Effects of apomorphine and amphetamine on patterns of locomotor and investigatory behavior in rats.

Rats were tested in a Behavioral Pattern Monitor after various doses of either amphetamine or apomorphine in order to characterize their behavioral profiles, including patterns and sequences of holepokes, rearings and locomotor movements. To enable direct comparisons between the behavioral effects of the two stimulants, doses and times for each drug were selected with which locomotor hyperactivity was the predominant behavioral response. Although both drugs increased the total amount of locomotor activity, amphetamine induced a relatively varied behavioral profile while apomorphine induced repetitive behavior with a restricted range of responses. These contrasting effects of the stimulants were interpreted as reflective of their differing modes of action with regard to central dopaminergic systems. It is suggested that, in the dose range used, the release of dopamine by amphetamine is coupled to neuronal firing and therefore this release increases behavioral activity without altering the normal response repertoire of the animal. Conversely, the direct agonist action of apomorphine results in a restricted and perseverative behavioral pattern because its activation of forebrain dopamine receptors is independent of the normal physiological pattern of dopaminergic neuronal firing.

Multivariate assessment of locomotor behavior: pharmacological and behavioral analyses.

A Behavioral Pattern Monitor (BPM) is described which is designed to assess the spatial and temporal sequences of the locomotor movements, investigatory holepokes, and rearings of rats. The system records these behavioral responses with 0.1 sec resolution in time and 1.5 inch resolution in space, and permanently stores all the resulting data. The sequences of these responses may then be displayed on a video terminal or on paper and are also available for the calculation of a variety of descriptive statistics. Studies are described in which rats were tested repeatedly without any pharmacological treatments or in single test sessions following the administration of saline or one of five stimulant drugs. A variety of descriptive measures of the temporal or spatial patterning of the animals' behavior are described and applied to the data resulting from the studies of the various stimulants. It is concluded that the combination of these measures enables distinctions to be made among these drugs which cannot be made on the basis of measures of the amount of locomotor activity.

Sonication, calcium, and peptides have systematic effects on the nonlinear dynamics of tyrosine hydroxylase activity.

Sonication, dialysis, calcium, and peptides have systematic effects on the nonlinear dynamics of tyrosine hydroxylase (TOH). Under standard assay conditions TOH shows a high amplitude fluctuation in catalytic output across time that is eliminated either by sonication or by dialysis. This coherent dynamic is restored with the addition to the dialyzed preparation of either calcium in micromolar concentrations or certain peptides (SOM, MSH), but not others (CCK, TRH).

The influence of neuropeptides on amine synthesis: Cholecystokinin-8 and neurotensin reduce striatal tyrosine hydroxylase activity.

Cholecystokinin-8 and neurotensin, neuropeptides found in relatively high concentrations in some catcholaminergic neurons and/or terminal or cell body areas, reduced native and polyanion-activated rat striatal tyrosine hydroxylase activity, but not that of the enzyme activated by phosphorylating conditions. Substance P, ?(3)-melanocyte-stimulating hormone, [d-ala(2), d-leu(5)]-enkephalin, or thyrotropin-releasing hormone had no effect on the native enzyme or on either activated form. Cholecystokinin-8 and neurotensin may interact with polyanion-activated or membrane bound-activated tyrosine hydroxylase to modulate its activity.

Metrics from nonlinear dynamics adapted for characterizing the behavior of nonequilibrium enzymatic rate functions.

Several metrics from nonlinear dynamics and statistical mechanics have been characterized on computer-generated number series with various signal-to-noise ratios, demonstrating their individual reliability as a function of sample size and their relationships to each other. The root mean square (RMS) evaluates amplitude, and the power spectral density (PSD) provides a visual display of the frequency spectrum; both measures have very high reliability even for an N as low as 50. The Fractal Dimension (D) is shown to converge rapidly and also to be reliable when N is as low as 50. These three measures (RMS, PSD, and D) have been applied to the complex kinetics of tyrosine hydroxylase time courses (50-point curves) at various BH4 concentrations (near physiological, but far from equilibrium levels). Recently developed measures of spectral entropy and the Liapunov Exponent, -lambda are also characterized.

A kinetic scattering approach to the non-linear instabilities of rat brain tyrosine hydroxylase preparations at several levels of tetrahydrobiopterin cofactor demonstrates evolutionary behavior characteristic of global dynamical systems.

Statistical patterns from the time-dependent fluctuations in kinetic scattering of a complex rat brain tyrosine hydroxylating system reveal near periodic, quasi-periodic, and chaotic regimes that alternate in a non-linear manner across linear changes in tetrahydrobiopterin cofactor concentrations, a phenomenon characteristic of the initial condition- and parameter-sensitive evolutionary behavior of global dynamical systems.

Strain differences in kinetic and thermal stability of two mouse brain tryptophan hydroxylase activities.

