Home > Conscious > Chapter 6 > 6.4. GIRK Channels Suppress ISO-nested Oscillations

 

The infra-slow oscillation (ISO) typically contains faster oscillations and a long silence period (Figure 5-7). Experiments have demonstrated that this silence period is caused by GIRK channels which can reduce neuronal excitability.

  1. Barium (Ba2+) is a GIRK channel blocker. It can prevent suppression of high-frequency oscillations (Figure 6-5).
  2. As mentioned in the previous section, activated adenosine A1 receptor can open GIRK channels. Therefore, its antagonist, DPCPX, should be able to affect the ISO-nested oscillations. Indeed, high concentration of DPCPX (5μM) completely eliminates the silent period, a lower concentration of DPCPX (2μM) shortens the silence period (Figure 6-6).
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Figure 6-5. The GIRK channel blocker, Ba2+, prevents suppression of faster oscillations. (A) Under control conditions, ISO contains faster oscillations and a long silence period. (B) The addition of Ba2+ eliminates the silence period. [Source: Lörincz et al., 2009]

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Figure 6-6. The effects of A1 receptor antagonist, DPCPX, on ISO-nested oscillations. (A) High concentration of DPCPX (5μM) completely eliminates the silence period. (B) 1. The results under control conditions. 2. Addition of DPCPX (2μM) for 30 minutes. 3. Addition of DPCPX (2μM) for 40 minutes. 4. DPCPX was washed out. [Source: Lörincz et al., 2009]

Hence, within a neuron, the more GIRK channels are activated, the more ISO-nested α oscillations will be suppressed, resulting in longer silence period. According to the Alpha Hypothesis, consciousness arises from globally synchronized α oscillations. This explains why adenosine and melatonin can influence sleep (Chapter 7). Chapter 12 will present further evidence that the ISO-nested oscillations also affect the feeling of pleasure and pain. "Seek pleasure, avoid pain" is the animal nature. Thus, GIRK channels are involved not only in feeling, but also play important roles in behavior, such as drug addiction.