Search PubMed⌕ Search

Biomedical subjects

S Ahlenius

Publications and source records attributed to S Ahlenius.

At least 145 records · Page 8Linked to original sources
PubMed1979

Effects of locally applied dopamine to the nucleus accumbens on the motor activity of normal rats and following alpha-methyltyrosine or reserpine.

The motor activity of rats was investigated following bilateral application of various doses (0--80 micrograms) of dopamine to the nucleus accumbens. A high dose (80 micrograms) of dopamine increased the motor activity of normal as well as alpha-methyltyrosine- and reserpine-treated rats. It also increased the late motor activity (6--9 min) of normal rats, probably due to stimulation of postsynaptic dopamine receptors. Lower doses (10--40 micrograms) of dopamine suppressed initial (0--3 min) motor activity of normal rats, perhaps due to stimulation of dopamine autoreceptors on the dopamine nerve terminals in the nucleus accumbens with a subsequent inhibition of dopamine neurotransmission. An intermediate dose (40 micrograms) of dopamine was able to restore the motor activity of alpha-methyltyrosine-treated but not of reserpine-treated rats at all time intervals. This difference, indicating a restoration of the normal pattern of habituation by dopamine only in animals pretreated with alpha-methyltyrosine, suggests that normal behaviour is dependent on release of dopamine by nerve impulses.

Animals↗
PubMed1979

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 inhibitory of peripheral 5-HTP decarboxylase (benserazide, 25 mg/kg) produced, like chlorimipramine and thioridazine, a prolongation of ejactulation 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 not change in the ejaculatory latency. It is concluded tha the prolonged ejaculation latencies observed following treatment with thioridazine or chlorimipramine is not due to a blockade of central or peripheral adrenergic alpha-receptors.

5-Hydroxytryptophan↗
PubMed1979

Effects of gonadectomy and hormone replacement on brain monoamine synthesis in male rats.

The synthesis of catecholamines and serotonin in the brains of castrated male rats was analyzed at either various times after castration or at various ages. It was found that (a) castration of rats at 50 days or later causes an increase in brain monoamine synthesis, and (b) this phenomenon was not observed until 20 days after castration. The increase in brain monoamine synthesis following castration was counteracted by treatment with testosterone, thus relating the biochemical consequences of castration with changed hormonal conditions of the animal. It is suggested that testosterone exerts an inhibitory influence on monoamine synthesis.

5-Hydroxytryptophan↗
PubMed1978

The effect of lithium on amphetamine-induced locomotor stimulation.

A behavioural study was performed to investigate how lithium interacts with monoamine mechanisms. Acute lithium pretreatment partially antagonized amphetamine-induced locomotor stimulation in mice. A rather small dose of L-dopa, which had no stimulant effect on locomotor activity of its own, caused a dose-dependent antagonism of the lithium-induced suppression of the amphetamine-induced locomotor stimulation. Additionally, acute lithium pretreatment had no effect on the apomorphine-clonidine-induced locomotor stimulation after elimination of presynaptic activity by means of pretreatment with reserpine and alpha-MT. Our interpretation of these results is that the inhibitory effect on amphetamine-induced locomotor stimulation is likely to be mediated via presynaptic mechanisms (i.e., decreased release of catecholamines or inhibition of catecholamine synthesis or a combination of both mechanisms) and, further, lithium seems to have no effect at or beyond the catecholamine receptors. However, the possibility that lithium may increase the activity in neuronal systems antagonizing the catecholamine neurons cannot be excluded.

Amphetamine↗
PubMed1977

The effect of chronic ethanol treatment on behaviour and central monoamines in the rat.

Rats weaned at 16 days of age were treated with various ethanol concentrations (8--24% w/v) for 270 days. The effect of the chronic ethanol treatment on the growth rate, the diurnal pattern of drinking, the open field activity, and the conditioned avoidance acquisition and retention of the rats were studied. Termination of the chronic ethanol administration caused two types of withdrawal syndromes. The first, an acute withdrawal syndrome was observed within 12 h after the discontinuation of the ethanol treatment and was characterized by extreme hyperexcitability. The second, a delayed withdrawal syndrome was characterized by a more coordinated behavioural stimulation and developed first after about 3 days after the discontinuation of the ethanol treatment. Biochemically, the latter withdrawal syndrome was accompanied by an increased rate of tyrosine hydroxylation (measured as the accumulation of dopa after inhibition of aromatic amino acid decarboxylase) in the striatum and dopamine-rich limbic structures. No differences in the accumulation of 5-hydroxytryptophan were observed. Furthermore, there was an increased level of dopamine concomitant with a decreased level of noradrenaline in the limbic areas during ongoing ethanol treatment. On the 4th day after withdrawal of ethanol the endogenous levels of dopamine and noradrenaline were statistically significantly reduced in the limbic structures. The data of the present study indicate that chronic ethanol administration induces various kinds of behavioural changes and that these changes at least partially are mediated via central catecholamine mechanisms.

