Obesity and increased growth following partial or complete isolation of ventromedial hypothalamus

Physiology and Behavior, Vol. 7, pp. 187-194. Pergamon Prtss, 1971. Printed in Great Britain

Obesity and Increased Growth Following Partial or Complete Isolation of Ventromedial Hypothalamus' Y. P A L K A ~, R. A. L I E B E L T A N D V. C R I T C H L O W

Department of Anatomy, Baylor College of Medicine, Houston, Texas 77025, U.S.A. (Received 25 June 1970) PALKA, Y., R. A. LIEBELTAND V. CR1TCHLOW. Obesity and increasedgrowthfollowing partial or complete isolation of ventromedial hypothalamus. Pro'reeL. BEVL~V.7 (2) 187-194, 1971.--Two series of adult female rats were studied for

approximately 6 months following partial or complete surgical isolation of the ventromedial (VM) region of the hypothalamus from adjacent brain. Complete, anterior, and horizontal hypothalamic cuts produced high incidences of marked weight gain, obesity, hyperphagia, and visceral and somatic growth. The most pronounced effects were associated with cuts that reached the ventral surface of the brain bilaterally along the lateral border oftbe rostral half of the ventromedial nuclei or which extended laterally to the brain surface in a horizontal plane that bisected these nuclei. In the series in which body length was measured, 11 of 19 obese rats showed evidence of significant somatic growth, and some had nose-anal lengths 3-4 cm longer than controls. These results are compatible with the view that the VM region inhibits feeding behavior via connections to the lateral hypothalamus. In addition, these data suggest the presence of growth-promoting elements in the VM area which are subject to inhibition by connections from other brain structures. Feeding behavior

Hyperphagia

Ventromedial nucleus

THE VENTROMEDIAL(VM) region of the hypothalamus has long been implicated in a satiety mechanism which inhibits feeding behavior. Results from several experimental approaches support the general view that fiber connections to the lateral hypothalamus mediate this inhibitory influence [16, 29, 33, 34]. The present report describes the effects of completely or partially isolating the VM region from surrounding brain with modifications of the brain knife of Hal/tsz and Pupp [20] The principal aim of these experiments was to examine the effects of such isolation on certain neuroendocrine mechanisms. However, in addition to producing endocrine deficits, reported elsewhere [30], the several surgical lesions used resulted in high incidence of hyperphagia, obesity, and increased growth. The effects on food intake and body weight showed considerable variation, and these variations appeared correlated with location and extent of brain cuts. Several recent papers also describe increased body weight and/or food intake following similar ablative procedures [1, 13, 24, 32]. However, to our knowledge, this is the first report associating increases in body length with hypothalamic lesions. MATERIALS AND METHOD

These experiments involved two series (I and II) of adult female rats (Charles River, CD) studied approximately 6 months apart. A modification of the Hal/tsz-Pupp knife [20]

Growth

Obesity

Hypothalamus

was used for most of the surgical lesions and its shape and dimensions are shown in Fig. 1A. This knife was formed from 28 gauge stainless steel tubing and was inserted inside a 22 gauge guide tube. The knife was inserted at an angle of l0 ° posterior to the vertical plane with the rat positioned according to the DeGroot atlas [8]; the knife was lowered through midline to the base of the brain with the tip facing anteriorly. In Series I, the knife was rotated 360° in 12 rats to isolate the VM region completely (complete cuts); in 12 rats the knife was rotated 90° to each side of midline to produce anterior cuts. Eleven rats served as sham-operated controls and 12 were used as intact controls. Sham-operation consisted of lowering the knife to the base of the brain without rotation. The dimensions of the knife were such that rotation through 360° produced an island of isolated hypothalamic tissue which extended from the posterior border of the optic chiasm to the premamillary region, and it extended laterally to the plane of the fornix. Series II consisted of 16 rats with complete cuts performed as described above, 9 intact controls, and 7 rats in which a small (1.5 mm long) horizontally-oriented knife (Fig. 1B) was rotated 360° through the VM area to produce horizontal cuts. Following surgery, rats were housed in individual cages under controlled lighting (fluorescent illumination, 04:0018:00) and temperature (26 + 2°C) and food and water were available ad lib. Body weights were recorded at 3-day

