Neocortical and hippocampal electrical activity following decapitation in the rat

Abstract

It has been debated whether or not decapitation of conscious animals is a humane procedure. This problem may be clarified on the basis of recent research that has indicated that neocortical low voltage fast activity (LVFA) and hippocampal rhythmical slow activity (RSA) can result from activity in either the cholinergic corticipetal projections from the basal forebrain or the serotonergic corticipetal projections from the brainstem. These inputs appear to produce, respectively, atropine-sensitive LVFA and RSA and atropine-resistant LVFA and RSA. In waking animals, atropine-resistant LVFA and RSA occur only in close correlation with motor activities such as spontaneous changes in posture, walking or struggling (Type 1 behavior). Painful stimuli readily elicit both Type 1 behavior and LVFA and RSA in atropine-treated rats. Atropine-sensitive LVFA and RSA may occur in anesthetized as well as in conscious animals, but atropine-resistant LVFA and RSA are generally absent during anesthesia. In the experiments reported here, rats were decapitated: (1) in the normal waking state; (2) after pretreatment with atropine or scopolamine; or (3) following induction of anesthesia with ethyl ether. Clear hippocampal RSA and neocortical LVFA were observed in conditions 1 and 3 but not in condition 2. It is concluded: (A) that atropine-sensitive LVFA and RSA are not good indices of conscious perception of pain since these waveforms occur during anesthesia as well as in the waking state; and (B) that the cerebral reaction to decapitation does not resemble the usual cerebral reaction to painful stimuli. This is consistent with the view that decapitation is not inhumane.