Animals↗
PubMed1977

Antagonism by locally applied dopamine into the nucleus accumbens or the corpus striatum of alpha-methyltyrosine-induced disruption of conditioned avoidance behaviour.

Male Sprague-Dawley rats were trained to avoid an electric shock in a two-way shuttle-box. The local application of dopamine into the nucleus accumbens or the corpus striatum was found to antagonize the suppression of conditioned avoidance behaviour induced by systemically administered alpha-methyltyrosine, emphasizing the importance of these dopamine-rich brain structures in mediating conditioned avoidance behaviour.

Animals↗
PubMed1977

Open field behavior and gross motor development in offspring of nursing rat mothers given penfluridol.

Nursing rat mothers were injected with penfluridol, a dopamine receptor blocking agent, at Day 1, 3, 5 and 7 after delivery, and their offspring were investigated at 6-18 days of age for various aspects of motor behavior development, and at 4, 8 and 12 weeks of age for open field behavior. No deficits were found in the development of locomotion, air righting, startle response and eye opening. Open field ambulation decreased from an abnormally high level at 4 weeks of age to an abnormally low level at 8 and 12 weeks of age. The ability to habituate to an open field decreased from a normal level at 4 weeks of age to an abnormally low level after 8 weeks of age. The behavior deficits were related to a decreased functional activity of the mesolimbic dopamine neuron system, and the possible relation to a clinical dysfunction among children - minimal brain dysfunction - was discussed.

Age Factors↗
PubMed1977

The effect of amphetamine and L-dopa on tetrabenazine-induced suppression of intracranial self-stimulation in the rat.

The administration of d-amphetamine sulphate resulted in a restoration of intracranial self-stimulation (ICSS) suppressed by tetrabenazine (TBZ). A dose-dependent increase in the rate of ICSS was seen after L-dopa in animals pretreated with TBZ. d-Amhetamine is believed to act by facilitating the nerve-impulse induced release of central catecholamines (CA) whereas the blockage of the granular uptake-storage mechanism by TBZ will prevent the storage of CA formed from the administrated L-dopa and thereby interfere with their release by nerve-impulses. Thus, in the latter case, an activation of central CA receptors in all probability will be due to a dose-dependent diffusion of CA from nerve terminals. It is suggested that the failure to completely antagonize the TBZ-induced suppression of behaviour by L-dopa is due to the fact that a direct activation, independent of the nerve-impulse flow, of central CA receptors easily results in an overstimulation and a reduced specificity in behaviour.

Amphetamine↗
PubMed1977

Potentiation by alpha-methyltyrosine of the suppression of food-reinforced lever-pressing behaviour induced by antipsychotic drugs.

The mode of action whereby alpha-methyltyrosine (alpha-MT) potentiates the behavioural effects induced by catecholamine receptor blocking antipsychotic drugs was investigated in rats trained to lever-press for food on a fixed-ratio 40 schedule of reinforcement. It was found that alpha-MT (20 mg/kg intraperitoneally - 4 hrs potentiates the effects induced by pimace, causing an alteration of the neuronal function.

Animals↗
PubMed1976

Ontogenetic development of locomotor activity and rate of tyrosine hydroxylation.

A combined biochemical and behavioral study was performed postnatally on albino rats. An almost linear increase in total motor activity was observed from 1 to 15 days of age followed by a pronounced decrease in motor activity between days 15 and 18. The in vivo rate of tyrosine hydroxylase activity in whole brain was estimated by means of measuring accumulation of L-3,4-dihydroxyphenylalanine (Dopa) after administration of an inhibitor of aromatic amino acid decarboxylase NSD 1015. Additionally, Dopa accumulation was studied in regional brain areas in 10 and 14-day-old animals. A slight gradual increase in the amount of Dopa accumulation in whole brain was observed from 1 to 10 days of age, followed by a pronounced increase between 10 and 14 days. Regional studies revealed that the increase in Dopa accumulation was primarily located to striatum. The data suggest an involvement of central catecholamine neurons possibly dopaminergic, terminating in striatum. The decrease in motor activity observed after 15 days of age is interpreted as involvement of maturing inhibitory pathways of noncatecholaminergic origin.