1This research was supported in part by NIH grants AM-03385 to V.C. and AM 0-1230 to R.A.L. Excellent technical assistance was furnished by Jessie Kroning and Lucile Perkins. aPresent Address: Department of Biological Structure, School of Medicine, University of Washington, Seattle, Washington, 98105. 187

188

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intervals for the first 6 weeks and at weekly intervals thereafter. In Series I, daily food and water intake were measured for a 3-week period, 4-7 weeks post operatively. F o o d intake was measured by weighing food hoppers containing powdered Purina Lab Chow after allowing 3 days for adjustment to the powdered diet. Since the animals were used primarily for studies on hypothalamic control of adrenal function, they were subjected to periodic stresses and blood withdrawal performed at intervals of at least 14 days. The animals were autopsied approximately 6 months after surgery. In Series I the total weight of lipid in gonadal, inguinal, and perirenal fat depots was determined by the method described by McBurney et al. 1"27]. In Series II, nose-anal length and heart and kidney weights were used as indices of growth. Brains were removed, fixed in 1 0 ~ formalin, and frozen 50~ sections were stained with thionin. Brains were sectioned in the coronal plane and sagittal reconstructions prepared to visualize antero-posterior dimensions of the islands. Treatments were assigned and perfomed according to a completely randomized design. Analysis of variance and the multiple range test of Duncan [9] performed with the program of Sakiz [31] by the Common Research Computer Facility (supported by N I H grant RR-00254), were used to evaluate effects of treatments on groups. Because of potential heterogeneity of brain lesions within treatment groups, it was considered important to estimate the significance of responses of individual rats and to correlate these with the morphology

of their cuts. F o r this purpose, effects of treatments on individual animals were estimated by reference to controls; values for individual rats are considered exceptional if they differ from the mean of controls by more than two standard deviations (2 S.D.).

RESULTS

Body Weight In Series I, both complete and anterior cuts resulted in increased body weight (p < 0.01, Table 1A); 9 of 12 rats with complete cuts and 9 of 12 with anterior cuts had body weights that exceeded the mean of intact controls by more than 2 S.D. at autopsy (Fig. 2). There were, however, marked differences in terminal body weights. It appeared that the brain cuts produced several distinct populations of weight responses, and these responses were independent of whether the animals received anterior or complete brain cuts. These different patterns of weight gain offered an opportunity to analyze brain cuts on the basis of weight responses. Therefore, the animals are regrouped as in Table 1B and Fig. 3 on the basis of variations in terminal body weight. Eight rats are designated as demonstrating marked weight gain; this group weighed approximately 5110g 7-9 weeks following surgery and had terminal weights of 700-1000 g at autopsy. Five rats demonstrated moderate weight gain, attaining body weights of 500 g 14--16 weeks post-operatively and had final weights of approximately 625 g. Five rats had final body weights of approximately 430 g and are designated as demonstrating only

OBESITY AND GROWTH WITH HYPOTHALAMIC CUTS

189 TABLE 1

EFFECTS OF HYPOTHALAMICCUTS ON SOMATICAND METABOLICPARAMETERS,SERIES I

No. Rats

Body Weight (g)

Food Intake (g/day)

Water Intake (ml/day)

A. Treatment groups Intact Controls 12 321 i 5* 16.8 ± 0.7 Sham-operated 11 321 dz 11 20.4 ! 1.2t Complete Cuts 11 636 d= 73I" -Anterior Cuts 13 562 Jz 59~ -B. Rats with hypothalamic cuts grouped according to weight responses** No weight gain 6 359 ~ 4 -Slight weight gain 5 431 :~ 7 22.7 ~= 0.9 Moderate weight gain 5 624 d= 9 24.3 ~z 1.0 Marked weight gain 8 844 d= 45 33.5 d: 0.7

Lipid Content (g)

33.2 ± 2.0 37.6 dz 2.6 ---

6.75 ± 9.52 ± 43.8 ± 31.6 ±

0.57 0.78 8.55t 6.31t

-33.9 ~ 2.2 33.2 ± 1.9 51.9 ~ 2.2

13.16 ~ 17.09 + 39.28 + 64.72 +

1.58 1.94 3.60 6.60

*Mean i S.E. I"P < 0.01 vs. intact controls. **Because of grouping based on dependent variable, statistical analyses were not performed on B part of table.

