title: Ongoing nicotinic and non-nicotinic inputs to inhibitory neurons in the mouse colon.
abstract: 1. Intracellular microelectrodes were used to record spontaneous and evoked inhibitory junction potentials (IJP) from the circular muscle layer of the mid-distal region of the mouse isolated colon in the presence of nifedipine (1 micromol/L) and hyoscine (1 micromol/L). 2. The length of the tissue preparation (> 1 cm) or the presence of the mucosa had no effect on the frequency of spontaneous IJP. 3. Hexamethonium (500 micromol/L) reduced the frequency of spontaneous IJP to approximately 70% of the control frequency, whereas D-tubocurarine (280 micromol/L) reduced the frequency to approximately 17% of control. Apamin (250 nmol/L) abolished all spontaneous IJP activity. 4. The greater inhibition of spontaneous IJP in the presence of D-tubocurarine compared with hexamethonium is discussed as a possible 'apamin-like' effect. 5. Although electrically evoked IJP (single pulse at 15 V, 0.6 msec) were not significantly affected by hexamethonium, D-tubocurarine and apamin reduced the amplitude of evoked IJP to approximately 65 and 50% of control, respectively. 6. These results suggest that the properties of spontaneous IJP cannot be inferred by a study of evoked IJP alone.
authors.affiliation: Department of Physiology, Monash University, Victoria, Australia. andrew.powell@med.monash.edu
authors.forename: A K
authors.initials: AK
authors.lastname: Powell
authors.forename: R
authors.initials: R
authors.lastname: Fida
authors.forename: R A
authors.initials: RA
authors.lastname: Bywater
mesh_terms: D000818:Animals; D003106:Colon / Q000187:drug effects* / Q000502:physiology; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D018738:Hexamethonium / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008817:Mice, Mutant Strains; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018733:Nicotinic Antagonists / Q000494:pharmacology*; D011978:Receptors, Nicotinic / Q000502:physiology; D014403:Tubocurarine / Q000494:pharmacology
chemical_list: D018733:Nicotinic Antagonists; D011978:Receptors, Nicotinic; D018738:Hexamethonium; D014403:Tubocurarine