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W C de Groat

Publications and source records attributed to W C de Groat.

At least 109 records · Page 6Linked to original sources
PubMed1995

Effect of capsaicin on micturition and associated reflexes in chronic spinal rats.

The role of capsaicin-sensitive bladder afferents in micturition was studied in unanesthetized chronic spinal rats. Reflex voiding in response to tactile stimulation of the perigenital region appeared 5-9 days after spinal cord injury (SCI) whereas voiding induced by bladder distension occurred 2-3 weeks after SCI. The frequency and amplitude of reflex bladder contractions recorded under isovolumetric conditions were similar in chronic spinal and urethane-anesthetized CNS-intact rats. However, cystometrograms (CMGs) performed 6-8 weeks after SCI revealed that the chronic spinal rats had larger bladder capacities (1.86 ml) than CNS-intact rats (0.48 ml) and also exhibited multiple, small-amplitude, nonvoiding bladder contractions that were not detected in CNS-intact rats. Administration of capsaicin (50 mg/kg s.c.) acutely (onset 14-40 min) suppressed reflex bladder activity induced by bladder distension or by perigenital stimulation in chronic spinal animals. However, pretreatment of chronic spinal rats with capsaicin (125 mg/kg s.c.) 4 days before the experiment did not depress voiding reflexes or change bladder capacity but did eliminate the nonvoiding contractions. Inhibition of reflex bladder contractions by mechanical stimulation of rectoanal canal or the uterine cervix-vagina was not altered by pretreatment with capsaicin. These data indicate that capsaicin-sensitive bladder afferents are not essential for the initiation of reflex micturition in chronic spinal rats. However, these afferents do contribute to hyperactivity of the bladder during the filling phase of the CMG. Thus, capsaicin-sensitive bladder afferents should be evaluated as possible targets for the pharmacological treatment of bladder hyperreflexia in patients with SCI.

Afferent Pathways↗
PubMed1995

Role of glutamate and NMDA receptors in the descending limb of the spinobulbospinal micturition reflex pathway of the rat.

MK-801, an NMDA receptor antagonist administered intravenously or intrathecally to the L6-S1 spinal cord inhibited in a dose dependent manner the amplitude of isovolumetric bladder contractions evoked by electrical stimulation in the pontine micturition center (PMC) in urethane anesthetized rats. The mean threshold dose of MK-801 was 10 +/- 6 micrograms/kg i.v. and 10 +/- 1 micrograms i.t. Bladder contractions were completely inhibited at doses ranging from 300 to 3000 micrograms/kg i.v. and from 18 to 48 micrograms i.t. These data indicate that NMDA glutamatergic receptors play an important role in excitatory transmission in the descending pathway from the PMC to the spinal segmental circuitry involved in the control of the urinary bladder.

Animals↗
PubMed1995

Increased expression of neuronal nitric oxide synthase in dorsal root ganglion neurons after systemic capsaicin administration.

Nitric oxide synthase which is constitutively expressed in some neurons can be induced in other neurons by pathological conditions. For example, sciatic nerve or pelvic nerve transection induced nitric oxide synthase expression in lumbosacral dorsal root ganglion cells. This occurred in small to medium sized dorsal root ganglion neurons suggesting that this change might be limited to, or most prominent in, C-fiber afferents. These afferents are also very sensitive to the neurotoxin, capsaicin, which can deplete neuropeptide stores in C-fibers and in high doses cause degeneration of C-fiber afferent pathways. The present study was undertaken to determine if a chemically induced injury elicited in small diameter afferent neurons by systemic administration of capsaicin can induce a change in nitric oxide synthase expression similar to that elicited by peripheral nerve injury. Following capsaicin pretreatment (three days) a significant increase in the number of nitric oxide synthase-immunoreactive cells was detected in dorsal root ganglia. The increase was most prominent (34-63 fold) in the L5-S1 dorsal root ganglia but also substantial (2-17 fold) in cervical, caudal thoracic and rostral lumbar dorsal root ganglia. These results indicate that the expression of nitric oxide synthase-immunoreactivity in afferent neurons in the dorsal root ganglia is plastic and can be upregulated in response to chemical stimulation and/or injury. It is possible that nitric oxide formed by enhanced expression of nitric oxide synthase may play a role in capsaicin-induced neurotoxicity.