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FIG. 2. Effects of complete and anterior cuts on body weights, Series I. Columns indicate group means and vertical bars signify standard errors. Black circles denote weights of individual rats. Interrupted horizontal lines mark 2 S.D. above and below the mean of controls.

slight weight gain. Six rats with brain cuts failed to demonstrate noticeable weight gain and weighed less than 400 g at autopsy. Both sham-operated and intact controls weighed approximately 320 g at autopsy. Table 2 and Fig. 4 summarize the effects of brain cuts on final body weights of animals in Series II; 13 of 16 rats with complete cuts weighed more than 700 g at the termination of the experiment and were thus comparable to the group of Series I which showed marked weight gain. Two rats with complete cuts showed less marked weight gain but differed from intact controls by more than 2 S.D. Only one rat with a complete cut failed to show a weight response. Two of the seven rats with horizontal cuts showed marked weight responses and had terminal body weights in excess of 1 kg; two additional rats with horizontal cuts weighed somewhat less but

had body weights which exceeded the mean of controls by more than 2 S.D. Two animals had body weights that were more than 2 S.D. below the mean of controls.

Food and Water Intake Food and water intakes of animals in Series I were measured during weeks 4-7 after surgery (Table 1). Rats showing marked weight gain had a daily food intake that was approximately twice that of controls. Food intake was also elevated in those demonstrating moderate and slight weight gain and in sham-operated animals. Water intake for all rats in Series I, except those with marked weight gain, was normal. Marked weight gain was associated with an increase in water intake, averaging 51.9 ml/day. Because of the limited number of metabolic cages available, food and water intake were not

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TABLE 2 EFFECTS OF HYPOTHALAMIC CUTS ON SOMATIC PARAMETERS, SERIE~ I [

Group

No. Rats

Body Weight (g)

Nose-Anal Length (cm)

Kidney Weight (mg)

Heart Weight (rag)

10 16 7

396 -t: 16" 788 ~ 43t 597 :}: 116~+

23.8 ~: 0.2 25.2 -[: 0.2,+ 24.2 _+_0.9

1011.7 -~ 42.6 1531.7 :k 129.6t 1282.1 ~ 121.6

996.2 ~ 32.5 1382.5 -1::67.5~" 1223.6 :~ 91.0

Controls Complete cuts Horizontal cuts * Mean ~ S.E. 'fp < 0.0l vs. controls. ++p < 0.05 vs. controls.

measured in experimental rats with normal body weights.

criterion, two rats with horizontal cuts were lighter and shorter than controls.

Lipid Content and Growth It was obvious from direct examination that the increased body weight in operated animals was accompanied by marked fat deposition. As shown in Table 1, increased body weight in rats with complete and anterior cuts was associated with increased lipid content in fat depots (p < 0.01). Table 2 summarizes the effects of complete and horizontal brain cuts on body and organ weights and nose-anal lengths in Series II. Body weights, nose-anal length, and kidney and heart weights in rats with complete cuts were greater than those of controls (p < 0.01). The relationship between effects of brain cuts on body weight and length in individual animals is presented in Fig. 4. The correlation coefficient for all of the data in Fig. 4 (r----- 0.947, p < 0.01) indicates a linear relationship between body weight and length regardless of whether or not brain lesions were imposed. Comparable correlation coefficients were found for the subpopulations presented in Fig. 4. Eight rats with complete cuts and 3 with horizontal cuts had nose-anal lengths and body weights that exceeded the means of controls by 2 S.D. Using the same

