Biomedical subjects
W R van Furth
Publications and source records attributed to W R van Furth.
Sexual motivation: involvement of endogenous opioids in the ventral tegmental area.
The sexual motivation and performance of male rats were observed in a bilevel testing chamber after bilateral infusion of 40 pmol beta-endorphin, 2.75 nmol naloxone or saline into the ventral tegmental area for four succeeding, weekly tests. In the 5 min prior to introduction of the female rat, the male rat explores the bilevel testing chamber. It was previously shown that the increase over tests of these anticipatory level changes is sexually motivated and a response to olfactory stimuli. Naloxone infusion into the VTA prevented the increase of anticipatory level changes. beta-Endorphin failed to affect the anticipatory level-changing behavior. The sexual performance was unaffected by naloxone or beta-endorphin treatment, but the number of ejaculating rats decreased with repeated testing after naloxone treatment. It is concluded that endogenous opioid systems in the ventral tegmental area contribute to the stimulation of sexual motivation and/or reward, presumably by stimulating the mesolimbic dopamine system in response to sex-related olfactory stimuli.
Regulation of masculine sexual behavior: involvement of brain opioids and dopamine.
In recent years much has become known about the substrates in the brain involved in the regulation of masculine sexual behavior and the involvement of specific neurochemicals in these brain areas. In the present paper the experimental data concerning the involvement of a number of brain areas in sexual behavior are reviewed, in relation to an incentive motivational theory of sexual behavior. The review is restricted to the involvement of opioids and dopamine, of which the role in sexual motivation and behavior is best documented. Opioids in the medial preoptic area (mPOA) impair sexual performance, although the endogenous opioids systems may be quiescent in normal, sexually active rats. Dopamine in the mPOA has a facilitative role in the masculine sexual performance. The corticomedial amygdala is involved in processing of sensory information, especially olfactory stimuli, which are subsequently directed towards the mPOA. Local beta-endorphin infusion interferes with this processing. Endogenous opioids in the ventral tegmental area activate the mesoaccumbens dopamine system and stimulate the sexual motivation. Increased dopamine transmission in the nucleus accumbens correlates with increased sexual motivation and vice versa. The basolateral amygdala plays an essential role in the association of environmental stimuli with reward and therefore in the expression of conditioned sexual motivation. Finally, the reviewed data are integrated and a comprehensive view on the relations between various neural substrates is composed.
Opioids and sexual behavior of male rats: involvement of the medial preoptic area.
Local infusion of beta-endorphin (beta-END) into the medial preoptic area (MPOA) dose-dependently impaired the gating of the copulatory response and the execution of the sexual performance of sexually experienced, intact male rats. Local naloxone treatment prevented the impairment of the sexual response by beta-END, but failed to facilitate unimpaired copulation. Local infusion into the MPOA of equimolar doses of alpha-endorphin, dynorphin-A-(1-17) or met-enkephalin were less effective than beta-END. It is suggested that endogenous opioid systems in the MPOA are normally quiescent, and increased activity may be related to disrupted or inhibited male sexual behavior.
Endogenous opioids and sexual motivation and performance during the light phase of the diurnal cycle.
The sexual motivation and performance of sexually experienced male rats were tested during the light phase of the diurnal cycle after treatment with saline or 1 mg.kg-1 naloxone in a bilevel testing box. The sexual motivation during the light phase, as assessed by the increase in anticipatory level changes prior to introduction of a receptive female on subsequent weekly sessions, was comparable to that during the dark phase. Opioid blockade reduced the increase of level changes, suggesting that endogenous opioids are involved in sexual motivation. The sexual performance was impaired during the light phase. Naloxone treatment failed to affect the sexual performance, other than that the post ejaculatory refractory period was increased. This increased latency to re-initiate copulation may be an expression of the reduced sexual motivation. It is concluded that endogenous opioids are not involved in the regulation of the impaired sexual performance during the light phase of the diurnal cycle. In contrast, the sexual motivation, which displays no marked diurnal variation, may be stimulated by endogenous opioids.
[A little less sodium is not without hazard].
Explore the source record for details and available documents.