Animals↗
PubMed1995

Prejunctional facilitatory alpha 1-adrenoceptors in the rat urinary bladder.

1. The effect of activation of alpha 1-adrenoceptors on acetylcholine (ACh) release and neurally evoked contractile responses induced by electrical field stimulation was investigated in smooth muscle strips from the rat urinary bladder. 2. Neurogenic contractions were facilitated by the alpha 1-adrenoceptor agonists, phenylephrine (PE) (2-128 microM) and methoxamine (2-128 microM) in a dose-dependent manner. These agents also increased small amplitude spontaneous contractions of bladder strips and in 10% of strips increased basal tone. However, contractions elicited by exogenous ACh (1-10 microM) were not affected by alpha 1-agonists. 3. The magnitude of the PE facilitation was higher at lower frequencies (1-5 Hz) or at submaximal intensities of stimulation and at lower Ca2+ concentrations (0.5-1 mM). The selective alpha 1-adrenoceptor antagonist, terazosin (TRZ) (0.05-1 microM), competitively inhibited (pA2 value: 8.6) the PE facilitation of the neurally evoked contractions but not the PE induced increase of spontaneous contractions. 4. [3H]-noradrenaline (NA) and [14C]-ACh release evoked by electrical field stimulation were increased (140% and 173%, respectively) by 2 microM PE. TRZ (0.05-0.1 microM) blocked the PE facilitation of ACh release but not the facilitation of NA release. TRZ alone did not alter the release of ACh or NA nor the amplitude of the neurogenic contractions. 5. PE (2 microM) did not alter the basal release of ACh but did increase (by 180%) the basal release of NA. Desipramine (2 microM) blocked this effect of PE and also the PE-facilitation of evoked ACh and NA release. 6. It is concluded that cholinergic terminals in the rat urinary bladder exhibit alpha 1-adrenoceptors which can facilitate the release of transmitter. However, under the conditions of our experiments it appears that cholinergic transmission is not modulated by alpha 1 adrenergic mechanisms. Further studies are necessary to determine whether these receptors can be activated by endogenous noradrenaline released within the bladder.

Acetylcholine↗
PubMed1995

Increased expression of neuronal nitric oxide synthase (NOS) in visceral neurons after nerve injury.

The distribution of nitric oxide synthase immunoreactivity (NOS-IR) and the changes in this distribution after peripheral axotomy were examined in lumbosacral afferent and preganglionic neurons (PGNs) innervating the pelvic viscera of the male rat. The visceral neurons in L6-S1 and L1-L2 dorsal root ganglia (DRG) and in the spinal cord were identified by retrograde axonal transport following injection of Fluorogold (FG) into the major pelvic ganglion (MPG). Axotomy was performed by removing the MPG on one side 2-4 weeks prior to sacrificing the animals. A differential distribution of NOS-IR was detected in DRG cells at different segmental levels of control animals. Significantly greater numbers of NOS-IR cells were present in thoracic (T8, T10, T12; 30-44 cell profiles/section) and rostral lumbar DRGs (L1-L2; 3-15 NOS-IR cell profiles/section) compared to caudal lumbosacral (L5-S1) DRGs (0.2-0.7 cell profiles/section). A significant increase in the number of NOS-IR cells was detected in the L6-S1 DRG (p < or = 0.001; 11 NOS-IR cell profiles/section) but not in the L2 or L5 DRG ipsilateral to axotomy. In these ganglia, an average of 37.0 +/- 4.0% (L6) and 20.6 +/- 2.2% (S1), respectively, of FG-labeled pelvic afferent neurons were NOS-IR compared to 1.1 +/- 0.5% (L6) and 2.5 +/- 1.4% (S1) contralateral to the axotomy. Following axotomy, a significantly greater percentage of dye-labeled pelvic visceral afferents in the L1 and L2 DRG also exhibited NOS-IR in comparison to the contralateral side. Following axotomy, NOS-IR fibers were detected along the lateral edge of the dorsal horn extending from Lissauer's tract to the region of the sacral parasympathetic nucleus (SPN) on the ipsilateral side of the L6 and S1 spinal segments. These NOS-IR fibers were not detected in adjacent spinal segments (L4, L5, or S2). Axotomy also changed the numbers of NADPH-d-positive and NOS-IR cells in the region of the SPN in the L6 spinal segment. Contralateral to the axotomy 38.3 +/- 4.0% of PGNs in the L6 spinal segment were colabeled with NOS-IR; however, ipsilateral to axotomy, a significantly greater percentage (61.0 +/- 3.0%; p < or = 0.01) of PGNs exhibited NOS-IR. Axotomy did not alter the distribution of PGNs in the S1 segment exhibiting NOS-IR. These results indicate that NOS-IR in visceral afferent and PGNs is plastic and can be upregulated by peripheral nerve injury.

