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Query: UMLS:C0231530 (twitching)
 2,043 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1 Neuronal effects and the pharmacological properties of the bovine ciliary muscle were investigated in vitro. The bovine ciliary muscle exhibited no spontaneous activity. 2 Electrical stimulation of an isolated short ciliary nerve produced distinct contractions. The minimal stimulus duration required to evoke a contraction was 0.2 ms and amplitude of the contraction was maximal at 2 ms. Twitch or incomplete tetanus reached a complete tetanus with 4 Hz stimulation. 3 Raising the external potassium concentration from 5.9 to 158.8 mM produced a contracture which consisted of an initial phasic and then tonic components. 4 The contractions generated by either electrical stimulation (0.2-100 ms) or high K were potentiated by physostigmine and completely inhibited by atropine. Neither adrenoceptor agonists nor blockers influenced these contractions. 5 Application of tetraethylammonium (TEA), potentiated the electrically-induced ciliary muscle contraction, and the effect of TEA was not completely inhibited by high concentrations of either atropine or tetrodotoxin. Thus, TEA presumably acts both pre-junctionally and post-junctionally to increase the contractile development of ciliary muscle. 6 The ciliary contractile response is primarily mediated by acetylcholine released from nerves, and this response is accompanied by a negligible contribution from the sympathetic nerves. Depolarization induced by electrical currents or by high K was ineffective in evoking contraction of the ciliary muscle. 7 The results suggest that excitation of the ciliary muscle is probably mediated via junction potentials or by a direct transmitter action without any very great change in the potential. Action potentials are probably generated in the presence of TEA.
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PMID:Neuronal influence on the mechanical activity of the ciliary muscle. 683 64

The neonatal hippocampus exhibits regularly recurring waves of synchronized neuronal activity in vitro. Because active sleep (AS), characterized by bursts of phasic motor activity in the form of myoclonic twitching, may provide conditions that are conducive to activity-dependent development of hippocampal circuits, we hypothesized that the waves of synchronous neuronal activity that have been observed in vitro would be associated with AS-related twitching. Using unanesthetized 1- to 12-d-old rats, we report here that the majority of neurons in CA1 and the dentate gyrus (DG) are significantly more active during AS than during either quiet sleep or wakefulness. Neuronal activity typically occurs in phasic bursts, during which most neurons are significantly cross-correlated both within and across the CA1 and DG fields. All AS-active neurons increase their firing rates during periods of myoclonic twitching of the limbs, and a subset of these neurons exhibit a burst of activity immediately after limb twitches, suggesting that the twitches themselves provide sensory feedback to the infant hippocampus, as occurs in the infant spinal cord and neocortex. Finally, the synchronous bursts of neuronal activity are coupled to the emergence of the AS-related hippocampal gamma rhythm during the first postnatal week, as well as the emergence of the AS-related theta rhythm during the second postnatal week. We hypothesize that the phasic motor events of active sleep provide the developing hippocampus with discrete sensory stimulation that contributes to the development and refinement of hippocampal circuits as well as the development of synchronized interactions between hippocampus and neocortex.
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PMID:Synchronous bursts of neuronal activity in the developing hippocampus: modulation by active sleep and association with emerging gamma and theta rhythms. 1882 71