Effects of 5-HT1A and 5-HT4 receptor agonists on slow synaptic potentials in enteric neurons.
Intracellular electrophysiological methods were used to examine the effects of 5-hydroxytryptamine (5-HT), 5-carboxamidotryptamine (5-CT), 5-methoxytryptamine (5-MeOT), 4-amino-5-chloro-2-methoxy-N-(4-[1-azabicyclo[3,3,1]nonyl]) benzamide hydrochloride (renzapride), cis-4-amino-5-chloro-N[1-[3- (4-fluorophenoxy)propyl]-3-methoxy-4-piperidinyl[-2-methoxybenzamide monohydrate (cisapride) and endo-N-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dihydro-3- (1-methyl)ethyl-2-oxo-1 H-benzimidazole-1-carboxamidehydrochloride (BIMU 8) on noncholineric slow excitatory postsynaptic potentials (slow EPSPs) in myenteric afterhyperpolarization (AH) neurons of guinea pig ileum. 5-HT (0.01-1 microM) and 5-CT (0.001-0.1 microM) produced a concentration-dependent inhibition of slow EPSPs. The 5-HT1A receptor antagonist 1-(2-methoxyphenyl)-4-[4-(2-phthalimidobutyl]piperazine (NAN-190) produced rightward shifts in 5-HT and 5-CT concentration-response curves; facilitation of slow EPSPs was never observed. 5-MeOT caused a depolarization and inhibited spike afterhyperpolarizations in a concentration-dependent manner but this effect was not blocked by the 5-HT3/5-HT4 receptor antagonist, tropisetron (1 microM). Renzapride (0.01-0.3 microM), cisapride (0.01-1.0 microM) and BIMU 8 (0.01-1.0 microM) did not change the membrane potential of any neuron tested. Renzapride and BIMU 8 did not change the amplitude of slow EPSPs. In 13 of 19 neurons cisapride did not change the amplitude of slow EPSPs; in 6 neurons cisapride (1 microM) reversibly inhibited the slow EPSP. Responses to substance P which mimicked the slow EPSP were not affected by cisapride.(ABSTRACT TRUNCATED AT 250 WORDS)
Pan
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Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824, USA.
Galligan
J J
JJ
D008735:5-Methoxytryptamine / Q000494:pharmacology; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D001562:Benzimidazoles / Q000494:pharmacology; D001643:Bridged Bicyclo Compounds / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic; D020117:Cisapride; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009197:Myenteric Plexus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D012701:Serotonin / Q000031:analogs & derivatives / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D000077526:Tropisetron
D001549:Benzamides; D001562:Benzimidazoles; D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D007211:Indoles; D010879:Piperazines; D010880:Piperidines; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C058895:1-(2-methoxyphenyl)-4-(4-(2-phthalimido)butyl)piperazine; C070189:(endo-N-8-methyl-8-azabicyclo-(3.2.1)oct-3-yl)-2,3-dihydro-3-isopropyl-2-oxo-1H-benzimidazol-1-carboxamide; D012701:Serotonin; D008735:5-Methoxytryptamine; D000077526:Tropisetron; C053006:renzapride; C047087:5-carboxamidotryptamine; D020117:Cisapride