Afferent Pathways↗
PubMed1995

Neural control of urethral outlet activity in vivo: role of nitric oxide.

The present study investigated the role of nitric oxide (NO) in the reflex changes in urethral outlet activity during micturition. Isovolumetric bladder contractions, urethral pressure and external urethral sphincter electromyogram (EUS EMG) activity were recorded independently in urethane-anesthetized rats. During reflex bladder contractions, the urethra exhibited reflex responses characterized by an initial decrease in urethral pressure in conjunction with a rise in bladder pressure. This was followed by a period of high frequency oscillations (HFOs) associated with maximal urethral relaxation and burst type EUS EMG activity. Administration of N-nitro-L-arginine (L-NOARG) 10 mg./kg. intravenously, a nitric oxide synthase inhibitor, reversibly decreased the magnitude (62%, p < 0.05) and duration (40%, p < 0.05) of reflex urethral relaxation (N = 7). In 4 additional experiments, L-NOARG (10 to 15 mg./kg. intravenously) completely eliminated reflex urethral relaxation during micturition, and this effect was reversed in all animals by the administration of L-arginine (100 to 150 mg./kg. intravenously). Administration of N-nitro-D-arginine (D-NOARG) (10 to 30 mg./kg. intravenously) had no effect on reflex urethral relaxation. Neuromuscular blockade (vecuronium bromide 5 mg./kg. intravenously) reversibly decreased resting urethral pressure and eliminated the HFOs. The urethral smooth muscle relaxation that remained after neuromuscular blockade was eliminated following administration of L-NOARG (10 mg./kg. intravenously) in 2 of 3 animals. These results suggest that reflex urethral responses during micturition involve changes in both smooth and striated muscle activity, and that the predominant neurotransmitter mechanisms that mediate reflex urethral smooth muscle relaxation involve NO.

Animals↗
PubMed1994

M1 muscarinic receptor-mediated facilitation of acetylcholine release in the rat urinary bladder.

1. Release of [3H]ACh in response to electrical field stimulation (10 Hz) was measured in strips of rat urinary bladder and cardiac atrial tissues previously incubated with [3H]choline. 2. The volley output of [3H]ACh release was positively correlated with frequency of stimulation in the urinary bladder but negatively correlated in the atrium. 3. The quantity of [3H]ACh release was influenced by the pattern and duration of stimulation. Continuous stimulation (CS) with trains of 100 shocks released 10 times larger amounts of ACh than the same number of shocks presented as short trains of intermittent stimulation (IS): ten shocks per train with 5 s inter-train intervals. 4. The facilitation of transmitter release was antagonized completely by the administration of atropine (1 microM) or pirenzepine (0.05 microM), a selective M1 antagonist. Eserine, an anticholinesterase agent, markedly facilitated ACh release induced by CS and IS. This effect was blocked by atropine. 5. Release of ACh from atrial strips did not exhibit CS-induced facilitation. Eserine decreased IS- and CS-evoked ACh release in the atrium. 6. It is concluded that continuous stimulation of postganglionic cholinergic nerves in the rat urinary bladder leads to the activation of M1 muscarinic, facilitatory presynaptic receptors which enhance the release of ACh. Presynaptic facilitation may be an important mechanism for modulating neural input to the bladder during micturition.

