Co-localisation of functional nicotinic and ionotropic nucleotide receptors in isolated cholinergic synaptic terminals.
The combination of immunological and microfluorimetric techniques has permitted the identification and analysis of the Ca2+ influx responses in single rat midbrain cholinergic terminals. These terminals represent 22% of the total synaptosomal population and about 63% of them responded to nucleotides by a Ca2+ influx. The nucleotide response distribution in cholinergic synaptic terminals is as follows; 22.4% to diadenosine pentaphosphate (Ap5A), 24.7% to adenosine 5'-triphosphate (ATP) and 16.3% to both agonists. The ATP and Ap5A are able to induce acetylcholine release in a dose- and calcium-dependent way, being the EC50 values 0.22+/-0.1 microM and 1.5+/-0.1 microM respectively. Specific inhibitors can block this secretory effect. The studies of Ca2+ influx responses in isolated single synaptic terminals have also permitted to demonstrate the wide co-expression of functional nicotinic and nucleotidic receptors. The percentage values of the terminals responding to both ATP/nicotine and Ap5A/nicotine were 18.4% and 19.1%, respectively, considering the total population. Immunological studies also confirmed the presence of P2X3 subunits and alpha4 and alpha7 nicotinic receptor subunits in about 36%, 30% and 20%, respectively, of the cholinergic terminals.
Díaz-Hernández
Miguel
M
Department of Biochemistry, Facultad de Veterinaria, Universidad Complutense, 28040, Madrid, Spain.
Pintor
Jesús
J
Castro
Enrique
E
Miras-Portugal
M Teresa
MT
D000109:Acetylcholine / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015226:Dinucleoside Phosphates / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D008636:Mesencephalon / Q000187:drug effects / Q000378:metabolism; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D011978:Receptors, Nicotinic / Q000378:metabolism*; D011983:Receptors, Purinergic / Q000187:drug effects / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
D015226:Dinucleoside Phosphates; D005456:Fluorescent Dyes; D011978:Receptors, Nicotinic; D011983:Receptors, Purinergic; C012275:P(1),P(5)-di(adenosine-5'-)pentaphosphate; D000255:Adenosine Triphosphate; D000109:Acetylcholine; D002118:Calcium; D016257:Fura-2