Nicotinic acetylcholine receptors in cultured neurons from the hippocampus and brain stem of the rat characterized by single channel recording

Abstract

Single channel recording techniques have been applied to neurons cultured from the hippocampus and the respiratory area of the brain stem of fetal rats in order to search for nicotinic acetylcholine receptors (nAChR) in the central nervous system. In addition to acetylcholine (ACh), the potent and specific agonist (+)-anatoxin-a was also used to characterize nicotinic channels. nAChRs were concentrated on the somal surface near the base of the apical dendrite, and in some patches their density was sufficient to record 2 or more channel openings simultaneously. Although a multiplicity of conductance states was also evident, the predominant population showed a single channel conductance of 20 pS at 10°C. Thus, these neuronal nAChRs resembled the embryonic or denervated-type nAChRs in muscle. However, channel opening and closing kinetics were faster than reported for similar conductance channels in muscle. Therefore the nicotinic channels described here are similar but not identical to those of the well-characterized muscle nAChR, in agreement with biochemical, pharmacological, and molecular genetic studies on brain AChR.

Acetylcholine‐evoked currents in cultured neurones dissociated from rat parasympathetic cardiac ganglia.

“…Single-channel conductances of 20-50 pS have been determined for other nicotinic receptor channels in mammalian central and peripheral neurones (Aracava et al 1987;Derkach, North, Selyanko & Skok, 1987;Lipton et al 1987;Mathie et al 1987). The amplitude ratio of whole-cell current to single-channel current suggests that there are > 103 functional nicotinic receptor channels per cardiac neurone and, for an estimated surface area of 2000 ,Um2, the average channel density is -0 5 channels per /tm2.…”

“…It appears that a functional neuronal receptor channel consists of at least one ACh-binding and one non-ACh-binding subunit (Ballivet, Nef, Couturier, Rungger, Bader, Bertrand & Cooper, 1988; Papke, Boulter, Patrick & Heinemann, 1989). Electrophysiological studies of membrane currents evoked in response to exogenous ACh in mammalian cultured central and peripheral neurones provide evidence of numerous types of neuronal nicotinic receptor channels (O'Lague, Potter & Furshpan, 1978;Ogden, Gray, Colquhoun Aracava, Deshpande, Swanson, Rapoport, Wonnacott, Lunt & Albuquerque, 1987; Lipton, Aizenman & Loring, 1987; Mathie, Cull-Candy & Colquhoun, 1987). Although the pharmacological actions of ganglionic blocking agents on neurally evoked postsynaptic currents in rat parasympathetic submandibular ganglia (Ascher, Large & Rang, 1979;Rang, 1982) and amphibian parasympathetic cardiac ganglia (Hartzell et al 1977;Lipscombe & Rang, 1988) have been described, neuronal nicotinic receptor function has not been investigated extensively in isolated neurones.…”

Unconventional ligands and modulators of nicotinic receptors

“…Although the psychologic effects of tobacco smoking have been acknowledged for centuries (reviewed in Schalling and Waller, 1980), it was not until the late 1980s that the existence of functional nicotinic acetylcholine receptors (nAChRs) in the brain was demonstrated (Aracava et al, 1987;Lipton et al, 1988;Vidal and Changeux, 1989;Ramoa et al, 1990). Nicotinic receptors (nAChRs) are acetylcholine-gated cationic channels present in neuronal and non-neuronal cells (see Clementi et al, 2000).…”

Effects of Chronic Nicotine Treatment on the Accumulation of [3H]Tetraphenylphosphonium by Cerebral Cortical Synaptosomes

“…We have preliminary evidence that synaptosomes from nicotine-treated rats are capable of responding to other depolarizing agents, such as 10 mA4 KCI or 60 puM veratridine (Hillard and Pounds, 1991b), and so it is likely that the lack of effect of nicotine in vitro is due to insufficient sodium influx through nAChR. Patchclamp studies of CNS nAChR have shown that the amplitude of inward current activated by nicotine decreases with depolarization (Aracava et al, 1987;Mulle and Changeux, 1990), which supports the possibility that the nAChR are less likely to open following chronic nicotine treatment in vivo.…”