Vesical Parasympathetic Ganglia Research Articles

Purinergic cation channels in neurons of rabbit vesical parasympathetic ganglia

Membrane current was recorded from neurons in rabbit vesical parasympathetic ganglia, utilizing single electrode voltage clamp techniques. ATP (0.1–1 mM) caused an inward current ( I ATp) associated with an increased conductance at a holding potential of −50 mV. ADP (0.1–1 mM) and 5′- O-3-thiotriphosphate (0.1–0.6 mM) but not AMP (0.3–2 mM) and adenosine (0.1–2 mM) mimicked the actions of ATP. The I ATp reversed its polarity at −12.1 ± 1.4 mV. The amplitude of the I ATp was depressed in low sodium solutions and in nominally calcium-free solutions but not in low chloride solutions. Suramin (10–100 μM) and reactive blue 2 (10–100 μM), P 2-antagonists, reversibly depressed the I ATp. In contrast, hexamethonium (100 μM) did not affect the I ATp. These data suggest that ATP activates cation channels through P 2X receptor subtypes in rabbit parasympathetic neurons.

Activation of calcium-dependent chloride channels causes post-tetanic depolarization in rabbit parasympathetic neurons

Intracellular recordings were made from neurons in rabbit and feline vesical parasympathetic ganglia in vitro. In response to cathodal current injection (0.1–1 nA for 2–20 ms) the majority of rabbit neurons (229 out of 250) exhibited a single action potential that was followed by a fast and slow after-hyperpolarization (sAHP neuron). The remainder of the cells exhibited an action potential followed by only a fast after-hyperpolarization (fAHP neuron). fAHP neurons did not exhibit anomalous rectification and a spontaneous rhythmic hyperpolarization, which were common membrane properties in sAHP neurons. In response to a train of cathodal current pulses (5–20 Hz for 0.1–10 s), fAHP neurons exhibited action potentials followed by a post-tetanic depolarization (PTD). The PTD was associated with a decrease in membrane input resistance. The amplitude and duration of the PTD were a function of the number of action potentials in the train. The amplitude of the PTD was increased by membrane hyperpolarization and its estimated reversal potential was approximately −30 mV. Low-chloride solution and intracellular injection of chloride ions augmented the amplitude and duration of the PTD, whereas low-sodium, high-potassium and low-potassium solutions did not affect them. Tetraethylammonium (5–10 mM) and barium (0.5–1 mM) increased the amplitude and duration of the PTD. Nominal calcium-free solutions and ω-conotoxin (500 nM) abolished the PTD. The data suggest that activation of chloride channels by calcium influx through ω-conotoxin-sensitive calcium channels mediates the PTD. Repetitive stimulation of the pelvic nerve evoked a train of orthodromic action potentials followed by the PTD of fAHP neurons. (+)-Tubocurarine (10 μM) and hexamethonium (200 μM), but not atropine (1 μM), abolished orthodromic action potentials and the PTD, whereas these cholinergic antagonists did not depress the PTD evoked by direct action potentials. In summary, the data suggest that the PTD may function as a slow synaptic potential in fAHP neurons. This appears likely because neither slow excitatory nor inhibitory postsynaptic potentials are present in neurons of rabbit vesical parasympathetic ganglia. In contrast, slow inhibitory and excitatory postsynaptic potentials were recorded from neurons in feline vesical parasympathetic ganglia.

Guanosine 3',5'-cyclic monophosphate regulates calcium channels in neurones of rabbit vesical pelvic ganglia.

1. The effects of dibutyryl guanosine 3',5'-cyclic monophosphate (db-cyclic GMP) were studied in vitro on calcium channels of neurones in rabbit vesical parasympathetic ganglia, using intracellular and single-electrode voltage-clamp recordings. 2. Db-cyclic GMP (100 microM) caused membrane depolarization associated with a decrease in membrane input resistance and an after-hyperpolarization associated with an increase in membrane input resistance. 3. Db-cyclic GMP (0.01-1 mM) caused a concentration-dependent, transient inward current followed by a long-lasting outward current. Membrane conductance was increased and decreased during the inward and outward currents, respectively. 4. The db-cyclic GMP-induced inward current was depressed in nominally calcium-free solutions, by cobalt (1 mM) and nicardipine (10 microM). The mean reversal potentials of the inward current were +42 and -20 mV in the presence and absence of calcium in the external solution, respectively. 5. The db-cyclic GMP-induced inward current was not altered by lowering the external sodium concentration, raising external potassium concentration or by intracellular injection of caesium. 6. A calcium-insensitive component of the db-cyclic GMP-induced current was increased by lowering the external chloride concentration and blocked by 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid, a chloride channel blocker. 7. Voltage-dependent, high-threshold calcium currents were depressed during the db-cyclic GMP-induced inward current and facilitated during the outward current. 8. Cyclic GMP was less potent than db-cyclic GMP in causing both inward and outward currents or modulation of calcium currents. GTP, GDP, GMP, guanosine, 8-bromoadenosine 3',5'-cyclic monophosphate and forskolin did not alter the holding current or voltage-dependent calcium currents. 9. It is concluded that intracellular cyclic GMP causes not only activation of resting calcium and chloride channels but also a transient depression followed by long-lasting facilitation of voltage-dependent calcium currents in neurones of vesical parasympathetic ganglia.

