The purpose of this experiment was to determine the importance of handling to the expression of hyperemotional behaviors, i.e., rage, known to occur after chronic depletion of brain norepinephrine (NE) and dopamine (DA) following central injection of 6-hydroxydopamine (6-OHDA) in rats. Five min of handling per day for 6 consecutive days reduced resistane to capture as well as the magnitude and frequency of startle responding following one 300 mug injection of 6-OHDA intracisternally. Both 6-OHDA-handled and 6-OHDA-unhandled rats showed comparable levels of brain NE, DA, serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), comparable resting levels of plasma corticosterone, and comparable adrenal weights. These data demonstrate the importance of handling to the expression of 6-OHDA-induced rage and emphasize the importance of controlling for handling as a variable which can significantly affect the assessment of rage by behavioral criteria in this animal model of hyperemotionality.

Anger↗

PubMedDate not supplied

Effect of midbrain raphé lesions or intracisternal 6-hydroxydopamine administration on D, L-5-hydroxytryptophan-14C metabolism after peripheral decarboxylase inhibition.

Brain and blood 14C-5-hydroxyindole metabolism was studied in normal, raphé-lesioned and 6-hydroxydopamine (60HDA)-treated rats given L-(-)-alpha-hydrazino-3, 4-dihydroxy-alpha-methylhydrocinnamic acid (MK-486) (50 mg/kg) intraperitoneally and 5-hydroxytryptophan (5-HTP)-14C (5 muCi, 0.51 mCi/mmol) intravenously. Raphé lesioning and 60HDA treatment caused significant decrements in brain 5-hydroxytryptamine (5-HT)-14C and 5-hydroxyindoleacetic acid (5-HIAA)-14C levels and 5-HT concentrations compared to those in normal controls. In normal and 60HDA-treated rats there were decreased brain dopamine levels, possibly a consequence of non-specific metabolism of 5-HTP in brain. Blood 5-HIAA-14C levels were significantly decreased in 60HDA-treated but not raphé-lesioned rats. As increased brain 5-HT turnover was observed in raphé-lesioned rats, this may have prevented a decrease in blood 5-HIAA-14C levels. The results suggest that changes in blood 5-HIAA-14C following MK-486 and 5-HTP-14C may be related to changes in brain 5-HT-14C metabolism.

5-Hydroxytryptophan↗

PubMedDate not supplied

CNS 3-methoxy-4-hydroxyphenylglycol: its peripheral assessment by isotopic dilution and theoretical significance.

An isotope dilution model for the peripheral measurement of CNS catecholamine metabolism was examined in rabbits. 3H-norepinephrine (3H-norepinephrine (3H-NE) infusions were performed on rabbits before and after central sympathectomy via intraventricular 6-hydroxydopamine (6-OHDA) treatment. Urine samples were obtained 72 hr after 3H-NE infusion and analysed for specific activities (SAs) of 3-methoxy-4-hydroxyphenylglycol (MHPG) and 3-methoxy-4-hydroxymandelic acid (VMA). The SA of MHPG was lower than that of VMA in all animals suggesting a source of unlabelled MHPG. The difference between the SAs of VMA and MHPG was abolished when the brain MHPG was markedly lowered by 6-OHDA injections. In animals which received 6-OHDA but retained moderate levels of brain MHPG, the difference between SAs of VMA and MHPG was maintained. The proposed model is able to predict and differentiate between rabbits that have severe depletion of CNS catecholamines and normal controls. The results suggest important relationships between CNS and peripheral NE metabolism and the compensatory capacity of the CNS to insult.

Animals↗