Knut Larsson

Mating behavior in the male rat treated with p-chlorophenylalanine methyl ester alone and in combination with pargyline

The methyl-ester-hydrochloride of p-chlorophenylalanine alone (50 or 150 mg/kg i.p.) and in combination (4×100 mg/kg i.p.) with pargyline (100 mg/kg i.p.) caused a shortening of the ejaculation latencies in male rats and an increase in the number of intromissions per minute. No changes were observed in other components of the sexual behavior including intromission latency, post-ejaculatory interval and the number of mounts and intromissions preceding ejaculation.

Laissez-faire in research education — an inquiry into a Swedish doctoral program

It is a matter of concern that the number of doctoral examinations in social sciences at the Swedish universities is low. The vast majority of the accepted doctoral students never complete their studies, and very few finish within the stipulated four years. In an attempt to find the causes of this situation, we singled out a social science department at a major Swedish university, and interviewed those doctoral students who had dropped-out of it. Those students had all completed at least 50% of their PhD studies. A number of shortcomings were found: random and infrequent meetings between student and supervisor; thesis goals seldom set; freedom for the student and for the supervisor as how to pursue the research education towards a PhD. We concluded that the entire research education was characterized by a Laissez-faire leadership (a leader nominated but abdicated). Using a concept borrowed from psychotherapy, we suggested that a ‘working alliance’ should be established between the supervisor and the student. At the core of the working alliance is the notion of the mutual forming of a platform out of which work emerges in common collaboration. The working alliance implies a contract for work, stating its goals, the tasks to reach these goals, and the interpersonal bonding which is needed to give force and endurance to the endeavor. The constant scrutiny of this contract, the mutual concern with the working alliance, by itself, contributes to its strength.

Non-Specific Stimulation and Sexual Behaviour in the Male Rat

Male rats in one group were 5-6 months of age and in another group 20-24 months. These were allowed to copulate under two conditions. At one occasion they mated without any interference of the experimenter and at another they were handled approximately twice a minute. The older males, although sexually less vigorous than the younger males when copulating under non-handling conditions, when handled became quite as active as the younger males. It was concluded that the mating activity is determined not only by sexual stimuli but by non-sexual stimuli as well, and that the decrease in sexual activity characteristic to the old rat can be compensated for by an increase in the non-sexual sensory stimulation of the animal.

Evidence for an involvement of 5-HT1B receptors in the inhibition of male rat ejaculatory behavior produced by 5-HTP

Abstract The administration of the 5-hydroxytryptamine (5-HT) precursor 5hydroxytryptophan (5-HTP) (25mg/kg IP), in combination with an inhibitor of peripheral 5-HTP decarboxylase, produced a dose-dependent increase in the ejaculation latency of male rats, and this effect was enhanced by additional treatment with the 5-HT1 receptor antagonist (−)-pindolol (2mg/kg SC). The 5-HT2A/C receptor agonist (±)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) (0.125–0.5mg/kg SC) did not by itself affect male ejaculatory behavior, but additional treatment with (−)-pindolol (2mg/kg SC) produced a dose-dependent decrease in number of ejaculating animals. The increased ejaculation latency produced by 5-HTP was fully antagonized by treatment with the 5-HT1B receptor antagonist isamoltane (4mg/kg SC), but not by ritanserin (2mg/kg SC) treatment. The selective 5HT1A receptor antagonist WAY-100635 (0.15mg/kg SC) enhanced the inhibitory actions of 5-HTP on the male rat ejaculatory behavior, and this dose of WAY-100635 fully antagonized 8-OH-DPAT-induced facilitation (0.25mg/kg SC) of the ejaculatory behavior. WAY-100635 (0.04–0.60mg/kg SC) did not, by itself, significantly affect male rat sexual behavior. Taken together, the results suggest an inhibitory role for postsynaptic 5-HT1B receptors in the effects produced by 5-HTP on male rat ejaculatory behavior. Furthermore, 5-HTP-induced inhibition of male rat ejaculatory behavior is partially controlled by stimulation of inhibitory 5-HT1A autoreceptors, since the effects of 5-HTP were accentuated by treatment with (−)-pindolol, as well as by the more selective 5-HT1A receptor antagonist WAY-100635.

Prolongation of the ejaculation latency in the male rat by thioridazine and chlorimipramine.

Thioridazine (3 mg/kg) and chlorimipramine (1.5–6.0 mg/kg) prolonged the ejaculation latency and increased the number of mounts but did not change the number of intromissions preceding ejaculation. Blockade of peripheral and central noradrenaline receptors by phentolamine and phenoxybenzamine respectively resulted in a suppression of all aspects of the sexual behavior with increasing doses. dl-5-HTP (25–100 mg/kg) in combination with an inhibitor of peripheral 5-HTP decarboxylase (benserazide, 25 mg/kg) produced, like chlorimipramine and thioridazine, a prolongation of ejaculation latency and an increase in the number of mounts preceding ejaculation. Selective inhibition of 5-HT reuptake however, by zimelidine (0–20 mg/kg) or alaproclate (0–20 mg/kg) did not affect the mating behavior. At higher doses of these drugs some animals failed to initiate sexual activities. There was an increase in the postejaculatory interval but no change in the ejaculatory latency.It is concluded that the prolonged ejaculation latencies observed following treatment with thioridazine or chlorimipramine is not due to a blockade of central or peripheral adrenergic α-receptors.

