Hypothermia-produced retrograde amnesia in young and adult rats

Nociceptive and antinociceptive systems change dramatically during the first 10 days of life in rats. The present studies sought to determine whether exposure to water stress can produce analgesia during this period, and when in the ontogeny changes in magnitude and duration of such stress-induced analgesia occur. It was found that exposure to water reliably induced analgesia as early as 3 days postnatally. This analgesia increased in magnitude and duration at the age of 17-20 days, when supra-spinal descending inhibition develops, and depended on the temperature of the water and duration of exposure.

Section: Discussioncontrasting

confidence: 46%

Development of water‐immersion produced analgesia

Stolberg

Frenk

1995

“…The 10-day , 28-day, and 3-month-old rats were immersed in 14°C water, 10°C water, and 6°C water, respectively. Exposing different age groups to different water temperature as an attempt to equate the severity of the stressor across age groups is a commonly employed procedure in studies of developmental differences in reactions to cold-water stress (e.g., Hinderliter & Riccio, 1976).…”

Section: Cold-water Groupsmentioning

confidence: 99%

Ontogeny of an endogenous, nonopioid and hormonally mediated analgesic system

Hamm¹,

Knisely²

1987

Rats of different ages (10-day, 28-day, and 3-month-old) were exposed to cold-water stress in order to activate an endogenous analgesic system. The effects of naltrexone (7 mg/kg) and dexamethasone (.4 mg/kg) were also studied to examine the role of the opioid and hormonal systems in cold-water-induced analgesia. Following cold-water exposure, nociception was measured with the tail-flick procedure for 2 hr. Results revealed that cold water produced a significant level of analgesia in the 10-day, 28-day, and 3-month-old age groups with no differences between age groups. In addition, in each age group naltrexone did not block the analgesia while dexamethasone attenuated the analgesia produced by cold water. The effects of naltrexone and dexamethasone confirm that cold-water immersion activates a nonopioid, hormonally mediated analgesic system in each age group. Thus, this experiment found that the endogenous, nonopioid, and hormonally mediated analgesic system activated by cold water is functional early in the development of the rat. The early development of this hormonally mediated analgesic system is in contrast to the slower development of endogenous analgesia systems that are mediated by the central nervous system.

“…In an attempt to equate the impact of the amnesic treatment for different age groups, Hinderliter and Riccio (1976) employed hypothermia as the amnesia agent. By using hypothermia, the investigators could measure and equate the physiological 358 HAMM impact that the amnesic treatment has on the body temperature of rats of different ages.…”

mentioning

confidence: 99%

Hypothermia‐induced retrograde amnesia in mature and aged rats

Hamm

1981

Mature (10-month-old) and aged (25-month-old) rats were trained on a passive avoidance task. Following training, rats in each age group were exposed to a hypothermia treatment, restraint alone, or no treatment. The hypothermia treatment involved immersing the mature rats in 4 degrees C water for 12 min and immersing the aged rats in 1 degrees C water for 12 min. This treatment reduced the body temperature of both age groups to an equivalent temperature (22 degrees C). Following immersion, the body temperature of the aged rats continued to decline to a lower level and recovered at a slower rate than the mature rat's temperatures. When all rats were tested 24 hr after training for retention of the avoidance task, mature rats performed better than aged rats when trained with the same shock intensity. Increasing the shock duration for the aged rats eliminated the performance differences on the passive avoidance task between ages. Rats exposed to hypothermia showed poorer retention of the task (i.e., retrograde amnesia) than all control conditions. However, no age differences in the degree of amnesia induced by the hypothermia treatment were apparent once age groups were equated on the intensity of the amnesic agent (hypothermia) and degree of initial learning.