6-cyano-7-nitroquinoxaline-2-3-dione and chelerythrine

Chronic amphetamine intake leads to neurogenic bladder and chronic urinary retention. The mechanism underlying persistent urinary retention is unclear. The pelvic-urethral reflex (PUR) is essential for the urethra to develop sufficient resistance to maintain urine continence, an important function of the urinary system. Recent studies on PUR activities have indicated that repetitive/tetanic stimulation of the pelvic afferent fibers induces spinal reflex potentiation (SRP) in PUR activities, which further increases urinary retention. In this study, results showed that test stimulation (TS, 1/30 Hz) evoked a baseline reflex activity, while repetitive stimulation (RS, 1 Hz) induced reflex potentiation in the external urethral sphincter. Intrathecal d-amphetamine (AMPH, 30 μM) did not but higher AMPH concentration (100 μM) induced SRP in TS-induced reflex activity. H89 (10 μM, a protein kinase A inhibitor), but not chelerythrine chloride (CTC, 10 μM, a protein kinase C inhibitor), prevented the 100 μM AMPH-elicited SRP. At 30 μM, forskolin, an activator of adenylyl cyclase, elicited SRP. The co-administration of 10 μM forskolin and 30 μM AMPH induced SRP in TS-induced reflex activity. These results implied that the repetitive/tetanic stimulation of the pelvic afferent fibers could induce SRP in PUR activities, so that the urethra can produce sufficient resistance and played a significant role in urinary retention. Findings in this study demonstrated that amphetamine could induce bladder dysfunction by triggering protein kinase A activation, and provide a practical basis for the development of treatment for amphetamine-associated urinary retention.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Afferent Pathways; Amidines; Amphetamine-Related Disorders; Animals; Benzophenanthridines; Central Nervous System Stimulants; Chronic Disease; Colforsin; Dextroamphetamine; Excitatory Amino Acid Agonists; Female; Glutamic Acid; Isoquinolines; N-Methylaspartate; Oxidants; Protein Kinase Inhibitors; Rats, Wistar; Reflex; Spinal Cord; Sulfonamides; Urinary Retention; Urination; Valine

There is evidence suggesting that protein kinase C (PKC) activation can prevent the enhanced network excitability associated with status epilepticus and group I metabotropic glutamate receptor (mGluR)-induced epileptogenesis. However, we observed no suppression of mGluR-induced burst prolongation in the guinea pig hippocampal slice when applied in the presence of the PKC activator phorbol-12,13-dibutyrate (PDBu). Furthermore, PDBu alone converted picrotoxin-induced interictal bursts into ictal-length discharges ranging from 2 to 6s in length. This effect could not be elicited by the inactive analog 4-alpha-PDBu and was suppressed with the PKC inhibitor chelerythrine, indicating PKC dependence. PKC activation can enhance neurotransmitter release, and both glutamate and acetylcholine are capable of eliciting similar prolonged synchronized discharges. However, neither mGluR1 nor NMDA receptor antagonist suppressed PDBu-driven burst prolongation, suggesting that increased glutamate release alone is unlikely to account for the PKC-induced expression of ictaform discharges. Similarly, atropine, a broad-spectrum muscarinic receptor antagonist, had no effect on PKC-induced burst prolongation. By contrast, AMPA/kainate receptor antagonist abolished PKC-induced burst prolongation, and mGluR5 antagonist significantly blunted the maximum burst length induced by PKC. These data suggest that PKC-induced prolongation of epileptiform bursts is dependent on changes specific to mGluR5 and AMPA/kainate receptors and not mediated simply by a generalized increase in transmitter release.

Topics: 2-Amino-5-phosphonovalerate; 6-Cyano-7-nitroquinoxaline-2,3-dione; Acetylcholine; Action Potentials; Animals; Atropine; Benzoates; Benzophenanthridines; Enzyme Activation; Epilepsy; Glutamic Acid; Glycine; Guinea Pigs; Hippocampus; In Vitro Techniques; Neurotransmitter Agents; Phorbol 12,13-Dibutyrate; Picrotoxin; Protein Kinase C; Pyridines; Receptor, Metabotropic Glutamate 5; Receptors, Kainic Acid; Receptors, Metabotropic Glutamate; Signal Transduction

Mammalian circadian rhythms originate in the hypothalamic suprachiasmatic nuclei (SCN), from which rhythmic neural activity can be recorded in vitro. Application of neurochemicals can reset this rhythm. Here we determine cellular correlates of the phase-shifting properties of neuropeptide Y (NPY) on the hamster circadian clock in vitro. Drug or control treatments were applied to hypothalamic slices containing the SCN on the first day in vitro. The firing rates of individual cells were sampled on the second day in vitro. Control slices exhibited a peak in firing rate in the middle of the day. Microdrop application of NPY to the SCN phase advanced the time of peak firing rate. This phase-shifting effect of NPY was not altered by block of sodium channels with tetrodotoxin or block of calcium channels with cadmium and nickel, consistent with a direct postsynaptic site of action. Pretreatment with the glutamate receptor antagonists (DL-2-amino-5-phosphonovaleric acid and 6-cyano-7-nitroquinoxaline-2,3-dione disodium) also did not alter phase shifts to NPY. Blocking GABAA receptors with bicuculline (Bic) had effects only at very high (millimolar) doses of Bic, whereas blocking GABAB receptors did not alter effects of NPY. Phase shifts to NPY were blocked by pretreatment with inhibitors of protein kinase C (PKC), suggesting that PKC activation may be necessary for these effects. Bathing the slice in low Ca2+/high Mg2+ can block phase shifts to NPY, possibly via a depolarizing action. A depolarizing high K+ bath can also block NPY phase shifts. The results are consistent with direct action of NPY on pacemaker neurons, mediated through a signal transduction pathway that depends on activation of PKC.

Topics: 2-Amino-5-phosphonovalerate; 6-Cyano-7-nitroquinoxaline-2,3-dione; Action Potentials; Alkaloids; Animals; Benzophenanthridines; Bicuculline; Calcium Channel Blockers; Cations, Divalent; Cell Communication; Circadian Rhythm; Cricetinae; Enzyme Activation; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; GABA Antagonists; Indoles; Ion Channels; Isoquinolines; Male; Maleimides; Mesocricetus; Naphthalenes; Nerve Tissue Proteins; Neuropeptide Y; Phenanthridines; Phorbol Esters; Protein Kinase C; Receptors, GABA-A; Receptors, GABA-B; Receptors, Glutamate; Signal Transduction; Sulfonamides; Suprachiasmatic Nucleus; Tetrodotoxin