Effects of cysteamine and pantethine on open-field behavior, hypothalamic catecholamine concentrations, and somatostatin-induced barrel rotation in rats.

Cysteamine administered in a dose of 1.95 mM/kg subcutaneously (SC) markedly reduced several open-field behaviors (locomotion, rearing, grooming and defecation), while pantethine, administered in an equimolar dose, reduced the locomotion only. However, administered in a dose of 3.90 mM/kg (SC), pantethine also markedly reduced all open-field parameters. Cysteamine, and to less extent pantethine, reduced noradrenaline, and increased dopamine and DOPAC concentrations in the hypothalamus. It is discussed whether the lower potency of pantethine on open-field behaviors and hypothalamic catecholaminergic neurotransmission is connected with the limited activity of pantetheinase, the cysteamine-generating enzyme. Intracerebroventricularly (ICV) administered somatostatin did not influence the pantethine-induced (1.95 mM/kg SC) behavioral changes in the open-field test. It is possible that the peptide did not reach at the receptor sites in a sufficient concentration because of the reduced endogenous somatostatin content, or that the pantethine-induced noradrenaline depletion is connected with the ineffectiveness of somatostatin. Furthermore, pretreatment with cysteamine (1.95 mM/kg SC) or pantethine (1.95 mM/kg or 3.90 mM/kg SC) attenuated the somatostatin-induced (10 micrograms ICV) barrel rotation, suggesting that the level of endogenous somatostatin may play a role in the pathogenesis of this motor disturbance.