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Peciña and Berridge (2005; J Neurosci 25:11777-11786) observed that an injection of the μ-opioid receptor agonist DAMGO (D-ala2-N-Me-Phe4-Glycol5-enkephalin) into the rostrodorsal part of the accumbens shell (rdAcbSh) enhances expression of hedonic 'liking' responses to the taste of an appetitive sucrose solution. Insofar as the connections of this hedonic 'hotspot' were not singled out for special attention in the earlier neuroanatomical literature, we undertook to examine them. We observed that the patterns of inputs and outputs of the rdAcbSh are not qualitatively different from those of the rest of the Acb, except that outputs from the rdAcbSh to the lateral preoptic area and anterior and lateral hypothalamic areas are anomalously robust and overlap extensively with those of the lateral septum. We also detected reciprocal interconnections between the rdAcbSh and lateral septum. Whether and how these connections subserve hedonic impact remains to be learned, but these observations lead us to hypothesize that the rdAcbSh represents a basal forebrain transition area, in the sense that it is invaded by neurons of the lateral septum, or possibly transitional neuronal forms sharing properties of both structures. We note that the proposed transition zone between lateral septum and rdAcbSh would be but one of many in the basal forebrain and conclude by reiterating the longstanding argument that the transitional nature of such boundary areas has functional importance, of which the precise nature will remain elusive until the neurophysiological and neuropharmacological implications of such zones of transition are more generally acknowledged and better addressed. J. Comp. Neurol. 521:50-68, 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Neurotensin exerts complex effects on the mesolimbic dopamine system that alter motivation and contribute to neuroadaptations associated with psychostimulant drug administration. Activation of abundant neurotensin receptors in the ventral tegmental area (VTA) enhances dopamine neuron activity and associated release of dopamine in the nucleus accumbens (Acb) and cortex. In view of recent anatomical studies demonstrating that 70% of all neurotensin-containing neurons projecting to the VTA occupy the lateral preoptic area–rostral lateral hypothalamus (LPH) and lateral part of the medial preoptic area (MPOA), the present study examined functionality in the LPH–MPOA neurotensinergic pathway in the rat. Disinhibition (resulting ultimately in stimulation-like effects) of LPH–MPOA neurons with microinjected bicuculline (50 or 100 ng in 0.25 µL) produced locomotor activation that was considerably attenuated by systemic administration of the neurotensin antagonist SR 142948 A (0.03 and 0.1 mg/kg). In contrast, locomotion elicited in this manner was completely blocked by SR 142948 A infused directly into the VTA (5.0 and 15.0 ng in 0.25 µL). Baseline locomotion was unaffected by systemic or intra-VTA administration of SR 142948 A and LPH–MPOA-elicited locomotion was unaffected by infusion of SR 142948 A into the substantia nigra pars compacta and sites rostral and dorsal to the VTA. Locomotion was not elicited by infusions of bicuculline into the lateral hypothalamus at sites caudal to the LPH–MPOA, where neurotensin neurons projecting to the VTA are fewer. The results demonstrate the capacity of a neurotensin-containing pathway from LPH–MPOA to VTA to modulate locomotion. This pathway may be important in linking hippocampal and mesolimbic mechanisms in normal behaviour and drug addiction. [ABSTRACT FROM AUTHOR]