Effects of MIF-I and melatonin on novelty-induced defecation and associated plasma 11-OHCS and brain catecholamines

Effects of melatonin on startle reflex in rat

“…Startle reflex Defecation Habituation Inhibition THE inhibitory effect of melatonin on stress responses in human and infrahuman subjects has been well documented [1, 3, 4-6, 9, 20, 23, 24, 26]. Datta and King demonstrated that melatonin administered intraperitoneally (IP) leads to a decrease in defecation in passive avoidance (PA) tasks [4] and in novel environments [5]. Rats treated with melatonin and exposed daily to test box show a significant habituation of plasma 11-hydroxycorticosterone (11-OHCS) levels along with an inhibition of defecation response [5].…”

“…Datta and King demonstrated that melatonin administered intraperitoneally (IP) leads to a decrease in defecation in passive avoidance (PA) tasks [4] and in novel environments [5]. Rats treated with melatonin and exposed daily to test box show a significant habituation of plasma 11-hydroxycorticosterone (11-OHCS) levels along with an inhibition of defecation response [5]. Concomitant with the inhibitory effect on stress responses (defecation and plasma 11-OHCS) treatment with melatonin also leads to an increase in whole brain dopamine (DA) [5].…”

“…Rats treated with melatonin and exposed daily to test box show a significant habituation of plasma 11-hydroxycorticosterone (11-OHCS) levels along with an inhibition of defecation response [5]. Concomitant with the inhibitory effect on stress responses (defecation and plasma 11-OHCS) treatment with melatonin also leads to an increase in whole brain dopamine (DA) [5]. Datta and King [5,6] have suggested that melatonin may inhibit or habituate stress responses via action on either the serotonergic [2] or the dopaminergic systems [5].…”

“…Concomitant with the inhibitory effect on stress responses (defecation and plasma 11-OHCS) treatment with melatonin also leads to an increase in whole brain dopamine (DA) [5]. Datta and King [5,6] have suggested that melatonin may inhibit or habituate stress responses via action on either the serotonergic [2] or the dopaminergic systems [5]. This modulation of the inhibitory neurotransmitters by melatonin may account for behavioral effects observed with other behavioral paradigms.…”

“…Evidence of the putative relationship between melatonin and behavior is equivocal. Some reports indicate that melatonin exerts inhibitory effects on motoric behavior [12,25,30,31], whereas other reports indicate that melatonin has no inhibiting influence on motor behavior [4,5,17]. Perhaps the aspect of motoric activity which should be investigated after treatment with melatonin is the startle reflex (SR), elicited by an intense stimulus.…”