Reduction of the N‐type calcium current by noradrenaline in neurones of rabbit vesical parasympathetic ganglia.

1. Intracellular and single-electrode voltage-clamp recordings were made from neurones of vesical parasympathetic ganglia (VPG) isolated from the rabbit urinary bladder. 2. Noradrenaline (NA, 0.5-5 microM) shortened the duration of the action potentials and depressed the amplitudes of both spike after-hyperpolarization and after-current. 3. Voltage-dependent calcium currents (ICa) were recorded by using microelectrodes filled with 2 M-caesium chloride in a superfusing solution containing tetraethylammonium (TEA, 50 mM) and tetrodotoxin (TTX, 500 nM). Noradrenaline (0.5-5 microM) depressed both the ICa and the tail current evoked by depolarizing voltage jumps from -100 to -50 mV to -30 to +20 mV. 4. Substitution of barium for calcium also produced an inward current (IBa) with no obvious tail current. Noradrenaline (1 microM) reduced the magnitude of the IBa without affecting the voltage dependence of the current-voltage relationship for IBa. 5. Yohimbine (1 microM), but not prazosin (1 microM) or propranolol (1 microM), antagonized the NA-induced inhibition of the IBa. UK 14304, a potent alpha 2-adrenoceptor agonist, mimicked NA in depressing the IBa. 6. The transient low-threshold (T), the transient high-threshold (N) and the slowly inactivating high-threshold (L) calcium currents co-existed in VPG neurones. 7. Noradrenaline reduced the IBa evoked at clamp potentials more positive than -20 mV from holding potentials near the resting membrane potential (-70 to -50 mV). Under these conditions, the IBa consisted primarily of N- and L-current components. In contrast, NA had no effect on the isolated T- and L-currents. It is concluded that NA selectively inhibits the N-type calcium channels by an action at alpha 2-adrenoceptors in the rabbit VPG neurones.

αAl2‐Adrenoceptors mediate the inhibition of cholinergic transmission in parasympathetic ganglia of the rabbit urinary bladder

Intracellular recordings were made from neurons of vesical parasympathetic ganglia (VPG) isolated from the rabbit urinary bladder and maintained, in vitro. Bath-application of norepinephrine (NE, 500 nM-5 microM) caused a hyperpolarizing response at the postsynaptic membrane of VPG neurons in a concentration-dependent manner. NE blocked the action potential elicited by an orthodromic stimulation of preganglionic (pelvic) nerve fibers. At a relatively low concentration (5-100 nM), NE depressed the fast excitatory postsynaptic potential (EPSP), without producing the hyperpolarization. NE (100 nM) produced 49 +/- 17% (N = 5) decrease in the amplitude of the fast EPSP. NE did not depress the acetylcholine (ACh) potential produced by iontophoretic application of ACh to the ganglion cells. NE did not affect the amplitude of the miniature EPSP, while it reduced the frequency of miniature EPSPs. These results suggest that NE inhibits the nicotinic transmission in the rabbit VPG, probably reducing the ACh release from presynaptic nerve terminals. Epinephrine (1 microM) was more potent than NE (1 microM) in producing the hyperpolarization as well as the blockade of the fast EPSP amplitude. Isoproterenol was ineffective as an agonist for these inhibitory adrenoceptors. Clonidine mimicked the effect of NE on the fast EPSP. Yohimbine and idazoxan antagonized both the inhibition of the fast EPSP and the hyperpolarization produced by NE. These results suggest that alpha 2-adrenoceptors are responsible for the inhibition of the neuronal activity in parasympathetic ganglia of the rabbit urinary bladder. Immunohistochemical study demonstrated the presence of tyrosine hydroxylase (TH)-labelled neuronal elements in the VPG. They were a small proportion of principal neurons, their dendrites, and many varicose fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Excitatory effect of substance P in parasympathetic ganglia of cat urinary bladder