Brain Histology Figures 5A and B show photomicrographs of brain sections from rats from Series I and II, respectively, which became markedly obese following placement of complete cuts. In both brains, the anterior borders of the cuts wore immediately caudal to the optic chiasm. In the mid portion of the arcs, the cuts were adjacent to the lateral borders of the VM nuclei; caudally they traversed the mamillary recess. In most brains examined, as in both sections in Fig. 5, VM nuclei were visible within the islands approximately 6 months after surgery. Whereas the dorsal parts of glial scars produced by the cuts were easily visualized histologically, the ventral 0.1-0.2 m m extent of these scars was not always identifiable in all sections in all rats. Despite this qualification, cuts made by moving the knife through an arc of 360 ° or 180° are labeled for convem'ence as complete or anterior cuts, respectively. In some brains, deficiencies and difforences in completeness of cuts were obvious and, as discussed below, appeared to be correlated with differences in patterns of weight gain.

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191 The relationship between weight gained by rats in Series I and extent and placement of hypothalamic cuts is indicated in Fig 6. Of 8 animals showing marked weight gain, 5 had complete cuts that were slightly asymmetrical and which passed through the anterior poles of one V M nucleus unilaterally (Fig. 6A). Three of the heaviest and most obese rats had anterior cuts which extended along the lateral margin of only the rostral halves of each nucleus. Two types of hypothalamic cuts were associated with moderate weight gain (Fig. 6B): 3 complete cuts definitely failed to reach the ventral surface of the brain on one side and in two rats anterior cuts reached the lateral aspect of VM nuclei only on one side. Five rats that showed slight weight gain had anterior cuts which were less extensive than those described above or which were grossly asymmetrical (Fig. 6C). Six of the 24 rats with brain cuts in Series I showed normal weight gain. These rats had either unilateral cuts, anterior cuts which did not extend posteriorly to the plane of the VM nuclei, or as in one case, a complete island which included only posterior parts of the VM region within the island (Fig. 6D). In Series II, 13 of 16 rats with complete cuts showed marked weight gain. These 13 rats had cuts similar to those shown in Figs. 5 and 6A. The two operated rats which weighed less than 650 g but which exceeded the 2 S.D. criterion had cuts which did not reach the floor of the brain bilaterally. The one rat which failed to show weight response had a unilateral cut. Four of the seven rats with horizontal cuts had final body weights which were more than 2 S.D. greater than the mean of controls (Fig. 4). Two of these rats had terminal weights in excess of 1 kg, so that the effects of surgery in these animals were as extreme as any observed with complete or anterior cuts. The surgical scars in both of these extremely obese rats, one of which is shown in Fig. 7A, passed horizontally through the mid portion of the VM nuclei and reached the surface of the diencephalon laterally. Two rats with horizontal cuts showed less marked weight responses and in both cases the cuts passed in a plane between VM and arcuate nuclei; one of these cuts is shown in Fig. 7B. The cuts in the 3 rats with the lowest body weights were in the arcuate nucleus-median eminence zone; one of these cuts is shown in Fig. 7C. Consistent with the high correlation between nose-anal length and body weight in Series II, brain cuts associated with the most extreme increases in body weight and obesity were also associated with the greatest increases in body length. DISCUSSION

C

SLIGHI

WEIGHT

GAIN

D

NO WEIGHT

GAIN

FIG. 6. Relation between extent and location of cuts and pattern of weight gain. Oulines of cuts are superimposed on diagrams of the ventral surface of the hypothalamus. Numbers in parentheses indicate the number of animals with that particular cut.

