Neurotransmitters in the intestine of the Atlantic cod, Gadus morhua.
The effects of the putative neurotransmitters acetylcholine, adrenaline, adenosine, ATP, bombesin, 5-hydroxytryptamine, met-enkephalin, neurotensin, somatostatin, substance P and VIP have been investigated in the perfused intestine of the cod, Gadus morhua. The presence and distribution of the different types of nerves was investigated with immunohistochemistry and Falck-Hillarp fluorescence histochemistry. A spontaneous rhythmic activity of the perfused preparations usually occurred within a few minutes from the start of the experiment. This activity was diminished or abolished by addition of atropine, methysergide or tetrodotoxin to the perfusion fluid. Acetylcholine, 5-hydroxytryptamine or substance P caused a contraction of the intestinal wall. The response to acetylcholine was blocked by atropine but not by tetrodotoxin, while the response to 5-hydroxytryptamine was blocked by methysergide and usually also by tetrodotoxin. This indicates that the effect of acetylcholine is direct on the muscle cells, while the effect of 5-hydroxytryptamine may be at least partly via a second neuron. All adrenergic agonists (adrenaline, isoprenaline and phenylephrine) had a dominating inhibitory effect on the intestine. Experiments with antagonists showed that the inhibition is due to stimulation of both alpha-adrenoceptors and beta-adrenoceptors. ATP, adenosine and somatostatin also caused a relaxation of the intestinal wall, often followed by a contraction. Met-enkephalin produced variable responses, either a relaxation, a contraction or both. Bombesin caused a weak inhibition, if anything. Neurotensin and VIP did not visibly affect the intestinal motility. 5-HT-, substance P- and VIP-like immunoreactivity and catecholamine fluorescence were observed in the myenteric plexus, submucosa and muscle layers in all parts of the intestine.(ABSTRACT TRUNCATED AT 250 WORDS)
J
J
Jensen
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S
Holmgren
D000109:Acetylcholine / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001839:Bombesin / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D005399:Fishes / Q000502:physiology*; D005769:Gastrointestinal Motility / Q000187:drug effects; D007422:Intestines / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D009496:Neurotensin / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology; D013004:Somatostatin / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D018377:Neurotransmitter Agents; D010656:Phenylephrine; D012701:Serotonin; D013373:Substance P; D014660:Vasoactive Intestinal Peptide; D009496:Neurotensin; D013004:Somatostatin; D004744:Enkephalin, Methionine; D000255:Adenosine Triphosphate; D000241:Adenosine; D007545:Isoproterenol; D000109:Acetylcholine; D001839:Bombesin; D004837:Epinephrine