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Cyclic AMP mediates inhibition of the Na(+)‐K+ electrogenic pump by serotonin in tactile sensory neurones of the leech.
Author(s) -
Catarsi S,
Scuri R,
Brunelli M
Publication year - 1993
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1993.sp019552
Subject(s) - leech , serotonin , sensory system , chemistry , neuroscience , communication , biophysics , psychology , biology , biochemistry , computer science , receptor , world wide web
1. Serotonin (5‐HT) reduced the after‐hyperpolarization (AHP) amplitude in tactile sensory neurones (T) but not in pressor (P) or nociceptive (N) cells of the leech. 2. Adenylate cyclase activators, phosphodiesterase inhibitors and membrane permeant analogues of cyclic adenosine monophosphate (cyclic AMP) mimicked the effect of 5‐HT in reducing the AHP amplitude in T neurones. 3. Ionophoretic injection of cyclic AMP in T cells reduced the AHP amplitude, while cyclic guanosine monophosphate (cyclic GMP) or adenosine‐5'‐monophosphate (AMP) were without effect. 4. Inhibition of adenylate cyclase by the drug RMI 12330A (also known as MDL 12330A) suggested that 5‐HT reduced the AHP amplitude through cyclic AMP. 5. 8‐Bromoadenosine‐3'‐5'‐cyclic monophosphate (8‐Br‐cyclic AMP) was still able to reduce the AHP amplitude after blocking the Ca(2+)‐activated K+ conductance with CdCl2 and converted the normal hyperpolarization which follows the intracellular injection of Na+ into a depolarization. In addition, the cyclic AMP analogue slowed down and reduced the repolarization usually induced by CsCl after perfusion with K(+)‐free solution. It is proposed that, in T sensory neurones, cyclic AMP mediates the inhibition of the Na(+)‐K+ electrogenic pump induced by 5‐HT application.