The changes in the activity of pudendal motoneurons in relation to reflex micturition evoked in decerebrate cats

Shimoda, Naotake; Takakusaki, Kaoru; Nishizawa, Osamu; Tsuchida, Seigi; Mori, Shigemi

doi:10.1016/0304-3940(92)90430-f

Cited by 25 publications

(20 citation statements)

References 19 publications

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“…In the present study it was possible to evoke orthodromic action potentials that failed when the motoneuron membrane hyperpolarized during micturition (see also Shimoda et al, 1992). Hyperpolarization of EUS motoneurons decreases the likelihood of EPSPs reaching threshold for an action potential, and thus, the EUS muscle is less likely to be active during micturition.…”

Section: Discussionmentioning

confidence: 94%

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Reduction of perineal evoked excitatory postsynaptic potentials in cat lumbar and sacral motoneurons during micturition

Fedirchuk

Shefchyk

1994

J. Neurosci.

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These experiments were undertaken to examine whether both premotoneuronal mechanisms and direct actions on motoneurons could contribute to suppression of excitatory perineal reflex pathways during micturition. Intracellular recordings were obtained from motoneurons innervating the external urethral sphincter (EUS), external anal sphincter (EAS), and selected hindlimb muscles in decerebrate male cats. The peak amplitudes of EPSPs evoked by electrical stimulation of peripheral cutaneous afferents were measured during micturition. In the EUS, EAS, and hindlimb motoneurons examined, EPSPs produced by stimulation of perineal afferents (superficial perineal or sensory pudendal nerves) were reduced in amplitude during micturition. The sample of PSPs evoked by stimulation of hindlimb cutaneous nerves recorded in hindlimb motoneurons revealed that these PSPs could also be reduced. In contrast, no changes were seen in monosynaptic EPSPs evoked by muscle afferent stimulation. The present study demonstrates that during micturition there is a strong suppression of perineal reflexes to both sphincter and hindlimb motoneurons. Since reduced EUS activity is required for efficient micturition, suppression of the strong excitatory perineal input to EUS motoneurons likely contributes to decreased EUS activity during the bladder contraction. It appears that the micturition circuitry utilizes both premotoneuronal mechanisms and direct motoneuronal inhibition to achieve this reflex suppression. The function of the micturition-related reduction of perineal reflexes to hindlimb or EAS motoneurons is not known at this time and further investigations are required to elucidate the interaction between micturition circuitry and hindlimb cutaneous pathways.

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Section: Discussionmentioning

confidence: 94%

“…Previous studies have demonstrated that EUS motoneurons hyperpolarize during micturition (Shimoda et al, 1992;Fedirchuk and Shefchyk, 1993). This hyperpolarization was associated with an increase in motoneuronal membrane conductance and was reversed with injection of chloride into the motoneuron (Fedirchuk and Shefchyk, 1993).…”

mentioning

confidence: 97%

Reduction of perineal evoked excitatory postsynaptic potentials in cat lumbar and sacral motoneurons during micturition

Fedirchuk

Shefchyk

1994

J. Neurosci.

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“…In many species, EUS activity increases during the early stages of bladder filling in a way that is dependent on both descending and segmental inputs (Garry et al 1959;Mackel 1979;Pikov et al 1998;Shimoda et al 1992). For example, tonic EUS activity increases during bladder filling in a manner that helps maintain continence (i.e., guarding reflex; Cruz and Downie 2005;.…”

Section: Relationship Between Eus Motoneuron Properties and Motor Funmentioning

confidence: 99%

External Urethral Sphincter Motoneuron Properties in Adult Female Rats Studied In Vitro

