Brain areas activated after ejaculation in healthy young human subjects.

Brain mechanisms for the refractory period that characteristically follows ejaculation in animals and human are poorly understood. The possibility of active inhibition of brain areas being responsible for the post-ejaculatory inhibitory state has not been ruled out. Using Blood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) we have mapped brain areas in healthy young volunteers immediately after ejaculation. Functional imaging of the brain for 30 minutes beginning after three minutes of ejaculation induced by masturbation showed spatio-temporal activation in amygdala, temporal lobes and septal areas. The septal areas were observed to be active for a shorter duration than the amygdala and the temporal lobe. Thus the temporal sequence of involvement of the above neural structures may contribute to temporary inhibition of sexual arousal/penile erection during the post-ejaculatory refractory period in humans.

Gating of the dorsal penile nerve inputs by norepinephrine at the medial preoptic area in rats.

The medial preoptic area neurons related to male sexual behaviour in rats were identified by their responses to dorsal penile nerve stimulation. These neurons were further tested with norepinephrine applied iontophoretically. From the 21 medial preoptic area neurons recorded in urethane anaesthetized rats, 17 neurons responded to dorsal penile nerve stimulation. Excitatory and inhibitory responses were found in almost equal number of neurons. 14 neurons responded to norepinephrine application, out of which six neurons were excited and eight were inhibited. The direction of changes produced by dorsal penile nerve stimulation and norepinephrine application were similar in 10 neurons. The results suggest that the sensory inputs from the genitalia are possibly gated by norepinephrine at the level of the medial preoptic area. Afferent information from the genitalia carried by dorsal penile nerve and the availability of norepinephrine at the level of the medial preoptic area probably help in maintaining adequate level of sexual arousal.

Atenolol or butoxamine injection at the lateral septum doesn't inhibit male sexual behavior in rats.

To investigate the role of specific adrenoreceptors subtypes on sexual behavior, atenolol, butoxamine, a mixture of atenolol and butoxamine, and saline (vehicle) were injected into the lateral septum in four different groups of sexually active male rats. Application of a mixture of atenolol and butoxamine produced inhibition of copulatory activity. On the other hand, application of either atenolol or butoxamine alone did not inhibit copulatory activity. But it produced stimulation of some of the components of male sexual behavior. Inability of either atenolol or butoxamine to inhibit the male sexual behavior, and inhibition of the same by the mixture of atenolol and butoxamine, indicate that both beta-adrenoreceptors at the lateral septum are involved in the elaboration of male sexual behavior. Stimulation of some components of sexual behavior on application of atenolol or butoxamine could be attributed to an unbalanced activity of beta-adrenoreceptors.

Role of the medial preoptic area in thermal preference of rats.

This study was conducted to find out whether the medial preoptic area (mPOA) plays a role in the selection of ambient temperature by rats. Adult male Wistar rats were kept in an environmental chamber having three interconnected compartments, maintained at three different temperatures (18 degrees, 24 degrees and 30 degrees C) in which the animals could move freely from one compartment to the other. Normal rats preferred to stay at the chamber maintained at 24 degrees C for most of the time, during day and night. The temperature preference shifted to 30 degrees C after the mPOA of these rats had been lesioned by local administration of 5 micrograms of N-methyl D-aspartic acid (NMDA) in 0.2 microliter distilled water. The results of the study suggest that the mPOA acts as a fine tuning center for homeostatic regulation of thermal balance, including selection of appropriate thermal environment. It is proposed that after the mPOA lesion, the animal cannot assess properly the energy status of the body and thereby prefers a higher ambient temperature.

Micropropagation of Paulownia fortuneii through in vitro axillary shoot proliferation.

