PubMed Health⌕ Search

Biomedical subjects

R Eikelboom

Publications and source records attributed to R Eikelboom.

29 records · Page 2Linked to original sources
PubMed1983

Human pancreas GH-releasing factor analog restores high-amplitude GH pulses in CNS lesion-induced GH deficiency.

Lesions of the ventromedial-arcuate (VMH-ARC) region of the hypothalamus result in impaired growth accompanied by a marked suppression in spontaneous GH secretory bursts. We studied the effects of an analog of the recently characterized human pancreas GH-releasing factor hpGRF(1-40) on GH secretory dynamics in freely-moving chronically cannulated rats bearing electrolytic lesions of the VMH-ARC. Intravenous administration of the hpGRF analog (hpGRFa) caused a dramatic surge of GH within 5 min; plasma GH levels rose to values as high as 2900 ng/ml and remained significantly elevated for 15-30 min post treatment. The simultaneous iv administration of somatostatin-14 and hpGRFa resulted in a significant inhibition of the hpGRFa-induced GH release at 5 min but not at 15 min. These results clearly demonstrate that impaired GH secretion resulting from VMH-ARC lesions can be restored by hpGRF. The findings are promising in that hpGRF and its analogs may provide valuable agents for the diagnosis and treatment of disorders of growth secondary to CNS dysfunction.

Animals↗
PubMed1981

Temporal and environmental cues in conditioned hypothermia and hyperthermia associated with morphine.

The effectiveness of temporal and environmental cues in eliciting conditioned hypothermia and hyperthermia was studied in male Wistar rats using as an unconditioned stimulus an IP injection of 20 mg/kg of morphine sulfate. The relevance of temporal stimuli was minimized in Experiment 1 by administering morphine at irregular times on alternate days. For one group (Cond) morphine injections were preceded and followed by periods in distinctive environments. Group Pseudo animals, though exposed to the environments, received morphine on the intervening days in the home cage; group Saline received only saline. All animals receiving morphine showed a non-specific hypothermia when not under the direct influence of morphine. A "conditioned hyperthermia" was evident in group Cond animals in the distinctive environments. In Experiment 2, in which animals remained in their home cages at all times, the relevance of temporal cues was emphasized by administering morphine at exactly 24 h intervals. These animals became hypothermic only around the time of the expected injection. Animals in another group that received morphine at irregular times showed the non-specific hypothermia seen previously. There was no evidence for a conditioned hyperthermia in this second experiment.

Animals↗
PubMed1981

Conditioned temperature effects using amphetamine as the unconditioned stimulus.

Three groups of male Wistar rats received daily IP injections of either 1, 2 or 5 mg/kg amphetamine at 11:15 h; a fourth group received saline injections throughout. Rectal temperature was measured in the home cage, in a pre-injection environment in which animals were placed for a period of time before the daily injection, and in an injection environment in which animals remained following the injection. Conditioned hyperthermia, a response that mimicked the unconditioned effect of amphetamine, was elicited by cues of the injection environment both during conditioning and after the drug-free period. During conditioning, hypothermia occurred at 10:30 h regardless of where the animals were, but could not be elicited at other times of day. The results with amphetamine parallel those found previously with morphine (Eikelboom and Stewart 1979, 1981).

Amphetamine↗
PubMed1978

Pre-exposure to morphine and the attenuation of conditioned taste aversion in rats.

Three experiments were done using male Wistar rats to determine whether the mechanisms underlying the attenuation of a conditioned taste aversion to morphine by pre-exposure to the drug were similar to those involved in the development of tolerance to the analgesic response to morphine. This was tested by determining whether the effect of pre-exposure on conditioned taste aversion was situation-specific. In Experiment 1 it was found that having different environments for the pre-exposure injections and for the conditioning injections of morphine had no effect on the attenuation of the taste aversion. This finding was replicated in Experiment 2 in which it was also found that the attenuation of the analgesic effect, tested for in the same animals, was specific to the environment in which repeated injections were given. It was concluded that the attenuation of conditioned taste aversion involved processes different from those responsible for the attenuation of the analgesic effect of morphine. Experiment 3 showed that pairing the pre-exposure injections of morphine with one distinctive taste stimulus prevented the attenuation of the conditioned taste aversion to a second taste stimulus. These results suggest that different associative processes are responsible for the two types of attenuation.

Analgesics↗
PubMedDate not supplied

Pair housing induced feeding suppression: individual housing not novelty.

Male rats that are moved from individual to pair housing suppress their feeding for a few days [O'Connor R, Eikelboom R. The effects of changes in housing on feeding and wheel running. Physiol Behav 2000;68:361-371]. The present study explored whether the suppression was a result of the period of individual housing or the novelty of the other animal. Two groups of 16 rats were pair-housed and one group of rats was individually housed for 21 days. The individually housed rats were then pair-housed (IP group) and rats in one of the pair-housed groups were re-housed with novel partners (NP group), while rats in the other pair-housed group remained with the same partner (SP group). Feeding was suppressed only for rats in the IP group, suggesting that the novelty of the partner did not suppress feeding, but rather, the change from individual to pair housing did. Water consumption was also measured, but was unaffected by the re-housing manipulation.

Animals↗