Biomedical subjects

Pablo Pacheco

Publications and source records attributed to Pablo Pacheco.

5 recordsLinked to original sources

PubMed2005

Olfactory conditioned partner preference in the female rat.

Paced copulation induces conditioned place preference in female rats. The authors examined whether associating almond-scented males with paced copulation induces conditioned partner preference. The paired group received 4 paced copulations with almond-scented males and 4 nonpaced copulations with unscented males sequentially at 4-day intervals. The unpaired group received the opposite order of association, whereas the randomly paired group received random associations. A 4th group received a single pairing. On the final test, females were placed into an open field with 2 males, 1 scented and 1 unscented. Females in the paired group solicited the scented male more frequently, and most chose the scented male for their 1st ejaculation. Thus, an odor paired with paced copulation elicits conditioned partner preference in female rats.

Analysis of Variance↗

PubMed2004

Pattern of sensory innervation of the perineal skin in the female rat.

Here we describe the nerves innervating the perineal skin together with their sensory fields in the adult female rat. Electrophysiological recording showed that the lumbosacral and L6-S1 trunks, in part by way of the sacral plexus, transmit sensory information from the perineal skin via four nerves: the viscerocutaneous branch of the pelvic nerve innervating the skin at the midline between the vaginal opening and anus, the sensory branch of the pudendal nerve innervating the clitoral sheath, the distal perineal branch of the pudendal nerve innervating a broad area of skin adjacent to the vaginal opening and anus, and the proximal perineal branch of the sacral plexus innervating a broad area of skin adjacent to the clitoris and vaginal opening. The sensory fields of three of these nerves overlapped to some degree: the viscerocutaneous branch of the pelvic and the distal perineal branch of the pudendal nerves at the midline skin between the vaginal opening and the anus, and the distal perineal branch of the pudendal nerve and the proximal perineal branch of the sacral plexus at the skin lateral to the vaginal opening. Such overlap might provide a safeguard helping to ensure that somatosensory input from the perineal region important for triggering reproductive and nonreproductive reflexes reaches the CNS.

Animals↗

PubMed2004

Timing between ejaculations changes paternity success.

It is believed that when two male rats copulate with a single female, the last one that ejaculates fathers significantly more pups than the first one. To determine the effects of order and elapsed time between two males copulating with the same female, albino Wistar (W) and pigmented Long-Evans (LE) male rats copulated with a W female. Paternity was confirmed by the pups' pigmentation. Three groups were made according to the elapsed time between the first male's ejaculation and the placement of the female with the second male; T0 (0-min group); T5 (5-min group); and T10 (10-min group). Male order was counterbalanced in each group. The results showed that the second male had the advantage in T0, but the first males had the advantage in T5 and T10. These data indicate that in a two-male situation, the advantage in paternity for a second male occurs only during copulations following the first few minutes of a first male's ejaculation. After 5 min, a second male has no advantage in fathering pups.

Animals↗

PubMed2003

Influence of testosterone on the electrical properties of scrotal nerves at the cutaneous and spinal levels in the male rat.

The scrotal nerves in the rat were studied electrophysiologically to describe their topographic organization in the skin and in the dorsal roots, and to determine if the electrical properties of these afferents are under the influence of testosterone. There are 2 afferent nerve branches innervating this area, the proximal scrotal branch supplying the proximal half of the scrotum (PSb), and the distal scrotal branch supplying the distal half (DSb). Results showed that afferent axons from PSb enter the spinal cord through the L5 and L6 dorsal roots, and axons from DSb enter the cord through the L6 and S1 dorsal roots. Mechanical stimulation of the scrotal skin exposed 3 dermatome areas, the L5, L6, and S1, with L6 being the longest dermatome with intermingled terminals from PSb and DSb. Decreased levels of testosterone after castration increased the threshold to trigger the activity of scrotal afferents, and the exogenous administration of the hormone reverted it. This effect was similar in the dorsal penile nerve. The decrease in androgen levels produced a reduction in the skin sensory field to mechanical stimuli that was restored after the administration of the hormone. As the scrotal nerves are highly stimulated during copulation in parallel with the dorsal penile nerve, it is suggested that the sensory field of the scrotal skin could be closely related to the modifications in sexual behavior after testosterone manipulation.

Animals↗

PubMedDate not supplied

Anatomical and physiological characteristics of perineal muscles in the female rabbit.

Little information is available on the participation of the perineal striated muscles in female reproductive processes. Here, we describe the gross anatomy and innervation of two striated perineal muscles in the female rabbit, the bulbospongiosus (BSM) and ischiocavernosus (ISM), and analyze their reflex electromyographic (EMG) activity in response to stimulation of the perigenital skin and vaginal tract. Twenty-four mature chinchilla-breed rabbit does were used: 12 to describe the anatomy and innervation of the muscles, 9 to determine reflex EMG activity of the muscles in response to stimulation of the perigenital skin and specific levels of the vaginal tract and 3 to analyze the effect of contraction of the muscles on intravaginal pressure. Both muscles were well developed, with their fibers originating at the ischiadic arch and inserting onto the ligamentum suspensorium clitoridis. Branches of the clitoral and perineal nerves innervated the BSM and ISM, respectively. Bilateral electrical stimulation of these nerves provoked retraction of the clitoral sheath and an increase in intravaginal pressure at the level of the perineal vagina. Whereas neither muscle responded to stimulation of the perigenital skin, both were reflexively activated during mechanical stimulation of the inner walls of the perineal vagina. Prolonged cervical stimulation inhibited this reflex. Thus, in reproductive processes such as copulation and/or parturition, the contraction of these muscles may be induced during stimulation of the perineal vagina.

Animals↗