. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 212 REPORTS FROM THE MBL GENERAL SCIENTIFIC MEETINGS A \ B \. Figure 1. Comparison of PSPs evoked hy electrical stimulation of the skin in supramedullary/dorsal cells. (A, B, C> A calibration pulse of 80 in \'. 2 ms is present at the beginning of each recording. Cells fired action potentials in response to a short intracellular depolarising pulse in one of the ni'o superimposed traces. This pulse was followed bv electrical stim- iilution of the skin of the right opeiriili/in (to provide a baseline, in one of the nm superi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 212 REPORTS FROM THE MBL GENERAL SCIENTIFIC MEETINGS A \ B \. Figure 1. Comparison of PSPs evoked hy electrical stimulation of the skin in supramedullary/dorsal cells. (A, B, C> A calibration pulse of 80 in \'. 2 ms is present at the beginning of each recording. Cells fired action potentials in response to a short intracellular depolarising pulse in one of the ni'o superimposed traces. This pulse was followed bv electrical stim- iilution of the skin of the right opeiriili/in (to provide a baseline, in one of the nm superimposed traces this stimulus was not given: stimulus artifacts are designated with arrowheads). I A) Recordings from a fish in which tricaine was used transiently to remove the telencephalon. A PSP (arrow) gives rise to an action potential. IB I Recordings from an unanesthetized p\h. A PSP farrow) gives rise to an action potential. (C) Recordings from a fish under general tricaine anesthesia. No PSPs could be evoked to electrical stimulation of the right operciilitm. the right operculum in both conditions. This was not the case in animals under general anesthesia (1; Fig. 1). In anesthetic-free experiments, stimulation of the telencephalic hemispheres at only the high voltages (80-100 V) activated the dorsal cells. To test whether this activation was the result of direct or indirect telencephalic input to the supramedullary/dorsal cells and not current spread to adjacent nervous tissue, in three exper- iments the telencephalic hemispheres were removed and then replaced in their original positions. The disconnected telencephalic hemispheres were stimulated again at roughly the same location and the same voltages. The response to stimulation persisted. These results indicate that activation was through current spread to adjacent structures such as the trigeminal nerve, which is known to contain processes of dorsal cells. General anesthetics, such as tricaine, are known to reduce s
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