Real-Time Imaging of Biomarkers in the Parkinson’s Brain Using Mini-Implantable Biosensors. II. Pharmaceutical Therapy with Bromocriptine
1.2. NMI and the BRODERICK PROBE®
Figure 1 shows a schematic design of the mini-implantable biosensor, the BRODERICK PROBE®. Several formulations of the carbon-based biosensors, patented by CUNY and NYU, have been tested in controlled studies. Details for the manufacture of these biosensors, which include description of specific components of each formulation, in addition to the use, design and applications for these biosensors, are published. The NMI biotechnology, such as detector/potentiostat electrical circuits, are also published [3,4,5,6,7,8,9,10,11,12]. Patents and pending patents listed in the references herein depict novel inventive constructions and formulations of biosensors. Biosensors use electron transfer kinetics to select an image for a specific neurochemical at an electroactive oxidation/half wave potential. An electroactive signature for each neurochemical is detected in subunits of volts, amperes, dependent on the electronic circuitry chosen for use in the detector/potentiostat. In the studies presented here, a semidifferential electrical circuit was chosen because several neurotransmitters and neurochemicals can be separately imaged within one minute, each neurochemical within seconds and recordings can be repeated continuously for hours and longer periods of time, e.g., weeks and months. Using the semidifferential electrical circuit, millivolts are shown on the x-axis and current in nano and picoamperes is shown on the y-axis. Current is derived from electron transfer kinetics which are determined by specific biosensor properties, such as hydrophobicity and hydrophilicity of biosensor formulation within the context of interaction with specific neurotransmitters and neuromolecules. Synaptic release mechanisms are primarily studied with NMI .
Figure 1. A schematic diagram of the BRODERICK PROBE® biosensor. Some of the formulations are comprised of fatty acids and lipids, normal constituents of brain.
i = current at time, t
n = number of electron transfers, eq/mol
F = Faraday’s constant, 96486 C/eq
A = electrode area, cm 2
C = concentration of O, mol/cm3
D = Diffusion coefficient of O, cm3/s
NMI has made several advances in the field of electrochemistry. One of these significant advances is the fact that NMI biosensors do not form gliosis, i.e., scar tissue which impedes detection of neurotransmitters, causing electroactive signals to decay. This property improves the sensitivity, selectivity and operational stability of the biosensors, allowing the detection of reliable electroactive signals for long periods of time, enabling their use not only for diagnosis and treatment for PD, which we discuss here, but also for cardiac disease, e.g., acute ischemic stroke  and hypoxia [15,16] as well as for peripheral body disorders such as human uterine cervical cancer [4,6,7,10]. In contrast, body imaging technologies for cancer specifically that image flourescent cells also deserve mention [17,18,19,20,21]. Nonetheless, the present manuscript shows a distinct advantage over fluorescent protein imaging because unlike previous methods, The BRODERICK PROBE® biosensors, have made the critical advance to clinicaluse, successfully, imaging neurotransmitters, neurochemicals and peptides in neocortex of epilepsy patients on line, in real time and in vivo during patients’ intraoperative surgery. It is important to note that the pathology reports from epilepsy patients implanted with our biosensors do not exhibit gliosis/sclerosis/scar tissue, nor do the biosensors produce bacterial growth [22,23].
1.3. The PD paradigm
2. Results and Discussion
2.1. In vivo comparison of endogenous neurochemicals in PD versus non-PD striatal brain
Figure 2 show the results of NMI detecting endogenous neurochemicals in the PD versus the non-PD animals. Neurochemical profiles are drawn from original in vivo data. This is the first report of an in vivo neurochemical comparison between PD and non-PD in motor neurons in dorsal striatal brain. This is the first in vivo neurochemical profile study of PD in any neuroanatomic substrate of animal. The present data are derived from 10 NMI studies in dorsal striatum of PD versus another 10 studies in non-PD animals.
Figure 2. Representative NMI endogenous (baseline, control) neurochemical signature profiles in dorsal striatum of (left) the PD and (right) the non-PD animal in vivo, on line and in real time. Neurochemical profiles are drawn from original recordings.
The results showed that DA and its metabolite HVA were not imaged in striatal brain of PD. What was readily apparent in striatal brain of PD, was the selective imaging of the neurotransmitter, 5-HT and its precursor, L-TP. Moreover, two neurotransmitter peptides, Dyn A and SRIF were also separately imaged in striatal brain of PD. Repeatedly imaged to a significant degree, was a peptide at an oxidation/half-wave potential of about 0.83 V, which this laboratory is in the process of defining. These peptide neurotransmitters were not imaged in dorsal striatal brain of non-PD animals. In the non-PD dorsal striatum, selective electroactive signals for DA, 5-HT, HVA and L-TP were repeatedly imaged. Another observation from the data in Figure 2 is that the non-PD striatal brain endogenously exhibits higher concentrations of 5-HT and L-TP than the PD striatal brain; this interpretation derives from the Cottrell Equation which calculates that concentration of each neurochemical is directly proportional to its resultant current.
2.2. In vivo Bromocriptine Studies in dorsal striatal brain of PD versus non-PD animals
Thus, the following questions were addressed:
- Is bromocriptine useful for PD if it may reduce DA in motor neurons?
- What is the mechanism of action for bromocriptine in PD patients?
- Can the effects of bromocriptine be biphasically dose dependent?
- Does bromocriptine act through other neurochemicals, neurotransmitters in PD?
- Is this study of bromocriptine relevant to the clinical treatment of PD?