Intra-arterial administration of substance P (0.1-50 micrograms/kg) to the urinary bladder of the cat produced slow-onset and sustained bladder contractions, asynchronous firing of bladder postganglionic nerves, and facilitation of nicotinic transmission in bladder ganglia. Intracellular recording from bladder ganglia in vitro revealed that substance P depolarized ganglion cells and initiated burst of action potentials (maximal frequency 6-7 Hz). The ganglionic excitatory effect of substance P in situ was blocked by gamma-aminobutyric acid (2-20 micrograms/kg) and the substance P antagonist [D-Arg1,D-Pro2,D-Trp7.9,Leu11]substance P (0.5-20 micrograms/kg) but was not altered by atropine (10-100 micrograms/kg), hexamethonium (0.5-2 mg/kg), norepinephrine (2-20 micrograms/kg), or leucine enkephalin (0.5-20 micrograms/kg). The bladder contractions elicited by substance P were not blocked by atropine, hexamethonium, or [D-Arg1,D-Pro2,D-Trp7.9,Leu11]substance P (0.1-10 micrograms/kg) but were blocked by another substance P antagonist, [D-Pro2,D-Phe7,D-Trp9]substance P. These data indicate that substance P has a direct postsynaptic excitatory effect on neurons in the vesical parasympathetic ganglia and on bladder smooth muscle cells. The differential effects of substance P antagonists on the excitatory responses at these two sites indicate the responses were mediated by different types of tachykinin receptors.

The effects of purine nucleotides on transmission in vesical parasympathetic ganglia of the cat

1. In adult cats, postganglionic nerve fibres on the surface of the bladder were isolated and multiunit activity of these fibres was recorded. In these cats, the urinary bladder was cannulated and intravesical pressure was also recorded. 2. ATP, APPCP, ADP, AMP and adenosine depress transmission in vesical parasympathetic ganglia equipotently; however, 2-chloroadenosine was 10-fold more potent than ATP. 3. 2-chloroadenosine, ATP, ADP, AMP, adenosine and APPCP inhibit neurally evoked bladder contractions in the same order or potency with which they depress pelvic ganglionic transmission; however, adenine, inosine, IMP and ITP were ineffective. 4. 3',5'-cyclic AMP and dibutyryl cAMP produced little or no effect on bladder activity. 5. ATP and APPCP produced a transient rise in intravesical pressure at doses 2 to 50 times the dose needed for inhibition, presumably through ATP (P2) receptors. APPCP was 10 to 20 times more potent in exciting the bladder than ATP. 6. Theophylline and caffeine effectively antagonized purinergic effects mediated through adenosine (P1) receptors on both pelvic ganglia and bladder smooth muscle. 7. ATP inhibition of TMA-evoked bladder contractions and postganglionic nerve firing suggests that purinergic inhibition occurs, at least in part, at a postsynaptic site in the ganglia.

Norepinephrine inhibits calcium action potential through α2-adrenoceptors in rabbit vesical parasympathetic neurons

Intracellular and voltage-clamp recordings were made from neurons in rabbit vesical parasympathetic ganglia (VPG) maintained in vitro. Norepinephrine (NE, 10 nM-10 μM) reduced the Ca 2+ component of the action potential and the afterhyperpolarization. Clonidine and UK14304, the selective α 2-adrenoceptor agonists, mimicked the inhibitory effects of NE on the action potential. NE and UK14304 blocked the Ca 2+ spike elicited in the presence of tetrodotoxin and tetraethylammonium. UK14304 suppressed the inward Ca 2+ current induced by depolarizing step command under the voltage-clamp condition. These inhibitory actions were antagonized by yohimbine and idazoxan but not by prazosin and propranolol. It is suggested that α 2-adrenoceptors mediate the inhibition of voltage-dependent Ca 2+ entry during the action potential.

5-Hydroxytryptamine inhibits cholinergic transmission through 5-HT 1A receptor subtypes in rabbit vesical parasympathetic ganglia

Intracellular recordings were made from parasympathetic neurons of the rabbit vesical pelvic ganglia (VPG) maintained in vitro. 5-Hydroxytryptamine (5-HT) inhibited cholinergic transmission in the VPG by reducing the fast excitatory postsynaptic potential (EPSP) evoked by stimulations of pelvic nerves. 8-Hydroxy-2-(di- n-propyl-amino) tetralin hydrochloride mimicked the inhibitory effect of 5-HT on the ganglionic transmission. 5-HT-induced inhibition of the fast EPSP was antagonized by spiperone. The results suggest that 5-HT 1A receptor subtypes mediate the inhibition of cholinergic transmission in the rabbit VPG.