Levels of forebrain serotonin (5-HT), tryptophan, 5-hydroxyindoleacetic acid (5-HIAA) and hydroxylase cofactor (BH4) were comparable in two experimental mouse strains (A/J and C57Bl/6J) despite 2-3-fold differences in vitro in the relative activities of forebrain and midbrain tryptophan-5-monooxygenase (TPOH; EC 1.14.16.4). The enzyme activities did not differ with respect to Km for cofactor at saturating levels, but manifested different degrees of cooperativity with respect to cofactor when examined with BH4 concentrations within a physiological range. They differed also in the frequency and amplitude of kinetic variation around comparable mean velocity slopes across cofactor and time; in resistance to pre-incubation inactivation and responsiveness to its facilitation by calcium; in molecular weight heterogeneity as reflected in the distribution of molecular weight forms by gel diffusion chromatography; and in the number of peaks in power spectral analysis of kinetic variation patterns. Although the potential roles of small-molecule ligand and/or regulator proteins have not been ruled out, we hypothesize that differences in conformational stability underlie the differences in regulatory properties and make one enzyme activity more vulnerable to occlusive influences in vivo.

Short-term regulation of hydroxylase cofactor activity in rat brain.

Differential drug effects on hydroxylase cofactor activities were observed in the corpus striatum and the locus coeruleus when conditions of sacrifice were controlled. A conformational stability-dependent variable degree of stoichiometric coupling between quinonoid dihydropteridine reductase and tyrosine hydroxylase is proposed as a short-latency influence on hydroxylase cofactor levels.

Striatal tyrosine hydroxylase activity: multiple conformational kinetic oscillators and product concentration frequencies.

Samples from rat striate cortices, taken in triplicate at 2-min intervals from a supernatant maintained at 4 degree C, then assayed for 1 min at 37 degree C for tyrosine hydroxylase activity, manifested average amplitudes of time-dependent variation that were related to the level of mean velocity and were not influenced by changing temperature or pharmacological ligands. In contrast, the frequencies of variation manifested characteristic wavelengths of about 26, 7.5, and 5 min, and the relative proportions of those frequencies were changed by an increase in temperature and by certain drugs that are active in the dopamine system (D-amphetamine, haloperidol, and propranolol). Hypothetical, contemporaneous multiple quasi-stable states, each with a characteristic spectral frequency of fluctuation, are consistent with the appearance of reiterative enzyme saturation functions when supernatant and column-enriched preparations were examined within the physiological cofactor range over increasing substrate concentrations. Pharmacologically sensitive time distribution of multipole enzyme conformations, each a kinetic oscillator, determining product concentration frequencies, may be a mechanism by which drugs influence neurotransmitter periodicities in brain.

The influence of D-amphetamine on rat brain striatal reduced biopterin concentration.

Rat brain striatal reduced biopterin (BH4) levels vary diurnally by 2-fold, oscillating around a concentration of 3 micrometer. D-Amphetamine consistently induced a decrease in BH4 levels that did not exceed 25 to 30% with increasing doses; recovery of control levels required several hours. A large number of other psychotropic drugs, including other stimulants and phenylethylamine congeners, failed to induce a similar change. The amphetamine effect was blocked by methylphenidate and reserpine. The prolonged time for BH4 recovery could be explained by an amphetamine-induced functional uncoupling of quinonoid dihydropteridine reductase from striatal tyrosine hydroxylase as reported for various cofactor analogs, leading to spontaneous isomerization of the partially reduced pterin to its nonquinonoid form, which is not a substrate for the BH4 regenerating enzyme. If relevant to dopamine biosynthesis, such an uncoupling phenomenon might account for a unique neuropharmacology of the postamphetamine state.

Regional and subcellular distribution and some factors in the regulation of reduced pterins in rat brain.

We have studied the regional and subcellular distribution, functional role, and pharmacology of quinoid dihydropterin reductase (QDPR) and endogenous reduced pterins (PH4) subserving tyrosin hydroxylase (TOH) and tryptophan hydroxylase in the rat brain. There is a significant correlation between the regional distribution of PH4 and TOH but not between PH4 and tryptophan hydroxylase or between either TOH or tryptophan hydroxylase and QDPR. This suggests that a major portion of PH4 is associated with the biosynthetic activity of brain catecholaminergic systems. The regional and subcellular distribution of QDPR was inconsistent with a regulatory function for QDPR in monoamine synthesis. In vitro measures of PH4, TOH, and synaptosomal dopamine (DA) and serotonin synthesis in the striate cortex of untreated animals and animals subjected to neurotoxin or electrolytic lesions of the dorsal raphe or substantia nigra exhibit significant covariation of PH4 with synaptosomal DA but not serotonin synthesis and a significant partial correlation of PH4 with DA synthesis. The subcellular distribution of PH4 in the striatum demonstrates an association of PH4 with the biosynthetic function of dopaminergic nerve terminals. Reserpine and d-amphetamine in vivo elicited an increase and decrease, respectively, in striatal PH4 paralleling induced changes in synaptosomal DA synthesis. Other drugs altering central catecholaminergic function did not alter striatal PH4 levels significantly. The data suggest that 1) a major portion of total PH4 (as much as 90% in the striatum) is related to the function of catecholaminergic rather than serotonergic systems, 2) PH4 levels is a determinant of the velocity of DA synthesis and 3) PH4 levels are altered by some psychoactive drugs in association with changes in synaptosomal catecholamine biosynthetic rates.