capsazepine and alpha-beta-methyleneadenosine-5--triphosphate

The present study explored differences in sensitivity to purinergic agonists, protons, and capsaicin in lumbosacral (LS) and thoracolumbar (TL) sensory neurons that innervate the rat urinary bladder. The majority of LS neurons (93%) were sensitive to alpha,beta-methyleneATP (alpha,beta-metATP) compared with 50% of TL neurons. Based on inactivation kinetics, a slowly desensitizing current evoked by alpha,beta-metATP predominated in LS neurons (86%) compared with mixed components that characterized TL neuron responses (58%). The density of the slowly desensitizing current was greater in LS than in TL neurons (LS, 34.4 +/- 5.3 pA/pF; TL, 2.5 +/- 0.8 pA/pF). Almost all neurons in both ganglia responded to protons and to capsaicin (LS, 100%; TL, 98%). Proton-activated currents in bladder sensory neurons exhibited distinct inactivation kinetics as fast, intermediate, slowly desensitizing, and sustained components. More than one component was expressed in every cell. Although there was no difference in the percentage of neurons expressing more than one component, the density of the sustained current was significantly greater in LS than in TL neurons (LS, 86.1 +/- 16 pA/pF; TL, 30.3 +/- 7 pA/pF). Similarly, the capsaicin-evoked current was greater in LS than in TL neurons (LS, 129.6 +/- 17 pA/pF; TL, 86.9 +/- 11 pA/pF). Finally, a greater percentage of TL neurons bound isolectin B4 than LS neurons (LS, 61%; TL, 85%). The greater degree of alpha,beta-metATP, proton, and capsaicin responsiveness, in addition to differences in current type and current densities, in LS and TL neurons suggests that bladder pelvic and hypogastric/lumbar splanchnic afferents are functionally distinct and likely mediate different sensations arising from the urinary bladder.

Topics: Adenosine Triphosphate; Amiloride; Amino Acids; Animals; Capsaicin; Cells, Cultured; Dose-Response Relationship, Drug; Drug Interactions; Electric Stimulation; Enzyme Inhibitors; Ganglia, Spinal; Hydrogen-Ion Concentration; Immunohistochemistry; Lectins; Lumbosacral Region; Male; Membrane Potentials; Neurons, Afferent; Patch-Clamp Techniques; Phenols; Polycyclic Compounds; Protons; Purinergic Agonists; Purinergic Antagonists; Rats; Rats, Sprague-Dawley; Receptors, Purinergic; Sodium Channel Blockers; Thoracic Vertebrae; Time Factors; TRPV Cation Channels; Urinary Bladder

Vanilloid (VR1) and purinergic (P2X) receptors are found in cranial afferent neurons in nodose ganglia and their central terminations within the solitary tract nucleus (NTS), but little is known about their function. We mechanically dissociated dorsomedial NTS neurons to preserve attached native synapses and tested for VR1 and P2X function primarily in spindle-shaped neurons resembling intact second-order neurons. All neurons (n = 95) exhibited spontaneous glutamate (EPSCs) and GABA (IPSCs)-mediated synaptic currents. VR1 agonist capsaicin (CAP; 100 nm) reversibly increased EPSC frequency, effects blocked by capsazepine. ATP (100 microm) increased EPSC frequency, actions blocked by P2X antagonist pyridoxalphosphate-6-azophenyl-2', 4'-disulfonic acid (PPADS; 20 microm). In all CAP-resistant neurons, P2X agonist alphabeta-methylene-ATP (alphabeta-m-ATP) increased EPSC frequency. Neither CAP nor alphabeta-m-ATP altered EPSC amplitudes, kinetics, or holding currents. Thus, activation of VR1 and P2X receptors selectively facilitated presynaptic glutamate release on different NTS neurons. PPADS and 2',3'-O-(2,4,6-trinitrophenyl)-ATP blocked alphabeta-m-ATP responses, but P2X1-selective antagonist NF023 (8,8'-[carbonylbis (imino-3,1-phenylene carbonylimino)]bis-1,3,5-naphthalenetrisulfonic acid) did not. The pharmacological profile and transient kinetics of ATP responses are consistent with P2X3 homomeric receptors. TTX and Cd(2+) did not eliminate agonist-evoked EPSC frequency increases, suggesting that voltage-gated sodium and calcium channels are not required. In nodose ganglia, CAP but not alphabeta-m-ATP evoked inward currents in slow conducting neurons and the converse pattern in myelinated, rapidly conducting neurons (n = 14). Together, results are consistent with segregation of glutamatergic terminals into either P2X sensitive or VR1 sensitive that correspondingly identify myelinated and unmyelinated afferent pathways at the NTS.

Topics: Adenosine Triphosphate; Afferent Pathways; Animals; Capsaicin; Cell Separation; Excitatory Postsynaptic Potentials; Glutamic Acid; In Vitro Techniques; Male; Neural Inhibition; Neurons; Nodose Ganglion; Patch-Clamp Techniques; Presynaptic Terminals; Purinergic P2 Receptor Agonists; Purinergic P2 Receptor Antagonists; Pyridoxal Phosphate; Rats; Rats, Sprague-Dawley; Receptors, Drug; Receptors, Purinergic P2; Solitary Nucleus

To evaluate the effect of St. John's wort (SJW), an effective and safe herbal antidepressant, on rat bladder contractility. Recent data have suggested a strong association between depression and urinary incontinence.. Strips were cut from the bladder body and placed in organ baths containing Krebs solution. Contractions were induced by electrical field stimulation (EFS) and, in some experiments, by exogenous alpha,beta (alpha,beta)-methylene adenosine triphosphate.. St. John's wort was significantly more active in inhibiting the EFS-induced contractions than the alpha,beta-methylene adenosine triphosphate-induced contractions, suggesting both a presynaptic site of action and a direct inhibition of bladder smooth muscle. The inhibitory effect of SJW on EFS-induced contractions was unaffected by methysergide, haloperidol, phentolamine plus propranolol (antagonists that block the action of the neurotransmitters 5-hydroxytriptamine, dopamine, and noradrenaline on their own receptors), the L-type calcium channel antagonist verapamil, capsazepine (which blocks the vanilloid receptor), or cannabinoid CB1 receptor antagonist SR141716A. However, the opioid receptor antagonist naloxone significantly reduced the inhibitory effect of SJW on EFS-induced contractions. Among the chemical constituents of SJW tested, hyperforin and, to a lesser extent, the flavonoid kaempferol showed inhibitory effects.. The results of our study demonstrated that SJW inhibits excitatory transmission of the rat urinary bladder and also directly inhibits smooth muscle contractility. The inhibitory effect on excitatory transmission could involve, at least in part, opioid receptors. SJW may be evaluated for its possible use in treating urinary incontinence in depressed patients.

Topics: Acetylcholine; Adenosine Triphosphate; Animals; Anthracenes; Antidepressive Agents; Atropine; Bridged Bicyclo Compounds; Capsaicin; Depression; Electric Stimulation; Female; Haloperidol; Hypericum; Kaempferols; Male; Methysergide; Muscle Contraction; Muscle, Smooth; Naloxone; Perylene; Phentolamine; Phloroglucinol; Piperidines; Plant Extracts; Propranolol; Pyrazoles; Quercetin; Rats; Rats, Wistar; Rimonabant; Rutin; Terpenes; Tetrodotoxin; Urinary Bladder; Urinary Incontinence; Verapamil