A dose of 5 mg/kg ip was administered to the animal in the first study. In the second study, a dose of 5 mg/kg followed by a dose of 10 mg/kg, ip was administered to the animal. For animal studies, these doses are considered the low and high dose. The initial clinical dose for bromocriptine can start at 1.25 mg and then continue daily at levels of 2.5–7.5 mg daily. Nonetheless, there are reports of daily doses of bromocriptine for PD patients between 7.0 and 30 mg daily. Clinically, the low dose for PD patients has been reported to be about 30 mg daily , whereas the high dose has been reported to be about 52 mg daily . Figure 3 show the effects of bromocriptine (5 mg/kg ip; low dose) in striatal brain of PD versus non-PD animals.
Figure 3. Representative NMI neurochemical signature profiles in dorsal striatum of the (left) PD and (right) the non-PD animal, after administration of the dopamine agonist, bromocriptine (5 mg/kg, ip; low dose) in vivo, on line and in real time. Neurochemical profiles in PD versus non-PD are drawn from original recordings.
2.3. In vivo studies of low dose bromocriptine effects on dorsal striatum in PD versus non-PD animals
2.4. In vivo studies of high dose bromocriptine effects on dorsal striatum in PD versus non-PD animals
Figure 4 show the results from the administration of bromocriptine (5 mg/kg ip followed by 10 mg/kg, ip), the high dose, in dorsal striatal brain of PD versus non-PD. The results from the administration of bromocriptine, at the high dose, showed that: in PD, 5-HT increased about 75% above baseline, L-TP decreased about 10% from baseline, Dyn A increased about 50% above baseline and peptideat 0.83 V increased about 100% above baseline.
Figure 4. Representative NMI neurochemical signature profiles in dorsal striatum of (left) the PD and (right) the non-PD animal, after administration of the dopamine agonist, bromocriptine (5 mg/kg ip followed by 10 mg/kg ip) (high dose) in vivo, on line and in real time. Neurochemical profiles are drawn from original recordings.
These percentages are derived from the maximum effect of the high dose of bromocriptine. SRIFincreased in dorsal striatum of PD; final percentage is in process. It is important to note that bromocriptine at the high dose did not enable an increase in the concentration of DA and HVA release. The results from the administration of bromocriptine at the high dose in dorsal striatal brain of non-PD animals, taken at maximum points, showed that DA decreased about 25% below baseline, as expected due to its autoreceptor inhibitory action and in support of microdialysis studies performed in dorsal striatal brain of non-PD animals . Serotonin (5-HT) increased about 30% above baseline, HVA decreased virtually to baseline, also expectedly because as previously mentioned, HVA is a metabolite of DA; these data support those of others as studied in the non-PD animal . LTP decreased about 20% from baseline. It is important to note that the peptide biomarkers were not imaged in the dorsal striatal brain of the non-PD animal whether they were bromocriptine treated or not.
2.5. Line graphs showing the time course of endogenous effects in PD versus non-PD animals
Interestingly, in Figure 5, the results showed that bromocriptine, at 5 mg/kg ip, low dose, had significantly greater effects on 5-HT and L-TP in PD animals than in non-PD animals (ANOVA; p < 0.0001), even though endogenously, 5-HT and L-TP were higher in concentration in non-PD than in PD.
Figure 5. These figures show line graphs of the temporal course of neurochemical events for the PD animal (left) and the non-PD animal (right) at the 5 mg/kg dose (low dose).
2.6. Line graphs showing the time course of bromocriptine effects in PD versus non-PD animals
In Figure 6, bromocriptine, at the high dose, also showed significantly greater effects on 5-HT and L-TP in PD animals versus non-PD animals (ANOVA; p<0.0001). It is suggested that 5-HT-ergic function may be compensating for the lack of endogenous DA and HVA in dorsal striatal brain of PD, in addition to compensating for the decreased DA and HVA biphasic effect of the high dose of bromocriptine in dorsal striatal brain of non-PD animals.
Figure 6. (A) This figure shows a line graph of the temporal course of neurochemical events in dorsal striatum for PD animals after the low dose followed by the high dose of bromocriptine. (B) This figure shows a line graph of the temporal course of neurochemical events in dorsal striatum of non-PD animals after administration of the high dose of bromocriptine.
3.1. Study design
Results from PD and non-PD animals were compared by One-Way Analysis of Variance (ANOVA) with alpha level set at P=0.05. Endogenous effects and bromocriptine effects on neurotransmitters and neurochemicals in PD as compared with non-PD were statistically significant (p < 0.001). Saline effects were not significant. In Figure 5 and Figure 6, asterisks denote significance above baseline at 95% Confidence Limits (p < 0.05) and above.
For the first time, neurochemical profiles for dorsal striatal brain of PD versus dorsal striatal brain of non-PD animals are reported herein in vivo, on line and in real time, using the advanced NMI biotechnology. Moreover, the effects of the pharmaceutical agent, routinely used to treat PD patients, bromocriptine (Parlodel®), was studied for its effects on neurochemical profiles for PD compared with non-PD. Critical for the treatment of PD are data reported herein that show that peptidergic neurochemistry is imaged in endogenous PD and bromocriptine-treated PD and not in endogenous non-PD whether treated with bromocriptine or not. Previous literature has shown that peptides assist the positive effects of Brain-Derived Neurotrophic Factor (BDNF) in PD . However, in this paper, unique in vivo data show that peptides may actually perform as biomarkers for PD. The data suggest, in support of the work of Lu and Stoessel  that SRIF may help to treat PD patients. In support of the work of Henry and Brotchie  the present data show that antagonists of DYN A may assist in the pharmacotherapy of PD. The findings show that DA is not the sole arbiter for the treatment of PD! Thus, the present findings are highly applicable to the clinical treatment of PD.