Plateau potentials in hindlimb motoneurones of female cats under anaesthesia.

Central respiratory drive potentials (CRDPs) were observed in intracellular recordings from hindlimb motoneurones of anaesthetized, paralysed, ovariohysterectomized female cats, artificially ventilated so as to have a strong respiratory drive under hyperoxic hypercapnea. The animals comprised two groups: three animals treated for 7 days with oestradiol benzoate (oestrous), and three untreated (non-oestrous). Several features of the CRDPs suggested the involvement of voltage-sensitive channels, including variability in the CRDP amplitude and potentiation of the CRDP by depolarizing currents. Clear plateau potentials, related to or triggered by depolarizing phases of the CRDPs, occurred in six motoneurones, three in response to depolarizing currents, three spontaneously. This is the first report of plateau potentials in mammalian motoneurones under anaesthesia. The mechanisms accessed here by the respiratory inputs are deduced to be particularly potent, perhaps because of a distal dendritic location. Plateau-like effects were more common in the oestrous animals, which suggests a specific role for the plateau potentials in the production of the stereotyped movements of female receptive behaviour.