◽  
Epsp Amplitude ◽  
Marked Variability ◽  
Frequency Stimulation ◽  
Frequency Burst ◽  
Stimulation Of

1. High-frequency stimulation of single group Ia-fibers results in modulation of excitatory postsynaptic potential (EPSP) amplitude recorded in target motoneurons. This can be either positive (EPSP amplitude increases in response to successive stimuli in the high-frequency burst) or negative (decrease in EPSP amplitude). We have investigated whether the magnitude of modulation is associated with the stimulated afferent, the responding motoneuron, or the amplitude of the EPSP. 2. In agreement with previous findings, we found that positive modulation tends to occur at connections generating small EPSPs and negative modulation, at those producing large EPSPs. Because large EPSPs generally are evoked in motoneurons with low values of rheobase, we found, as anticipated, that connections on low rheobase motoneurons are prone to negative modulation during high-frequency stimulation, whereas those on high rheobase motoneurons (which tend to generate small EPSPs) are prone to positive modulation. 3. In experiments where the projection of multiple afferents to a single motoneuron was studied, we found that amplitude modulation was similar despite differences in EPSP amplitude. Thus in a given motoneuron there is no relationship between modulation and amplitude, in contrast to the existence of such a relationship in the population of connections as a whole. 4. In the converse experiments where the projection of single afferents to multiple motoneurons was studied, we found marked variability in the modulation patterns with clear indications that amplitude and modulation are correlated as in the entire population of Ia/motoneuron connections. 5. We tested the constancy of modulation patterns evoked in a given motoneuron by comparing the modulation patterns evoked in motoneurons by single fibers, and by stimulation of the heteronymous nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterosynaptic LTD and Depotentiation in the Medial Perforant Path of the Dentate Gyrus in the Freely Moving Rat

1997 ◽  
Vol 77 (2) ◽  
pp. 571-578 ◽  
Author(s):  
Valérie Doyère ◽  
Bolek Srebro ◽  
Serge Laroche
Keyword(s):  
Dentate Gyrus ◽  
High Frequency ◽  
Long Term Potentiation ◽  
Perforant Path ◽  
High Frequency Stimulation ◽  
Tetanic Stimulation ◽  
Frequency Stimulation ◽  
Freely Moving ◽  
Stimulation Of

Doyère, Valérie, Bolek Srebro, and Serge Laroche. Heterosynaptic LTD and depotentiation in the medial perforant path of the dentate gyrus in the freely moving rat. J. Neurophysiol. 77: 571–578, 1997. We examined the characteristics of heterosynaptic long-term depression (LTD) and depotentiation of previously established long-term potentiation (LTP) in the medial and lateral entorhinal afferents to the dentate gyrus in the awake rat. Rats were prepared for chronic recording of dentate gyrus evoked potentials to activation of the medial and lateral perforant paths. This study in awake rats confirms that heterosynaptic LTD can be induced at inactive medial perforant path synapses in conjunction with the induction of LTP produced by high-frequency stimulation of the lateral perforant path. This form of LTD was long lasting and reversible by tetanic stimulation delivered to the depressed pathway. In contrast, tetanic stimulation of the medial perforant path had only a small heterosynaptic effect on the lateral pathway, suggesting that the two input pathways to the dentate gyrus are not symmetrical in their ability to induce heterosynaptic LTD. We also examined the ability of high-frequency stimulation of one pathway to produce depotentiation of the other pathway. We found that when LTP was first induced in the medial perforant path, depotentiation was induced heterosynaptically by tetanization of the lateral pathway. Both newly established LTP (30 min) and LTP induced and saturated by repeated tetanic stimulation over several days can be depotentiated heterosynaptically. Moreover, depotentiation of the medial perforant path synapses was found to be linearly correlated with the magnitude of LTP induced in the lateral perforant path synapses, and subsequent tetanic stimulation of the depotentiated medial perforant path restored LTP to an extent that counterbalanced depotentiation. The saturation and repotentiation experiments provide clear support for the conclusion that the rapid reversal of LTP reflects true depotentiation of the medial input. Again, as with heterosynaptic LTD, tetanization of the medial perforant path had little effect on previously induced LTP in the lateral path. These results provide evidence that medial perforant path synapses can be depressed and depotentiated heterosynaptically. They suggest that in the intact rat synaptic changes in the afferents to the dentate gyrus from the lateral entorhinal cortex exert powerful control over ongoing or recent synaptic plasticity in the medial entorhinal afferents.

