Sigurd H. Ackerman

Age at maternal separation and gastric erosion susceptibility in the rat.

The development of susceptibility to immobilization-induced gastric erosions was studied in laboratory rats previously separated from their mothers at 15, 21 or 25 days of age. Early separation (day 15) produced animals whose maximum susceptibility occurred at a much younger age, generated a susceptibility curve over life that was the inverse of the curve for animals separated later and led to severe gastrointestinal hemorrhage as a common and distinguishing complication in younger rats. The pathogenesis of erosion formation in early separated rats may be unique in that, for that group only, the food deprivation component of the immobilization paradigm, when presented alone, also produced erosion of the glandular stomach, with hemorrhage.

Premature maternal separation and lymphocyte function

Premature separation of rat pups from their mothers, on postnatal Day 15, produced a decreased response of peripheral blood lymphocytes to phytohemagglutinin (PHA) at 40 days of age. A significant lymphopenia was also found in the early weaned animals at 40 days of age although this was accounted for statistically by their lower body weight. These consequences of early maternal separation may have been mediated through the effects of early separation on nutritional state, hypothalamic function, or maturation of the immune system.

Antidepressants and weight gain.

Weight gain is an often reported, but incompletely understood, side effect of many antidepressant medications. We will discuss the literature with respect to the following issues: weight gain as a pharmacological effect of antidepressants or as an effect of recovery from depression; the incidence of antidepressant-induced weight gain and possible reasons for individual variability in its occurrence; possible mechanisms of antidepressant-induced weight gain; and options for clinical management. Further elucidation of these issues may contribute to our understanding of the neurobiology of affective disorders and appetitive mechanisms.

Sleep and temperature regulation during restraint stress in rats is affected by prior maternal separation.

&NA; During restraint stress, 30‐day‐old rats uniformly show an abrupt and persistent decrease in activity with a corresponding increase in quiet wakefulness. However, the effect of restraint on sleep and body temperature depends on whether maternal separation had previously occurred at the customary age (day 22) or 7 days earleir (day 15). If maternal separation took place on day 22, subsequent restraint on day 30 has no effect on the amount of time spend in sleep or on body temperature, relative to a comparison sgroup of unrestrained rats. But if maternal separation took place on day 15, restraint on day 30 elicits a marked initial increase in sleep and a later decrease in sleep and body temperature. The results are consistent with the interpretation that premature maternal separation retards the normal maturation of these behavioral and thermoregulatory responses to restraint stress.

Chronobiologic Factors in Experimental Stress Ulcer

The available literature on chronobiologic factors in experimental stress ulcer is extremely small and thematically limited. It focuses almost exclusively on circadian rhythms and, within that, on rhythms related to light-dark cycles, activity and body temperature. Among these, only differences in ulcer induction related to circadian activity patterns have been adequately demonstrated. Other circadian patterns and other temporal phase relationships might be profitably explored, including those related to postnatal development. It is also likely that the important relationships between biorhythms and stress ulcer are not limited to ulcer induction. Future studies should address chronobiologic factors in predisposition, severity of illness, the probability of recovery and response to various therapeutic interventions.

Salivation and depression: a role for appetitive factors.

A decrease in salivary flow rate (SFR) is associated with depressive illness although the mechanisms underlying this association are unknown. Appetitive factors are known to influence SFR, but are not adequately considered in the studies of salivation and depression. Diminished SFR in depressive illness may be more closely related to the appetite disturbances commonly associated with depressive illness than to mood disorder or depressive illness per se. The implications for considering SFR as a physiological correlate of depressive illness are discussed in light of this possibility.

Ontogeny of gastric secretion in the rat: Ultrastructural changes in relation to secretory changes

Basal and stimulated gastric acid secretion are three to four times greater in the juvenile (30-day-old) rat than in the adult (100-day-old) rat, even though the parietal cell mass is greater in the adult. In this study we examined the possibility that the H+ secretory activity of individual parietal cells is greater in juvenile rats. To do this we used quantitative measures of secretory canaliculi and tubulovesicles as indirect measures of parietal cell H+ secretory activity. We determined that, under the experimental conditions used, the morphologic measures bear a sufficiently close linear relationship to total gastric H+ output to justify their use. We then found that when individual parietal cells from 30-day-old rats are compared quantitatively with those from 100-day-old rats, each cell from the younger rats has, on average, significantly more of the morphologic characteristics associated with higher H+ output. We inferred that individual parietal cells of 30-day-old rats, on average, may be secreting more H+ than corresponding cells of 100-day-old rats under comparable stimulation conditions.

Factors in the Etiology of Restraint Erosions in Parabiotic Rats

Rats joined in surgical parabiosis for 25 to 30 days were tested by restraining one member of the pair on a movable cart while allowing the second member to remain free to move about. These rats were compared with other rats joined in pseudoparabiosis for 25 to 30 days so that the behavioral aspects of parabiosis were reproduced but blood sharing did not occur. Pseudoparabiotic rats were also tested on the movable cart at the end of the recovery and adaptation period. Gastric erosions formed in the unrestrained members of both the parabiotic and pseudoparabiotic pairs with an incidence and severity that did not differ statistically. The experimental results fail to support the hypothesis that humoral factor(s) are critical in restraint ulcer pathogenesis in the rat.