In some species of songbirds, including canaries, song is sung primarily by males, but even in species in which the female does not sing at all (e. g. role of the song system to include consummatory as well as appetitive aspects of reproductive behaviour. Keywords: canary, copulation solicitation display, cloacal motoneurons, nucleus retroambigualis == 1 . Background == A major function of male song is to attract a female, and because singing is often correlated with reproduction, singing can be seen as a form of appetitive behaviour (courtship) that may Dicarbine be consummated by sexual union in which the male’s sperm is transferred to the female by the apposition of the birds’ cloacae (the avian reproductive organ). In some species of songbirds, including canaries, song is sung primarily by males, but even in species in which the female does Dicarbine not sing at all (e. g. zebra finch), similar Dicarbine pathways intended for vocal production are present in females as in males [1]. The motor pathway for song (figure 1) proceeds from HVC (proper name) to nucleus robustus arcopallialis (RA), which then projects directly to vocal motoneurons (XIIts) and to respiratory premotor neurons in nucleus retroambigualis (RAm) in the lower medulla. In turn, RAm projects upon spinal motoneurons that innervate expiratory muscles (which provide the pressure head for vocalization), and upon XIIts to effect vocalrespiratory coordination [2, 3]. == Figure 1 . == (a) Canary CSD showing the proposed pathway HVCRARAmcloacal motoneurons. (b) The full sequence of pathways intended for appetitive (singing) and consummatory (cloacal focus) reproductive behaviour. DM, dorsomedial nucleus of the intercollicular complex. Female songbirds choose their sexual partner largely on the basis of their auditory assessment of various aspects of his song [4] and, given an appropriate hormonal state, they may respond by presenting the copulation solicitation display (CSD) [5], a suite of extensor postural responses resembling lordosis in mammals, which facilitates insemination. The neural mechanisms by which the CSD is evoked and manifestand it can be evoked by the male’s song even in his physical absence [6]are unclear, but in female canaries the elicitation and intensity of the CSD is under the control of highly specific, possibly innate, acoustic components of male song, called sexy syllables [7]. Moreover, although partial lesions of HVC cause female canaries to present the CSD indiscriminately, their CSDs remain most intensely evoked by canary sexy syllables [8]. This would seem to indicate that the pathway originating in HVC and descending via RA to RAm contributes in some way to the control of the CSD (figure 1). Although males do not normally present the CSD, cloacal positioning and associated movements are presumably as important as those in females for successful insemination and may, therefore , be controlled in part by the same pathways as those in females. The cloaca is arguably the focus of the CSD for both the Mouse monoclonal to CD95 male and the female. Its external aperture (the vent) is enclosed by a sphincter muscle (mSC) [9], which in male Japanese make bones about has been shown electromyographically to be active during copulation and defaecation [10]. Furthermore, mSC motoneurons in quail receive a direct projection from RAm [11], but because quail are non-songbirds, they do not possess a forebrain song system. We ask here, therefore , whether the song system of songbirds is involved not only in appetitive aspects of reproductive behaviour (singing), but also in consummatory aspects of reproductive behaviour (copulation). Neuroanatomical evidence that it could be is presented below. == 2 . Material and methods == Subjects were 21 male and female canaries (Serinus canarius). Surgery was undertaken following induction of general anaesthesia by an intramuscular injection of ketamine (50 mg kg1) and xylazine (20 mg.