Circling and consumatory behavior induced by striatal and neocortical spreading depression

Single waves of spreading depression (SD) were induced in freely moving Sprague Dawley rats by microinjection of KCl solution into either neocortex or caudate nucleus. DC recordings of slow potential changes (SPC) revealed that a wave of SD propagates from the neocortex to the caudate nucleus in only a very few cases (12.5% of trials, involving 4.3% of the SPC waves). This result contrasts with earlier reported higher incidences of neocortical-striatal transmission of SD, and suggests that such transmission may vary across rat strains. Invasion of the caudate nucleus by a wave of neocortical SD was accompanied by contralateral circling in 50% of the cases. Similarly, SD induced by injection of KCl into the striatum was accompanied by circling in 43% of trials. It was also found that neocortical SD-induced feeding generally occurred only upon recovery of neocortex from the slow potential negativity, and that invasion of the caudate nucleus by SD is not involved in the elicited feeding phenomenon.