Acetylcholine↗
PubMed1994

Ontogeny of nitric oxide synthase in the lumbosacral spinal cord of the neonatal rat.

The present experiments were performed to determine the temporal pattern of expression of nitric oxide synthase (NOS) immunoreactivity in cells and fibers in the lumbosacral spinal cord during early postnatal development and to examine the relationship between NADPH-diaphorase (NADPH-d) activity and NOS-immunoreactivity (IR). At postnatal days 0-1 and 4-5, NADPH-d and NOS-IR were detected in L6-S1 segments of the spinal cord in cells and fibers in the region of the sacral parasympathetic nucleus (SPN), dorsal commissure and around the central canal but were absent in the superficial layers of the dorsal horn. Fiber staining on the lateral edge of the dorsal horn (the lateral collateral pathway, LCP) in a region containing primary afferent projections from the pelvic viscera and in a fiber tract in the dorsolateral funiculus was also not detectable. At days 4-5 some stained cells were detected in the deeper laminae of the dorsal horn. At postnatal days 10-12 and 20-22, cells in the region of the SPN, around the central canal and in the superficial laminae of the dorsal horn exhibited NADPH-d and NOS-IR. NADPH-d and NOS-IR fiber staining in the superficial laminae of the dorsal horn and the dorsolateral funiculus was observed at postnatal days 10-12 and increased in staining intensity by postnatal days 20-22. NADPH-d fiber staining in the LCP was not prominent at postnatal days 10-12; however, prominent fiber staining at this site did occur by postnatal days 20-22 and in adult animals. In postnatal days 20-22 and in adult animals NADPH-d activity and NOS-IR had a similar distribution except in the LCP where NADPH-d stained fibers did not exhibit NOS-IR. These data indicate that NADPH-d and NOS-IR in the spinal cord exhibit marked changes during the early postnatal development. The changes in afferent projections in the LCP may be related to maturation of visceral reflex pathways including micturition.

Amino Acid Oxidoreductases↗
PubMed1994

Differential distribution of nitric oxide synthase in neural pathways to the urogenital organs (urethra, penis, urinary bladder) of the rat.

Axonal tracing techniques were used in combination with histochemical methods (NADPH-diaphorase activity and nitric oxide synthase immunoreactivity) to examine the distribution of nitric oxide synthase (NOS) in the neural pathways to the urogenital organs of the male rat. The major goal of this study was to compare the histochemical properties of the efferent and afferent neurons innervating the urethra with the properties of neurons innervating the penis and bladder. In the major pelvic ganglion (MPG) large percentages of postganglionic neurons innervating the urethra (44%) and the penis (97%) exhibited NADPH-diaphorase (NADPH-d) staining whereas only a small percentage (3.5%) of neurons innervating the bladder were N-d positive. Urethral neurons stained for N-d were on average smaller (33.3 microns diameter) than unstained neurons (54.5 microns diameter). The histochemical difference between the three types of neurons was also reflected in NOS-immunoreactivity (IR); however, the absolute percentage of neurons exhibiting NOS-IR was low: penis (21%), urethra (11%) and bladder (0%). Axonal varicosities staining for N-d or NOS-IR were noted in the MPG in close proximity to unidentified neurons and neurons innervating the urogenital organs. A considerable number of afferent neurons in the lumbosacral dorsal root ganglia (DRG) stained for N-d (64 cells/L6, 35 cells/S1 section); however, only small numbers of neurons (average 1 cell/section) exhibited NOS-IR. N-d activity was detected in a large percentage of urethral (55%) and bladder (80%) afferent neurons in the L6-S1 dorsal root ganglia (DRG) but in relatively few (12%) penile afferent neurons in the L6 ganglia. These results suggest that the contribution of nitric oxide (NO) to neurotransmission varies considerably in different urogenital organs. NO could have a significant role in postganglionic efferent pathways to the urethra and penis but very likely has no role in the efferent pathways to the bladder. Similarly, the prominence of N-d staining in some DRG neurons (e.g. urethra and bladder) but not others (penile) also raises the possibility of a varying role of NO in afferent pathways. However, in these neurons N-d staining was not paralleled by NOS-IR, which was present in only a small percentage of neurons. Thus, N-d staining may not reflect the presence of NO in afferent pathways to the pelvic viscera.

