A retrograde labeling technique for the functional study of airway-specific visceral afferent neurons

5. In the presence of 10 /M TCP, BK no longer produced significant effects on the AHPSloW In contrast, 10 #M TCP did not prevent PGI2 from blocking the AHPSlow.6. These results suggest that vagal afferents that exhibit AHPSlow also possess the B2 type of BK receptor. Activation of these BK receptors results in the production of PGI2, which in turn controls spike frequency adaptation by affecting the amplitude of the AHPSlow.

“…The changes produced by BK in the frequency of spike firing are illustrated in Fig. 2A properties (Christian et al 1993;Leal-Cardoso et al 1993). …”

Section: Resultsmentioning

confidence: 99%

Prevention of the excitatory actions of bradykinin by inhibition of PGI2 formation in nodose neurones of the guinea‐pig.

Weinreich

Koschorke

Undem

et al. 1995

“…The question of possible changes in the properties of the neurones by dye labelling or the dissociation procedure can only be partially answered. Prolonged exposure of dyelabelled cells to UV light (Christian et al 1993;Yoshimura et al 1994) and exposure to high concentrations of trypsin during dissociation can elicit prominent changes in cellular…”

Section: Discussionmentioning

confidence: 99%

“…These neurones were labelled by retrograde axonal transport of a fluorescent dye injected into the urinary bladder and then individual dye-labelled neurones were identified by fluorescence microscopy after 5269 I chemical dissociation of the DRG (Christian, Togo, Naper, Koschorke, Taylor & Weinreich, 1993;Yoshimura, White, Weight & de Groat, 1994). Although many patch-clamp studies have been performed on isolated sensory neurones (Ikeda, Schofield & Weight, 1985;White, 1990;Ogata & Tatebayashi, 1992Elliott & Elliott, 1993), relatively few have been conducted on target-specific neurones.…”

mentioning

confidence: 99%

Different types of Na+ and A‐type K+ currents in dorsal root ganglion neurones innervating the rat urinary bladder.

Yoshimura¹,

White²,

Weight³

et al. 1996

118

148

1. Whole-cell patch-clamp recording in combination with axonal tracing techniques was used to examine the electrical properties of afferent neurones innervating the urinary bladder of the adult rat. Individual bladder afferent cells were labelled by Fast Blue (FB), injected into the bladder wall.2. Passive and active electrical parameters at room temperature (20-22 'C) in FB-labelled bladder afferent neurones were comparable with those in unlabelled neurones. Unselected dorsal root ganglion (DRG) neurones as well as bladder afferent neurones exhibited two different types of action potential: high-threshold humped spikes in small-sized neurones and low-threshold narrow spikes in large-sized neurones. 3. The majority (70%) of bladder neurones which were small in size expressed high-threshold tetrodotoxin (ITX)-resistant Nae channels and slow-inactivating A-type K+ channels (KA), which were available at the resting membrane potential, whereas large-sized DRG neurones had low-threshold TTX-sensitive Na+ channels and fast-inactivating KA channels, which were almost completely inactivated at the resting membrane potential.4. Half-maximal conductances of activation of 'ITX-resistant and TTX-sensitive Na+ currents were obtained at -10-3 and -25-3 mV, respectively. The TTX-resistant and ITX-sensitive Na+ currents were half-inactivated at -25-3 and -56 mV, respectively. 5. In the TTX-resistant neurones, the transient outward K+ current (A-type current, IA) with half-maximal conductance at -40-8 mV was half-inactivated at -77-5 mV, and exhibited slower decaying kinetics (mean decay constant ('r), 240 ms) than the IA current recorded from the large-sized TTX-sensitive neurones (mean r, 20 ms). 6. These results suggest that the majority of bladder afferent neurones have high electrical thresholds for spike activation due to the TTX-resistant Na+ current and the slowinactivating IA current, which reflect the large population of unmyelinated high-threshold C fibre afferents that innervate the urinary bladder.

“…Storage did not measurably affect the electrophysiological or pharmacological characteristics of the dissociated cells. Neurones were enzymatically dissociated from desheathed ganglia using the procedure described by Christian, Togo, Naper, Koschorke, Taylor & Weinreich (1993 Hyperpolarizing substance P responses A semi-logarithmic plot of the concentration-response relationship was iteratively fitted using the four parameter logistic equation: (max -min)…”

Section: Methods Preparation Of Tissuementioning

confidence: 99%

Substance P hyperpolarizes vagal sensory neurones of the ferret.

Jafri

Weinreich

1996

1. Intracellular recordings were made in intact and in acutely dissociated vagal afferent neurones (nodose ganglion cells) of the ferret to investigate the effects of substance P (SP). 2. In current-clamp recordings, SP (100 nM) applied by superfusion hyperpolarized the membrane potential (7 + 0 7 mV; mean + S.E.M.; n = 105) and decreased the input resistance in 80 % of the neurones. With voltage-clamp recording, SP produced an outward current of 3 + 0-2 nA (n = 10). 3. The SP current was concentration dependent with an estimated EC50 of 68 nm. The SP-induced hyperpolarization or current was mimicked by the tachykinin receptor NK1agonist Ac-[Arg6, Sar9, Met(02)'1]SP(6-1 1) (ASM-SP; 100 nM; n = 10) and blocked by the NK1 antagonist CP-96,345 (10 nM; n = 6), but not by the NK2 antagonist SR48968(100 nM; n = 4). No measurable change in membrane potential or input resistance was observed with application of either [/J-Ala8]neurokinin A or senktide, selective NK2 and NK3 receptor agonists, respectively (100 nM; n = 3 for each agonist).4. The reversal potential (Erev) for the SP outward current was -85 + 2-5 mV (n = 4). The Erev for the SP response shifted in a Nernstian manner with changes in extracellular potassium concentration. Alterations in extracellular sodium or chloride concentrations had no significant effect on the E for the SP response (n = 3 for each ion).5. Nominally Ca2+-free external solution abolished the SP response. Removal of magnesium from the extracellular solution had no effect on the response.6. Caesium (100 /,M), barium (1 mM), tetraethylammonium (TEA; 5 mm), apamin (10 nM) and 4-aminopyridine (4-AP; 4 mm) each completely prevented the SP response (n > 3 for each).7. These results indicate that SP, via an NK1 receptor, can induce a Ca2+-dependent outward potassium current which hyperpolarizes the resting membrane potential of vagal afferent somata.