Prazosin increases immobility episodes in taiep rats without changes in the properties of α1 receptors

The taiep rat is a myelin mutant in which immobility episodes (IEs) can be induced in adult males by gripping. EEG recordings during gripping-induced IEs show a rapid eye movement (REM) sleep-like pattern, similar to that reported for narcolepsy-cataplexy suggesting that IEs represent a disorder of REM-sleep. An α2 adrenoceptor agonist increases gripping-induced IEs, whereas α2 antagonists decrease these. We have studied the effect of prazosin on IEs and the levels of α1 adrenoceptors were evaluated in cerebro-cortical homogenates of taiep and control rats. Systemic administration of prazosin results in a significant increase in both the frequency and duration of gripping-induced IEs. Our results show that cerebro-cortical tissue is not an adequate candidate for the expression of cataplexy-like symptoms, but prazosin, an α1 antagonist, is a potent inducer of gripping-induced immobility episodes in taiep rats.