The Effect of Anoxia and Glucose-Free Solutions on the Contractile Response of Guinea-Pig Detrusor Strips to Intrinsic Nerve Stimulation and the Application of Excitatory Agonists

Intracellular recordings were taken from the smooth muscle of the guinea pig trachea, and the effects of intrinsic nerve stimulation were examined. Approximately 50% of the cells had stable resting membrane potentials of −50 ± 1 mV. The remaining cells displayed spontaneous oscillations in membrane potential, which were abolished either by blocking voltage-dependent Ca2+channels with nifedipine or by depleting intracellular Ca2+stores with ryanodine. In quiescent cells, stimulation with a single impulse evoked an excitatory junction potential (EJP). In 30% of these cells, trains of stimuli evoked an EJP that was followed by oscillations in membrane potential. Transmural nerve stimulation caused an increase in the frequency of spontaneous oscillations. All responses were abolished by the muscarinic-receptor antagonist hyoscine (1 μM). In quiescent cells, nifedipine (1 μM) reduced EJPs by 30%, whereas ryanodine (10 μM) reduced EJPs by 93%. These results suggest that both the release of Ca2+ from intracellular stores and the influx of Ca2+ through voltage-dependent Ca2+channels are important determinants of spontaneous and nerve-evoked electrical activity of guinea pig tracheal smooth muscle.

Download Full-text

The effects of nucleotides on the response of the isolated guinea pig urinary bladder to nonadrenergic, noncholinergic nerve stimulation

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y81-187 ◽

1981 ◽

Vol 59 (11) ◽

pp. 1199-1201 ◽

Cited By ~ 12

Author(s):

P. Lukacsko ◽

R. D. Krell

Keyword(s):

Electrical Stimulation ◽

Urinary Bladder ◽

Guinea Pig ◽

Nerve Stimulation ◽

Purinergic Receptors ◽

Contractile Response ◽

Krebs Solution ◽

Metabolic Products ◽

Per Se ◽

Intramural Nerve

The ability of adenosine 5′-triphosphate (ATP) to suppress the contractile response of guinea pig urinary bladder to nonadrenergic, noncholinergic nerve stimulation was investigated. Strips of guinea pig urinary bladder were incubated for 1 h at 37 °C in a modified Krebs solution containing atropine (2 × 10−7 M), guanethidine (1 × 10−6 M), and indomethacin (5.5 × 10−6 M). Four successive administrations of ATP, guanosine 5′-triphosphate (GTP), or cytidine 5′-triphosphate (CTP), each at 5 × 10−4 M, in the absence of washout resulted in complete desensitization of the tissue to the contractile effect of the nucleotide. Strips desensitized to GTP or CTP were also nonresponsive to ATP. The response of the strips to electrical stimulation (100 V, 0.1-ms pulse, 5-s train at 3 Hz) was markedly reduced following desensitization with ATP but only slightly with GTP or CTP. Under similar conditions, adenosine 5′-monophosphate (AMP) or diphosphate (ADP) or adenosine (A) also reduced the response of the strips to intramural nerve stimulation, but guanosine.5′-monophosphate (GMP) or diphosphate (GDP), guanosine (G), cytidine 5′-monophosphate (CMP) or diphosphate (CDP), or cytidine (C) did not. The present data suggest that desensitization of smooth muscle to exogenous ATP may be predominantly the result of its conversion to metabolic products rather than inactivation of "purinergic" receptors per se.

Download Full-text