Primary cultures were established with nodal segments from juvenile shoots of two- year-old Paulownia fortuneii trees from a clonal plantation in Andhra Pradesh. A medium containing half-strength MS salts + RAP (1 mg/L) + sucrose (2%) produced optimum bud break in nodal explants. The same basal medium with reduced hormone level (0.5 mg/L) supported maximum multiplication of secondary cultures of P. fortuneii (1:6 in 6 weeks). Specific treatments were tested to enhance this rate of multiplication. In one approach, five to six week old in vitro grown shoots were ratooned (cutting the main shoot at the bottom leaving one node). The stumps (ratooned basal node) produced 2 to 3 axillary shoots, which grew into 4 to 5 nodes by 3 weeks; thus, providing additional shoots from the same explant. This provided 30% additional shoots in 4 cycles. Secondly, reducing the light intensity to 1200 lux resulted in higher shoot elongation, i.e, formation of 8 nodes in 5 weeks with healthier shoots than the normal intensity of 3000 lux under which only 6 nodes were produced in 6 weeks. In vitro-grown shoots could be successfully rooted ex vitro in vermiculite + cocopeat mixture (1:1 v/v) under 90% humidity, transferred to soil in polybags for hardening in the green house for 2 weeks and shifted to shade net for further hardening. After one month, the plants could be successfully transplanted to field with 95% survival. Micropropagated plants showed an excellent growth in the field attaining a height of 1.5 m and a collar diameter of 2.8 cm in 3 months.

Neural regulation of glucose homeostasis.

The regulation of blood glucose is generally stated to be under the control of the endocrine system. But the endocrine secretion is itself regulated by the central nervous system, especially the hypothalamus. The brain can sense the energy status of the body by using neural afferent signals and metabolic cues such as glucose. A variety of experimental evidences have been put forth to support the postulate that there are "glucoreceptors", sensitive to blood glucose and glucose utilization, in the hypothalamus. Gastrointestinal afferents, which carry information about the energy intake, reach the hypothalamic regions and interact with the glucose sensitive mechanisms. Available evidence suggests that obesity and decreased body weight, resulting from lesions of the hypothalamic 'satiety' and 'feeding' centres respectively, are not only due to altered food intake, but also to derangement in glucose homeostasis. The medial preoptic area does the fine tuning of energy balance (regulation of food intake) in response to alterations in the temperature, locomotor activity and sleep wakefulness. Thus the hypothalamus regulates energy balance through its control of energy intake on the one hand, and its expenditure and storage on the other. Neuroendocrine system and autonomic nervous system deal with storage and expenditure of energy.

Toxic effect of systemic administration of low doses of the plasticizer di-(2-ethyl hexyl) phthalate [DEHP] in rats.

DEHP [di-(2 ethyl hexyl) phthalate], a widely used plasticizer in blood storage bags, leaches out in appreciable amounts into blood (about 10 mg/100 ml) resulting in exposure of recipients of blood transfusion to this compound. Various reports indicate the toxicity of DEHP, particularly in liver and reproductive organs but all these studies used large doses (up to 2 g or more/Kg body weight) and oral route of administration which are not relevant to the intravenous administration during blood transfusion or the low amounts present in blood. We have studied changes in the activity of some important enzymes-gamma-GT, ALT, CPK, LDH, alkaline phosphatase, acid phosphatase, beta-glucuronidase and few other parameters like vitamin E, glutathione, serum albumin etc in rats administered low doses of DEHP (corresponding to transfusion of 2, 4, 6 and 10 units of blood). Histopathology of the organs has also been carried out. The results obtained indicate no serious toxic effects for DEHP at the level present in blood stored in DEHP plasticized blood bags as evidenced by the lack of any significant alteration in most of the biochemical parameters studied. Even in those cases where there was alteration (for e.g., decrease in the level of vitamin E) 24 hr after administration of DEHP, it returned to near normal level with in 72 hr to 7 days. No histopathological changes were observed in any of the organs at these levels of DEHP. It is concluded that DEHP did not cause any serious toxic effect even at doses corresponding to transfusion of several units of blood in a recipient.

Effect of application of gamma amino butyric acid at the medial preoptic area on sleep-wakefulness.