Specific involvement of central 5-HT1A receptors in the mediation of male rat ejaculatory behavior

The aminotetralin 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), pharmacologically characterized as a 5-HT1A receptor agonist, produces a pronounced decrease in ejaculation latency in the male rat. Stimulation of 5-HT receptors by a pharmacologically induced increase in the synaptic availability of 5-HT has been shown to produce the opposite effect. The 8-OH-DPAT-induced decrease in ejaculation latency is specific for this compound, and some chemically related ergot derivatives. In this paper we review the evidence in support for stimulation of serotonergic auto-receptors of the 5-HT1A receptor subtype as a mechanism of action for effects by 8-OH-DPAT on male rat ejaculatory behavior. We also present the questions posed by the fact that quinpirole and lisuride both produce 8-OH-DPAT-like effects on male rat ejaculatory behavior. The effects by quinpirole, lisuride or 8-OH-DPAT are not sensitive to pretreatment with the DA D2/3 receptor antagonist raclopride. Continued studies will show whether the effects of quinpirole and lisuride can be related to stimulation of 5-HT1A receptors, or if all these compounds have as yet undefined common properties.

Experience and Maturation in the Development of Sexual Behaviour in Male Puberty Rat

[The sexual activity of male rats which had not been engaged in heterosexual activity was compared with that of others having a certain amount of sexual experience. The development of the pattern of behaviour in the later group was followed from 105 days of age to 138. It was found that: 1. Continuous changes in the sexual behaviour occurred, the frequency of ejaculations per hour increased, the number of intromissions before ejaculation decreased, the duration of the series of copulations preceding an ejaculation was shortened and the post-ejaculatory latency was shortened. 2. Comparing experienced with non-experienced rats of the same age it became evident that learning intervened only determining the lengths of the post-ejaculatory latencies the other components being unaffected. It is concluded that individual experience affects the length of the post-ejaculatory latency, other changes appearing in the pattern of behaviour with increasing age dependent on maturing processes in the biological organism., The sexual activity of male rats which had not been engaged in heterosexual activity was compared with that of others having a certain amount of sexual experience. The development of the pattern of behaviour in the later group was followed from 105 days of age to 138. It was found that: 1. Continuous changes in the sexual behaviour occurred, the frequency of ejaculations per hour increased, the number of intromissions before ejaculation decreased, the duration of the series of copulations preceding an ejaculation was shortened and the post-ejaculatory latency was shortened. 2. Comparing experienced with non-experienced rats of the same age it became evident that learning intervened only determining the lengths of the post-ejaculatory latencies the other components being unaffected. It is concluded that individual experience affects the length of the post-ejaculatory latency, other changes appearing in the pattern of behaviour with increasing age dependent on maturing processes in the biological organism.]

Excitatory effects of intromission in mating behaviour of the male rat.

The effects of one or several intromissions on the appearance of a following series of copulations was studied when intervals of different lengths separated the series from the preceding intromission(s). It was found that: 1. When the isolated intromission was separated from the following series by intervals of 20, 40, 60, 120, 240 and 360 minutes, the intromission was seen to affect the series up to and including 120 minutes after is occurrence. 2. An additional number of 5, 8, 15 or 25 intromissions separated by intervals of twenty minutes raised the excitation level until a certain point. This was reached after between 5 and 8 intromissions. In one exceptional case the ejaculatory threshold was exceeded and the animal ejaculated after 26 intromissions. In the other cases ejaculation only appeared when the animal was allowed an additional number of intromissions separated by 90 second intervals. 3. Five intromissions separated by 20 minute periods raised the degree of excitation above the level attained by five intromissions separated by 60 minutes. 4. The results were interpreted as indicating an accumulation and reduction of the excitatory effects created by the intromissions.

Lordosis behavior in male rats treated with estrogen in combination with tetrabenazine and nialamide

Injection of 10 mg/kg tetrabenazine in castrated male rats, treated with daily injections of 50 μg/kg estradiol benzoate, resulted in lordosis behavior in the majority of the animals. Nialamide (50 mg/kg) antagonized the effect of tetrabenazine. It was suggested that the occurrence of the lordosis pattern in estrogen pretreated rats is related to levels of monoamines.

Abnormally fast vibrissa movements induced by tetrabenazine in rats.

During exploratory behavior, rats normally display large amplitude, sweeping movements of the vibrissae in regular rhythm of about 7 sweeps per second. Tetrabenazine (a monoamine depleting agent), in a dosage of 10 mg/kg, induced abnormal high frequency, low amplitude movements (“buzzing”) in the vibrissae. This behavioral effect was quantified by high-speed motion picture analysis.