Afferent Pathways↗
PubMed1994

Morphological and electrophysiological analysis of the peripheral and central afferent pathways from the clitoris of the cat.

Afferent neurons projecting to the clitoris of the cat were identified by WGA-HRP tracing in the S1 and S2 dorsal root ganglia. An average of 433 cells were identified on each side of the animal. 85% and 15% of the labeled cells were located in the S1 and S2 dorsal root ganglia, respectively. The average cross sectional area of clitoral afferent neuron profiles was 1,479 +/- 627 micron2. Unilateral transection of the pudendal nerve reduced the number of labeled cells to 1% of that on the control side. Central projections of clitoral afferents were identified in the lumbo-sacral segments (L7-S3) of the spinal cord. HRP labeled fibers were located in the marginal zone on the medial side of dorsal horn and extended into the dorsal half of the dorsal gray commissure. Electrophysiological recordings detected axonal volleys in the pudendal nerve and S1 dorsal root in response to electrical stimulation (threshold, 1-4 V) of the clitoral surface. Estimated axonal conduction velocities at the two sites ranged from 7-27 m/s and 0.6-30 m/s, respectively. Multi-unit recordings from dorsal roots in the lumbo-sacral segments revealed that non-noxious pressure stimulation of the clitoris evoked discharges in the S1 dorsal root. Small increases were also detected in the S2 and L7 roots. Single unit discharges recorded from S1 dorsal roots were activated by electrical stimulation of the clitoral surface at thresholds of 0.6-1.2 V and latencies of 1.5-1.8 ms (estimated conduction velocities of 24-30 m/s.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1994

Effects of MK-801 and CNQX, glutamate receptor antagonists, on bladder activity in neonatal rats.

This study was undertaken to examine the role of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) glutamatergic receptors in the regulation of urinary bladder activity in the neonatal rat. Experiments were conducted using an in vitro spinal cord-bladder (SB) preparation from 1- to 5-day-old rats or awake neonatal rats 6 and 7 days old. SB preparations were isolated under hypothermic anesthesia. Isovolumetric bladder contractions occurred spontaneously, were induced by electrical stimulation (ES) of the bladder wall or were evoked reflexly by perineal tactile stimulation (PS). MK-801 (3-30 microM), an NMDA receptor antagonist, enhanced the amplitude of spontaneous, ES- and PS-evoked contractions. Removal of the spinal cord after MK-801 abolished PS-evoked reflex contractions but did not change the amplitude of spontaneous and ES-evoked contractions. Removal of the spinal cord in the absence of MK-801 increased the amplitude of spontaneous and ES-evoked contractions, indicating that the bladder is subject to a tonic inhibitory control originating in the spinal cord. 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 3-30 microM), an AMPA receptor antagonist, decreased the amplitude of PS-evoked contractions and the frequency of spontaneous contractions in the SB preparation. Removal of the spinal cord after CNQX enhanced the amplitude of spontaneous and ES-evoked contractions but abolished PS-evoked contractions. The frequency of spontaneous contractions which decreased after CNQX increased to near control levels after removal of the spinal cord. In awake neonatal rats, intraperitoneal injection of MK-801 (3 mg/kg) induced spontaneous micturition. A large dose of CNQX (30 mg/kg) decreased PS-evoked micturition volume. These results suggest that NMDA glutamatergic receptors are involved in a lumbosacral spinal inhibitory mechanism controlling bladder activity; whereas AMPA glutamatergic receptors are involved in the perineal-to-bladder reflex pathway in neonatal rats.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1994

Interactions between glutamatergic and monoaminergic systems controlling the micturition reflex in the urethane-anesthetized rat.