DETERMINATION OF THE DETAILED HYPOTHALAMIC ROUTE OF THE MILK-EJECTION REFLEX IN THE GUINEA-PIG

1971 ◽  
Vol 50 (1) ◽  
pp. 135-152 ◽  
Author(s):  
J. S. TINDAL ◽  
G. S. KNAGGS
Keyword(s):  
Electrical Stimulation ◽  
Lateral Hypothalamus ◽  
Third Ventricle ◽  
Milk Ejection ◽  
Lateral Direction ◽  
Reflex Pathway ◽  
Oxytocin Release ◽  
Far Lateral ◽  
Milk Ejection Reflex ◽  
Stimulation Of

SUMMARY The effect of various types of surgical damage to the forebrain on the release of oxytocin in response to electrical stimulation of the discrete ascending milk-ejection reflex pathway in the mid-brain was investigated in 99 anaesthetized lactating guinea-pigs. Oxytocin release was measured by comparison of experimental milk-ejection responses with the response to i.v. injection of known amounts of synthetic oxytocin. Removal of the entire telencephalon, including cerebral cortex, hippocampi, amygdalae and forebrain rostral to the hypothalamus, did not affect the subsequent release of oxytocin after electrical stimulation of the pathway in the mid-brain, from which it was concluded that the reflex pathway within the forebrain is entirely diencephalic. Transection of the hypothalamus immediately rostral to the paraventricular (PV) nuclei was without effect, while transection immediately caudal to the PV nuclei blocked the release of oxytocin. Destruction of the PV nuclei by a radiofrequency lesion which spared the supraoptic (SO) nuclei blocked the release of oxytocin. Undercutting both PV nuclei so as to isolate them from the ventral hypothalamus blocked the release of oxytocin. Undercutting the PV nucleus ipsilateral to the stimulated side of the mid-brain blocked the release of oxytocin, while undercutting the contralateral PV nucleus had no effect. The PV nuclei, therefore, lie on the ascending path of the milk-ejection reflex, the SO nuclei do not, and, from the mid-brain forwards, the ascending pathway remains uncrossed. The course of the reflex pathway was traced rostrally from the mesodiencephalic junction by making narrow transverse knife-cuts and determining which cuts reduced or blocked the release of oxytocin after mid-brain stimulation. At this level, the pathway on each side of the brain is represented by separate dorsal and ventral paths and in the present study it was found that the ventral path is more important than the dorsal path in terms of oxytocin release. The ventral path passes forward in the medial forebrain bundle, in the far-lateral hypothalamus, while the dorsal path enters the posterior hypothalamus dorsally in the periventricular region at the top of the third ventricle and impinges on the thalamic reuniens nucleus. Shortly afterwards the dorsal path swings abruptly in the lateral direction to join the ventral path in the lateral hypothalamus. The reunited pathway then moves forward in this position until it is level with the PV nuclei, where it swings dorsomedially to relay with the lateral tip of the ipsilateral PV nucleus, and in doing so intermingles with the descending neurosecretory fibres from this nucleus.

scholarly journals Crayfish extraretinal photoreception. I. Behavioral and motorneuronal responses to abdominal illumination

1984 ◽  
Vol 109 (1) ◽  
pp. 291-306
Author(s):  
D. H. Edwards
Keyword(s):  
High Frequency ◽  
Response Latencies ◽  
Backward Walking ◽  
Motor Circuits ◽  
Visual Inputs ◽  
Freely Behaving ◽  
Caudal Photoreceptor ◽  
Frequency Burst ◽  
Rostral Part ◽  
Stimulation Of

Stimulation of blinded and sighted crayfish with ventrally directed light evokes a slow tail flexion response or a tail flexion accompanied by backward walking. The response latencies and durations of sighted animals are shorter than those of blinded animals, which indicates that visual inputs can speed a response which can be released by extraretinal photoreceptors alone. Recordings from electrodes implanted in intact, freely behaving animals demonstrate that ventral illumination tonically excites abdominal postural flexor motoneurones. The motoneurone discharge occurs first in caudal segments and then spreads rostrally, as does abdominal flexion around each segmental joint. Illumination of individual abdominal ganglia (A2-A5) tonically excites a similar flexor motoneurone response in cells of the stimulated ganglion and more caudal ganglia. Swimmeret motoneurones are also tonically excited by this stimulus. These responses can be evoked in isolated abdominal nerve cords, indicating that extraretinal photoreceptors present in these ganglia activate motor circuits that are local to the abdomen. Stimulation of A6 excites the caudal photoreceptor neurones, but only excites flexor motoneurones if the abdominal ventral nerve cord is connected to the rostral part of the CNS. The motoneurones respond with repeated bursts of activity that long outlast the stimulus or the initial high-frequency burst of the caudal photoreceptor neurones. These motoneurone responses are similar to those evoked by stimulation of command fibres that also evoke backward walking (Kovac, 1974a).