It is clear from the present studies and those of others [I, 13, 24, 32] that hypothalamic cuts placed immediately lateral to the VM nuclei result in a high incidence of hyperphagia, weight gain, and obesity. In addition, the results reported here indicate that such cuts may produce augmented somatic growth. With respect to effects on body weight and obesity, the present findings suggest a relationship between the severity of the symptoms produced and the morphology of the cuts separating the VM region from lateral hypothalamus. In Series I, most of the rats with complete or anterior cuts showed increases in body weight and fat deposition. The most pronounced effects were associated with cuts that reached the ventral surface of the brain bilaterally along the lateral borders of the VM nuclei. If cuts obviously failed to reach the ventral surface of the brain on one side or if they extended only along the anterior poles of the V M nuclei, weight gain was less marked. Cuts that were unilateral or

192 which, as in one case, involved only the posterior part of the VM region did not result in an increase in body weight. In Series II, most of the rats with complete cuts showed a pattern of marked and rapid weight gain. The cuts in these obese rats were relatively uniform and generally complete along the lateral borders of VM nuclei bilaterally. In addition, 4 of 7 rats with horizontal cuts demonstrated increases in body weight. Relationships observed between anatomic features of individual bypothalamic cuts and effects on body weight suggest several morphologic characteristics of the connections between VM and lateral hypothalamus which are presumed to function in the control of food intake. First, the finding that weight gain was less if cuts were obviously incomplete ventrally suggests that a significant portion of these neural connections exits laterally from the ventral VM region and sweeps dorsolaterally to the lateral hypothalamus in a path that approaches and parallels the ventral surface of the brain. This postulated trajectory is also compatible with the results obtained in rats with horizontal cuts; cuts which reached the brain surface in a plane that bisected the VM area into dorsal and ventral halves in two rats resulted in patterns of weight gain and obesity that were as extreme as those observed in animals with complete or anterior cuts. The intermediate weight responses in two rats with more ventrally-placed basal cuts may reflect less complete disruption of the postulated ventral fiber system. This proposed pathway is compatible with the pattern of fiber degeneration produced in mice by goldthioglucose administration [3] and with the pathway suggested by several investigators on the basis of location of obesity-producing electrolytic lesions (see [33]). Another anatomical feature suggested by these results concerns the relative importance of rostral and caudal halves of the VM region to the control of body weight and food intake. The finding that three anterior cuts which impinged upon the lateral border of the rostral VM area produced obesity comparable to that observed with complete isolation suggests that connections of the rostrat half are important in this regard. Although the series of rats reported here did not include a group with posterior cuts, preliminary observations [7] suggest that posterior hypothalamic cuts, unless they extend to the rostral half of VM nuclei, are ineffective in producing obesity. Gold recently reached similar conclusions on the basis of responses to anterior and posterior hypothalamic cuts [13]. The importance of posterior connections has been emphasized previously because extensive lesions placed in this region resulted in hyperphagia and obesity [14, 23]. Kennedy, however, did not observe obesity with lesions placed posteriorly in the VM region [25]. In addition to implicating rostral connections of the VM area to control of food intake, the spectrum of weight responses obtained in Series I and the apparent correlation with morphologic features of lesions imply a quantitative relationship between degree of interruption achieved and weight gain. It seems clear from these and other data that hypothalamic obesity and hyperphagia are not all-or-none phenomena, and it has been suggested that the degree of obesity following placement of electrolytic lesions is determined by the size of the lesions [2, 4, 14, 23, 26]. It has also been reported that a direct relationship exists between the residual volume of the VM nuclei and the degree of obesity produced in mice by graded doses of goldthioglucose [27]. Although three rats with unilateral cuts in the present series failed to show a weight response, Gold recently reported slight but significant weight gain following placement of

