Relation of endogenous opioid peptides and morphine to neuroendocrine functions

To assess the role of serotonin function in the development of panic anxiety, the behavioral and biochemical responses to the serotonin receptor agonist, m-chlorophenylpiperazine (MCPP) was examined in healthy subjects and agoraphobic and panic disorder patients. MCPP had anxiogenic effects in both the healthy subjects and patients. Panic attacks meeting DSM-III criteria occurred following MCPP in 12 of 23 patients and 6 of 19 healthy subjects (NS) and other ratings of anxiety also did not distinguish the two groups. MCPP resulted in significant but similar increases in cortisol, prolactin, and growth hormone in the healthy subjects and patients. The results of this investigation suggest that serotonin neuronal dysfunction may not be of etiologic significance in most panic disorder patients. However, the observed anxiogenic properties of MCPP suggest that additional studies of the role of serotonin systems in the pathophysiology of human anxiety disorders are indicated.

Serotonin function in anxiety. II. Effects of the serotonin agonist MCPP in panic disorder patients and healthy subjects.

• To evaluate serotonergic (5-hydroxytryptamine) function in obsessive-compulsive disorder, behavioral and neuroendocrine responses to m-chlorophenylpiperazine (m-CPP; 0.5 mg/kg orally) and fenfluramine hydrochloride (60 mg orally) were examined in 20 patients and 10 healthy controls under double-blind, placebo-controlled conditions. Following m-CPP, but not fenfluramine or placebo, 55% (11/20) of the patients with obsessive-compulsive disorder experienced a transient exacerbation of obsessivecompulsive disorder. Prolactin response was blunted in patients following m-CPP but not following fenfluramine. Patients with greater behavioral response to m-CPP had smaller prolactin responses. Cortisol response to m-CPP and fenfluramine did not significantly differ between the groups. Behavioral and neuroendocrine responses appeared divergent. This does not suggest simply upregulation or downregulation of 5-hydroxytryptamine receptors, but rather complex mechanisms involving multiple neurotransmitter and neuromodulator systems.

Serotonergic function in obsessive-compulsive disorder. Behavioral and neuroendocrine responses to oral m-chlorophenylpiperazine and fenfluramine in patients and healthy volunteers.

To evaluate the role of serotonin (5-HT) function in obsessive-compulsive disorder (OCD), behavioral and biochemical responses to the 5-HT receptor agonist m-chlorophenylpiperazine (MCPP) and the 5-HT precursor tryptophan were examined in healthy subjects and patients with OCD. Baseline prolactin levels and the prolactin rise following MCPP were significantly reduced in female patients compared with female healthy subjects. In contrast, the increase in prolactin level following tryptophan administration was not significantly different between male or female patients with OCD and the respective sex-matched healthy subjects. The prolactin responses to MCPP and tryptophan were both significantly higher in female patients and healthy subjects than in their male counterparts. The cortisol and growth hormone responses to MCPP and tryptophan were similar in the patients and healthy subjects and were not related to gender. The behavioral responses to MCPP or tryptophan were not consistently different between patients and healthy subjects, and neither MCPP nor tryptophan had effects on obsessive or compulsive symptoms. These results lend only partial support to the hypothesis that 5-HT dysfunction may be linked to the pathophysiology of OCD and point to the need for the evaluation of other neurotransmitter systems in future investigations of OCD.

Serotonin function in obsessive-compulsive disorder. A comparison of the effects of tryptophan and m-chlorophenylpiperazine in patients and healthy subjects.

C.P. Twohy

Papers

Effects of L-tryptophan and restraint stress on hypothalmic and brain serotonin turnover, and pituitary TSH and prolactin release in rats