Exercise-induced growth in golden hamsters: Effects of age, weight, and activity level

Abstract

The relationship between the exercise-induced growth and the endogenous controls of growth was examined in 356 golden hamsters of which equal numbers were given access to horizontal disc exercisers and maintained sedentary at different ages (17 and 42 days) and body weights (25-180 g). Hamsters started exercising around Day 35, increased their activity levels to 30,000 revolutions per day (RPD) by Day 35, and ran progressively less as their weight increased above 65 g. Exercise accelerated growth only in hamsters which have entered the slow asymptotic phase of growth, which weighed between 60-180 g and generated over 15,000 RPD.. Disc exercise appears to reinstate higher rates of ponderal and linear growth after hamsters have entered the slow asymptotic phase of growth. Sustained inhibition of exponential growth may participate in the long-term regulation of body size in adult rodents. Voluntary exercise Exponential growth Asymptotic growth Weight regulation Ontogeny

Hippocampal serotonin mediates hypoactivity in dietarily obese hamsters: A possible manifestation of aging?

“…A similar pattern of age-associated changes have been reported in the humans (25). In the hamster, the reciprocal association between the weight gain of maturity and the levels of spontaneous activity is established as early as 7 weeks of life when the animals weigh about 75 to 80 g (8). A very orderly relationship between weight gain and increasing hypoactivity predicts running levels as a function of weight throughout hamster adult life span [(8), Fig.…”

“…This is apparent at the time of sexual maturation in rodents when there is a rapid increase in spontaneous running activity to an all-time high at the same time as the rate of somatic growth and of weight gain rapidly decline (8). It is also evident after the onset of sexual maturity, during the period of slow weight gain when activity levels decline in inverse proportion to increases in body size (4,8,37). Thus, when the weight of mature hamsters doubles, their spontaneous activity levels are reduced by about 50% (4,8).…”

“…It is also evident after the onset of sexual maturity, during the period of slow weight gain when activity levels decline in inverse proportion to increases in body size (4,8,37). Thus, when the weight of mature hamsters doubles, their spontaneous activity levels are reduced by about 50% (4,8). Furthermore, when accumulation of excess energy results in obesity, mice (45), rats (37,40), and hamsters (5) display even greater spontaneous hypoactivity.…”

Simvastatin Impairs Spatial Memory in Rats at a Specific Dose Level

“…The effects of simvastatin on neurotransmitters and also on behavioral functions such as coordination, memory and other higher functions affecting locomotor systems have not been well established in the literature. A possible explanation might be that weight gain affects walking times on the rotarod (Borer et al 1977;Ardevol et al 1998). With applied rotarod tests, anxiety may be elicited by stimuli associated with the omission or loss of reward or simply falling from the rod.…”

Counterregulation of insulin by leptin as key component of autonomic regulation of body weight

“…Remarkably, increases in body mass setpoint without obesity also can be triggered by voluntary running in this species [318] proving Gordon Kennedy right about the interconnectedness of voluntary activity, weight regulation, and body growth [30,[319][320][321] . The facility of producing upward displacement of body mass setpoint by voluntary running in neurologically intact mature animals provides an exceptional opportunity to examine the location and nature of neural changes responsible for termination of statural growth and initiation of regulatory defenses of the adult body mass setpoint [322,323] . That this is a maturational event is seen by growth acceleration not being possible during animals' natural early rapid growth [323] .…”