Effects of hypothalamic and amygdaloid stimulation on reaching behaviour in the rat

Thirty adult rats were trained in a reaching behaviour schedule, after which bipolar steel electrodes were bilaterally implanted into the ventromedial hypothalamus (VMH), lateral hypothalamic area (LHA) or basolateral amygdala (BLA). On subsequent training sessions, these structures were electrically stimulated employing a movement-synchronized stimulation design. The results show that VMH stimulation produces aversive effects: the animals go away from the feeder after the first stimulus. Reaching impairment resulting from LHA or BLA stimulation mainly affected the grasping phase; additionally, repetition of movement sequence was observed. The results are discussed in the framework of Kornhuber's concept of preprogrammed ballistic movements.     

Epinephrine-independent production of hyperuricemia by means of hypothalamic stimulation in the conscious rat

The electrical stimulation of the ventromedial hypothalamus with 0.6 mA current produced an acute hyperuricemia associated with a rise in plasma allantoin in the conscious rat. Adrenal demedullation did not depress the hyperuricemic response. Even after the demedullation, neither propranolol nor phentolamine had any significant effects as well. These results indicate that endogeneous catecholamines are not involved in the production of the hyperuricemia; this is in sharp contrast with our previous result demonstrating the development of hyperuricemia via adrenal epinephrine by stimulating the ventromedial nucleus with 0.2 mA current. It is concluded therefore that ventromedial hypothalamic stimulation is capable of producing two different types of hyperuricemia, i.e. adrenal-epinephrine-dependent and epinephrine-independent, by varying the intensity of the stimulation current.     

Modifications of neuronal activity in the rat hypothalamic supraoptic nucleus after long-lasting vibrational stimulation

We analyzed the background impulse activity (BIA) generated by neurons of the rat hypothalamic supraoptic nucleus in the norm and under conditions of long-lasting vibrational stimulation (exposure 5, 10, or 15 days). Distributions of neurons by the level of regularity, dynamics of discharge trains, form of histograms of interspike intervals (ISIs), as well as distributions of neurons by the BIA frequency ranges, were studied. We also calculated the mean frequency of impulsation of the neurons under study and the coefficient of variation of ISIs. After vibrational influences, we found modifications of both the internal structure of the recorded spike trains and the mean frequency of impulsation within the entire studied group and different frequency subgroups. Neirofiziologiya/Neurophysiology, Vol. 38, No. 3, pp. 224–230, May–June, 2006.     

Elimination of vasopressin analgesia following lesions placed in the rat hypothalamic paraventricular nucleus

Pain thresholds are increased following central administration of arginine vasopressin (AVP), an effect which appears not to be mediated through opioid analgesic processes. In addition to magnocellular projections to the posterior lobe of the pituitary gland and parvocellular projections to the zona externa of the median eminence, the paraventricular nucleus (PVN) of the hypothalamus contains VP parvocellular neurons which also project to extrahypothalamic structures involved in pain inhibition. The present study examined whether AVP analgesia as measured by the tail-flick test was altered in animals with lesions placed in the PVN at either 7 or 35 days after surgery. VP levels in the pons-medulla and the lumbo-sacral spinal cord were measured by radioimmunoassay, as well as VP-like immunoreactivity in the PVN and spinal cord with immunocytochemistry. Lesions placed in the PVN eliminated AVP analgesia on the tail-flick test at both 7 and 35 days after surgery, and decreased radioimmunoassayable VP by 59% in the lumbo-sacral spinal cord and 36% in the pons-medulla. The extent of the lesions ranged from complete destruction of the PVN to partial sparing of ventro-medial PVN cells with VP-like immunoreactivity. These data indicate that the PVN is a critical structure for the integrity of AVP analgesia.     

Adrenomedullary hormonal stimulation and hyperglycemia following intermale aggression in the bandicoot rat

The aim of the present investigation is to evaluate adrenomedullary hormones and blood glucose responses to intermale aggression in the bandicoot rat. Aggression elicited a rise in adrenaline and noradrenaline content of the adrenal gland and in blood glucose level in the subordinate rats. No significant change was marked in the dominant rats after aggression. It is suggested that during aggression the subordinate rats suffered from psychosomatic stress that resulted in hyperactivity of the adrenal medulla and consequently hyperglycemia.     

Content and turnover of gangliosides in rat brain following behavioural stimulation

Abstract— Rats were placed in a tank of deep water to swim until they learned to escape (Group E) or were lifted out (Group F). Controls (Group C) were left in their home cages. Specific radioactivities of purified gangliosides, other glycolipids and nonlipid carbohydrates were measured at 9 and 24 h after intracranial injection of D-[1-¹⁴C]glucosamine and the subsequent swimming trials. Nonspecific effects of behavioural stimulation (similar changes in Groups E and F) included decreased net incorporation of radioactivity into monosialogangliosides and nonganglioside carbohydrates, a relative increase in content of G_T1 gangliosides and decreased content of G_T1 gangliosides. Specific effects (different changes in Groupe E and F) included in Group E decreased net uptake of radioactivity into disialogangliosides. These results demonstrate that in rat brain: (1) ganglioside metabolism is affected by behavioural stimulation; (2) metabolism of other heteropolysaccharides is also affected; and (3) some biochemical changes are consequences of nonspecific stimulation whereas others are associated with specific elements of experience.