An electrophysiological study of excitatory purinergic neuromuscular transmission in longitudinal smooth muscle of chicken anterior mesenteric artery

Abstract

1 The object of the present study was to clarify the neurotransmitters controlling membrane responses to electrical field stimulation (EFS) in the longitudinal smooth muscle cells of the chicken anterior mesenteric artery. 2 EFS (5 pulses at 20 Hz) evoked a depolarization of amplitude 19.772.1 mV, total duration 29.673.1 s and latency 413.0767.8 ms. This depolarization was tetrodotoxin (TTX)-sensitive and its amplitude was partially decreased by atropine (0.5 mM); however, its duration was shortened by further addition of prazosin (10 mM). 3 Atropine/prazosin-resistant component was blocked by the nonspecific purinergic antagonist, suramin, in a dose-dependent manner, indicating that this component is mediated by the neurotransmitter adenosine 5 0 -triphosphate (ATP).4 Neither desensitization nor blocking of P2X receptor with its putative receptor agonist a,bmethylene ATP (a,b-MeATP, 1 mM) and its antagonist pyridoxalphosphate-6-azophenyl-2 0 ,4 0 -disulfonic (PPADS, up to 50 mM), had significant effect on the purinergic depolarization. In contrast, either desensitization or blocking of P2Y receptor with its putative agonist 2-methylthioATP (2-MeSATP, 1 mM) and its antagonist Cibacron blue F3GA (CBF3GA, 10 mM) abolished the purinergic depolarization, indicating that this response is mediated through P2Y but not P2X receptor. 5 The purinergic depolarization was inhibited by pertussis toxin (PTX, 600 ng ml À1). Furthermore, it was significantly inhibited by a phospholipase C (PLC) inhibitor, U-73122 (10 mM), indicating that the receptors involved in mediating the purinergic depolarization are linked to a PTX-sensitive G-protein, which is involved in a PLC-mediated signaling pathway. 6 Data of the present study suggest that the EFS-induced excitatory membrane response occurring in the longitudinal smooth muscle of the chicken anterior mesenteric artery is mainly purinergic in nature and is mediated via P2Y purinoceptors.

Purinergic Signaling and Blood Vessels in Health and Disease

“…The relaxant action of ATP released by electrical field stimulation of rabbit small mesenteric arteries was similarly claimed to be partially endothelium dependent, but was resistant to inhibition of NOS (Kakuyama et al, 1998). An electrophysiological study of the longitudinal smooth muscle of the chicken anterior mesenteric artery showed that electrical field stimulation produced excitatory membrane responses mediated by ATP acting largely via P2Y receptors (Khalifa et al, 2005).…”

Postnatal development of excitatory innervations in longitudinal smooth muscle of the chicken anterior mesenteric artery

“…Each preparation was perfused with warmed (29°C) PSS at a constant flow rate (3 mL/min). The temperature of 29°C was used in this experiment since spontaneous activity, which makes recording from the cells difficult, was frequently produced at 35°C (Khalifa et al, 2005). Tissue preparations were subsequently allowed to equilibrate for 1 h. Microelectrode insertions were made in longitudinal muscle cells through the adventitial side, within 2 mm of the stimulation electrode.…”

“…Arteries were placed in a partition chamber in which large extracellular silver-silver chloride plates were placed to elicit nerve stimulation, as described previously (Khalifa et al, 2005). Each preparation was perfused with warmed (29°C) PSS at a constant flow rate (3 mL/min).…”

“…It has been shown that cholinergic and purinergic neurons play crucial roles in excitatory transmission at the longitudinal smooth muscle of the anterior mesenteric artery of adult chickens (Bolton, 1968(Bolton, , 1969Bell, 1969;Khalifa et al, 2005). However, there have been few reports on postnatal development of innervation to the muscles.…”

“…In addition, there is an apparent difference in non-adrenergic noncholinergic (NANC) regulation between longitudinal and circular smooth muscles. We have demonstrated that ATP released from perivascular nerves induces depolarization in longitudinal smooth muscles (Khalifa et al, 2005), whereas it causes hyperpolarization in circular smooth muscles through an endothelium-dependent mechanism (Draid et al, 2005).…”