Dopaminergic modulation of reproductive behavior and activity in male zebra finches

Abstract

We previously demonstrated that hormone treatments which stimulate female-directed singing increased levels and turnover of dopamine (DA) in brain areas controlling the motor patterning of song. To help determine how DA affects singing, we quantified the effects of treating adult male finches with the D 1 /D 2 receptor antagonist cis-flupenthixol. Adult males were given subcutaneous silastic implants of androgen, in case drug treatment interfered with androgen secretion. One week later, they were tested with females. Males were divided into three groups matched for levels of courtship singing. Males were then subcutaneously implanted with osmotic minipumps containing either saline, a low, or a high dose of cis-flupenthixol. Each male was tested with a different female 5 and 10 days after implantation to determine how this D 1 /D 2 receptor antagonist affected behavior. Both drug doses affected female-directed singing 5 days after initiation of treatment. High-dose males sang to females significantly less often than males in the other two groups. Low-dose males showed fewer high-intensity courtship displays in which males dance towards females as they sing. These effects on courtship singing were not seen at day 10, though other behavioral effects were seen at this time. Male beak wipes, rocks, following females and female withdrawals from males were also affected by drug treatment. General activity in the home cage was decreased by day 11. These data demonstrate that singing and several other female-directed behaviors are sensitive to perturbations in DA receptor function.

Midbrain dopamine neurons reflect affiliation phenotypes in finches and are tightly coupled to courtship

“…However, we here observed very close relationships between TH-Fos colocalization and courtship singing, and also between TH cell number and constitutive courtship motivation, as established through behavioral prescreenings. Considering that TH-ir neurons in the CG and VTA project directly to areas involved in singing and sexual motivation (16,17), and that DA promotes singing (8,28), our interpretations for courting males are fairly straightforward; the more DA neurons that a male exhibits in the CG and caudal VTA, and the greater their Fos activity, the greater the male's behavioral output. This interpretation is likewise consistent with the fact that non-courters express low levels of colocalization after exposure to female.…”

“…Recent findings demonstrate that DA signals derived from the VTA-substantia nigra pars compacta complex are essential for the context-dependent modulation of song in the zebra finch (6,36), and various other findings likewise show that DA is important for the regulation of song (8,28,37). However, previous experiments have found that singing is correlated with immediate early gene expression only within nondopaminergic neurons of the VTA (6,32), although those studies appear to have focused predominantly on the rostral portion of the VTA.…”

“…DA influences numerous affiliation behaviors such as pair bonding (5), sexual communication (6)(7)(8), and copulation (9)(10)(11). Of particular interest are DA cells in the ventral tegmental area (VTA), which are well known to regulate incentive and reward-related processes (12,13).…”

Evidence that dopamine within motivation and song control brain regions regulates birdsong context-dependently

“…Additional data from pharmacological manipulations in zebra finches support a role for DA in stimulating directed vocal communication [24]. Because these drugs were administered systemically, it is impossible to discern where in the brain altered dopaminergic function influences sexually motivated vocal communication.…”

“…We have found that within a breeding context, peripheral injections of DA agonists stimulate whereas DA antagonists inhibit song produced by male starlings in response to the introduction of a female [23]. In male zebra finches, DA antagonists also inhibit courtship singing [24] and in vivo microdialysis reveals that levels of DA in the avian basal ganglia (Area X) are elevated during song that is directed towards a conspecific [25]. A role for DA in the regulation of goal-directed vocal behavior extends beyond songbird model systems.…”