Abstract
BackgroundRecent evidence indicates that hypothalamic neurons acquire or lose the capacity to synthesize and release dopamine (DA) in response to environmental stimuli, and this has functional and behavioral consequences for adult rats. We have evidence that neuronal activity, including that driven by afferent input, regulates acquisition and loss of the DA phenotype by substantia nigra pars compacta (SNc) neurons in adult mice.Hypotheses The aims of the present study were to determine whether the environment or behavior regulates the number of SNc DA neurons in adult mice, and whether this is mediated by afferent input.MethodsAdult mice were subject to two different environments/behaviors: “mating” for 1 week or “environment enrichment” (EE) for 2 weeks; then the numbers of tyrosine hydroxylase (TH, the rate limiting enzyme in DA synthesis) immunopositive (TH+) and immunonegative (TH−) SNc neurons were counted.ResultsMore TH+ neurons were present in mated males whereas less TH+ neurons were present in mated females. Also, more TH+ neurons were present in EE males, and this increase was completely abolished by concurrent local infusion of GABAA receptor antagonists.ConclusionsThe number of DA neurons in the adult SNc is not fixed, but readily increases and decreases in response to environmental stimuli and/or behaviors. These changes are mediated by afferent input relaying information about the environment or behavior to SNc neurons.
Highlights
Behavioral adaptation to our environment is mediated by changes in our nervous system
Males paired with females for 7 days had significantly more TH+ substantia nigra pars compacta (SNc) neurons than males paired with males (Fig. 1A; Table 1)
A similar increase was seen in the ventral tegmental area (VTA) just medial to SNc (Fig. 1B; Table 1), but TH+ cell numbers were unchanged in another catecholaminergic nucleus, the locus ceruleus (LC) (Fig. 1C; Table 1)
Summary
Behavioral adaptation to our environment is mediated by changes in our nervous system. Acquisition or loss of the capacity of hypothalamic neurons to synthesize and release dopamine (DA) in response to environmental stimuli has functional and behavioral consequences for adult rats (Dulcis et al 2013). We have evidence that neuronal activity, including that driven by afferent input, regulates acquisition and loss of the DA phenotype by substantia nigra pars compacta (SNc) neurons in adult mice. Hypotheses: The aims of the present study were to determine whether the environment or behavior regulates the number of SNc DA neurons in adult mice, and whether this is mediated by afferent input. Conclusions: The number of DA neurons in the adult SNc is not fixed, but readily increases and decreases in response to environmental stimuli and/or behaviors These changes are mediated by afferent input relaying information about the environment or behavior to SNc neurons
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