. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 242 E. T. WALTERS to trigger vigorous defensive responses, and to cause gen- eral sensitization of the animal for several minutes. The term "sensitization" has been used independently by psy- chologists and physiologists to describe an increase in sensitivity or magnitude of. respectively, a behavioral or physiological response. I define nociceptive sensitization as sensitization produced by noxious stimulation, where sensitization is defined physiologically as an increase in sensitivity or responsiveness of the or
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 242 E. T. WALTERS to trigger vigorous defensive responses, and to cause gen- eral sensitization of the animal for several minutes. The term "sensitization" has been used independently by psy- chologists and physiologists to describe an increase in sensitivity or magnitude of. respectively, a behavioral or physiological response. I define nociceptive sensitization as sensitization produced by noxious stimulation, where sensitization is defined physiologically as an increase in sensitivity or responsiveness of the organism to a constant test stimulus. Such hypersensitivity after noxious stimu- lation need not be expressed as overt behavior, but is often expressed as a decrease in threshold and an increase in the magnitude of defensive responses evoked by a test stimulus. By this definition, sensitization may also be ex- pressed as inhibition of ongoing behavior (usually non- defensive) by the test stimulus. Nociceptive sensitization can be general (expressed by changes in response to a broad range of test stimuli and stimulation sites) or, as discussed below, specific to a warning signal or to a re- stricted site on the body. The apparent function of general nociceptive sensitization is to prime the animal for con- tinued defense, so that it responds rapidly and energeti- cally to a wide range of stimuli that might presage an attack. The first clue that nociceptive plasticity involves more than a brief, general sensitization came from the obser- vation that repeated application of noxious stimuli over hours or days causes general sensitization of siphon with- drawal that can last for weeks (Pinsker et 1973; Frost el al., 1985). It was then discovered that sensitization can be conditioned to a warning signal; a variety of defensive responses are selectively facilitated by a chemosensory cue (, shrimp extract) if it is repeatedly paired with noxious shock (Walters et al., 1981; Colw
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