Animals↗
PubMed1976

Normalization by antipsychotic drugs of biochemically induced abnormal behavior in rats.

Male rats were trained to perform a conditioned avoidance response combined with a successive discrimination in a modified shuttle box. The administration of L-Dopa, 100 mg/kg i.p., after inhibition of peripheral aromatic amino acid decarboxylase, or apomorphine, 2 mg/kg i.p., was found to disrupt the discriminative but not the avoidance behavior. The dopamine receptor antagonist pimozide (0.5 mg/kg i.p.), but not the noradrenaline receptor antagonist phenoxybenzamine (10 or 20 mg/kg i.p.) completely antagonized the L-Dopa-induced abnormal behavior, indicating sn involvement of central dopamine mechanisms. The present data show that antipsychotic drugs not only inhibit behavior but can also improve behavior in animals with a disturbed function.

Animals↗
PubMed1976

Stimulation of mounting behavior but not lordosis behavior in ovariectomized female rats by p-chlorophenylalanine.

Treatment with 126 mg/kg of the 5-hydroxytryptamine synthesis inhibitor p-chlorophenylalanine (PCPA) for 3 days or daily treatment with 40 mg/kg of PCPA stimulated the display of mounting behavior, including ejaculatory patterns, by ovariactomized hormonally untreated female rats. PCPA treatment failed to induce lordosis behavior and did not affect the induction of lordosis behavior by daily injections of 2.0 mug/kg estradiol benzoate. These results show that mounting and lordosis behavior can be dissociated and it is suggested that these two sexual behavior patterns may be regulated by different neurotransmission mechanisms.

Animals↗
PubMed1975

Antagonism by d-amphetamine of learning deficits in rats induced by exposure to antipsychotic drugs during early postnatal life.

The acquisition of a conditioned avoidance response (CAR) was investigated in rats of nursing mothers given pimozide 0.5 mg/kg on days 1, 2, 3, 4, 5, 6, and 7 after delivery. Four weeks after birth, the male litter-mates were tested for CAR acquisition in a two-way avoidance situation or for correct CAR acquisition in a brightness discrimination situation. Offspring of mothers treated with pimozide were markedly inferior in the CAR acquisition in both behavioural situations as compared to those of mothers given glucose. The administration of d-amphetamine 15 min prior to the training session specifically counteracted the behavioural impairment obtained in the offspring of pimozide-treated mothers. The results obtained in the present investigation lend further support to the contention that the behavioural deficits in offspring of nursing mothers treated with neuroleptic agents are due to a developmental disturbance in central catecholamine neurones.

Animals↗
PubMed1975

Antagonism by haloperidol of the L-DOPA-induced disruption of a successive discrimination in the rat.

Male rats were trained to perform a conditioned avoidance response combined with a successive discrimination in a shuttle-box. The administration of L-DOPA, 100 mg/kg i.p., after inhibition of peripheral dopa decarboxylase, disrupts the discrimination but not the acoidance behaviour, whereas the administration of the antipsychotic agent haloperidol (HPD), 0.125 mg/kg i.p., disrupts the avoidance behaviour but not the discrimination. The L-DOPA-induced disruption of the successive discrimination was completely antagonized by 0.25 mg/kg of HPD. The present data show that administration of the antipsychotic agent HPD not only inhibits behaviour but also can improve the behaviour in animals with a disturbed function.

Animals↗
PubMed1975

Antagonism by baclophen of the d-amphetamine-induced disruption of a successive discrimination in the rat.

Male rats were trained to performa conditioned avoidance response combined with a successive discrimination in a shuttle-box. The administration of -amphetamine, 4 mg/kg i.p., caused a disruption of the discriminative but not thee avoidance behavior. Baclophen (beta-[-4-clorophenyl]-psi-aminobutyric acid), a GBA-derivative, given in a dose (4 mg/kg i.p.) that had no effect per se on the behavior in this test situation antagonized the -amphetamine-induced hypermotility. The present findins that baclophen antagonized a biochemically induced abnormal behaviour point to an "antipsychotic" action of baclophen in a successive discrimination avoidance test.

Aminobutyrates↗