PAI.KA, I_IFBLI I ANI)t RI!~.I't|I.~.I\~., unilateral cuts [13]. In contrast, unilateral electrolyiic lesions may be more effective in causing increased weight gain [26]. As pointed out by Gold [I 3], the relative ineffectiveness of unilateral cuts is unexplained by current theories of regulation of food intake. The morphological features of hypothalamic cuts which produced marked weight gain and obesity offer some explanation for several reports which describe a lack of or only occasional increases in body weight following isolation of the VM hypothalamus. In some reports [15, 19, 20] hypothalamic cuts were apparently more medially placed, i.e. they passed through rather than lateral to VM nuclei. In the report of Voloschin and co-workers [35], it is not clear as to whether the cuts extended to the ventral surface of the hypothatamus. No evidence was found in the present studies to support the suggestion of Voloschin et aL that involvement of the columns of the fornix is essential to induction of hypothalamic obesity; the fornix columns were clearly intact in the four rats that showed weight responses following placement of horizontal cuts. In contrast to the results obtained with cuts located medially in the hypothalamus, those placed at the lateral border of the lateral hypothalamus produced aphagia ailcl adipsia rather than obesity [10]. The present experiments showed that animals which became markedly obese ate almost twice as much as controls during the three week observation period. Unfortunately, the rats soon became too large to enter the food hoppers of the metabolic cages and it was impossible to determine duration of hyperphagia. Jansen and Hutchison reported a tapering off of food intake by 28 days after surgery [24]. In the present study and in that of Gold [13], hyperphagia was of longer duration. As in previous reports [6, 22, 23], hypothalamic obesity obtained in the present experiments was associated with visceral hypertrophy. The basis of such hypertrophy is unknown, but it is often accompanied by reduced linear growth [5, 21]. Thus it was surprising that many of the obese rats in these studies showed increases in nose-anal length; additional studies [7] have shown that this effect on body length is highly reproducible. The present findings indicate that hypothalamic obesity is compatible with increased growth and do not support the view that obesity is due to an absolute or relative deficiency in growth hormone [5, 21]. The increased length produced by several types of hypothalamic cuts suggests that some of the neural connections of the VM region normally inhibit growth. Although the number of' animals was small, the spectrum of effects observed with horizontal cuts was especially intriguing in this regard. Cuts which passed horizontally through the vertical midsection of VM nuclei appeared to cause the greatest growth, while cuts between VM and arcuate nuclei were associated with normal length. In contrast, two horizontal cuts in the arcuate nucleus-median eminence zone resulted in animals that were shorter than controls. These findings suggest that neural elements responsible for growth reside in the V M region and that these elements receive inhibitory connections from other structures. Results of hypothalamic lesions [4, 11 ] and stimulation [12] and transplantation of pituitaries to the hypothalamus [17] have previously implicated the VM region in the control of growth hormone secretion. It is possible that the increased growth obtained with brain cuts is due to interruption of inhibitory influences on neurons which control pituitary secretion of growth hormone; recent experiments in this laboratory [28] demonstrated marked elevations in radioimmunoassayable growth hormone in plasma 7-11 weeks

,6,

FIG. 5. Photomicrographs of brains with complete cuts. A. Section through VM region of rat in Series I which showed marked weight gain and hyperphagia. B. Section from rat in Series II which showed both marked weight gain and increased nose-anal length: terminal body weight and length in this rat were 950 g and 25.7 cm, respectively. Arrows mark cuts at brain surface.

FIG. 7. Photomicrographs of brains with horizontal cuts. A. A cut that passed through the mid-section of VM nuclei and which produced marked weight gain (1012 g) and increased nose-anal length (26.0 cm). B. A cut that passed horizontally in a plane between VM and arcuate nuclei and which was associated with moderate weight gain (624 g) and normal nose-anal length (24.5 cm). C. A cut located in the arcuate nucleus-median eminence region which did not produce an increase in body weight (294 g), but the nose-anal length (21.0 cm) was shorter than that of controls.

(facing page 192)

OBESITY AND GROWTH WITH HYPOTHALAMIC CUTS following surgical isolation of the VM region. The failure of obesity-producing electrolytic lesions in the VM area to result in augmented somatic growth may be due to the fact that most of such lesions are large and destroy both the growthpromoting elements and the inhibitory connections. However, Hal~isz did not observe increased growth or elevated plasma growth hormone levels following neural isolation of the medial basal hypothalamus [18]. The discrepancy between the present results and those of Halfisz may be due to the fact that his observation period was only 7 weeks or to differences in lesion morphology. Despite the high positive correlation between effects of lesions on nose-anal length and body weight, the present observations juxtaposed with those which indicate that hypothalamic obesity is commonly accompanied by decreased linear growth [4, 5, 21] suggest that these functions are dissociable. The recent paper by Bernardis and Frohman [4] presents interesting evidence in this regard. Unpublished observations lead us to believe that it may be possible to dissociate the linear growth and obesity responses with appropriate hypothalamic cuts.

