*Frequency of Dopamine Concentration Transients Increases in Dorsal and Ventral Striatum of Male Rats during Introduction of Conspeciﬁcs
Donita L. Robinson, Michael L. A. V. Heien
Transient, elevated concentrations of extracellular dopamine were characterized in the dorsal and ventral striatum of male rats during solitude, brief interaction with a conspeciﬁc, and copulation. Conspeciﬁc rats were systematically presented to male rats and allowed to interact for 30 sec; the males were kept in solitude between each presentation. During these episodes, 125 dopamine concentration transients from 17 rats were detected with fast-scan cyclic voltammetry at carbonﬁber microelectrodes (peak amplitude, 210 10 nM; duration, 530 20 msec). The frequency of dopamine transients increased sixfold during conspeciﬁc episodes compared with solitude. However, the phasic dopamine activity habituated on the second presentation of the conspeciﬁcs. When males were allowed to copulate with receptive females, additional dopamine transients were observed at frequencies 20% of those during the previous interaction episodes. A subset of these transients immediately preceded intromission. Overall, phasic
dopamine activity appeared to be associated with input from multiple sensory modalities and was followed by a variety of approach and appetitive behaviors, consistent with electrophysiological observations of dopaminergic neuron burst-ﬁring. In summary, (1) dopamine concentration transients occur in awake rats during solitude, in the absence of overt external cues; (2) dopamine transients are signiﬁcantly more frequent in the presence of a conspeciﬁc, although this effect habituates; and (3) dopamine transients are less frequent during copulation than during brief conspeciﬁc episodes. These results establish for the ﬁrst time that transient dopamine ﬂuctuations occur throughout the dorsal and ventral striatum and demonstrate that they are more frequent with salient stimuli that elicit a response behavior.
•Acromegaly is a syndrome that results when the anterior pituitary gland produces excess growth hormone after epiphyseal plate closure at puberty. A number of disorders may increase the pituitary's GH output, although most commonly it involves a tumor called pituitary adenoma, derived from a distinct type of cell.