Electrical high frequency stimulation of the caudate nucleus induces local GABA outflow in freely moving rats

2007 ◽  
Vol 159 (2) ◽  
pp. 286-290 ◽  
Author(s):  
A. Hiller ◽  
S. Loeffler ◽  
C. Haupt ◽  
M. Litza ◽  
U. Hofmann ◽  
...  
Keyword(s):  
Caudate Nucleus ◽  
High Frequency ◽  
High Frequency Stimulation ◽  
Freely Moving Rats ◽  
Frequency Stimulation ◽  
Freely Moving ◽  
Stimulation Of

Prolonged force increase following a high-frequency burst is not due to a sustained elevation of [Ca2+]i

2002 ◽  
Vol 283 (1) ◽  
pp. C42-C47 ◽  
Author(s):  
F. Abbate ◽  
J. D. Bruton ◽  
A. De Haan ◽  
H. Westerblad
Keyword(s):  
Skeletal Muscle ◽  
High Frequency ◽  
Action Potentials ◽  
Stimulation Frequency ◽  
Single Fibers ◽  
Force Increase ◽  
Frequency Burst ◽  
Sustained Increase

A brief high-frequency burst of action potentials results in a sustained force increase in skeletal muscle. The present study investigates whether this force potentiation is the result of a sustained increase of the free myoplasmic [Ca2+] ([Ca2+]i). Single fibers from mouse flexor brevis muscles were stimulated with three impulses at 150 Hz (triplet) at the start of a 350-ms tetanus or in the middle of a 700-ms tetanus; the stimulation frequency of the rest of the tetanus ranged from 20 to 60 Hz. After the triplet, force was significantly ( P < 0.05) increased between 17 and 20% when the triplet was given at the start of the tetanus and between 5 and 18% when the triplet was given in the middle ( n = 7). However, during this potentiation, [Ca2+]iwas not consistently increased. Hence, the increased force following a high-frequency burst is likely due to changes in the myofibrillar properties.

Synchronous bursting in a subset of interneurons inhibitory to the goldfish Mauthner cell: synaptic mediation and plasticity

1994 ◽  
Vol 72 (2) ◽  
pp. 531-541 ◽  
Author(s):  
S. Charpier ◽  
J. C. Behrends ◽  
Y. T. Chang ◽  
C. Sur ◽  
H. Korn
Keyword(s):  
High Frequency ◽  
Action Potentials ◽  
Vestibular Nerve ◽  
Membrane Properties ◽  
Repetitive Firing ◽  
Intracellular Recordings ◽  
M Cell ◽  
Antidromic Activation ◽  
Inhibitory Network ◽  
Stimulation Of

1. Presynaptic activity in the inhibitory network impinging on the Mauthner (M-) cell was investigated in the goldfish medulla in vivo using extra- and intracellular recordings. The inhibitory presynaptic volley elicited by stimulation of the contralateral vestibular nerve consisted of multiple successive peaks at high frequency (up to 1,000 Hz). Less pronounced multicomponent responses were recorded after antidromic activation of the M-cell. Such high-frequency “oscillatory” field potentials also occurred spontaneously. 2. In intracellular recordings, a subset of inhibitory interneurons showed evoked and spontaneous burst discharge. Burst action potentials were correlated with the peaks in the extracellular volley, suggesting that repetitive firing of these cells is synchronized. Nonbursting cells, on the other hand, fired single action potentials in response to vestibular stimuli and were not activated via the M-cell collateral network. 3. Bursting cells were determined morphologically to be part of the feedback inhibitory circuit. Their responses to stimulation of the contralateral vestibular nerve thus suggest the existence of a crossed excitatory pathway to these interneurons. 4. Vestibular-evoked excitatory postsynaptic potentials (EPSPs) in bursting interneurons had a short latency of 0.781 +/- 0.08 ms (mean +/- SD, n = 18) but reached threshold at 2.25 +/- 1 ms (n = 21). These characteristics are suggestive of a chemically mediated EPSP. Indeed, the evoked synchronous repetitive activity of these cells was prevented by superfusion with excitatory amino-acid receptor antagonists. 5. Bursting neurons showed several characteristics that differentiate them from nonbursting cells, including brief action potentials, plateau responses, and intense spontaneous subthreshold activity. 6. With extracellular recordings, tetanization of contralateral vestibular primary afferents evoked a long-lasting potentiation of oscillatory population responses in 11 of 27 cases. Furthermore in three experiments, the frequency of occurrence of spontaneous bursts was enhanced and a similar facilitation was detected at the intracellular level. 7. We conclude that a subset of interneurons in this inhibitory network is capable of repetitive discharges and that evoked as well as spontaneous firing in this population is synchronized. Although electrical coupling between interneurons may mediate synchronization and intrinsic membrane properties may promote burst activity, our data suggest strongly that repetitive firing requires chemically mediated transmission. Furthermore they indicate that the mechanisms underlying evoked as well as spontaneous bursting in this population show activity-dependent plasticity.

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