Excitation of neurones in a restricted portion of the midbrain periaqueductal grey elicits both behavioural and cardiovascular components of the defence reaction in the unanaesthetised decerebrate cat.
Microinjections of the excitant amino acid D,L-homocysteic acid (DLH) into a restricted part of the midbrain periaqueductal grey (PAG) of unanaesthetized decerebrate cats evoked a distinctive pattern of facio-vocal and cardiovascular changes characteristic of a defence reaction, including pupillary dilatation, howling vocalization, an increase in arterial pressure and heart rate, and skeletal muscle vasoconstriction. These facio-vocal and cardiovascular responses always occurred together, and thus may arise from excitation of a common population of neurones. DLH injections within a greater extent of the PAG elicited other facio-vocal changes characteristic of defence, such as hissing or growling, but these were not accompanied by significant cardiovascular changes.
Department of Anatomy, University of Sydney, N.S.W., Australia.
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D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000187:drug effects; D002415:Cats; D003655:Decerebrate State; D004525:Efferent Pathways / Q000187:drug effects / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006710:Homocysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D010487:Periaqueductal Gray / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D014661:Vasoconstriction / Q000187:drug effects; D014828:Vocalization, Animal
D006710:Homocysteine; C007956:homocysteic acid