Perspectives on Behavioural
Function of Dopamine in the Nucleus Accumbens
Re: DA cell activity: cat vs monkey, SNc vs VTA
In reply to Brian Hyland, I want to state that the neurochemistry literature from rats also suggests that DA release and metabolism responds to a variety of stimuli; not necessarily "arbitrary" ones, but certainly stressful ones. DA-related activity is increased in situations involving footshock, tailshock, tailpinch, restraint, social stress, anxiogenic drugs and stimuli paired with shock. The selectivity for responsiveness to "rewards", which often is cited, is in fact a misrepresentation of the literature. Of course, one could argue about the differences between electrophysiology, dialysis and voltammetry (see review by Salamone, 1996). Nevertheless, I still feel that the full range of possible stimuli needs to be explored more in the monkey.
Even if it is true that the monkey shows unique characteristics in terms of response characteristics of DA neurons, the overall DA hypothesis of "reward" appears to be used uniformly across all mammalian species. Most of the pharmacological evidence that is typically cited as supporting that hypothesis is from rats. Thus, if one were to use the monkey data as support for this hyothesis, the rat neurochemistry literature would, of course, be just as appropriate.
In thinking about the monkey data from VTA neurons, I wonder to what extent these cells actually innervate prefrontal cortex as opposed to nucleus accumbens.
Sat Dec 12