Carp

Tennissen

Liebschutz

et al. 2010

Journal of Neurophysiology

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Carp JS, Tennissen AM, Liebschutz JE, Chen XY, Wolpaw JR. External urethral sphincter motoneuron properties in adult female rats studied in vitro. J Neurophysiol 104: 1286 -1300, 2010. First published June 23, 2010 doi:10.1152/jn.00224.2010. The external urethral sphincter (EUS) muscle plays a crucial role in lower urinary tract function: its activation helps maintain continence, whereas its relaxation contributes to micturition. To determine how the intrinsic properties of its motoneurons contribute to its physiological function, we have obtained intracellular current-clamp recordings from 49 EUS motoneurons in acutely isolated spinal cord slices from adult female rats. In all, 45% of EUS motoneurons fired spontaneously and steadily (average rate ϭ 12-27 pulses/s). EUS motoneurons were highly excitable, having lower rheobase, higher input resistance, and smaller threshold depolarization than those of rat hindlimb motoneurons recorded in vitro. Correlations between these properties and afterhyperpolarization half-decay time are consistent with EUS motoneurons having characteristics of both fast and slow motor unit types. EUS motoneurons with a slow-like spectrum of properties exhibited spontaneous firing more often than those with fast-like characteristics. During triangular current ramp-induced repetitive firing, recruitment typically occurred at lower current levels than those at derecruitment, although the opposite pattern occurred in 10% of EUS motoneurons. This percentage was likely underestimated due to firing rate adaptation. These findings are consistent with the presence of a basal level of persistent inward current (PIC) in at least some EUS motoneurons. The low EUS motoneuron current and voltage thresholds make them readily recruitable, rendering them well suited to their physiological role in continence. The expression of firing behaviors consistent with PIC activation in this highly reduced preparation raises the possibility that in the intact animal, PICs contribute to urinary function not only through neuromodulator-dependent but also through neuromodulatorindependent mechanisms. I N T R O D U C T I O NThe external urethral sphincter (EUS) muscle performs the critical function of restricting urinary flow through the urethra during continence and permitting flow during micturition. Much prior research has focused on how the brain controls spinal cord networks that operate this muscle and coordinate its function with the other muscles important in bladder control and on how peripheral input contributes to the control of lower urinary tract function (de Groat 2006).A full understanding of how descending and sensory inputs contribute to control of urethral function requires knowledge of how the EUS motoneuron integrates and transforms supraspinal motor commands, sensory inputs, and spinal interneuronal activity into sphincter muscle activity. The intrinsic properties of EUS motoneurons are similar in many ways to the much more extensively studied hindlimb motoneurons, but with specific differences tha...

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“…8. During micturition there is postsynaptic inhibition of sphincter motoneurones (Shimoda et al 1992;Fedirchuk & Shefchyk, 1993) and perhaps inhibition of excitatory interneuronal pathways. The results of this study suggest that during micturition, PAD of some perineal afferents contributes to the reduced sphincter activity necessary for efficient bladder emptying.…”

Section: Pad Of Perineal Afferents During Micturitionmentioning

confidence: 99%

Primary afferent depolarization of cat pudendal afferents during micturition and segmental afferent stimulation.

Angel¹,

Fyda²,

McCrea³

et al. 1994

The Journal of Physiology

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1. This investigation examined primary afferent depolarization (PAD) of perineal afferents during micturition and evoked by electrical stimulation of perineal, hindlimb cutaneous and muscle-nerves. PAD was inferred from changes in excitability of spinal terminals of single afferents in decerebrate and chloralose-anaesthetized paralysed male cats. Observations were made on perineal afferent fibres travelling in the sensory branch of the pudendal (SPud) and superficial perineal (SPeri) nerves.2. Micturition was evoked by distension of the bladder and excitability changes were measured in twenty-seven SPud afferents. In ten afferents, there was evidence of PAD during micturition. The time course of PAD was similar to the period of decreased activity in sphincter muscle efferents during micturition. In four afferents, there was decreased excitability during voiding that was interpreted as removal of tonic PAD. In the remaining thirteen afferents there were no detectable changes in excitability.Bladder distension in the absence of micturition failed to change the excitability of any SPud afferents tested. 3. Almost all SPud afferents were subject to PAD upon stimulation of cutaneous nerves.Superficial perineal, long saphenous, caudal cutaneous sural and the predominantly cutaneous posterior tibial nerves were particularly effective in evoking PAD. While group I strength stimulation of hindlimb muscle-nerves produced PAD of some SPud fibres, group II stimulation often increased the magnitude or incidence of PAD. The patterns and magnitude of PAD observed in SPeri afferents were similar to those observed in SPud afferents.4. Since some SPud afferents were subject to PAD during micturition, PAD is prpbably one mechanism responsible for suppression of sphincter reflexes during niicturition.Additional roles of PAD of perineal afferents evoked by activation of hindlimb cutaneous and muscle afferents are discussed.

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The changes in the activity of pudendal motoneurons in relation to reflex micturition evoked in decerebrate cats

Cited by 25 publications

References 19 publications

Reduction of perineal evoked excitatory postsynaptic potentials in cat lumbar and sacral motoneurons during micturition

Reduction of perineal evoked excitatory postsynaptic potentials in cat lumbar and sacral motoneurons during micturition

External Urethral Sphincter Motoneuron Properties in Adult Female Rats Studied In Vitro

Primary afferent depolarization of cat pudendal afferents during micturition and segmental afferent stimulation.

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