Presynaptic, muscarinic inhibition of non‐adrenergic, non‐cholinergic neuromuscular transmission in the chicken rectum

Abstract

1 Cholinergic inhibition of the non-adrenergic, non-cholinergic (NANC) transmission was investigated in the chicken isolated rectum with Remak's nerve attached. 2 Stimulation of Remak's nerve (RT stimulation) at frequencies higher than 5 Hz elicited a late, slow contraction of the rectum in addition to an initial, fast NANC contraction. The late, slow contraction was blocked by atropine (0.25 jig ml-'), potentiated by physostigmine (50 ng ml-') and accompanied by an overflow of acetylcholine into the vascular perfusate, indicating the existence of cholinergic innervation to the rectum via Remak's nerve. 3 RT stimulation (10 pulses at 0.5-1.0 Hz) elicited NANC-mediated excitatory junction potentials (e.j.ps). The e.j.p. amplitude declined at the second stimulus and then increased to reach a plateau. Atropine, by abolishing this decrease in amplitude, increased the mean amplitude of the e.j.ps during trains of stimuli but atropine did not affect the amplitude of the first e.j.p. Physostigmine reduced the mean e.j.p. amplitude, and this action was readily antagonized by atropine. 4 A single intramural nerve stimulation delivered 2 s or less before RT stimulation with trains of stimuli, suppressed the amplitude of the first e.j.p. of the train. This effect was abolished by atropine. 5 Atropine in concentrations high enough to affect the e.j.p. amplitude had no effect on the resting membrane potential, the threshold for generating an action potential, or membrane resistance of the smooth muscle. 6 It is concluded that RT stimulation at low frequencies causes the release of acetylcholine simultaneously with the NANC transmitter. The released acetylcholine acts mainly on prejunctional muscarinic receptors and mediates an inhibitory effect on the release of the NANC transmitter.

Some membrane properties of the circular muscle of chicken rectum and its non‐adrenergic non‐cholinergic innervation.

“…The inhibitory nerves mediating the IJP may originate from neurones in the myenteric plexus and the neurones may not have synaptic connections in such a way that they can be driven by the fibres in Remak's nerve. In cells in the longitudinal muscle, non-adrenergic, non-cholinergic nerve activation by field stimulation does not produce any IJP Ohashi, Naito, Takewaki & Okada, 1977;Komori & Ohashi, 1982, 1984. Therefore, the inhibitory innervation is one of the striking features of the circular muscle and may be involved in a physiological function in which the muscle plays an important part.…”

“…The active and passive membrane properties of the longitudinal muscle of chicken rectum have been investigated. The muscle presents the same cable-like properties as those of other intestinal smooth muscles of many species and readily discharges action potentials of relatively brief duration (10 ms or so) on depolarization in response to applied outward current and stimulant substances, or an excitatory junction potential following nerve stimulation (Komori, Ohashi & Takewaki, 1980;Komori & Ohashi, 1982, 1984. The innervation of the longitudinal muscle of the chicken rectum has been described in several papers (Bartlet & Hassan, 1971;Bartlet, 1974;Komori & Ohashi, 1984).…”

“…The muscle presents the same cable-like properties as those of other intestinal smooth muscles of many species and readily discharges action potentials of relatively brief duration (10 ms or so) on depolarization in response to applied outward current and stimulant substances, or an excitatory junction potential following nerve stimulation (Komori, Ohashi & Takewaki, 1980;Komori & Ohashi, 1982, 1984. The innervation of the longitudinal muscle of the chicken rectum has been described in several papers (Bartlet & Hassan, 1971;Bartlet, 1974;Komori & Ohashi, 1984). Nonadrenergic, non-cholinergic neurones whose cell bodies are located in Remak's ganglia (Kanazawa, Ohashi & Takewaki, 1980) are mainly responsible for the excitatory innervation, and excitatory junction potentials are recorded intracellularly from the smooth muscle cells Komori & Ohashi, 1982).…”

Alimentary Canal: Anatomy, Regulation of Feeding, and Motility

“…Stimulation of Remak's nerve in an isolated rectum preparation caused the release of a nonadrenergic, noncholinergic (NANC) transmitter resulting in an initial fast contraction. This was followed by a slow contraction (produced by low-frequency stimulation) and caused by the release of acetylcholine, which acts mainly on prejunctional muscarine receptors and mediates an inhibitory effect on the release of the NANC transmitter (Komeri and Ohashi, 1984).…”

Isolation of a Peptide Material Showing Strong Rectal Muscle-Contracting Activity from Chicken Rectum and Its Identification as Chicken Neurotensin

“…The excitatory nerve reaches the rectum via the Remak nerve, a unique ganglionated nerve trunk of fowls, and in these ganglia, it has synaptic trans mission. The post ganglionic neurone is non adrenergic and non-cholinergic (NANC) in nature (1)(2)(3)(4)(5). The transmitter released from axon terminals of NANC neurones has not been identified yet.…”