Figure 4.
Different manifestations of the slow (<1 Hz) oscillation in NRT neurons. A, Intracellular recording of an NRT neuron in the peri-VL sector in the presence of trans-ACPD (100 μm) displaying a basic slow oscillation. In this neuron, the slow oscillations were always of this type, regardless of the level of DC current. The underlined section is expanded on the right. B1, Intracellular recording of a peri-VB-sector neuron in the presence of trans-ACPD (100 μm) displaying a slow (<1 Hz) oscillation that groups rhythmic LTCP bursting at ∼1–2 Hz before the transition to the up phase. The underlined section is expanded below with the further marked section enlarged on the right. B2, Intracellular recording of a PGN neuron in the presence of trans-ACPD (100 μm), which also exhibits rhythmic sequences of LTCP bursts before the commencement of the up state. The underlined section is expanded below and reveals that there is a clear increase in interburst frequency in the LTCP sequence as it progresses, which is associated with an unambiguous underlying depolarization. The trace on the right is an enlargement of one of the underlined bursts. C, Plot showing the mean interburst frequency of successive bursts in five different NRT neurons that displayed the grouped LTCP subtype of the slow oscillation (3 cycles of the oscillation at the most positive level of DC current for which grouped episodes existed were used for this analysis). In each case, the interburst frequency increased during the grouped episodes. Neuron 1 corresponds to the neuron shown in B2 and neuron 2 is that depicted in B1. D, E, Examples of the different manifestations of the slow oscillation as observed with extracellular recordings in the presence of 50 μm trans-ACPD. F, Plot showing the mean interburst frequency of successive bursts in five different NRT neurons that displayed the grouped LTCP subtype of the slow oscillation in extracellular recordings. In all cases, the interburst frequency increased during the grouped episodes and was generally higher than that observed in intracellular recordings. CNQX (10 μm), APV (50 μm), SR95531 (20 μm), and CGP54626 (20 μm) were present in the recording medium for these experiments. Error bars indicate SE.