presyˈnaptic, a.
1. Cytology. [pre- B. 1.] Prior to meiotic synapsis.
| 1909 Ann. Bot. XXIII. 21 In common with Grégoire ('07), we may adopt, provisionally at least, the following scheme of phases for convenience of clearness in description. The prophases of division naturally fall into two periods, the pre-synaptic and the post-synaptic phases. 1912 [see leptotene]. 1921 Ann. Bot. XXXV. 367 Fig. 5 represents a presynaptic pollen mother-cell. |
2. Physiol. [pre- B 3] Of, pertaining to, or designating a neurone that transmits a nerve impulse across a synapse. Opp. postsynaptic a. 2.
| 1937 Proc. R. Soc. B. CXXII. 113 The response is erratic in that by no means every pre-synaptic stimulus yields a post-synaptic response. 1950 [see hyperpolarize v.]. 1965 G. H. Bell et al. Textbk. Physiol. & Biochem. (ed. 6) xxxix. 796 In general the presynaptic fibre divides up into numerous fine branches which then end in greatly expanded terminals, presynaptic knobs, which make intimate contact with part of the membrane of the cell body or dendrites of the postsynaptic cell. 1979 Internat. Rehabilit. Med. I. 45/1 New evidence of the blocking of pain specific receptors..by morphine-like substances produced by presynaptic dendrites. |
Hence presyˈnaptically adv.
| 1971 Nature 12 Nov. 102/1 In the central nervous system, amphetamine releases presynaptically bound NE [sc. norepinephrine] or DA [sc. dopamine] and blocks their re-uptake. 1976 Ibid. 3 June 418/1 The fact that chlorpromazine also blocks α-adrenoceptors, possibly presynaptically located, may also contribute to the enhanced presence of catecholamines at the synaptic cleft. |