Membrane potential and current responses to neurotensin in the longitudinal muscle of the rectum of the fowl

Abstract

1The effects of neurotensin (NT) on membrane potential and membrane current of the longitudinal smooth muscle of chicken rectum were investigated by intracellular recording and whole-cell voltage clamp. 2 NT (3 nM-1.2 SAM), when applied via the bathing medium, produced a concentration-dependent membrane depolarization with an EC50 of 18 ± 2 nM (n = 7) which was accompanied by an increase in the membrane conductance. The effect was biphasic: an initial, rapid depolarization reached a peak within 2-3 min and then declined to a lower but still elevated level which was sustained until washout. 3 Excitatory junction potentials (ej.ps), which were non-adrenergic non-cholinergic (NANC) in nature, were decreased in amplitude and total duration in the presence of NT (0.6 jLM). The depression of the e.j.p. was due mainly to the reduction of the membrane resistance. 4 When NT was applied locally by means of pressure ejection from a micropipette containing NT, some cells responded with a membrane depolarization and some failed to respond, whereas ej.ps could invariably be elicited from all of them. 6 The present results suggest that the membrane depolarization, which may arise from activation of non-selective cation channels, and release of calcium from internal stores produced by neurotensin are responsible for its contractile activity in the longitudinal smooth muscle of chicken rectum. Further, the depolarizing effect may provide support for the involvement of NT in the NANC transmission in this preparation.

Membrane current responses to externally‐applied ATP in the longitudinal muscle of the chicken rectum

“…Further, patch clamp experiments revealed that both ATP and neurotensin are channel activators with specific membrane receptors. Both agents activate current with a reversal potential close to 0 mV in a quasi-physiological ionic environment (Komori et al, 1992b; the present study). Activation of such currents leads to membrane depolarization.…”

“…Local application of either ATP or neurotensin by means of pressure ejection from micropipettes evokes a brief, monophasic membrane depolarization similar to the ej.p. (Komori & Ohashi, 1988b;Komori et al, 1992b). Further, patch clamp experiments revealed that both ATP and neurotensin are channel activators with specific membrane receptors.…”

The actions of neurotensin in rat bladder detrusor contractility

“…In the gastrointestinal tract, an increasing number of biological effects have been attributed to NTs discovery. The evidence indicates that NTs released from entero-endocrine N cells 22 is involved in slow wave regulation in the gastrointestinal tract and promotes the peristaltic activity of the intestine by acting on NTSR1 11 23 . Although the bladder, which is an urinary organ regulating the storage and elimination of urine, has a physiological function different from the gastrointestinal tract, the urinary tract and gastrointestinal tract share a common mechanism in generating spontaneous myogenic contractions.…”

“…New ideas and evidences have emerged regarding the role of NTs in the contraction and pacemaker currents of the small intestine. NTs induces contraction of the small intestine smooth muscle in a concentration-dependent manner via its action on the NTSR1 of SMCs and interstitial cells of Cajal (ICCs) 11 12 . In addition, the relationship between NTs and cholinergic systems has been documented in several research articles.…”

Molecular characterization of structure and tissue distribution of chicken neurotensin receptor

“…Chicken NT also induces Ca 2+ release from internal store, which is responsible for the contractile activity in the longitudinal smooth muscle of the rectum [24]. In this study, chicken NT induced an increase in intracellular Ca 2+ concentrations in the chicken NTR1-expressing cells.…”