The effect of mescaline, 3, 4-dimethoxyphenethylamine and 2, 5-dimethoxy-4-methylamphetamine on rat plasma prolactin: evidence for serotonergic mediation

Psychedelic and entactogenic drugs in the treatment of depression

CNS deficiency of 5-hydroxytryptamine (serotonin) has been implicated as a biochemical basis in some forms of depression. Existing drug modalities for treating depression include some with serotonergic effects. Studies suggest that psychedelic drugs are also serotonergic. This may indicate a role for psychedelics in the treatment of depression. Such treatment has already been attempted using psychedelic drugs in both the indoleamine and phenylalkylamine categories. Encouraging results seem to recommend further research, with special emphasis on drugs in the phenylisopropylamine subgroup of phenylalkylamines that are only peripherally psychedelic. Certain of these, called entactogens or empathogens, cause substantially less distortion of normative consciousness than classic psychedelics, such as LSD or mescaline. They could therefore be more easily assimilated into existing psychotherapy approaches, where their function would be to enhance the normal psychotherapeutic process rather than serving a maintenance role as chemotherapeutic agents. Their usefulness in such an application would be mainly at the start of psychotherapy in order to (1) reduce the client's "fear response" that often inhibits ability to deal with repressed traumatic material; (2) facilitate the client's interpersonal communications with the therapist, spouse or significant others; and (3) accelerate formation of a therapeutic alliance between client and therapist.

Evidence that the medial and dorsal raphe nuclei mediate serotonergically-induced increases in prolactin release from the pituitary

Electrolytic lesions of the medial (MR) or dorsal (DR) raphe nucleus significantly antagonized serum prolactin elevations produced by 5-hydroxytryptophan (5-HTP) in rats pretreated with fluoxetine or citalopram, (serotonin (5-HT) uptake blockers). Lesioned animals in which total blockade of serum prolactin elevations was observed also had total blockade of 5-HT accumulation in the median eminence. However, the increase in serum prolactin levels produced by 5-HTP plus 5-HT reuptake blockade in lesioned rats was not significantly different from sham-operated rats if as little as 15-20% of control median eminence accumulation was present. Serum prolactin elevations produced by quipazine, a direct acting 5-HT agonist, were not significantly affected by MR lesions. On the basis of these results, we suggest that: (1) serum prolactin elevations following 5-HT reuptake blockade plus 5-HTP are correlated with 5-HT concentration in the median eminence; (2) lesion-induced antagonism of 5-HTP-induced prolactin elevation is critically dependent upon complete blockade of median eminence 5-HT accumulation; and (3) 5-HT neurons arising from cell bodies located in the MR and DR are necessary for endogenous serotonergically mediated effects on prolactin secretion in the rat.

Pharmacological evidence of supersensitivity of central serotonergic receptors involved in the control of prolactin secretion

m-Chlorophenylpiperazine (m-CPP), a serotonin receptor agonist, induced dose-related increase in plasma prolactin levels in the rat. This effect was significantly prevented by pretreatment with metergoline, a serotonin receptor blocker. Long-term degeneration of hypothalamic serotonin nerve endings induced by intraventricular injection of 5, 7-dihydroxytryptamine, significantly enhanced the PRL-releasing action of m-CPP, as revealed by the shift to the left in the dose-response curve that relates the dose of m-CPP to plasma PRL levels. Thus the evidence suggests the possible development of supersensitivity of central serotonin receptors involved in the control of prolactin release.

Stimulation of human prolactin secretion by mescaline

Prolactin (PRL) and Growth Hormone (GH) secretions were studied in human serum after the oral administration of 5 mg/kg mescaline (3,4,5-trimethoxy-beta-phenylethylamine) or 2,3,4-trimethoxy-beta-phenylethylamine (2,3,4-TMPEA) respectively. Mescaline stimulated the secretion of PRL more than four-fold above base-line levels. Peak concentrations were found 90--120 min after drug intake. Five hours later serum PRL was still markedly increased. Mescaline also triggered GH secretion. There was no alteration of serum PRL and GH concentrations after intake of the non-hallucinogenic 2,3,4-TMPEA.