Electrotonic coupling between stratum oriens interneurones in the intact in vitro mouse juvenile hippocampus

• Published in: The Journal of physiology Vol. 558; no. 3; pp. 825 - 839
• Main Authors: Zhang, Xiao‐Lei, Zhang, Liang, Carlen, Peter L.
• Format: Journal Article
• Language: English
• Published: 9600 Garsington Road , Oxford , OX4 2DQ , UK The Physiological Society 01.08.2004; Blackwell Science Ltd; Blackwell Science Inc
• Subjects: Action Potentials - drug effects; Action Potentials - physiology; Animals; Animals, Newborn; Carbenoxolone - pharmacology; Hippocampus - cytology; Hippocampus - drug effects; Hippocampus - physiology; In Vitro Techniques; Interneurons - cytology; Interneurons - drug effects; Interneurons - physiology; Mice; Mice, Inbred C57BL; Research Papers
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.2004.065649

Using the isolated juvenile (7–14 days) mouse whole hippocampus preparation, which contains intact complex local circuitry, 145 dual whole cell recordings were made from stratum oriens (s.o.) interneurones under infrared microscopy. In 11.7% of paired recordings, evidence for direct electrotonic coupling between the s.o. interneurones was obtained from the response of one interneurone to a long (400–600 ms) constant current pulse passed into the coupled interneurone. When specifically orienting the dual recordings in the transectional plane of the hippocampus, 18.5% of paired recordings showed electrotonic coupling. The coupling coefficient, estimated from averaged data, was 6.9 ± 4.7%, ranging from 1.3 to 17.6%. The time constant of the electrotonically transmitted hyperpolarization was inversely related to the coupling coefficient between the two neurones. The electrotonic responses of one neurone to constant current pulses injected into the other coupled neurone were intermittent. Spikes in one of the coupled neurones were associated with small electrotonic EPSPs (spikelets) in the other coupled neurone, in those neuronal pairs with coupling coefficients greater than 10%. Failure of spikelet production following a spike in the coupled cell occurred 5–10% of the time. Electrotonic coupling and spikelets persisted in the presence of chemical synaptic transmission blockade by CNQX, APV and bicuculline, or in zero Ca 2+ perfusate, but were abolished by carbenoxolone (100 μ m ), a gap junctional blocker. These data confirm the existence of electrotonic coupling between s.o. interneurones, presumably via gap junctions located in dendrites.