Prevention of learned helplessness: In vivo correlation with cortical serotonin

Effects of Long-term Acetyl-L-carnitine Administration in Rats I. Increased Dopamine Output in Mesocorticolimbic Areas and Protection toward Acute Stress Exposure

“…These rats also show a decrease of D 2 DA receptor binding and mRNA levels in mesolimbic areas (Papp et al 1994;Dziedzicka-Wasylewska et al 1997), and a blunted phasic DA response to a feeding of palatable food in the NAcS and in the mPFC (Di Chiara and Tanda 1997). Both the behavioral and neurochemical changes induced by unavoidable stress exposure in the learned helplessness or CMS paradigms could be reversed by the chronic administration of classical antidepressant drugs (Muscat et al 1990(Muscat et al , 1992Petty et al 1992Petty et al , 1994Papp et al 1994Papp et al , 1996Di Chiara and Tanda 1997;Dziedzicka-Wasylewska et al 1997). Antidepressant compounds also revert the chronic escape deficit, and the drugs that we have tested in this paradigm, such as imipramine, fluoxetine, clomipramine, phenelzine, reboxetine, and a total extract of Hypericum perforatum, reinstated an avoidance response within three weeks of continuous treatment (Gambarana et al 1995a(Gambarana et al , 1999cGambarana, unpublished results).…”

“…Long-term exposure to different stress procedures impairs an animal's responsiveness to both aversive and pleasurable stimuli (Overmier and Seligman 1967;Papp et al 1991;Moreau et al 1992;Gambarana et al 1995a), and it decreases DA output in mesolimbic areas (Di Chiara et al 1999;Gambarana et al 1999a;Mangiavacchi et al 2001). Moreover, 5-HT output in the mPFC increases in response to acute exposure to unavoidable stress (Petty et al 1992), although no difference has been observed between helpless and non-helpless control rats in the spontaneous firing of serotonergic neurons in the dorsal raphe (Maudhuit et al 1997). After chronic exposure to unavoidable stress 5-HT output decreases in the mPFC and NAcS (Mangiavacchi et al 2001).…”

“…The involvement of brain monoamines in response to stress has been widely investigated (Bliss et al 1968;Konstandi et al 2000) and both 5-HT (Courzon 1971;Petty et al 1992;Chaouloff 2000) and DA (Pani et al 2000) are considered to play a crucial role in coping with stressful situations. Dopaminergic neurons in the ventral tegmental area are rapidly activated by sudden environmental events, including stressful circumstances (Kaneyuki et al 1991), and acute exposure to different forms of stress has been reported to increase DA release in the PFC (Sorg and Kalivas 1993;Finlay et al 1995;Yoshioka et al 1996) as well as in the NAc (Rouge-Pont et al 1993;Kalivas and Duffy 1995;Tidey and Miczek 1996).…”

Single and Repeated Stress-Induced Modulation of Phospholipase C Catalytic Activity and Expression: Role in LH Behavior

“…It is quite possible that the decrease in PLC may be in response to the activation of 5HT 2A receptors. Although a functional deficit of 5HT in LH rats has been reported (Hellhammer et al, 1984;Petty et al, 1992), the results pertaining to changes in 5HT 2A receptor number in LH behavior and stress have been inconsistent (Ferretti et al, 1995;Wu et al, 1999). Figure 5 mRNA levels of PLC isozymes in the frontal cortex and hippocampus of groups A (given inescapable shock on day 1 and tested for escape latency on day 2), B (given inescapable shock on day 1 and tested for escape latency on day 4), and C (given inescapable shock on day 1 and tested for escape latency on day 2; rats were again given shock on day 7 and tested for escape latency on day 8, and re-tested on day 14), comprised of TC, NLH, and LH rats.…”

“…Although several neurotransmitter systems have been studied in LH animals, including norepinephrine (Weiss et al, 1970;Minor et al, 1988;Petty et al, 1993), dopamine (Anisman and Zacharko, 1992), GABA (Drugan et al, 1989;Petty et al, 1992), serotonin (5HT) (Petty and Sherman, 1983;Maier et al, 1995;Maswood et al, 1998), adenosine (Minor et al, 2001), NMDA (Grahn et al, 2002), and opiate (Drugan and Maier, 1983), the role of signaling molecules beyond the receptors in LH behavior has not been fully investigated. In this regard, recently we showed that protein kinase A, a phosphorylating enzyme in the adenylyl cyclasecAMP signaling mechanism, is significantly altered in the frontal cortex and hippocampus of LH rats, the effect being greater in the repeated-stress paradigm than in the acutestress paradigm (Dwivedi et al, 2004).…”