Intracerebral microinjections of gamma amino butyric acid were given bilaterally at the medial preoptic area (mPOA) to determine the possible role of this neurotransmitter in the genesis and regulation of sleep-wakefulness. GABA (50 micrograms/0.2 microliters) when administered through chronically implanted cannulae in free moving rats, did not produce any significant alterations in sleep-wakefulness. This may be attributed either to the non-involvement of GABA at the level of mPOA in the regulation of sleep, or to other factors like the low dose and rapid breakdown of the injected drug.

Effect of carbachol injection in the medial preoptic area on sleep-wakefulness and body temperature in free moving rats.

The aim of the present study was to find out the changes in sleep-wakefulness and body temperature brought about by application of cholinergic agonist, carbachol, in the medial preoptic area (mPOA). Carbachol, when injected bilaterally into the mPOA of male rats, through chronically implanted cannulae, produced a fall in rectal temperature and long lasting arousal. There was temporal dissociation in the duration of changes produced in the two parameters. It is suggested that the cholinergic system at the medial preoptic area brings about arousal response and fall in body temperature through different circuits.

A computer programme for recording male sex behaviour in rats.

An accurate method of recording the frequencies of copulatory events, the latencies of initiation to copulation and the time spent in different behavioural categories is described. A microcomputer (IBM-PC) based data collection system for acquisition and analysis of male rodent sex behaviour has been developed. This software features ease of data entry and operation, using single key presses by assigning a preset code to each. Internal clock of the computer is made to function as a timer for accurate recording of latencies and intervals. A print out of the frequency or duration of data can be obtained either concurrently or after the completion of the experiment, as required. The least count of the technique is about 10(-4) min and this precludes its use for extremely rapidly changing behaviour.

Effect of rapid eye movement sleep deprivation on sexual behaviour of male rats.

Rapid eye movement sleep deprivation for 3 to 4 days by the platform pedestal procedure produced an increase in sexual behaviour of male rats. The possible factors contributing towards the increase in sexual behaviour are discussed.

REM sleep deprivation and food intake.

The effect of REM-sleep deprivation (REM-SD) on diet preference was studied in rats. REM-SD for a period of 72 hrs produced an increase in day, night and 24 hrs (day plus night) intakes of Carbohydrate Rich diet (CRD) and Total diet (TD). Body weight (BWt) was also increased. The maximum increase in the above parameters were recorded on the 2nd day of REM-SD. During recovery period the intakes of TD fully recovered, but the BWt and consumption of CRD remained high. Intakes of Balanced diet (BD) remained significantly on the lower side when compared to the pre REM-SD mean values. During REM-SD, the rats preferred CRD than BD. The body temperature did not show any change. The increase in TD intake and BWt could be the result of an increase in insulin level and the change appears to be mediated by the activation of hypothalamic feeding centre.

Thermal changes produced by norepinephrine application in the preoptic area of monkeys.

The effect of injection of norepinephrine in the anterior regions of hypothalamus on rectal temperature, skin temperature, heart rate and respiratory rate in rhesus monkeys was studied. The injection of 2 micrograms of norepinephrine in the preoptic area produced a fall in body temperature without any accompanying change in skin temperature, heart rate and respiratory rate. The findings suggest that the suppression of heat production may be responsible for the norepinephrine induced hypothermia in monkeys.

Correlation of preoptic neuronal activity with spontaneous and induced cortical EEG changes.

Preoptic area has neurons which change their firing rate along with spontaneous alterations of the cortical EEG between synchronization and desynchronization. The cortical EEG synchronization and desynchronization could be induced by stimulation of the caudal and the rostral brain stem respectively. This study was aimed at finding out whether stimulation of the brain stem structures produce the same change in the unit activity as that occurring during spontaneous alteration of the EEG. The changes in unit activity showed some concordance and dissociation between spontaneous and induced EEG alterations. The possible interaction of inputs from cortex and brain stem at the level of the preoptic area is discussed.