Elsevier

Neuroscience

Volume 106, Issue 2, 6 September 2001, Pages 395-403
Neuroscience

Nicotine induces calcium spikes in single nerve terminal varicosities: a role for intracellular calcium stores

https://doi.org/10.1016/S0306-4522(01)00280-9Get rights and content

Abstract

While nicotine is known to act at neuronal nicotinic acetylcholine receptors (nAChRs) to facilitate neurotransmitter release, the mechanisms underlying this action are poorly understood. Some of its effects are known to be mediated by presynaptic receptors. In the mouse vas deferens nicotine (10–30 μM) transiently increased the force of neurogenic contraction by 135±25%, increased the amplitude of excitatory junction potentials by 74±6% and increased the frequency of spontaneous excitatory junction potentials in four out of six preparations. Confocal microscopy and the calcium indicator Oregon Green 488 BAPTA-1 dextran were used to measure calcium concentration changes in the nerve terminals. Nicotine did not affect the action potential-evoked calcium transient but instead triggered small, random fluctuations (‘calcium spikes’) in intra-varicosity calcium concentrations at an average frequency of 0.09±0.02 Hz. These were insensitive to tetrodotoxin at a concentration that blocked action-potential evoked calcium transients (300 nM). They were abolished by the nAChR blocker hexamethonium (100 μM) and by both ryanodine (100 μM) and caffeine (3 mM), agents that modify calcium release from intracellular stores.

We propose a novel mechanism whereby nicotine’s action at nAChRs triggers calcium-induced calcium release from a ryanodine-sensitive calcium store in nerve terminals. This primes neurotransmitter release mechanisms and enhances both spontaneous and action potential-evoked neurotransmitter release.

Section snippets

Experimental procedures

Vasa deferentia were removed from 8–12-week-old Balb/c mice (Harlan, UK), which had been humanly killed by cervical fracture. All efforts were made to minimise the number of animals used and their suffering; all experiments were in accordance with the European Communities Council Directives (86/609/EEC of 24 November 1986) and approved by the local ethics committee (Department of Pharmacology, University of Oxford, Oxford, UK). A midline incision was made to expose the abdominal viscera and the

Results

The effect of nicotine on neurogenic contractions evoked by a train of 10 stimuli at 10 Hz was investigated in mouse vas deferens from which the sympathetic ganglia had been removed. Nicotine (10 μM) increased the force of the neurogenic contraction by 135±25% (n=6; P<0.01; Fig. 1A,C). The potentiating effect peaked about 30 s after the application of nicotine, after which the force of contraction returned towards its resting level. The time taken to return to control levels was not measured as

Discussion

The contraction studies demonstrate that nicotine acts within this tissue to increase the force of neurogenic contraction, an action previously attributed mainly to increased noradrenaline release (McGrath, 1978). The increase in the amplitude of EJPs and the increase in the frequency of SEJPs suggest that nicotine also acts on prejunctional sympathetic terminals to increase the release of the co-transmitter ATP, which is the neurotransmitter generating EJPs in the mouse vas deferens (Stjärne

Acknowledgements

K.L.B. was supported by a Sydney Tapping Postgraduate Research Award, The University of Sydney, Australia. S.J.T. is supported by The Wellcome Trust.

References (33)

  • J.A. Bevan et al.

    Electrical events associated with the action of nicotine at the adrenergic nerve terminal

    Arch. Int. Pharmacodyn.

    (1975)
  • K.L. Brain et al.

    Calcium in sympathetic varicosities of mouse vas deferens during facilitation, augmentation and autoinhibition

    J. Physiol.

    (1997)
  • J.A. Brock et al.

    Electrical activity at the sympathetic neuroeffector junction in the guinea-pig vas deferens

    J. Physiol.

    (1988)
  • V. Dolezal et al.

    Presynaptic nicotinic receptors stimulate increases in intraterminal calcium of chick sympathetic neurons in culture

    J. Neurochem.

    (1995)
  • S. Foucart et al.

    Increase in [Ca2+]i by CCh in adult rat sympathetic neurons are not dependent on intracellular Ca2+ pools

    Am. J. Physiol.

    (1995)
  • R. Gray et al.

    Hippocampal synaptic transmission enhanced by low concentrations of nicotine

    Nature

    (1996)
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