Effects of CRF1 receptor antagonists and benzodiazepines in the Morris water maze and delayed non-matching to position tests

RATIONALE

Benzodiazepines continue to be widely used for the treatment of anxiety, but it is well known that benzodiazepines have undesirable side effects, including sedation, ataxia, cognitive deficits and the risk of addiction and abuse. CRF(1) receptor antagonists are being developed as potential novel anxiolytics, but while CRF(1) receptor antagonists seem to have a better side-effect profile than benzodiazepines with respect to sedation and ataxia, the effects of CRF(1) receptor antagonists on cognitive function have not been well characterized. It is somewhat surprising that the potential cognitive effects of CRF(1) receptor antagonists have not been more fully characterized since there is some evidence to suggest that these compounds may impair cognitive function.

OBJECTIVE

The Morris water maze and the delayed non-matching to position test are sensitive tests of a range of cognitive functions, including spatial learning, attention and short-term memory, so the objective of the present experiments was to assess the effects of benzodiazepines and CRF(1) receptor antagonists in these tests.

RESULTS

The benzodiazepines chlordiazepoxide and alprazolam disrupted performance in the Morris water maze and delayed non-matching to position at doses close to their therapeutic, anxiolytic doses. In contrast, the CRF(1) receptor antagonists DMP-904 and DMP-696 produced little or no impairment in the Morris water maze or delayed non-matching to position test even at doses 10-fold higher than were necessary to produce anxiolytic effects.

CONCLUSIONS

The results of the present experiments suggest that, with respect to their effects on cognitive functions, CRF(1) receptor antagonists seem to have a wider therapeutic index than benzodiazepines.

Both corticotropin-releasing factor receptor type 1 and type 2 are involved in stress-induced inhibition of food intake in rats

RATIONALE

Stress-induced inhibition of food intake is reportedly blocked by a selective corticotropin-releasing factor (CRF) type 1 receptor (CRF1) antagonist, suggesting the involvement of CRF1 in the inhibitory mechanism. CRF1 and CRF2 are considered to function in the inhibition of food intake by CRF-related peptides with different time courses.

OBJECTIVES

This study was designed to clarify whether CRF2 is also involved in stress-induced inhibition of food intake and to examine the relation of CRF1to CRF2 in the inhibitory mechanism.

METHODS

Antisauvagine-30 (AS-30), a selective CRF2 antagonist, and/or CRA1000, a selective CRF1 antagonist, were pre-administered intracerebroventricularly and intraperitoneally, respectively, to male Wistar rats deprived of food for 24 h before the animals were exposed to a 1-h period of stressors and food intake in 1 h after stress exposure was examined. The effect of both antagonists on locomotor activity was also examined.

RESULTS

Pre-administration of 5-30 microg of AS-30 attenuated inhibition of food intake induced by restraint, electric footshock or emotional stress using a communication box. CRA1000 also attenuated the restraint-induced inhibition of food intake at doses of 5 and 10 mg/kg body weight. The reversal of restraint-induced inhibition of food intake by co-administration of AS-30 and CRA1000 was not larger than that by AS-30 or CRA1000 alone. Both antagonists did not affect locomotor activity.

CONCLUSIONS

These results suggest that not only CRF1, but also CRF2, are involved in stress-induced inhibition of food intake, and that both subtypes of CRF receptor function probably in series in 1 h after stress exposure.