Reserpine behavior

A second, more extensive experiment involved oral administration of three daily doses (100 mg/kg) of parachlorophenylalanine (PCPA). This tryptophan hydroxylase inhibitor (47), like reserpine, enhanced the behavioral effects of LSD (13) moreover, hypersensitivity occurred when 5-HT, but not other monoamine, concentrations were below normal in both forebrain and hindbrain (13). That is, effects were observed at 5 and 12 days (when 5-HT was depleted to 10-20% and 60-70% of normal) but not at 21 days (when 5-HT had returned to normal). Control experiments (13) indicated that (a) the interaction of PCPA, 5-HT, and LSD was probably not caused by generalized hyperactivity or hyperirritability sometimes seen after PCPA (73) (b) PCPA does not affect threshold doses of other psychoactive but nonserotonergic compounds, such as d-amphetamine (0.3 mg/kg) and (c) pretreatment with a-methylparatyrosine, a tyrosine hydroxylase inhibitor which depletes catecholamines rather than indoleamines, does not alter sensitivity to LSD. 

The behavioral syndrome induced in mice and rats by reserpine sedation, catalepsy and ptosis can be reversed by imipramine. 

Development of sexual behavior can be affected by neonatal pharmacological treatment with the monoamine oxidase inhibitor pargyline, the monoamine depletor reserpine as well as with the acetylcholine esterase inhibitor pyridostigmine. These results suggest that biogenic amines are involved in sexual differentiation of the brain (refs. 162, 163). Pargyline treatment from day 1 to 14 or day 15 to 28 resulted in earlier development of puberty in female rats and delayed appearance of puberty in male rats. Male sexual behavior was decreased in both sexes. Treatment with reserpine on days 1, 4, 7 and 10 delayed the manifestation of puberty in both sexes, and caused disturbed female ovarian cycles and decreased male mounting behavior. 

Ahlenius S, Salmi P (1994) Behavioral and biochemical effects of the dopamine D3 receptor-selective ligand, 7-OH-DPAT, in the normal and the reserpine-treated rat. Eur J Pharmacol 260 177-181. 

To obtain clearer understanding of the behavioral effects of reserpine and their possible relationship to levels of aromatic biogenic amines in the insect central nervous system, we injected unfed, 2-day old adult P. regina with 2 yig/fly of reserpine. 

Clearly, injection of adult blowflies with reserpine caused them to become less responsive to food stimuli, while at the same time inducing them to eat more when they were offered 1 M sucrose, a highly stimulating food. Similar observations have been made with blowflies fed on reserpine (34). While it is not possible to ascribe the behavioral effects of reserpine on blowflies solely to actions in the CNS, it seems quite likely that the CNS plays a major role, particularly in light of the demonstrated capacity for reserpine to deplete CNS aromatic biogenic amines. 

TABLE I. EFFECTS OF RESERPINE ON BLOWFLY FEEDING BEHAVIOR AND BRAIN... 

These observations, combined with those in the literature, support the concept that reserpine, if consumed by insects, could exert a profound and long-lasting effect on insect behavior, an effect which would decrease the insect s mobility and fitness to respond to environmental stimuli, and to predators. That effect, probably due largely to a central action of the substance, could result in plant protection by "psychomanipulation". 

The sedative effect of palmatine on locomotor activity and concentration of monoamine in rats was studied via behavioral and biochemical methods. Palmatine was shown to enhance the hypomotility induced by a-methyl-p-tyrosine, reserpine, and 5-hydroxytryptophan, but reduced the hypermotility produced by L-dopa plus benserazide and p-chlorophenylalanine. In addition, the alkaloid significantly decreased the concentration of dopamine and homovanillic acid in the cortex and the concentration of serotonin in the brain stem, but increased the concentration of 5-HT in the cortex and 5-hydroxyindole acetic acid in the brain stem. These results suggest that the sedative action associated with palmatine may be related to the decrease in catecholamine concentration in the cortex and serotonin in the brain stem, and the increase in the concentration of 5-HT in the cortex [309],... 

Ginos, J. Z., Stevens, J. M., Nichols, D. E. Structure-activity relationships of N-substituted dopamine and 2-amino-6,7-dihydroxy-l,2,3, 4-tetrahydronaphtalene analogues behavioral effects in lesioned and reserpinized mice. J. Med. Chem. 1979, 22, 1323-1329. 

Different distribution characteristics were also observed39 for dopamine (5) and its tris(trimethylsilyl) and tetrakis(trimethylsilyl) derivatives 6 and 7, respectively. In contrast to 5, for which the blood-brain barrier is nearly impermeable, the much more lipophilic silyl derivatives 6 and 7 were found to exhibit central effects when given intraperitoneally to rats. At a dosage of 100 mg per kg, they influence positively the rigid akinetic syndrom, which was induced by reserpine. These results may be explained in terms of a pro-drug behavior of 6 and 7. (In this context see also Reference 40.)... 

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