Abstract
Introduction
Our previous study has shown that there is a direct connection between GABAergic neurons in the nucleus pontis oralis (NPO) and neurons of the dorsal raphe nucleus (DR), providing a morphological basis for the hypothesis that GABAergic inhibitory processes in NPO play an important role in the generation and maintenance of wakefulness as well as active (REM) sleep through the interaction with neurons in the DR. However, the target of such a GABAergic projection from the NPO within the DR is unknown. In the present study, a double-fluorescent labeling technique was employed to examine the target of GABAergic inputs to the DR.
Methods
Adult cats were deeply anesthetized and perfused transcardially. Subsequently, the brainstem containing the DR was removed, postfixed and cut into 15 μm coronal sections with a Reichert-Jung cryostat. The sections were immunostained with antibodies against GABA-A or GABA-B receptors and GABA following the procedure of double fluorescence immunohistochemistry.
Results
Under fluorescence microscopy, a large number of neurons were labeled with antibodies against either GABA-A receptor or GABA-B receptor. In addition, neurons labeled with antibody against GABA were observed in the DR. With double fluorescence immunohistochemical techniques, some neurons labeled by anti-GABA antibody were also stained with antibodies against GABA-A or GABA-B receptors.
Conclusion
The expression of GABA-A or GABA-B receptors by GABAergic neurons in the DR indicates that GABAergic neurons in the DR receive GABAergic inputs. Our previous study has demonstrated that these GABAergic inputs are from the NPO. These data provide a morphological foundation to support our hypothesis that, during wakefulness, NPO GABAergic “Executive” neurons suppress “Second-Order” GABAergic neurons in the DR, which, in turn, activate (disinhibit) serotonergic wake-on neurons in this nucleus.
Support (if any)
NS092383
Dorsal raphe serotonin neurotransmission is required for the expression of nursing behavior and for pup survival
