TY - JOUR
T1 - Effects of divalent ions and drugs on synaptic transmission in phasic electroreceptors in a mormyrid fish
AU - Steinbach, A. B.
AU - Bennett, M. V.L.
PY - 1971/11/1
Y1 - 1971/11/1
N2 - We recorded impulses in afferent nerve fibers innervating two kinds of phasic electroreceptors in a mormyrid fish. We used an isolated preparation of skin, receptors, and sensory nerves to estimate synaptic delays, and to change solution in contact with the receptor-nerve synapse. The minimum delays between stimuli and sensory nerve responses, which must be slightly larger than synaptic delays, are about 0.7 msec in medium receptors and about 0.25 msec in large receptors. This result supports previous suggestions that transmission is chemically mediated in medium receptors and electrically mediated in large receptors. Furthermore, Mg+2 depresses synaptic transmission in medium receptors, and has little effect on transmission in large receptors. A complex dependence of response on both Mg+2 and Ca+2 masks divalent ion dependence of transmission, but a large excess of Mg+2 cannot completely block transmission in medium electroreceptors. L-glutamate, and not cholinergic drugs, produces a sequence of excitation and depression of medium receptor response which indicates that a similar chemical is the transmitter in the afferent synapse.
AB - We recorded impulses in afferent nerve fibers innervating two kinds of phasic electroreceptors in a mormyrid fish. We used an isolated preparation of skin, receptors, and sensory nerves to estimate synaptic delays, and to change solution in contact with the receptor-nerve synapse. The minimum delays between stimuli and sensory nerve responses, which must be slightly larger than synaptic delays, are about 0.7 msec in medium receptors and about 0.25 msec in large receptors. This result supports previous suggestions that transmission is chemically mediated in medium receptors and electrically mediated in large receptors. Furthermore, Mg+2 depresses synaptic transmission in medium receptors, and has little effect on transmission in large receptors. A complex dependence of response on both Mg+2 and Ca+2 masks divalent ion dependence of transmission, but a large excess of Mg+2 cannot completely block transmission in medium electroreceptors. L-glutamate, and not cholinergic drugs, produces a sequence of excitation and depression of medium receptor response which indicates that a similar chemical is the transmitter in the afferent synapse.
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U2 - 10.1085/jgp.58.5.580
DO - 10.1085/jgp.58.5.580
M3 - Article
C2 - 4330695
AN - SCOPUS:0015149869
SN - 0022-1295
VL - 58
SP - 580
EP - 598
JO - Journal of General Physiology
JF - Journal of General Physiology
IS - 5
ER -