Figure 4. Disinhibition of hypothalamic PF neurones results in a parallel suppression of all components of the REM sleep-like response elicited by pontine carbachol.

The graph shows the results from all pontine carbachol injections made in 6 experiments conducted according to the protocol illustrated in Fig. 3. The magnitudes of the different components of the response to carbachol are expressed as a percentage of the corresponding effect elicited in each animal by pontine carbachol prior to hypothalamic injection of bicuculline. To reflect the sequential nature of these experiments, the abscissa is normalized to the duration of bicuculline-induced activation (which varied among the animals; see text). Different symbols correspond to distinct output parameters, with each symbol of the same type representing one test with pontine carbachol. Carbachol was ineffective (corresponding to 0% on the ordinate) in all tests conducted within 12–54% of the duration of the response to bicuculline. All components of the response to pontine carbachol recovered around the time of termination of the activating effect of bicuculline (over ∼88% on the abscissa).