The effects of MK-801 (0.001-3 mg/kg i.v.), a non-competitive NMDA glutamate receptor antagonist, on the micturition reflex were examined during continuous saline infusion (0.21 ml/min) cystometrograms (CMGs) in urethane-anesthetized (1.2 g/kg s.c.) rats pretreated with either reserpine (5 mg/kg i.p.), p-chlorophenylalanine (p-CPA; 150 mg/kg i.p., twice a day, 3 consecutive days), L-DOPA (200 mg/kg i.p. + carbidopa 100 mg/kg i.p.) or apomorphine (10 mg/kg i.v.). Pretreatment with reserpine 8-12 h prior to the CMG recording, antagonized the inhibitory effect of MK-801 on the amplitude of micturition contractions while pretreatment with vehicle had no effect. However, pretreatment with the same dose of reserpine 18-22 h prior to the experiment failed to antagonize the inhibitory effect of MK-801. Both reserpine pretreatments enhanced the amplitude of reflex bladder contractions. Pretreatment with p-CPA did not alter bladder activity or the inhibitory effect of MK-801 on amplitude of micturition contractions. When administered 15 min prior to the MK-801, L-DOPA or apomorphine reduced by 70% or 63%, respectively, the maximal inhibitory effect of MK-801 on the amplitude of reflex bladder contractions. These data suggest that there is an interaction between glutamatergic and monoaminergic mechanisms in the regulation of micturition reflex. Since reserpine which reduces both catecholamine and serotonin levels in the nervous system altered the depressant effect of MK-801 on bladder activity, but p-CPA, an agent which depletes serotonin stores, did not, it is concluded that catecholaminergic pathways are involved in this interaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1994

Consequences of spinal cord injury during the neonatal period on micturition reflexes in the rat.

This study examined the changes in micturition reflexes following spinal cord transection in neonatal rats to determine: (1) whether injury to the immature nervous system allows greater recovery of function than injury in adult animals and (2) whether the management of the lower urinary tract during the initial period following spinal injury influences the subsequent recovery of function. In one experiment, bladder-to-bladder reflexes in decerebrate neonatal rats (Day 15-Day 26) were tested 5-11 days after T8-T10 spinalization. While there was no difference in the amplitude and duration of reflex bladder contractions or bladder capacity between these pups and their nonspinalized controls, the spinalized pups exhibited incomplete voiding and an uncoordinated urethral sphincter (bladder/sphincter dyssynergia). It is concluded that the dyssynergia is inherent to the spinal micturition reflexes and is not due to an initial period of bladder areflexia and overdistension since in both the control and spinalized neonates micturition is initiated by a somatobladder reflex triggered when the mother licks the perineum. A second experiment tested whether neonatal spinal cord injury led to improved bladder function in adulthood. Postnatal Day 1 rat pups were spinalized at T8-T10 and returned to their mothers for the remainder of the neonatal period, and their bladder reflexes were tested 4-6 months later under urethane anesthesia. These rats showed the same lower urinary tract dysfunctions (bladder/sphincter dyssynergia, high residual volumes, decreased percentage voided volumes, and large-amplitude, long-duration bladder contractions) as adult rats that were spinalized as adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Differential localization of neuronal nitric oxide synthase immunoreactivity and NADPH-diaphorase activity in the cat spinal cord.

