The lack of amphetamine-induced c-Fos activation in the Pitx3GFP/GFP grafted animals suggests that volume transmission, i.e. diffusion of released dopamine over distance from midbrain dopamine rich grafts is, at best, an inefficient means to normalize striatal neuron activity in the Parkinson's disease affected brain.
The presence of transient, quantal synaptic events involving the D2 receptor14, 22, 23 is at odds with the anatomical data indicating that D2 receptors primarily reside at distances from dopamine release sites requiring significant diffusion of the neurotransmitter24,25,26.
The higher KM values obtained for chitosan, from eggshell membranes, results from some diffusion limitation for dopamine.
Collectively, our results suggest that DA is released in a paracrine fashion and acts at ribbon synapses, likely enhancing the activity of presynaptic Cav1.3a channels and thereby increasing neurotransmission.The neurotransmitter dopamine acts in a paracrine fashion (diffusion over a short distance) in several tissues and bodily organs, influencing and regulating their activity.
Recent findings, however, suggest that dopamine may be subject to restricted diffusion processes in brain extracellular space.
Scan rate was varied to determine whether dopamine kinetics at CNTYMEs are limited by diffusion or adsorption.
Organic cation transporters function as membrane potential-dependent uniporters that mediate the facilitated diffusion of endogenous amines such as dopamine, or therapeutic drugs such as morphine and antihistamines.
Responses recorded in the dorsal and ventral striatum of the rat do not bear out the predictions of a numerical model that assumes the presence of a diffusion gap interposed between the recording electrode and nearby dopamine terminals.
Spread or diffusion of drugs injected into M1 could have resulted in dopamine depletion or blockade in other brain regions thereby confounding the behavioral observations.