Role of the sodium pump in regulating the excitability of neurons in the vesical parasympathetic ganglia of the rabbit.

Role of the sodium pump in regulating the excitability of neurons in the vesical parasympathetic ganglia of the rabbit.

Selective facilitatory effect of vasoactive intestinal polypeptide (VIP) on muscarinic firing in vesical ganglia of the cat

VIP immunoreactivity was identified in nerve fibers and in 10–13% of the neurons in pelvic and bladder ganglia of the cat. Ninety percent of the VIP positive neurons contained acetylcholinesterase. VIP immunoreactivity was not altered in decentralized ganglia 1 week to 8 months after transection of the pelvic and hypogastric nerves indicating that VIP fibers arose from neurons within the peripheral nervous system. The intra-arterial administration of VIP (1–50 μg/kg) enhanced the postganglionic discharge elicited by the muscarinic agonist, acetyl-ß-methylcholine, but did not alter the postganglionic firing elicited by the nicotinic agonist, tetramethylammonium or by electrical stimulation of preganglionic axons in the pelvic nerve. VIP did not elicit a postganglionic discharge in untreated ganglia, but did evoke a prolonged discharge in ganglia treated with an irreversible anticholinesterase agent, 217AO. This discharge was not affected by hexamethonium but was blocked by atropine. VIP suppressed the muscarinic inhibition of ganglionic transmission produced by acetyl-ß-methylcholine without altering the response to other inhibitory agents (norepinephrine, leucine-enkephalin and γ-aminobutyric acid (GABA). VIP (0.1–0.3 μg/kg) also had a direct inhibitory effect on bladder smooth muscle. These findings raise the possibility that intraganglionic pathways containing VIP may exert a selective modulatory influence on muscarinic transmission in vesical parasympathetic ganglia.

Noradrenaline hyperpolarization and depolarization in cat vesical parasympathetic neurones.

Responses to noradrenaline (NA) applied by superfusion, ionophoresis or pressure pulse were analysed using conventional intracellular recording and voltage-clamp methods in cat vesical parasympathetic ganglia. NA (1 microM) hyperpolarized 60% of the neurones, depolarized 25%, and produced a biphasic potential, which comprised a membrane hyperpolarization followed by a membrane depolarization, in 10%. About 5% of the neurones did not respond to NA. The NA hyperpolarization was blocked by yohimbine (1 microM), an alpha 2-adrenoceptor antagonist, whereas the NA depolarization was blocked by prazosin (0.1-1 microM), an alpha 1-adrenoceptor antagonist. These data indicated that the NA hyperpolarization was mediated through alpha 2-adrenoceptors and the NA depolarization through alpha 1-adrenoceptors. The NA hyperpolarization was accompanied by an increase in conductance, while the NA depolarization was associated with a decrease in conductance measured under manual-clamp conditions. Similar conductance changes were observed under voltage clamp. NA hyperpolarizations became smaller as the membrane was hyperpolarized and reversed polarity beyond -100 mV. NA depolarizations also became smaller at hyperpolarized membrane potentials and reversed polarity around -90 mV. The NA responses were enhanced in low-K media and depressed in high-K Krebs solution. The NA hyperpolarization was blocked by the Ca antagonists, Cd, Mn and Co. Intracellular injection of EGTA caused a slowly developing, progressive block of the NA hyperpolarization. The NA depolarization was not affected by low Ca concentrations, Ca antagonists or intracellular injection of EGTA. In some neurones the NA depolarization was unmasked in solutions containing Ca antagonists and after intracellular EGTA injection. The NA hyperpolarization was depressed by intracellular injection and extracellular superfusion of Cs but not by TEA. Ba (10-100 microM) depressed the NA hyperpolarization by 30%. The NA depolarization persisted in the presence of muscarine (10 microM) and was not blocked by Cs or TEA but was depressed 70% by Ba (10 microM). These data are consistent with the hypotheses that alpha 2-adrenoceptor activation produces a membrane hyperpolarization that is mediated through a Ca-dependent K conductance, and that alpha 1-adrenoceptor activation produces a membrane depolarization through closure of a voltage-insensitive K channel.