The distributions of neuronal nitric oxide synthase immunoreactivity (NOS-IR) and NADPH-diaphorase (NADPH-d) activity were compared in the cat spinal cord. NOS-IR in neurons around the central canal, in superficial laminae (I and II) of the dorsal horn, in the dorsal commissure, and in fibers in the superficial dorsal horn was observed at all levels of the spinal cord. In these regions, NOS-IR paralleled NADPH-d activity. The sympathetic autonomic nucleus in the rostral lumbar and thoracic segments exhibited prominent NOS-IR and NADPH-d activity, whereas the parasympathetic nucleus in the sacral segments did not exhibit NOS-IR or NADPH-d activity. Within the region of the sympathetic autonomic nucleus, fewer NOS-IR cells were identified compared with NADPH-d cells. The most prominent NADPH-d activity in the sacral segments occurred in fibers within and extending from Lissauer's tract in laminae I and V along the lateral edge of the dorsal horn to the region of the sacral parasympathetic nucleus. These afferent projections did not exhibit NOS-IR; however, NOS-IR and NADPH-d activity were demonstrated in dorsal root ganglion cells (L7-S2). The results of this study demonstrate that NADPH-d activity is not always a specific histochemical marker for NO-containing neural structures.

Amino Acid Oxidoreductases↗
PubMed1994

Patch-clamp recordings from subpopulations of autonomic and afferent neurons identified by axonal tracing techniques.

This study determined whether axonal tracing methods can be used in combination with patch-clamp techniques to examine the electrical properties of identified populations of autonomic and afferent neurons in the adult rat. Fluorescent dyes (Fast Blue, FB and Fluoro-Gold, FG) were injected into the wall of the urinary bladder or colon and into various somatic structures to label postganglionic neurons in the major pelvic ganglia (MPG) as well as visceral and somatic afferent neurons in the lumbosacral dorsal root ganglia (DRG) and trigeminal ganglia (TG). One to 3 weeks after dye injection, neurons were isolated from ganglia by enzymatic dissociation. Following dissociation, single neurons labelled with FB were identified in the three types of ganglion preparations; however FG was only identified consistently in TG neurons. FB was retained in neurons during short-term culture (1-5 days). Following 10 to 20 s exposure to UV light which was required for identification of the cells, whole-cell patch-clamp recordings revealed that the electrophysiological properties of FB-labelled cells did not differ from those of unlabelled cells. However, a more prolonged exposure (1-5 min) of the neurons to UV light produced irreversible damage to the cells which was evident as changes in the action potential, sodium current and resting membrane potential. These results indicate that patch-clamp recording in combination with axonal tracing is a useful approach for studying the electrical properties of identified populations of autonomic and afferent neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1994

Alterations in neural pathways to the urinary bladder of the rat in response to streptozotocin-induced diabetes.

Voiding dysfunction in diabetics has been attributed to a variety of causes including an axonopathy in autonomic pathways to the urinary bladder. The present study was undertaken to determine whether changes occurred in afferent and efferent neurons supplying bladders of streptozotocin (STZ)-induced diabetic rats. Nine weeks after STZ treatment, the mean cross-sectional area for retrogradely labeled (Fluoro-Gold) bladder neurons in the major pelvic ganglion (MPG) was greater in diabetics (364 microns 2) than controls (300 microns 2). The number of labeled neurons was similar in these groups. In contrast, mean cross-sectional areas of bladder afferent neurons labeled with WGA-HRP in the L6 and S1 dorsal root ganglia (DRG) were smaller (393 microns 2) in diabetics than in normal rats (528 microns 2). In addition, very few DRG neurons were labeled in STZ-treated rats and transganglionic labeling of bladder afferent projections in the L6 and S1 spinal cord with WGA-HRP was sparse. Radioimmunoassay studies revealed that substance P was reduced by 70% in the MPG and by 40% in L6 DRG, yet this peptide was unchanged in the bladders of diabetic rats. The amounts of VIP in the MPG and DRG of diabetics and controls were similar, while VIP in the bladder was increased in diabetics. These observations indicate that both afferent and efferent neurons innervating the urinary bladder are altered in the STZ-induced diabetic rat. In addition, axonal transport in visceral afferent pathways may be disrupted.

Afferent Pathways↗