193 The increase in water intake which occurred in rats with complete isolation of the VM area was relatively mild 4-7 weeks after surgery. However, in other experiments in this laboratory it has been observed that marked diabetes insipidus, persistent or transitory, usually appears acutely after anterior or complete cuts. The anatomical basis for differences in duration of effects on water metabolism is subtle and does not seem attributable solely to damage or lack of damage to the supraopticohypophysial tract. In summary, the present results are consistent with other reports [1, 13, 24, 32] which indicate that surgical interruption of connections between medial and lateral hypothalamus results in marked obesity and hyperphagia. Such findings are compatible with current views concerning the role of a medial satiety mechanism which controls food intake. In addition, these experiments demonstrate that hypothalamic cuts may produce augmentation of somatic growth, raising the possibility that the hypothalamus contains neural circuits that inhibit growth.

REFERENCES 1. Albert, D. J. and L. H. Storlien. Hyperphagia in rats with cuts between the ventrornedial and lateral hypothalamus. Science 165: 599-600, 1969. 2. Anand, B. K. and J. R. Brobeck. Hypothalamic control of food intake in rats and cats. Yale J. biol. Med. 24: 123-140, 1951. 3. Arees, E. A. and J. Mayer. Anatomical connections between medial and lateral regions of the hypothalamus concerned with food intake. Science 157: 1574-1575, 1967. 4. Bernardis, L. L. and L. A. Frohman. Effect of lesion size in the ventromedial hypothalamus on growth hormone and insulin levels in weanling rats. Neuroendocrinology 6: 319328, 1970. 5. Bernardis, L. L. and F. L. Skelton. Growth and obesity following ventromedial hypothalamic lesions placed in female rats at four different ages. Neuroendocrinology 1: 265-275, 1966. 6. Brobeck, J. R., J. Tepperman and C. N. H. Long. Experimental laypothalamic hyperphagia in the albino rat. Yale J. biol. Med. 15: 831-853, 1943. 7. Critchlow, V., R. Smyrl, Y. Palka, C. Bordelon, M. Hutchins, R. Liebelt and W. Schindler. Obesity and increased growth following isolation of medial-basal hypothalamus. Fed. Proc. 29: 377, 1970. 8. DeGroot, J. The rat forebrain in stereotaxic coordinates. Verh. Kon. Ned. Akad. Wet., A. Naturkunde. 52: 1-40, 1959. 9. Duncan, D. B. Multiple range and multiple F tests. Biometrics 11: 1-42, 1955. 10. Ellison, G. D. Appetitive behavior in rats after circumsection of the hypothalamus. Physiol. Behav. 3: 221-226, 1968. 11. Frohman, L. A. and L. L. Bernardis. Growth hormone and insulin levels in weanling rats with ventromedial hypothalamic lesions. Endocrinology 82:1125-1132, 1968. 12. Frohman, L. A., L. L. Bernardis and K. H. Kant. Hypothalamic stimulation of growth hormone secretion. Science 162: 580-582, 1968. t 3. Gold, R. M. Hypothalamic hyperphagia produced by parasagittal knife cuts. Physiol. Behav. 5: 23-25, 1970. 14. Graft, H. and E. Stellar. Hyperphagia, obesity and finickiness. J. comp. physiol. Psychol. 55" 418-424, 1962. 15. Greer, M. A. and C. Rookie. Inhibition by pentobarbital of ether-induced ACTH secretion in the rat. Endocrinology 83: 1247-1252, 1968. 16, Grossman, S. P. Hypothalamic and limbic influences on food intake. Fed. Proc. 27: 1349-1360, 1968.