α 2 and α 1-adrenoceptors mediate opposing actions on parasympathetic neurons

We used intracellular recording methods to analyze the membrane responses to norepinephrine in cat vesical parasympathetic ganglia. In parasympathetic neurons, norepinephrine (NE) produces a membrane hyperpolarization, a membrane depolarization often accompanied by cell firing and a biphasic potential, a hyperpolarization followed by a depolarization. We found that the NE hyperpolarization is mediated through α 2-adrenoceptors while the NE depolarization is mediated through α 1-adrenoceptors. This situation is different than in sympathetic neurons where ß-adrenoceptors mediate a NE depolarization 5,10,11.

Adenosine mediates a slow hyperpolarizing synaptic potential in autonomic neurones.

Considerable evidence has accumulated suggesting that purines, adenosine and ATP function as neurotransmitters in the central and peripheral nervous systems. Burnstock has proposed that purinergic receptors be classified into two types, P1 and P2, having adenosine and ATP, respectively, as agonist prototypes. Recent data suggest that ATP may mediate a synaptic potential in guinea pig vas deferens, but no such evidence exists for adenosine. The presence of a non-cholinergic, non-adrenergic nerve supply to the urinary bladder has been postulated and termed purinergic, as these nerves have been shown to release ATP. Furthermore, atropine-resistant contractions of bladder smooth muscle are thought to be mediated by ATP, while in situ experiments in vesical parasympathetic ganglia have suggested that a purinergic modulatory mechanism may control urinary bladder function. We now report the presence of a slow hyperpolarizing synaptic potential (slow-h.s.p.) in neurones of cat vesical parasympathetic ganglia, produced by stimulating the preganglionic nerves, and provide evidence that the slow-h.s.p. is mediated by adenosine.

A study of facilitation in vesical parasympathetic ganglia of the cat using intracellular recording techniques

A study of facilitation in vesical parasympathetic ganglia of the cat using intracellular recording techniques

Reflex activation of sympathetic pathways to vesical smooth muscle and parasympathetic ganglia by electrical stimulation of vesical afferents.

1. Activation of the sympathetic input to the urinary bladder by electrical stimulation of afferent fibres in the pelvic nerve evoked three responses: (1) an initial transient rise in intravesical pressure, (2) an inhibition of neurally evoked bladder contractions and (3) an inhibition of transmission in vesical parasympathetic ganglia. Similar responses were elicited by stimulation of the hypogastric nerve. 2. The reflex responses were observed in acute spinal preparations (T10-T12) and in cats with intact spinal cords, but were abolished by bilateral transection of the hypogastric nerves. 3. The inhibition of bladder contractions was antagonized by the administration of propranolol (200-400 mug, I.A.), a beta-adrenergic blocking agent. The inhibition of ganglionic transmission was antagonized by dihydroergotamine (30-75 mug, I.A.), an alpha-adrenergic blocking agent. The initial rise in intravesical pressure was not antagonized by either agent. 4. Electrical stimulation of other afferents (carotid sinus nerve and sciatic nerve) did not consistently elicit responses in the urinary bladder. However, stimulation of these afferents as well as pelvic nerve afferents evoked reflex firing in nerve filaments on the surface of the urinary bladder. The firing was abolished by transection of the ipsilateral hypogastric nerve. 5. It is concluded that stimulation of vesical afferents activates a spinal sympathetic reflex which results in closing of the internal urethral sphincter and a depression of bladder activity. The latter occurs by a direct depression of detrusor smooth muscle as well as a block of the neural input to the bladder. This vesico-sympathetic reflex represents a negative feed-back mechanism which may have an important role in the maintenance of urinary continence.

Sympathetic inhibition of the urinary bladder and of pelvic ganglionic transmission in the cat.

1. Electrophysiological techniques were utilized to study the mechanisms underlying adrenergic inhibition in the urinary bladder of the cat.2. It has been shown that catecholamines administered by close intraarterial injection or released endogenously by electrical stimulation of the hypogastric nerves elicit two distinct inhibitory responses in the bladder: (1) a direct depression of the vesical smooth muscle and (2) a depression of transmission in vesical parasympathetic ganglia.3. Pharmacological studies revealed that the inhibitory mechanisms were mediated via different adrenergic receptors: beta-receptors on the smooth muscle and alpha-receptors in the parasympathetic ganglia.4. We have been unable, however, to demonstrate that either of these mechanisms is activated by naturally occurring sympathetic firing.