Posted by zeugma on April 2, 2006, at 11:06:24
In reply to Re: melatonin, REM, Parkinson's disease, posted by jrbecker on April 1, 2006, at 22:15:41
The effect of melatonin on immobility time of rats in the FST paradigm was abolished by the simultaneous injection of the non-selective melatonin antagonist, luzindole (0.25 mg/kg, subcutaneously). Similarly, administration of small quantities of serotonin (5-HT, 5 ng/1 mul) or of the 5-HT(2A)/5-HT(2C) receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (2 ng/1 mul) injected into the amygdale totally suppressed the reduction of immobility time in the FST paradigm induced by melatonin 0.5 mg/kg.>>
It is intriguing to conjoin the above observation, which notes that melatonin's activity in a behavioral paradigm of depression can be reversed by a 5-HT2(A/C) agonist, with this study:
Brain Res. 2000 Mar 31;860(1-2):112-8.
Melatonin reversal of DOI-induced hypophagia in rats; possible mechanism by suppressing 5-HT(2A) receptor-mediated activation of HPA axis.Raghavendra V, Kulkarni SK.
Pharmacology Division, University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh, India.
Serotonin type 2A (5-HT(2A)) receptor-mediated neurotransmitter is known to activate hypothalamic-pituitary-adrenal (HPA) axis, regulate sleep-awake cycle, induce anorexia and hyperthermia. Interaction between melatonin and 5-HT(2A) receptors in the regulation of the sleep-awake cycle and head-twitch response in rat have been reported. Previous studies have shown that melatonin has suppressant effect on HPA axis activation, decreases core body temperature and induces hyperphagia in animals. However, melatonin interaction with 5-HT(2A) receptors in mediation of these actions is not yet reported. We have studied the acute effect of melatonin and its antagonist, luzindole on centrally administered (+/-)-1-(2, 5-dimethoxy-4-iodophenyl) 2-amino propane (DOI; a 5-HT(2A/2C) agonist)-induced activation of HPA axis, hypophagia and hyperthermia in 24-h food-deprived rats. Like ritanserin [(1 mg/kg, i.p.) 5-HT(2A/2C) antagonist], peripherally administered melatonin (1.5 and 3 mg/kg, i.p.) did not affect the food intake, rectal temperature or basal adrenal ascorbic acid level. However, pretreatment of rats with it significantly reversed DOI (10 microgram, intraventricular)-induced anorexia and activation of HPA axis. But the hyperthermia induced by DOI was not sensitive to reversal by melatonin. Mel(1) receptor subtype antagonist luzindole (5 microgram, intraventricular) did not modulate the DOI effect but antagonized the melatonin (3 mg/kg, i.p.) reversal of 5-HT(2A) agonist response. The present data suggest that melatonin reversal of DOI-induced hypophagia could be due to suppression of 5-HT(2A) mediated activation of HPA axis.>>
The HPA axis is ubiquitious in studies of mood disorder related pathology. It seems there is an important correlation here, those who know more about the HPA axis in pathologies of mood and body, please comment.
-z
poster:zeugma
thread:626219
URL: http://www.dr-bob.org/babble/20060329/msgs/627796.html