17. Halasz, B. Growth ofhypophysectomized rats bearing pituitary transplant in the hypothalamus. Acta Physiol. Acad. sci. hung. 23: 287-292, 1963. 18. Halfi.sz, B. The role of the hypothalamic hypophysiotrophic area in the control of growth hormone secretion. Int. Symposium on Growth Hormone, Milan. Excerpta Med. Int. Cong. Set. 158: 204-210, 1968. 19. Halfi.sz, B. and R. A. Gorski. Gonadotrophic hormone secretion in female rats after partial or total interruption of neural afferents to the medial basal hypothalamus. Endocrinology 80: 608-622, 1967. 20. Hal~isz, B. and L. Pupp. Hormone secretion of the anterior pituitary gland after physical interruption of all nervous pathways to the hypophysiotrophic area. Endocrinology 77: 553-562, 1965. 21. Han, P. W. Hypothalamic obesity in rats without hyperphagia. Trans. N.Y. ,4cad. Sci. 30: 229-243, 1967. 22. Hetherington, A. W. and S. W. Ranson. Hypothalamic lesions and adiposity in the rat. Anat. Rec. 78: 149-172, 1940. 23. Hetherington, A. W. and S. W. Ranson. The relation of various hypothalamic lesions to adiposity in the rat. J. comp. Neurol. 76: 475-499, 1942. 24. Jansen, G. R. and C. F. Hutchison. Production of hypothalamic obesity by microsurgery. Am. J. Physiol. 217: 487-493, 1969. 25. Kennedy, G. C. The hypothalamic control of food intake in rats. Proc. R. Sot'., Lond., Ser. B., 137: 535-549, 1950. 26. Mayer, J. and R. J. Barrnett. Obesity following unilateral hypothalamic lesions in rats. Science 121: 599-600, 1955. 27. McBurney, P. L., R. A. Liebelt and J. H. Perry. Quantitative relationships between food intake, lipid deposition and hypothalamic damage in goldthioglucose obesity. Tex. Rep. Biol. Med. 23: 737-752, 1965, 28. Mitchell, J. A., D. K. Belsare, M. Hutchins, W. J. Schindler and V. Critchlow. Increases in growth and plasma growth hormone levels following surgical isolation of medial basal hypothalamus in female rats. Proc. Endocr. Soc., Program 53rd Meeting, Endocrine Soc. 1971, p. 82. 29. Morgane, P. J. and H. L. Jacobs. Hunger and satiety. WId Rev. Nutr. Diet. 10: 100-213, 1969. 30. Palka, Y., D. Coyer and V. Critchlow. Effects of isolation of medial basal hypothalamus on pituitary-adrenal and pituitary-ovarian functions. Neuroendocrinology 5: 333-349, 1969.

194 31. Sakiz, E. Statistical analyses in experimental biology with single multiphase program. Program Exbiol. Common Research Computer Facility, Texas Medical Center. Houston, Texas, 1966. 32. Sclafani, A. and S. P. Grossman. Hyperphagia produced by knife cuts between the medial and lateral hypothalamus in the rat. Physiol. Behav. 4: 533-537, 1969. 33. Stevenson, J. A. F. Neural control of food and water intake. In: The Hypothalamus, edited by W. Haymaker, E. Anderson and W. J. H. Nauta. Springfield: Charles C. Thomas, 1969, pp. 524-621.

PAI.KA, IH:B[iLI- AND ~RII(711I.~Y',v 34. 'Feitelbaum, P. Motivation and control of food intake. In Handbook of Physiology, Sec. 6, Alimentao, Canal, Vol. 1. edited by C. F. Code. Washington, D.C.: American Physiological Society, 1967, pp. 319-335. 35. Voloschin, L., S. A. Joseph and K. M. Knigge. Endocrine function in male rats following complete and partial isolations of the hypothalamo-pituitary unit. Neuroendocrinoh~l' 3: 387-397, 1968.